// This is an open source non-commercial project. Dear PVS-Studio, please check
// it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com

/*
 * ops.c: implementation of various operators: op_shift, op_delete, op_tilde,
 *        op_change, op_yank, do_put, do_join
 */

#include <assert.h>
#include <inttypes.h>
#include <stdbool.h>
#include <string.h>

#include "nvim/vim.h"
#include "nvim/ascii.h"
#include "nvim/ops.h"
#include "nvim/buffer.h"
#include "nvim/change.h"
#include "nvim/charset.h"
#include "nvim/cursor.h"
#include "nvim/assert.h"
#include "nvim/edit.h"
#include "nvim/eval.h"
#include "nvim/eval/typval.h"
#include "nvim/ex_cmds.h"
#include "nvim/ex_cmds2.h"
#include "nvim/ex_getln.h"
#include "nvim/fileio.h"
#include "nvim/fold.h"
#include "nvim/getchar.h"
#include "nvim/indent.h"
#include "nvim/log.h"
#include "nvim/mark.h"
#include "nvim/extmark.h"
#include "nvim/mbyte.h"
#include "nvim/memline.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/misc1.h"
#include "nvim/move.h"
#include "nvim/normal.h"
#include "nvim/option.h"
#include "nvim/path.h"
#include "nvim/screen.h"
#include "nvim/search.h"
#include "nvim/state.h"
#include "nvim/strings.h"
#include "nvim/terminal.h"
#include "nvim/ui.h"
#include "nvim/undo.h"
#include "nvim/macros.h"
#include "nvim/window.h"
#include "nvim/lib/kvec.h"
#include "nvim/os/input.h"
#include "nvim/os/time.h"

static yankreg_T y_regs[NUM_REGISTERS];

static yankreg_T *y_previous = NULL; /* ptr to last written yankreg */

// for behavior between start_batch_changes() and end_batch_changes())
static int batch_change_count = 0;           // inside a script
static bool clipboard_delay_update = false;  // delay clipboard update
static bool clipboard_needs_update = false;  // clipboard was updated
static bool clipboard_didwarn = false;

/*
 * structure used by block_prep, op_delete and op_yank for blockwise operators
 * also op_change, op_shift, op_insert, op_replace - AKelly
 */
struct block_def {
  int startspaces;              /* 'extra' cols before first char */
  int endspaces;                /* 'extra' cols after last char */
  int textlen;                  /* chars in block */
  char_u      *textstart;       /* pointer to 1st char (partially) in block */
  colnr_T textcol;              /* index of chars (partially) in block */
  colnr_T start_vcol;           /* start col of 1st char wholly inside block */
  colnr_T end_vcol;             /* start col of 1st char wholly after block */
  int is_short;                 /* TRUE if line is too short to fit in block */
  int is_MAX;                   /* TRUE if curswant==MAXCOL when starting */
  int is_oneChar;               /* TRUE if block within one character */
  int pre_whitesp;              /* screen cols of ws before block */
  int pre_whitesp_c;            /* chars of ws before block */
  colnr_T end_char_vcols;       /* number of vcols of post-block char */
  colnr_T start_char_vcols;       /* number of vcols of pre-block char */
};

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "ops.c.generated.h"
#endif

// Flags for third item in "opchars".
#define OPF_LINES  1  // operator always works on lines
#define OPF_CHANGE 2  // operator changes text

/*
 * The names of operators.
 * IMPORTANT: Index must correspond with defines in vim.h!!!
 * The third field indicates whether the operator always works on lines.
 */
static char opchars[][3] =
{
  { NUL, NUL, 0 },                       // OP_NOP
  { 'd', NUL, OPF_CHANGE },              // OP_DELETE
  { 'y', NUL, 0 },                       // OP_YANK
  { 'c', NUL, OPF_CHANGE },              // OP_CHANGE
  { '<', NUL, OPF_LINES | OPF_CHANGE },  // OP_LSHIFT
  { '>', NUL, OPF_LINES | OPF_CHANGE },  // OP_RSHIFT
  { '!', NUL, OPF_LINES | OPF_CHANGE },  // OP_FILTER
  { 'g', '~', OPF_CHANGE },              // OP_TILDE
  { '=', NUL, OPF_LINES | OPF_CHANGE },  // OP_INDENT
  { 'g', 'q', OPF_LINES | OPF_CHANGE },  // OP_FORMAT
  { ':', NUL, OPF_LINES },               // OP_COLON
  { 'g', 'U', OPF_CHANGE },              // OP_UPPER
  { 'g', 'u', OPF_CHANGE },              // OP_LOWER
  { 'J', NUL, OPF_LINES | OPF_CHANGE },  // DO_JOIN
  { 'g', 'J', OPF_LINES | OPF_CHANGE },  // DO_JOIN_NS
  { 'g', '?', OPF_CHANGE },              // OP_ROT13
  { 'r', NUL, OPF_CHANGE },              // OP_REPLACE
  { 'I', NUL, OPF_CHANGE },              // OP_INSERT
  { 'A', NUL, OPF_CHANGE },              // OP_APPEND
  { 'z', 'f', 0         },               // OP_FOLD
  { 'z', 'o', OPF_LINES },               // OP_FOLDOPEN
  { 'z', 'O', OPF_LINES },               // OP_FOLDOPENREC
  { 'z', 'c', OPF_LINES },               // OP_FOLDCLOSE
  { 'z', 'C', OPF_LINES },               // OP_FOLDCLOSEREC
  { 'z', 'd', OPF_LINES },               // OP_FOLDDEL
  { 'z', 'D', OPF_LINES },               // OP_FOLDDELREC
  { 'g', 'w', OPF_LINES | OPF_CHANGE },  // OP_FORMAT2
  { 'g', '@', OPF_CHANGE },              // OP_FUNCTION
  { Ctrl_A, NUL, OPF_CHANGE },           // OP_NR_ADD
  { Ctrl_X, NUL, OPF_CHANGE },           // OP_NR_SUB
};

/*
 * Translate a command name into an operator type.
 * Must only be called with a valid operator name!
 */
int get_op_type(int char1, int char2)
{
  int i;

  if (char1 == 'r') {
    // ignore second character
    return OP_REPLACE;
  }
  if (char1 == '~') {
    // when tilde is an operator
    return OP_TILDE;
  }
  if (char1 == 'g' && char2 == Ctrl_A) {
    // add
    return OP_NR_ADD;
  }
  if (char1 == 'g' && char2 == Ctrl_X) {
    // subtract
    return OP_NR_SUB;
  }
  if (char1 == 'z' && char2 == 'y') {  // OP_YANK
    return OP_YANK;
  }
  for (i = 0;; i++) {
    if (opchars[i][0] == char1 && opchars[i][1] == char2) {
      break;
    }
    if (i == (int)(ARRAY_SIZE(opchars) - 1)) {
      internal_error("get_op_type()");
      break;
    }
  }
  return i;
}

/*
 * Return TRUE if operator "op" always works on whole lines.
 */
int op_on_lines(int op)
{
  return opchars[op][2] & OPF_LINES;
}

// Return TRUE if operator "op" changes text.
int op_is_change(int op)
{
    return opchars[op][2] & OPF_CHANGE;
}

/*
 * Get first operator command character.
 * Returns 'g' or 'z' if there is another command character.
 */
int get_op_char(int optype)
{
  return opchars[optype][0];
}

/*
 * Get second operator command character.
 */
int get_extra_op_char(int optype)
{
  return opchars[optype][1];
}

/*
 * op_shift - handle a shift operation
 */
void op_shift(oparg_T *oap, int curs_top, int amount)
{
  long i;
  int first_char;
  char_u          *s;
  int block_col = 0;

  if (u_save((linenr_T)(oap->start.lnum - 1),
          (linenr_T)(oap->end.lnum + 1)) == FAIL)
    return;

  if (oap->motion_type == kMTBlockWise) {
    block_col = curwin->w_cursor.col;
  }

  for (i = oap->line_count - 1; i >= 0; i--) {
    first_char = *get_cursor_line_ptr();
    if (first_char == NUL) {  // empty line
      curwin->w_cursor.col = 0;
    } else if (oap->motion_type == kMTBlockWise) {
      shift_block(oap, amount);
    } else if (first_char != '#' || !preprocs_left()) {
      // Move the line right if it doesn't start with '#', 'smartindent'
      // isn't set or 'cindent' isn't set or '#' isn't in 'cino'.
      shift_line(oap->op_type == OP_LSHIFT, p_sr, amount, false);
    }
    ++curwin->w_cursor.lnum;
  }

  if (oap->motion_type == kMTBlockWise) {
    curwin->w_cursor.lnum = oap->start.lnum;
    curwin->w_cursor.col = block_col;
  } else if (curs_top) { /* put cursor on first line, for ">>" */
    curwin->w_cursor.lnum = oap->start.lnum;
    beginline(BL_SOL | BL_FIX);       /* shift_line() may have set cursor.col */
  } else
    --curwin->w_cursor.lnum;            /* put cursor on last line, for ":>" */

  // The cursor line is not in a closed fold
  foldOpenCursor();

  if (oap->line_count > p_report) {
    if (oap->op_type == OP_RSHIFT)
      s = (char_u *)">";
    else
      s = (char_u *)"<";
    if (oap->line_count == 1) {
      if (amount == 1)
        sprintf((char *)IObuff, _("1 line %sed 1 time"), s);
      else
        sprintf((char *)IObuff, _("1 line %sed %d times"), s, amount);
    } else {
      if (amount == 1)
        sprintf((char *)IObuff, _("%" PRId64 " lines %sed 1 time"),
            (int64_t)oap->line_count, s);
      else
        sprintf((char *)IObuff, _("%" PRId64 " lines %sed %d times"),
            (int64_t)oap->line_count, s, amount);
    }
    msg_attr_keep(IObuff, 0, true, false);
  }

  /*
   * Set "'[" and "']" marks.
   */
  curbuf->b_op_start = oap->start;
  curbuf->b_op_end.lnum = oap->end.lnum;
  curbuf->b_op_end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
  if (curbuf->b_op_end.col > 0) {
    curbuf->b_op_end.col--;
  }

  changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
}

// Shift the current line one shiftwidth left (if left != 0) or right
// leaves cursor on first blank in the line.
void shift_line(
    int left,
    int round,
    int amount,
    int call_changed_bytes  // call changed_bytes()
)
{
  int count;
  int i, j;
  int p_sw = (int)get_sw_value_indent(curbuf);

  count = get_indent();  // get current indent

  if (round) {  // round off indent
    i = count / p_sw;  // number of p_sw rounded down
    j = count % p_sw;  // extra spaces
    if (j && left) {  // first remove extra spaces
      amount--;
    }
    if (left) {
      i -= amount;
      if (i < 0)
        i = 0;
    } else
      i += amount;
    count = i * p_sw;
  } else {  // original vi indent
    if (left) {
      count -= p_sw * amount;
      if (count < 0)
        count = 0;
    } else
      count += p_sw * amount;
  }

  // Set new indent
  if (State & VREPLACE_FLAG) {
    change_indent(INDENT_SET, count, false, NUL, call_changed_bytes);
  } else {
    (void)set_indent(count, call_changed_bytes ? SIN_CHANGED : 0);
  }
}

/*
 * Shift one line of the current block one shiftwidth right or left.
 * Leaves cursor on first character in block.
 */
static void shift_block(oparg_T *oap, int amount)
{
  const bool left = (oap->op_type == OP_LSHIFT);
  const int oldstate = State;
  char_u *newp;
  const int oldcol = curwin->w_cursor.col;
  int p_sw = (int)get_sw_value_indent(curbuf);
  long *p_vts = curbuf->b_p_vts_array;
  const long p_ts = curbuf->b_p_ts;
  struct block_def bd;
  int incr;
  int i = 0, j = 0;
  const int old_p_ri = p_ri;

  p_ri = 0;                     /* don't want revins in indent */

  State = INSERT;               // don't want REPLACE for State
  block_prep(oap, &bd, curwin->w_cursor.lnum, true);
  if (bd.is_short) {
    return;
  }

  // total is number of screen columns to be inserted/removed
  int total = (int)((unsigned)amount * (unsigned)p_sw);
  if ((total / p_sw) != amount) {
    return;   // multiplication overflow
  }

  char_u *const oldp = get_cursor_line_ptr();

  int startcol, oldlen, newlen;

  if (!left) {
    /*
     *  1. Get start vcol
     *  2. Total ws vcols
     *  3. Divvy into TABs & spp
     *  4. Construct new string
     */
    total += bd.pre_whitesp;    // all virtual WS up to & incl a split TAB
    colnr_T ws_vcol = bd.start_vcol - bd.pre_whitesp;
    char_u * old_textstart = bd.textstart;
    if (bd.startspaces) {
      if (utfc_ptr2len(bd.textstart) == 1) {
        bd.textstart++;
      } else {
        ws_vcol = 0;
        bd.startspaces = 0;
      }
    }
    for (; ascii_iswhite(*bd.textstart); ) {
      // TODO: is passing bd.textstart for start of the line OK?
      incr = lbr_chartabsize_adv(bd.textstart, &bd.textstart, (colnr_T)(bd.start_vcol));
      total += incr;
      bd.start_vcol += incr;
    }
    /* OK, now total=all the VWS reqd, and textstart points at the 1st
     * non-ws char in the block. */
    if (!curbuf->b_p_et) {
      tabstop_fromto(ws_vcol, ws_vcol + total, p_ts, p_vts, &i, &j);
    } else {
      j = total;
    }

    // if we're splitting a TAB, allow for it
    int col_pre = bd.pre_whitesp_c - (bd.startspaces != 0);
    bd.textcol -= col_pre;
    const int len = (int)STRLEN(bd.textstart) + 1;
    int col = bd.textcol + i +j + len;
    assert(col >= 0);
    newp = (char_u *)xmalloc((size_t)col);
    memset(newp, NUL, (size_t)col);
    memmove(newp, oldp, (size_t)bd.textcol);
    startcol = bd.textcol;
    oldlen = (int)(bd.textstart-old_textstart) + col_pre;
    newlen = i+j;
    memset(newp + bd.textcol, TAB, (size_t)i);
    memset(newp + bd.textcol + i, ' ', (size_t)j);
    /* the end */
    memmove(newp + bd.textcol + i + j, bd.textstart, (size_t)len);
  } else {  // left
    colnr_T destination_col;      // column to which text in block will
                                  // be shifted
    char_u *verbatim_copy_end;    // end of the part of the line which is
                                  // copied verbatim
    colnr_T verbatim_copy_width;  // the (displayed) width of this part
                                  // of line
    size_t fill;                  // nr of spaces that replace a TAB
    size_t new_line_len;          // the length of the line after the
                                  // block shift
    char_u      *non_white = bd.textstart;

    /*
     * Firstly, let's find the first non-whitespace character that is
     * displayed after the block's start column and the character's column
     * number. Also, let's calculate the width of all the whitespace
     * characters that are displayed in the block and precede the searched
     * non-whitespace character.
     */

    /* If "bd.startspaces" is set, "bd.textstart" points to the character,
     * the part of which is displayed at the block's beginning. Let's start
     * searching from the next character. */
    if (bd.startspaces) {
      MB_PTR_ADV(non_white);
    }

    // The character's column is in "bd.start_vcol".
    colnr_T non_white_col = bd.start_vcol;

    while (ascii_iswhite(*non_white)) {
      incr = lbr_chartabsize_adv(bd.textstart, &non_white, non_white_col);
      non_white_col += incr;
    }


    const colnr_T block_space_width = non_white_col - oap->start_vcol;
    // We will shift by "total" or "block_space_width", whichever is less.
    const colnr_T shift_amount = block_space_width < total
        ? block_space_width
        : total;
    // The column to which we will shift the text.
    destination_col = non_white_col - shift_amount;

    /* Now let's find out how much of the beginning of the line we can
     * reuse without modification.  */
    verbatim_copy_end = bd.textstart;
    verbatim_copy_width = bd.start_vcol;

    /* If "bd.startspaces" is set, "bd.textstart" points to the character
     * preceding the block. We have to subtract its width to obtain its
     * column number.  */
    if (bd.startspaces)
      verbatim_copy_width -= bd.start_char_vcols;
    while (verbatim_copy_width < destination_col) {
      char_u *line = verbatim_copy_end;

      // TODO: is passing verbatim_copy_end for start of the line OK?
      incr = lbr_chartabsize(line, verbatim_copy_end, verbatim_copy_width);
      if (verbatim_copy_width + incr > destination_col)
        break;
      verbatim_copy_width += incr;
      MB_PTR_ADV(verbatim_copy_end);
    }

    /* If "destination_col" is different from the width of the initial
    * part of the line that will be copied, it means we encountered a tab
    * character, which we will have to partly replace with spaces.  */
    assert(destination_col - verbatim_copy_width >= 0);
    fill = (size_t)(destination_col - verbatim_copy_width);

    assert(verbatim_copy_end - oldp >= 0);
    const size_t verbatim_diff = (size_t)(verbatim_copy_end - oldp);
    // The replacement line will consist of:
    // - the beginning of the original line up to "verbatim_copy_end",
    // - "fill" number of spaces,
    // - the rest of the line, pointed to by non_white.
    new_line_len = verbatim_diff + fill + STRLEN(non_white) + 1;

    newp = (char_u *)xmalloc(new_line_len);
    startcol = (int)verbatim_diff;
    oldlen = bd.textcol + (int)(non_white - bd.textstart) - (int)verbatim_diff;
    newlen = (int)fill;
    memmove(newp, oldp, verbatim_diff);
    memset(newp + verbatim_diff, ' ', fill);
    STRMOVE(newp + verbatim_diff + fill, non_white);
  }
  // replace the line
  ml_replace(curwin->w_cursor.lnum, newp, false);
  changed_bytes(curwin->w_cursor.lnum, (colnr_T)bd.textcol);
  extmark_splice_cols(curbuf, (int)curwin->w_cursor.lnum-1, startcol,
                      oldlen, newlen,
                      kExtmarkUndo);
  State = oldstate;
  curwin->w_cursor.col = oldcol;
  p_ri = old_p_ri;
}

/*
 * Insert string "s" (b_insert ? before : after) block :AKelly
 * Caller must prepare for undo.
 */
static void block_insert(oparg_T *oap, char_u *s, int b_insert, struct block_def *bdp)
{
  int p_ts;
  int count = 0;                // extra spaces to replace a cut TAB
  int spaces = 0;               // non-zero if cutting a TAB
  colnr_T offset;               // pointer along new line
  size_t s_len = STRLEN(s);
  char_u      *newp, *oldp;     // new, old lines
  linenr_T lnum;                // loop var
  int oldstate = State;
  State = INSERT;               // don't want REPLACE for State

  for (lnum = oap->start.lnum + 1; lnum <= oap->end.lnum; lnum++) {
    block_prep(oap, bdp, lnum, true);
    if (bdp->is_short && b_insert) {
      continue;  // OP_INSERT, line ends before block start
    }

    oldp = ml_get(lnum);

    if (b_insert) {
      p_ts = bdp->start_char_vcols;
      spaces = bdp->startspaces;
      if (spaces != 0)
        count = p_ts - 1;         /* we're cutting a TAB */
      offset = bdp->textcol;
    } else { /* append */
      p_ts = bdp->end_char_vcols;
      if (!bdp->is_short) {     /* spaces = padding after block */
        spaces = (bdp->endspaces ? p_ts - bdp->endspaces : 0);
        if (spaces != 0)
          count = p_ts - 1;           /* we're cutting a TAB */
        offset = bdp->textcol + bdp->textlen - (spaces != 0);
      } else { /* spaces = padding to block edge */
                 /* if $ used, just append to EOL (ie spaces==0) */
        if (!bdp->is_MAX)
          spaces = (oap->end_vcol - bdp->end_vcol) + 1;
        count = spaces;
        offset = bdp->textcol + bdp->textlen;
      }
    }

    if (spaces > 0) {
      int off;

      // Avoid starting halfway through a multi-byte character.
      if (b_insert) {
        off = utf_head_off(oldp, oldp + offset + spaces);
      } else {
        off = (*mb_off_next)(oldp, oldp + offset);
        offset += off;
      }
      spaces -= off;
      count -= off;
    }

    assert(count >= 0);
    newp = (char_u *)xmalloc(STRLEN(oldp) + s_len + (size_t)count + 1);

    // copy up to shifted part
    memmove(newp, oldp, (size_t)offset);
    oldp += offset;
    int startcol = offset;

    // insert pre-padding
    memset(newp + offset, ' ', (size_t)spaces);

    // copy the new text
    memmove(newp + offset + spaces, s, s_len);
    offset += (int)s_len;

    int skipped = 0;
    if (spaces && !bdp->is_short) {
      // insert post-padding
      memset(newp + offset + spaces, ' ', (size_t)(p_ts - spaces));
      // We're splitting a TAB, don't copy it.
      oldp++;
      // We allowed for that TAB, remember this now
      count++;
      skipped = 1;
    }

    if (spaces > 0)
      offset += count;
    STRMOVE(newp + offset, oldp);

    ml_replace(lnum, newp, false);
    extmark_splice_cols(curbuf, (int)lnum-1, startcol,
                        skipped, offset-startcol, kExtmarkUndo);

    if (lnum == oap->end.lnum) {
      /* Set "']" mark to the end of the block instead of the end of
       * the insert in the first line.  */
      curbuf->b_op_end.lnum = oap->end.lnum;
      curbuf->b_op_end.col = offset;
    }
  }   /* for all lnum */

  changed_lines(oap->start.lnum + 1, 0, oap->end.lnum + 1, 0L, true);

  State = oldstate;
}

/*
 * op_reindent - handle reindenting a block of lines.
 */
void op_reindent(oparg_T *oap, Indenter how)
{
  long i;
  char_u      *l;
  int amount;
  linenr_T first_changed = 0;
  linenr_T last_changed = 0;
  linenr_T start_lnum = curwin->w_cursor.lnum;

  /* Don't even try when 'modifiable' is off. */
  if (!MODIFIABLE(curbuf)) {
    EMSG(_(e_modifiable));
    return;
  }

  for (i = oap->line_count - 1; i >= 0 && !got_int; i--) {
    /* it's a slow thing to do, so give feedback so there's no worry that
     * the computer's just hung. */

    if (i > 1
        && (i % 50 == 0 || i == oap->line_count - 1)
        && oap->line_count > p_report)
      smsg(_("%" PRId64 " lines to indent... "), (int64_t)i);

    /*
     * Be vi-compatible: For lisp indenting the first line is not
     * indented, unless there is only one line.
     */
    if (i != oap->line_count - 1 || oap->line_count == 1
        || how != get_lisp_indent) {
      l = skipwhite(get_cursor_line_ptr());
      if (*l == NUL)                        /* empty or blank line */
        amount = 0;
      else
        amount = how();                     /* get the indent for this line */

      if (amount >= 0 && set_indent(amount, SIN_UNDO)) {
        // did change the indent, call changed_lines() later
        if (first_changed == 0) {
          first_changed = curwin->w_cursor.lnum;
        }
        last_changed = curwin->w_cursor.lnum;
      }
    }
    ++curwin->w_cursor.lnum;
    curwin->w_cursor.col = 0;      /* make sure it's valid */
  }

  /* put cursor on first non-blank of indented line */
  curwin->w_cursor.lnum = start_lnum;
  beginline(BL_SOL | BL_FIX);

  /* Mark changed lines so that they will be redrawn.  When Visual
   * highlighting was present, need to continue until the last line.  When
   * there is no change still need to remove the Visual highlighting. */
  if (last_changed != 0) {
    changed_lines(first_changed, 0,
                  oap->is_VIsual ? start_lnum + oap->line_count :
                  last_changed + 1, 0L, true);
  } else if (oap->is_VIsual) {
    redraw_curbuf_later(INVERTED);
  }

  if (oap->line_count > p_report) {
    i = oap->line_count - (i + 1);
    if (i == 1)
      MSG(_("1 line indented "));
    else
      smsg(_("%" PRId64 " lines indented "), (int64_t)i);
  }
  /* set '[ and '] marks */
  curbuf->b_op_start = oap->start;
  curbuf->b_op_end = oap->end;
}

/*
 * Keep the last expression line here, for repeating.
 */
static char_u   *expr_line = NULL;

/*
 * Get an expression for the "\"=expr1" or "CTRL-R =expr1"
 * Returns '=' when OK, NUL otherwise.
 */
int get_expr_register(void)
{
  char_u      *new_line;

  new_line = getcmdline('=', 0L, 0, true);
  if (new_line == NULL) {
    return NUL;
  }
  if (*new_line == NUL) {  // use previous line
    xfree(new_line);
  } else {
    set_expr_line(new_line);
  }
  return '=';
}

/*
 * Set the expression for the '=' register.
 * Argument must be an allocated string.
 */
void set_expr_line(char_u *new_line)
{
  xfree(expr_line);
  expr_line = new_line;
}

/*
 * Get the result of the '=' register expression.
 * Returns a pointer to allocated memory, or NULL for failure.
 */
char_u *get_expr_line(void)
{
  char_u      *expr_copy;
  char_u      *rv;
  static int nested = 0;

  if (expr_line == NULL)
    return NULL;

  /* Make a copy of the expression, because evaluating it may cause it to be
   * changed. */
  expr_copy = vim_strsave(expr_line);

  /* When we are invoked recursively limit the evaluation to 10 levels.
   * Then return the string as-is. */
  if (nested >= 10)
    return expr_copy;

  ++nested;
  rv = eval_to_string(expr_copy, NULL, TRUE);
  --nested;
  xfree(expr_copy);
  return rv;
}

/*
 * Get the '=' register expression itself, without evaluating it.
 */
char_u *get_expr_line_src(void)
{
  if (expr_line == NULL)
    return NULL;
  return vim_strsave(expr_line);
}

/// Returns whether `regname` is a valid name of a yank register.
/// Note: There is no check for 0 (default register), caller should do this.
/// The black hole register '_' is regarded as valid.
///
/// @param regname name of register
/// @param writing allow only writable registers
bool valid_yank_reg(int regname, bool writing)
{
  if ((regname > 0 && ASCII_ISALNUM(regname))
      || (!writing && vim_strchr((char_u *) "/.%:=" , regname) != NULL)
      || regname == '#'
      || regname == '"'
      || regname == '-'
      || regname == '_'
      || regname == '*'
      || regname == '+') {
    return true;
  }
  return false;
}

typedef enum {
  YREG_PASTE,
  YREG_YANK,
  YREG_PUT,
} yreg_mode_t;

/// Return yankreg_T to use, according to the value of `regname`.
/// Cannot handle the '_' (black hole) register.
/// Must only be called with a valid register name!
///
/// @param regname The name of the register used or 0 for the unnamed register
/// @param mode One of the following three flags:
///
/// `YREG_PASTE`:
/// Prepare for pasting the register `regname`. With no regname specified,
/// read from last written register, or from unnamed clipboard (depending on the
/// `clipboard=unnamed` option). Queries the clipboard provider if necessary.
///
/// `YREG_YANK`:
/// Preparare for yanking into `regname`. With no regname specified,
/// yank into `"0` register. Update `y_previous` for next unnamed paste.
///
/// `YREG_PUT`:
/// Obtain the location that would be read when pasting `regname`.
yankreg_T *get_yank_register(int regname, int mode)
{
  yankreg_T *reg;

  if (mode == YREG_PASTE && get_clipboard(regname, &reg, false)) {
    // reg is set to clipboard contents.
    return reg;
  } else if (mode != YREG_YANK
      && (regname == 0 || regname == '"' || regname == '*' || regname == '+')
      && y_previous != NULL) {
    // in case clipboard not available, paste from previous used register
    return y_previous;
  }

  int i = op_reg_index(regname);
  // when not 0-9, a-z, A-Z or '-'/'+'/'*': use register 0
  if (i == -1) {
    i = 0;
  }
  reg = &y_regs[i];

  if (mode == YREG_YANK) {
    // remember the written register for unnamed paste
    y_previous = reg;
  }
  return reg;
}

static bool is_append_register(int regname)
{
  return ASCII_ISUPPER(regname);
}

/// @see get_yank_register
/// @returns true when register should be inserted literally
/// (selection or clipboard)
static inline bool is_literal_register(int regname)
  FUNC_ATTR_CONST
{
  return regname == '*' || regname == '+';
}

/// Returns a copy of contents in register `name`
/// for use in do_put. Should be freed by caller.
yankreg_T *copy_register(int name)
  FUNC_ATTR_NONNULL_RET
{
  yankreg_T *reg = get_yank_register(name, YREG_PASTE);

  yankreg_T *copy = xmalloc(sizeof(yankreg_T));
  *copy = *reg;
  if (copy->y_size == 0) {
    copy->y_array = NULL;
  } else {
    copy->y_array = xcalloc(copy->y_size, sizeof(char_u *));
    for (size_t i = 0; i < copy->y_size; i++) {
      copy->y_array[i] = vim_strsave(reg->y_array[i]);
    }
  }
  return copy;
}

/// check if the current yank register has kMTLineWise register type
bool yank_register_mline(int regname)
{
  if (regname != 0 && !valid_yank_reg(regname, false)) {
    return false;
  }
  if (regname == '_') {  // black hole is always empty
    return false;
  }
  yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
  return reg->y_type == kMTLineWise;
}

/*
 * Start or stop recording into a yank register.
 *
 * Return FAIL for failure, OK otherwise.
 */
int do_record(int c)
{
  char_u          *p;
  static int regname;
  yankreg_T  *old_y_previous;
  int retval;

  if (reg_recording == 0) {
    // start recording
    // registers 0-9, a-z and " are allowed
    if (c < 0 || (!ASCII_ISALNUM(c) && c != '"')) {
      retval = FAIL;
    } else {
      reg_recording = c;
      showmode();
      regname = c;
      retval = OK;
    }
  } else {                        /* stop recording */
    /*
     * Get the recorded key hits.  K_SPECIAL and CSI will be escaped, this
     * needs to be removed again to put it in a register.  exec_reg then
     * adds the escaping back later.
     */
    reg_recording = 0;
    if (ui_has(kUIMessages)) {
      showmode();
    } else {
      MSG("");
    }
    p = get_recorded();
    if (p == NULL)
      retval = FAIL;
    else {
      /* Remove escaping for CSI and K_SPECIAL in multi-byte chars. */
      vim_unescape_csi(p);

      /*
       * We don't want to change the default register here, so save and
       * restore the current register name.
       */
      old_y_previous = y_previous;

      retval = stuff_yank(regname, p);

      y_previous = old_y_previous;
    }
  }
  return retval;
}

static void set_yreg_additional_data(yankreg_T *reg, dict_T *additional_data)
  FUNC_ATTR_NONNULL_ARG(1)
{
  if (reg->additional_data == additional_data) {
    return;
  }
  tv_dict_unref(reg->additional_data);
  reg->additional_data = additional_data;
}

/*
 * Stuff string "p" into yank register "regname" as a single line (append if
 * uppercase). "p" must have been alloced.
 *
 * return FAIL for failure, OK otherwise
 */
static int stuff_yank(int regname, char_u *p)
{
  /* check for read-only register */
  if (regname != 0 && !valid_yank_reg(regname, true)) {
    xfree(p);
    return FAIL;
  }
  if (regname == '_') {             /* black hole: don't do anything */
    xfree(p);
    return OK;
  }
  yankreg_T *reg = get_yank_register(regname, YREG_YANK);
  if (is_append_register(regname) && reg->y_array != NULL) {
    char_u **pp = &(reg->y_array[reg->y_size - 1]);
    char_u *lp = xmalloc(STRLEN(*pp) + STRLEN(p) + 1);
    STRCPY(lp, *pp);
    // TODO(philix): use xstpcpy() in stuff_yank()
    STRCAT(lp, p);
    xfree(p);
    xfree(*pp);
    *pp = lp;
  } else {
    free_register(reg);
    set_yreg_additional_data(reg, NULL);
    reg->y_array = (char_u **)xmalloc(sizeof(char_u *));
    reg->y_array[0] = p;
    reg->y_size = 1;
    reg->y_type = kMTCharWise;
  }
  reg->timestamp = os_time();
  return OK;
}

static int execreg_lastc = NUL;

/// Execute a yank register: copy it into the stuff buffer
///
/// Return FAIL for failure, OK otherwise
int
do_execreg(
    int regname,
    int colon,                      /* insert ':' before each line */
    int addcr,                      /* always add '\n' to end of line */
    int silent                     /* set "silent" flag in typeahead buffer */
)
{
  char_u *p;
  int retval = OK;

  if (regname == '@') {                 /* repeat previous one */
    if (execreg_lastc == NUL) {
      EMSG(_("E748: No previously used register"));
      return FAIL;
    }
    regname = execreg_lastc;
  }
  /* check for valid regname */
  if (regname == '%' || regname == '#' || !valid_yank_reg(regname, false)) {
    emsg_invreg(regname);
    return FAIL;
  }
  execreg_lastc = regname;

  if (regname == '_')                   /* black hole: don't stuff anything */
    return OK;

  if (regname == ':') {                 /* use last command line */
    if (last_cmdline == NULL) {
      EMSG(_(e_nolastcmd));
      return FAIL;
    }
    // don't keep the cmdline containing @:
    XFREE_CLEAR(new_last_cmdline);
    // Escape all control characters with a CTRL-V
    p = vim_strsave_escaped_ext(
        last_cmdline,
        (char_u *)"\001\002\003\004\005\006\007"
        "\010\011\012\013\014\015\016\017"
        "\020\021\022\023\024\025\026\027"
        "\030\031\032\033\034\035\036\037",
        Ctrl_V, false);
    // When in Visual mode "'<,'>" will be prepended to the command.
    // Remove it when it's already there.
    if (VIsual_active && STRNCMP(p, "'<,'>", 5) == 0) {
      retval = put_in_typebuf(p + 5, true, true, silent);
    } else {
      retval = put_in_typebuf(p, true, true, silent);
    }
    xfree(p);
  } else if (regname == '=') {
    p = get_expr_line();
    if (p == NULL)
      return FAIL;
    retval = put_in_typebuf(p, true, colon, silent);
    xfree(p);
  } else if (regname == '.') {        /* use last inserted text */
    p = get_last_insert_save();
    if (p == NULL) {
      EMSG(_(e_noinstext));
      return FAIL;
    }
    retval = put_in_typebuf(p, false, colon, silent);
    xfree(p);
  } else {
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
    if (reg->y_array == NULL)
      return FAIL;

    // Disallow remaping for ":@r".
    int remap = colon ? REMAP_NONE : REMAP_YES;

    /*
     * Insert lines into typeahead buffer, from last one to first one.
     */
    put_reedit_in_typebuf(silent);
    char_u *escaped;
    for (size_t i = reg->y_size; i-- > 0;) {  // from y_size - 1 to 0 included
      // insert NL between lines and after last line if type is kMTLineWise
      if (reg->y_type == kMTLineWise || i < reg->y_size - 1 || addcr) {
        if (ins_typebuf((char_u *)"\n", remap, 0, true, silent) == FAIL) {
          return FAIL;
        }
      }
      escaped = vim_strsave_escape_csi(reg->y_array[i]);
      retval = ins_typebuf(escaped, remap, 0, true, silent);
      xfree(escaped);
      if (retval == FAIL) {
        return FAIL;
      }
      if (colon
          && ins_typebuf((char_u *)":", remap, 0, true, silent) == FAIL) {
        return FAIL;
      }
    }
    reg_executing = regname == 0 ? '"' : regname;  // disable the 'q' command
  }
  return retval;
}

/*
 * If "restart_edit" is not zero, put it in the typeahead buffer, so that it's
 * used only after other typeahead has been processed.
 */
static void put_reedit_in_typebuf(int silent)
{
  char_u buf[3];

  if (restart_edit != NUL) {
    if (restart_edit == 'V') {
      buf[0] = 'g';
      buf[1] = 'R';
      buf[2] = NUL;
    } else {
      buf[0] = (char_u)(restart_edit == 'I' ? 'i' : restart_edit);
      buf[1] = NUL;
    }
    if (ins_typebuf(buf, REMAP_NONE, 0, true, silent) == OK) {
      restart_edit = NUL;
    }
  }
}

/*
 * Insert register contents "s" into the typeahead buffer, so that it will be
 * executed again.
 * When "esc" is TRUE it is to be taken literally: Escape CSI characters and
 * no remapping.
 */
static int put_in_typebuf(
    char_u *s,
    bool esc,
    bool colon,                 // add ':' before the line
    int silent
)
{
  int retval = OK;

  put_reedit_in_typebuf(silent);
  if (colon) {
    retval = ins_typebuf((char_u *)"\n", REMAP_NONE, 0, true, silent);
  }
  if (retval == OK) {
    char_u  *p;

    if (esc) {
      p = vim_strsave_escape_csi(s);
    } else {
      p = s;
    }
    if (p == NULL) {
      retval = FAIL;
    } else {
      retval = ins_typebuf(p, esc ? REMAP_NONE : REMAP_YES, 0, true, silent);
    }
    if (esc) {
      xfree(p);
    }
  }
  if (colon && retval == OK) {
    retval = ins_typebuf((char_u *)":", REMAP_NONE, 0, true, silent);
  }
  return retval;
}

/*
 * Insert a yank register: copy it into the Read buffer.
 * Used by CTRL-R command and middle mouse button in insert mode.
 *
 * return FAIL for failure, OK otherwise
 */
int insert_reg(
    int regname,
    bool literally_arg            // insert literally, not as if typed
)
{
  int retval = OK;
  bool allocated;
  const bool literally = literally_arg || is_literal_register(regname);

  /*
   * It is possible to get into an endless loop by having CTRL-R a in
   * register a and then, in insert mode, doing CTRL-R a.
   * If you hit CTRL-C, the loop will be broken here.
   */
  os_breakcheck();
  if (got_int)
    return FAIL;

  /* check for valid regname */
  if (regname != NUL && !valid_yank_reg(regname, false))
    return FAIL;

  char_u *arg;
  if (regname == '.') {  // Insert last inserted text.
    retval = stuff_inserted(NUL, 1L, true);
  } else if (get_spec_reg(regname, &arg, &allocated, true)) {
    if (arg == NULL) {
      return FAIL;
    }
    stuffescaped((const char *)arg, literally);
    if (allocated) {
      xfree(arg);
    }
  } else {  // Name or number register.
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
    if (reg->y_array == NULL) {
      retval = FAIL;
    } else {
      for (size_t i = 0; i < reg->y_size; i++) {
        if (regname == '-') {
          AppendCharToRedobuff(Ctrl_R);
          AppendCharToRedobuff(regname);
          do_put(regname, NULL, BACKWARD, 1L, PUT_CURSEND);
        } else {
          stuffescaped((const char *)reg->y_array[i], literally);
        }
        // Insert a newline between lines and after last line if
        // y_type is kMTLineWise.
        if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
          stuffcharReadbuff('\n');
        }
      }
    }
  }

  return retval;
}

/*
 * Stuff a string into the typeahead buffer, such that edit() will insert it
 * literally ("literally" TRUE) or interpret is as typed characters.
 */
static void stuffescaped(const char *arg, int literally)
{
  while (*arg != NUL) {
    // Stuff a sequence of normal ASCII characters, that's fast.  Also
    // stuff K_SPECIAL to get the effect of a special key when "literally"
    // is TRUE.
    const char *const start = arg;
    while ((*arg >= ' ' && *arg < DEL) || ((uint8_t)(*arg) == K_SPECIAL
                                           && !literally)) {
      arg++;
    }
    if (arg > start) {
      stuffReadbuffLen(start, (long)(arg - start));
    }

    /* stuff a single special character */
    if (*arg != NUL) {
      const int c = mb_cptr2char_adv((const char_u **)&arg);
      if (literally && ((c < ' ' && c != TAB) || c == DEL)) {
        stuffcharReadbuff(Ctrl_V);
      }
      stuffcharReadbuff(c);
    }
  }
}

// If "regname" is a special register, return true and store a pointer to its
// value in "argp".
bool get_spec_reg(
    int regname,
    char_u **argp,
    bool *allocated,        // return: true when value was allocated
    bool errmsg             // give error message when failing
)
{
  size_t cnt;

  *argp = NULL;
  *allocated = false;
  switch (regname) {
  case '%':                     /* file name */
    if (errmsg)
      check_fname();            /* will give emsg if not set */
    *argp = curbuf->b_fname;
    return true;

  case '#':                       // alternate file name
    *argp = getaltfname(errmsg);  // may give emsg if not set
    return true;

  case '=':                     /* result of expression */
    *argp = get_expr_line();
    *allocated = true;
    return true;

  case ':':                     /* last command line */
    if (last_cmdline == NULL && errmsg)
      EMSG(_(e_nolastcmd));
    *argp = last_cmdline;
    return true;

  case '/':                     /* last search-pattern */
    if (last_search_pat() == NULL && errmsg)
      EMSG(_(e_noprevre));
    *argp = last_search_pat();
    return true;

  case '.':                     /* last inserted text */
    *argp = get_last_insert_save();
    *allocated = true;
    if (*argp == NULL && errmsg) {
      EMSG(_(e_noinstext));
    }
    return true;

  case Ctrl_F:                  // Filename under cursor
  case Ctrl_P:                  // Path under cursor, expand via "path"
    if (!errmsg) {
      return false;
    }
    *argp = file_name_at_cursor(
        FNAME_MESS | FNAME_HYP | (regname == Ctrl_P ? FNAME_EXP : 0),
        1L, NULL);
    *allocated = true;
    return true;

  case Ctrl_W:                  // word under cursor
  case Ctrl_A:                  // WORD (mnemonic All) under cursor
    if (!errmsg) {
      return false;
    }
    cnt = find_ident_under_cursor(argp, (regname == Ctrl_W
                                         ? (FIND_IDENT|FIND_STRING)
                                         : FIND_STRING));
    *argp = cnt ? vim_strnsave(*argp, cnt) : NULL;
    *allocated = true;
    return true;

  case Ctrl_L:                  // Line under cursor
    if (!errmsg) {
      return false;
    }

    *argp = ml_get_buf(curwin->w_buffer, curwin->w_cursor.lnum, false);
    return true;

  case '_':                     /* black hole: always empty */
    *argp = (char_u *)"";
    return true;
  }

  return false;
}

/// Paste a yank register into the command line.
/// Only for non-special registers.
/// Used by CTRL-R in command-line mode.
/// insert_reg() can't be used here, because special characters from the
/// register contents will be interpreted as commands.
///
/// @param regname   Register name.
/// @param literally_arg Insert text literally instead of "as typed".
/// @param remcr     When true, don't add CR characters.
///
/// @returns FAIL for failure, OK otherwise
bool cmdline_paste_reg(int regname, bool literally_arg, bool remcr)
{
  const bool literally = literally_arg || is_literal_register(regname);

  yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
  if (reg->y_array == NULL)
    return FAIL;

  for (size_t i = 0; i < reg->y_size; i++) {
    cmdline_paste_str(reg->y_array[i], literally);

    // Insert ^M between lines, unless `remcr` is true.
    if (i < reg->y_size - 1 && !remcr) {
      cmdline_paste_str((char_u *)"\r", literally);
    }

    /* Check for CTRL-C, in case someone tries to paste a few thousand
     * lines and gets bored. */
    os_breakcheck();
    if (got_int)
      return FAIL;
  }
  return OK;
}

// Shift the delete registers: "9 is cleared, "8 becomes "9, etc.
static void shift_delete_registers(bool y_append)
{
  free_register(&y_regs[9]);  // free register "9
  for (int n = 9; n > 1; n--) {
    y_regs[n] = y_regs[n - 1];
  }
  if (!y_append) {
    y_previous = &y_regs[1];
  }
  y_regs[1].y_array = NULL;  // set register "1 to empty
}

/*
 * Handle a delete operation.
 *
 * Return FAIL if undo failed, OK otherwise.
 */
int op_delete(oparg_T *oap)
{
  int n;
  linenr_T lnum;
  char_u              *ptr;
  char_u              *newp, *oldp;
  struct block_def bd = { 0 };
  linenr_T old_lcount = curbuf->b_ml.ml_line_count;

  if (curbuf->b_ml.ml_flags & ML_EMPTY) {  // nothing to do
    return OK;
  }

  // Nothing to delete, return here. Do prepare undo, for op_change().
  if (oap->empty) {
    return u_save_cursor();
  }

  if (!MODIFIABLE(curbuf)) {
    EMSG(_(e_modifiable));
    return FAIL;
  }

  mb_adjust_opend(oap);

  /*
   * Imitate the strange Vi behaviour: If the delete spans more than one
   * line and motion_type == kMTCharWise and the result is a blank line, make the
   * delete linewise.  Don't do this for the change command or Visual mode.
   */
  if (oap->motion_type == kMTCharWise
      && !oap->is_VIsual
      && oap->line_count > 1
      && oap->motion_force == NUL
      && oap->op_type == OP_DELETE) {
    ptr = ml_get(oap->end.lnum) + oap->end.col;
    if (*ptr != NUL)
      ptr += oap->inclusive;
    ptr = skipwhite(ptr);
    if (*ptr == NUL && inindent(0)) {
      oap->motion_type = kMTLineWise;
    }
  }

  /*
   * Check for trying to delete (e.g. "D") in an empty line.
   * Note: For the change operator it is ok.
   */
  if (oap->motion_type != kMTLineWise
      && oap->line_count == 1
      && oap->op_type == OP_DELETE
      && *ml_get(oap->start.lnum) == NUL) {
    // It's an error to operate on an empty region, when 'E' included in
    // 'cpoptions' (Vi compatible).
    if (virtual_op) {
      // Virtual editing: Nothing gets deleted, but we set the '[ and ']
      // marks as if it happened.
      goto setmarks;
    }
    if (vim_strchr(p_cpo, CPO_EMPTYREGION) != NULL) {
      beep_flush();
    }
    return OK;
  }

  /*
   * Do a yank of whatever we're about to delete.
   * If a yank register was specified, put the deleted text into that
   * register.  For the black hole register '_' don't yank anything.
   */
  if (oap->regname != '_') {
    yankreg_T *reg = NULL;
    int did_yank = false;
    if (oap->regname != 0) {
      // yank without message
      did_yank = op_yank(oap, false, true);
      if (!did_yank) {
        // op_yank failed, don't do anything
        return OK;
      }
    }

    /*
     * Put deleted text into register 1 and shift number registers if the
     * delete contains a line break, or when a regname has been specified.
     */
    if (oap->regname != 0 || oap->motion_type == kMTLineWise
        || oap->line_count > 1 || oap->use_reg_one) {
      shift_delete_registers(is_append_register(oap->regname));
      reg = &y_regs[1];
      op_yank_reg(oap, false, reg, false);
      did_yank = true;
    }

    /* Yank into small delete register when no named register specified
     * and the delete is within one line. */
    if (oap->regname == 0 && oap->motion_type != kMTLineWise
        && oap->line_count == 1) {
      reg = get_yank_register('-', YREG_YANK);
      op_yank_reg(oap, false, reg, false);
      did_yank = true;
    }

    if (did_yank || oap->regname == 0) {
      if (reg == NULL) {
        abort();
      }
      set_clipboard(oap->regname, reg);
      do_autocmd_textyankpost(oap, reg);
    }

  }

  /*
   * block mode delete
   */
  if (oap->motion_type == kMTBlockWise) {
    if (u_save((linenr_T)(oap->start.lnum - 1),
               (linenr_T)(oap->end.lnum + 1)) == FAIL) {
      return FAIL;
    }

    for (lnum = curwin->w_cursor.lnum; lnum <= oap->end.lnum; lnum++) {
      block_prep(oap, &bd, lnum, true);
      if (bd.textlen == 0) {            // nothing to delete
        continue;
      }

      /* Adjust cursor position for tab replaced by spaces and 'lbr'. */
      if (lnum == curwin->w_cursor.lnum) {
        curwin->w_cursor.col = bd.textcol + bd.startspaces;
        curwin->w_cursor.coladd = 0;
      }

      // n == number of chars deleted
      // If we delete a TAB, it may be replaced by several characters.
      // Thus the number of characters may increase!
      n = bd.textlen - bd.startspaces - bd.endspaces;
      oldp = ml_get(lnum);
      newp = (char_u *)xmalloc(STRLEN(oldp) - (size_t)n + 1);
      // copy up to deleted part
      memmove(newp, oldp, (size_t)bd.textcol);
      // insert spaces
      memset(newp + bd.textcol, ' ', (size_t)bd.startspaces +
             (size_t)bd.endspaces);
      // copy the part after the deleted part
      oldp += bd.textcol + bd.textlen;
      STRMOVE(newp + bd.textcol + bd.startspaces + bd.endspaces, oldp);
      // replace the line
      ml_replace(lnum, newp, false);

      extmark_splice_cols(curbuf, (int)lnum-1, bd.textcol,
                          bd.textlen, bd.startspaces+bd.endspaces,
                          kExtmarkUndo);
    }

    check_cursor_col();
    changed_lines(curwin->w_cursor.lnum, curwin->w_cursor.col,
                  oap->end.lnum + 1, 0L, true);
    oap->line_count = 0;  // no lines deleted
  } else if (oap->motion_type == kMTLineWise) {
    if (oap->op_type == OP_CHANGE) {
      // Delete the lines except the first one.  Temporarily move the
      // cursor to the next line.  Save the current line number, if the
      // last line is deleted it may be changed.

      if (oap->line_count > 1) {
        lnum = curwin->w_cursor.lnum;
        ++curwin->w_cursor.lnum;
        del_lines(oap->line_count - 1, TRUE);
        curwin->w_cursor.lnum = lnum;
      }
      if (u_save_cursor() == FAIL)
        return FAIL;
      if (curbuf->b_p_ai) {                 // don't delete indent
        beginline(BL_WHITE);                // cursor on first non-white
        did_ai = true;                      // delete the indent when ESC hit
        ai_col = curwin->w_cursor.col;
      } else {
        beginline(0);                       // cursor in column 0
      }

      int old_len = (int)STRLEN(ml_get(curwin->w_cursor.lnum));
      truncate_line(false);         // delete the rest of the line

      extmark_splice_cols(curbuf,
                          (int)curwin->w_cursor.lnum-1, curwin->w_cursor.col,
                          old_len - curwin->w_cursor.col, 0, kExtmarkUndo);

                                    // leave cursor past last char in line
      if (oap->line_count > 1) {
        u_clearline();              // "U" command not possible after "2cc"
      }
    } else {
      del_lines(oap->line_count, TRUE);
      beginline(BL_WHITE | BL_FIX);
      u_clearline();            /* "U" command not possible after "dd" */
    }
  } else {
    if (virtual_op) {
      int endcol = 0;

      /* For virtualedit: break the tabs that are partly included. */
      if (gchar_pos(&oap->start) == '\t') {
        if (u_save_cursor() == FAIL)            /* save first line for undo */
          return FAIL;
        if (oap->line_count == 1)
          endcol = getviscol2(oap->end.col, oap->end.coladd);
        coladvance_force(getviscol2(oap->start.col, oap->start.coladd));
        oap->start = curwin->w_cursor;
        if (oap->line_count == 1) {
          coladvance(endcol);
          oap->end.col = curwin->w_cursor.col;
          oap->end.coladd = curwin->w_cursor.coladd;
          curwin->w_cursor = oap->start;
        }
      }

      /* Break a tab only when it's included in the area. */
      if (gchar_pos(&oap->end) == '\t'
          && oap->end.coladd == 0
          && oap->inclusive) {
        /* save last line for undo */
        if (u_save((linenr_T)(oap->end.lnum - 1),
                (linenr_T)(oap->end.lnum + 1)) == FAIL)
          return FAIL;
        curwin->w_cursor = oap->end;
        coladvance_force(getviscol2(oap->end.col, oap->end.coladd));
        oap->end = curwin->w_cursor;
        curwin->w_cursor = oap->start;
      }
      mb_adjust_opend(oap);
    }

    if (oap->line_count == 1) {         /* delete characters within one line */
      if (u_save_cursor() == FAIL)              /* save line for undo */
        return FAIL;

      /* if 'cpoptions' contains '$', display '$' at end of change */
      if (           vim_strchr(p_cpo, CPO_DOLLAR) != NULL
                     && oap->op_type == OP_CHANGE
                     && oap->end.lnum == curwin->w_cursor.lnum
                     && !oap->is_VIsual
                     )
        display_dollar(oap->end.col - !oap->inclusive);

      n = oap->end.col - oap->start.col + 1 - !oap->inclusive;

      if (virtual_op) {
        /* fix up things for virtualedit-delete:
         * break the tabs which are going to get in our way
         */
        char_u          *curline = get_cursor_line_ptr();
        int len = (int)STRLEN(curline);

        if (oap->end.coladd != 0
            && (int)oap->end.col >= len - 1
            && !(oap->start.coladd && (int)oap->end.col >= len - 1))
          n++;
        /* Delete at least one char (e.g, when on a control char). */
        if (n == 0 && oap->start.coladd != oap->end.coladd)
          n = 1;

        /* When deleted a char in the line, reset coladd. */
        if (gchar_cursor() != NUL)
          curwin->w_cursor.coladd = 0;
      }

      (void)del_bytes((colnr_T)n, !virtual_op,
                      oap->op_type == OP_DELETE && !oap->is_VIsual);
    } else {
      // delete characters between lines
      pos_T curpos;

      /* save deleted and changed lines for undo */
      if (u_save((linenr_T)(curwin->w_cursor.lnum - 1),
              (linenr_T)(curwin->w_cursor.lnum + oap->line_count)) == FAIL)
        return FAIL;

      curbuf_splice_pending++;
      pos_T startpos = curwin->w_cursor;  // start position for delete
      bcount_t deleted_bytes = get_region_bytecount(
          curbuf, startpos.lnum, oap->end.lnum, startpos.col,
          oap->end.col) + oap->inclusive;
      truncate_line(true);        // delete from cursor to end of line

      curpos = curwin->w_cursor;  // remember curwin->w_cursor
      curwin->w_cursor.lnum++;

      del_lines(oap->line_count - 2, false);

      // delete from start of line until op_end
      n = (oap->end.col + 1 - !oap->inclusive);
      curwin->w_cursor.col = 0;
      (void)del_bytes((colnr_T)n, !virtual_op,
                      oap->op_type == OP_DELETE && !oap->is_VIsual);
      curwin->w_cursor = curpos;  // restore curwin->w_cursor
      (void)do_join(2, false, false, false, false);
      curbuf_splice_pending--;
      extmark_splice(curbuf, (int)startpos.lnum-1, startpos.col,
                     (int)oap->line_count-1, n, deleted_bytes,
                     0, 0, 0, kExtmarkUndo);
    }
    auto_format(false, true);
  }

  msgmore(curbuf->b_ml.ml_line_count - old_lcount);

setmarks:
  if (oap->motion_type == kMTBlockWise) {
    curbuf->b_op_end.lnum = oap->end.lnum;
    curbuf->b_op_end.col = oap->start.col;
  } else {
    curbuf->b_op_end = oap->start;
  }
  curbuf->b_op_start = oap->start;

  return OK;
}

/*
 * Adjust end of operating area for ending on a multi-byte character.
 * Used for deletion.
 */
static void mb_adjust_opend(oparg_T *oap)
{
  char_u      *p;

  if (oap->inclusive) {
    p = ml_get(oap->end.lnum);
    oap->end.col += mb_tail_off(p, p + oap->end.col);
  }
}

/*
 * Put character 'c' at position 'lp'
 */
static inline void pbyte(pos_T lp, int c)
{
  assert(c <= UCHAR_MAX);
  *(ml_get_buf(curbuf, lp.lnum, true) + lp.col) = (char_u)c;
  if (!curbuf_splice_pending) {
    extmark_splice_cols(curbuf, (int)lp.lnum-1, lp.col, 1, 1, kExtmarkUndo);
  }
}

// Replace the character under the cursor with "c".
// This takes care of multi-byte characters.
static void replace_character(int c)
{
  const int n = State;

  State = REPLACE;
  ins_char(c);
  State = n;
  // Backup to the replaced character.
  dec_cursor();
}

/*
 * Replace a whole area with one character.
 */
int op_replace(oparg_T *oap, int c)
{
  int n, numc;
  int num_chars;
  char_u              *newp, *oldp;
  colnr_T oldlen;
  struct block_def bd;
  char_u              *after_p = NULL;
  int had_ctrl_v_cr = false;

  if ((curbuf->b_ml.ml_flags & ML_EMPTY ) || oap->empty)
    return OK;              /* nothing to do */

  if (c == REPLACE_CR_NCHAR) {
    had_ctrl_v_cr = true;
    c = CAR;
  } else if (c == REPLACE_NL_NCHAR) {
    had_ctrl_v_cr = true;
    c = NL;
  }

  mb_adjust_opend(oap);

  if (u_save((linenr_T)(oap->start.lnum - 1),
          (linenr_T)(oap->end.lnum + 1)) == FAIL)
    return FAIL;

  /*
   * block mode replace
   */
  if (oap->motion_type == kMTBlockWise) {
    bd.is_MAX = (curwin->w_curswant == MAXCOL);
    for (; curwin->w_cursor.lnum <= oap->end.lnum; curwin->w_cursor.lnum++) {
      curwin->w_cursor.col = 0;       // make sure cursor position is valid
      block_prep(oap, &bd, curwin->w_cursor.lnum, true);
      if (bd.textlen == 0 && (!virtual_op || bd.is_MAX)) {
        continue;                     // nothing to replace
      }

      /* n == number of extra chars required
       * If we split a TAB, it may be replaced by several characters.
       * Thus the number of characters may increase!
       */
      /* If the range starts in virtual space, count the initial
       * coladd offset as part of "startspaces" */
      if (virtual_op && bd.is_short && *bd.textstart == NUL) {
        pos_T vpos;

        vpos.lnum = curwin->w_cursor.lnum;
        getvpos(&vpos, oap->start_vcol);
        bd.startspaces += vpos.coladd;
        n = bd.startspaces;
      } else
        /* allow for pre spaces */
        n = (bd.startspaces ? bd.start_char_vcols - 1 : 0);

      /* allow for post spp */
      n += (bd.endspaces
            && !bd.is_oneChar
            && bd.end_char_vcols > 0) ? bd.end_char_vcols - 1 : 0;
      /* Figure out how many characters to replace. */
      numc = oap->end_vcol - oap->start_vcol + 1;
      if (bd.is_short && (!virtual_op || bd.is_MAX))
        numc -= (oap->end_vcol - bd.end_vcol) + 1;

      /* A double-wide character can be replaced only up to half the
       * times. */
      if ((*mb_char2cells)(c) > 1) {
        if ((numc & 1) && !bd.is_short) {
          ++bd.endspaces;
          ++n;
        }
        numc = numc / 2;
      }

      /* Compute bytes needed, move character count to num_chars. */
      num_chars = numc;
      numc *= (*mb_char2len)(c);

      oldp = get_cursor_line_ptr();
      oldlen = (int)STRLEN(oldp);

      size_t newp_size = (size_t)bd.textcol + (size_t)bd.startspaces;
      if (had_ctrl_v_cr || (c != '\r' && c != '\n')) {
        newp_size += (size_t)numc;
        if (!bd.is_short) {
          newp_size += (size_t)(bd.endspaces + oldlen
                                - bd.textcol - bd.textlen);
        }
      }
      newp = xmallocz(newp_size);
      // copy up to deleted part
      memmove(newp, oldp, (size_t)bd.textcol);
      oldp += bd.textcol + bd.textlen;
      // insert pre-spaces
      memset(newp + bd.textcol, ' ', (size_t)bd.startspaces);
      // insert replacement chars CHECK FOR ALLOCATED SPACE
      // REPLACE_CR_NCHAR/REPLACE_NL_NCHAR is used for entering CR literally.
      size_t after_p_len = 0;
      int col = oldlen - bd.textcol - bd.textlen + 1;
      assert(col >= 0);
      int newrows = 0, newcols = 0;
      if (had_ctrl_v_cr || (c != '\r' && c != '\n')) {
          // strlen(newp) at this point
          int newp_len = bd.textcol + bd.startspaces;
          while (--num_chars >= 0) {
            newp_len += utf_char2bytes(c, newp + newp_len);
          }
          if (!bd.is_short) {
            // insert post-spaces
            memset(newp + newp_len, ' ', (size_t)bd.endspaces);
            newp_len += bd.endspaces;
            // copy the part after the changed part
            memmove(newp + newp_len, oldp, (size_t)col);
          }
          newcols = newp_len - bd.textcol;
      } else {
        // Replacing with \r or \n means splitting the line.
        after_p_len = (size_t)col;
        after_p = (char_u *)xmalloc(after_p_len);
        memmove(after_p, oldp, after_p_len);
        newrows = 1;
      }
      // replace the line
      ml_replace(curwin->w_cursor.lnum, newp, false);
      curbuf_splice_pending++;
      linenr_T baselnum = curwin->w_cursor.lnum;
      if (after_p != NULL) {
        ml_append(curwin->w_cursor.lnum++, after_p, (int)after_p_len, false);
        appended_lines_mark(curwin->w_cursor.lnum, 1L);
        oap->end.lnum++;
        xfree(after_p);
      }
      curbuf_splice_pending--;
      extmark_splice(curbuf, (int)baselnum-1, bd.textcol,
                     0, bd.textlen, bd.textlen,
                     newrows, newcols, newrows+newcols, kExtmarkUndo);
    }
  } else {
    // Characterwise or linewise motion replace.
    if (oap->motion_type == kMTLineWise) {
      oap->start.col = 0;
      curwin->w_cursor.col = 0;
      oap->end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
      if (oap->end.col)
        --oap->end.col;
    } else if (!oap->inclusive)
      dec(&(oap->end));

    // TODO(bfredl): we could batch all the splicing
    // done on the same line, at least
    while (ltoreq(curwin->w_cursor, oap->end)) {
      n = gchar_cursor();
      if (n != NUL) {
        if ((*mb_char2len)(c) > 1 || (*mb_char2len)(n) > 1) {
          /* This is slow, but it handles replacing a single-byte
           * with a multi-byte and the other way around. */
          if (curwin->w_cursor.lnum == oap->end.lnum)
            oap->end.col += (*mb_char2len)(c) - (*mb_char2len)(n);
          replace_character(c);
        } else {
          if (n == TAB) {
            int end_vcol = 0;

            if (curwin->w_cursor.lnum == oap->end.lnum) {
              /* oap->end has to be recalculated when
               * the tab breaks */
              end_vcol = getviscol2(oap->end.col,
                  oap->end.coladd);
            }
            coladvance_force(getviscol());
            if (curwin->w_cursor.lnum == oap->end.lnum)
              getvpos(&oap->end, end_vcol);
          }
          pbyte(curwin->w_cursor, c);
        }
      } else if (virtual_op && curwin->w_cursor.lnum == oap->end.lnum) {
        int virtcols = oap->end.coladd;

        if (curwin->w_cursor.lnum == oap->start.lnum
            && oap->start.col == oap->end.col && oap->start.coladd)
          virtcols -= oap->start.coladd;

        /* oap->end has been trimmed so it's effectively inclusive;
         * as a result an extra +1 must be counted so we don't
         * trample the NUL byte. */
        coladvance_force(getviscol2(oap->end.col, oap->end.coladd) + 1);
        curwin->w_cursor.col -= (virtcols + 1);
        for (; virtcols >= 0; virtcols--) {
          if (utf_char2len(c) > 1) {
            replace_character(c);
          } else {
            pbyte(curwin->w_cursor, c);
          }
          if (inc(&curwin->w_cursor) == -1) {
            break;
          }
        }
      }

      /* Advance to next character, stop at the end of the file. */
      if (inc_cursor() == -1)
        break;
    }
  }

  curwin->w_cursor = oap->start;
  check_cursor();
  changed_lines(oap->start.lnum, oap->start.col, oap->end.lnum + 1, 0L, true);

  /* Set "'[" and "']" marks. */
  curbuf->b_op_start = oap->start;
  curbuf->b_op_end = oap->end;

  return OK;
}


/*
 * Handle the (non-standard vi) tilde operator.  Also for "gu", "gU" and "g?".
 */
void op_tilde(oparg_T *oap)
{
  pos_T pos;
  struct block_def bd;
  int did_change = FALSE;

  if (u_save((linenr_T)(oap->start.lnum - 1),
          (linenr_T)(oap->end.lnum + 1)) == FAIL)
    return;

  pos = oap->start;
  if (oap->motion_type == kMTBlockWise) {  // Visual block mode
    for (; pos.lnum <= oap->end.lnum; pos.lnum++) {
      int one_change;

      block_prep(oap, &bd, pos.lnum, false);
      pos.col = bd.textcol;
      one_change = swapchars(oap->op_type, &pos, bd.textlen);
      did_change |= one_change;

    }
    if (did_change) {
      changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
    }
  } else {  // not block mode
    if (oap->motion_type == kMTLineWise) {
      oap->start.col = 0;
      pos.col = 0;
      oap->end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
      if (oap->end.col)
        --oap->end.col;
    } else if (!oap->inclusive)
      dec(&(oap->end));

    if (pos.lnum == oap->end.lnum)
      did_change = swapchars(oap->op_type, &pos,
          oap->end.col - pos.col + 1);
    else
      for (;; ) {
        did_change |= swapchars(oap->op_type, &pos,
            pos.lnum == oap->end.lnum ? oap->end.col + 1 :
            (int)STRLEN(ml_get_pos(&pos)));
        if (ltoreq(oap->end, pos) || inc(&pos) == -1)
          break;
      }
    if (did_change) {
      changed_lines(oap->start.lnum, oap->start.col, oap->end.lnum + 1,
                    0L, true);
    }
  }

  if (!did_change && oap->is_VIsual)
    /* No change: need to remove the Visual selection */
    redraw_curbuf_later(INVERTED);

  /*
   * Set '[ and '] marks.
   */
  curbuf->b_op_start = oap->start;
  curbuf->b_op_end = oap->end;

  if (oap->line_count > p_report) {
    if (oap->line_count == 1)
      MSG(_("1 line changed"));
    else
      smsg(_("%" PRId64 " lines changed"), (int64_t)oap->line_count);
  }
}

/*
 * Invoke swapchar() on "length" bytes at position "pos".
 * "pos" is advanced to just after the changed characters.
 * "length" is rounded up to include the whole last multi-byte character.
 * Also works correctly when the number of bytes changes.
 * Returns TRUE if some character was changed.
 */
static int swapchars(int op_type, pos_T *pos, int length)
  FUNC_ATTR_NONNULL_ALL
{
  int did_change = 0;

  for (int todo = length; todo > 0; todo--) {
    const int len = utfc_ptr2len(ml_get_pos(pos));

    // we're counting bytes, not characters
    if (len > 0) {
      todo -= len - 1;
    }
    did_change |= swapchar(op_type, pos);
    if (inc(pos) == -1)        /* at end of file */
      break;
  }
  return did_change;
}

// If op_type == OP_UPPER: make uppercase,
// if op_type == OP_LOWER: make lowercase,
// if op_type == OP_ROT13: do rot13 encoding,
// else swap case of character at 'pos'
// returns true when something actually changed.
bool swapchar(int op_type, pos_T *pos)
  FUNC_ATTR_NONNULL_ARG(2)
{
  const int c = gchar_pos(pos);

  // Only do rot13 encoding for ASCII characters.
  if (c >= 0x80 && op_type == OP_ROT13) {
    return false;
  }

  if (op_type == OP_UPPER && c == 0xdf) {
    pos_T sp = curwin->w_cursor;

    /* Special handling of German sharp s: change to "SS". */
    curwin->w_cursor = *pos;
    del_char(false);
    ins_char('S');
    ins_char('S');
    curwin->w_cursor = sp;
    inc(pos);
  }

  int nc = c;
  if (mb_islower(c)) {
    if (op_type == OP_ROT13) {
      nc = ROT13(c, 'a');
    } else if (op_type != OP_LOWER) {
      nc = mb_toupper(c);
    }
  } else if (mb_isupper(c)) {
    if (op_type == OP_ROT13) {
      nc = ROT13(c, 'A');
    } else if (op_type != OP_UPPER) {
      nc = mb_tolower(c);
    }
  }
  if (nc != c) {
    if (c >= 0x80 || nc >= 0x80) {
      pos_T sp = curwin->w_cursor;

      curwin->w_cursor = *pos;
      // don't use del_char(), it also removes composing chars
      del_bytes(utf_ptr2len(get_cursor_pos_ptr()), false, false);
      ins_char(nc);
      curwin->w_cursor = sp;
    } else {
      pbyte(*pos, nc);
    }
    return true;
  }
  return false;
}

/*
 * op_insert - Insert and append operators for Visual mode.
 */
void op_insert(oparg_T *oap, long count1)
{
  long ins_len, pre_textlen = 0;
  char_u              *firstline, *ins_text;
  colnr_T ind_pre = 0;
  struct block_def bd;
  int i;
  pos_T t1;

  /* edit() changes this - record it for OP_APPEND */
  bd.is_MAX = (curwin->w_curswant == MAXCOL);

  /* vis block is still marked. Get rid of it now. */
  curwin->w_cursor.lnum = oap->start.lnum;
  update_screen(INVERTED);

  if (oap->motion_type == kMTBlockWise) {
    // When 'virtualedit' is used, need to insert the extra spaces before
    // doing block_prep().  When only "block" is used, virtual edit is
    // already disabled, but still need it when calling
    // coladvance_force().
    if (curwin->w_cursor.coladd > 0) {
      unsigned old_ve_flags = ve_flags;

      ve_flags = VE_ALL;
      if (u_save_cursor() == FAIL)
        return;
      coladvance_force(oap->op_type == OP_APPEND
          ? oap->end_vcol + 1 : getviscol());
      if (oap->op_type == OP_APPEND)
        --curwin->w_cursor.col;
      ve_flags = old_ve_flags;
    }
    // Get the info about the block before entering the text
    block_prep(oap, &bd, oap->start.lnum, true);
    // Get indent information
    ind_pre = (colnr_T)getwhitecols_curline();
    firstline = ml_get(oap->start.lnum) + bd.textcol;

    if (oap->op_type == OP_APPEND) {
      firstline += bd.textlen;
    }
    pre_textlen = (long)STRLEN(firstline);
  }

  if (oap->op_type == OP_APPEND) {
    if (oap->motion_type == kMTBlockWise
        && curwin->w_cursor.coladd == 0
        ) {
      /* Move the cursor to the character right of the block. */
      curwin->w_set_curswant = TRUE;
      while (*get_cursor_pos_ptr() != NUL
             && (curwin->w_cursor.col < bd.textcol + bd.textlen))
        ++curwin->w_cursor.col;
      if (bd.is_short && !bd.is_MAX) {
        /* First line was too short, make it longer and adjust the
         * values in "bd". */
        if (u_save_cursor() == FAIL)
          return;
        for (i = 0; i < bd.endspaces; i++) {
          ins_char(' ');
        }
        bd.textlen += bd.endspaces;
      }
    } else {
      curwin->w_cursor = oap->end;
      check_cursor_col();

      // Works just like an 'i'nsert on the next character.
      if (!LINEEMPTY(curwin->w_cursor.lnum)
          && oap->start_vcol != oap->end_vcol) {
        inc_cursor();
      }
    }
  }

  t1 = oap->start;
  (void)edit(NUL, false, (linenr_T)count1);

  // When a tab was inserted, and the characters in front of the tab
  // have been converted to a tab as well, the column of the cursor
  // might have actually been reduced, so need to adjust here. */
  if (t1.lnum == curbuf->b_op_start_orig.lnum
      && lt(curbuf->b_op_start_orig, t1)) {
    oap->start = curbuf->b_op_start_orig;
  }

  /* If user has moved off this line, we don't know what to do, so do
   * nothing.
   * Also don't repeat the insert when Insert mode ended with CTRL-C. */
  if (curwin->w_cursor.lnum != oap->start.lnum || got_int)
    return;

  if (oap->motion_type == kMTBlockWise) {
    struct block_def bd2;
    bool did_indent = false;

    // if indent kicked in, the firstline might have changed
    // but only do that, if the indent actually increased
    const colnr_T ind_post = (colnr_T)getwhitecols_curline();
    if (curbuf->b_op_start.col > ind_pre && ind_post > ind_pre) {
      bd.textcol += ind_post - ind_pre;
      bd.start_vcol += ind_post - ind_pre;
      did_indent = true;
    }

    // The user may have moved the cursor before inserting something, try
    // to adjust the block for that.  But only do it, if the difference
    // does not come from indent kicking in.
    if (oap->start.lnum == curbuf->b_op_start_orig.lnum
        && !bd.is_MAX
        && !did_indent) {
      if (oap->op_type == OP_INSERT
          && oap->start.col + oap->start.coladd
          != curbuf->b_op_start_orig.col + curbuf->b_op_start_orig.coladd) {
        int t = getviscol2(curbuf->b_op_start_orig.col,
                           curbuf->b_op_start_orig.coladd);
        oap->start.col = curbuf->b_op_start_orig.col;
        pre_textlen -= t - oap->start_vcol;
        oap->start_vcol = t;
      } else if (oap->op_type == OP_APPEND
                 && oap->end.col + oap->end.coladd
                 >= curbuf->b_op_start_orig.col
                 + curbuf->b_op_start_orig.coladd) {
        int t = getviscol2(curbuf->b_op_start_orig.col,
                           curbuf->b_op_start_orig.coladd);
        oap->start.col = curbuf->b_op_start_orig.col;
        /* reset pre_textlen to the value of OP_INSERT */
        pre_textlen += bd.textlen;
        pre_textlen -= t - oap->start_vcol;
        oap->start_vcol = t;
        oap->op_type = OP_INSERT;
      }
    }

    /*
     * Spaces and tabs in the indent may have changed to other spaces and
     * tabs.  Get the starting column again and correct the length.
     * Don't do this when "$" used, end-of-line will have changed.
     */
    block_prep(oap, &bd2, oap->start.lnum, true);
    if (!bd.is_MAX || bd2.textlen < bd.textlen) {
      if (oap->op_type == OP_APPEND) {
        pre_textlen += bd2.textlen - bd.textlen;
        if (bd2.endspaces)
          --bd2.textlen;
      }
      bd.textcol = bd2.textcol;
      bd.textlen = bd2.textlen;
    }

    /*
     * Subsequent calls to ml_get() flush the firstline data - take a
     * copy of the required string.
     */
    firstline = ml_get(oap->start.lnum);
    const size_t len = STRLEN(firstline);
    colnr_T add = bd.textcol;
    if (oap->op_type == OP_APPEND) {
      add += bd.textlen;
    }
    if ((size_t)add > len) {
      firstline += len;  // short line, point to the NUL
    } else {
      firstline += add;
    }
    ins_len = (long)STRLEN(firstline) - pre_textlen;
    if (pre_textlen >= 0 && ins_len > 0) {
      ins_text = vim_strnsave(firstline, (size_t)ins_len);
      // block handled here
      if (u_save(oap->start.lnum, (linenr_T)(oap->end.lnum + 1)) == OK) {
        block_insert(oap, ins_text, (oap->op_type == OP_INSERT), &bd);
      }

      curwin->w_cursor.col = oap->start.col;
      check_cursor();
      xfree(ins_text);
    }
  }
}

/*
 * op_change - handle a change operation
 *
 * return TRUE if edit() returns because of a CTRL-O command
 */
int op_change(oparg_T *oap)
{
  colnr_T l;
  int retval;
  long offset;
  linenr_T linenr;
  long ins_len;
  long pre_textlen = 0;
  long pre_indent = 0;
  char_u *newp;
  char_u *firstline;
  char_u *ins_text;
  char_u *oldp;
  struct block_def bd;

  l = oap->start.col;
  if (oap->motion_type == kMTLineWise) {
    l = 0;
    if (!p_paste && curbuf->b_p_si
        && !curbuf->b_p_cin
        )
      can_si = true;            // It's like opening a new line, do si
  }

  /* First delete the text in the region.  In an empty buffer only need to
   * save for undo */
  if (curbuf->b_ml.ml_flags & ML_EMPTY) {
    if (u_save_cursor() == FAIL)
      return FALSE;
  } else if (op_delete(oap) == FAIL)
    return FALSE;

  if ((l > curwin->w_cursor.col) && !LINEEMPTY(curwin->w_cursor.lnum)
      && !virtual_op) {
    inc_cursor();
  }

  // check for still on same line (<CR> in inserted text meaningless)
  // skip blank lines too
  if (oap->motion_type == kMTBlockWise) {
    // Add spaces before getting the current line length.
    if (virtual_op && (curwin->w_cursor.coladd > 0
                       || gchar_cursor() == NUL)) {
      coladvance_force(getviscol());
    }
    firstline = ml_get(oap->start.lnum);
    pre_textlen = (long)STRLEN(firstline);
    pre_indent = (long)getwhitecols(firstline);
    bd.textcol = curwin->w_cursor.col;
  }

  if (oap->motion_type == kMTLineWise) {
    fix_indent();
  }

  retval = edit(NUL, FALSE, (linenr_T)1);

  /*
   * In Visual block mode, handle copying the new text to all lines of the
   * block.
   * Don't repeat the insert when Insert mode ended with CTRL-C.
   */
  if (oap->motion_type == kMTBlockWise
      && oap->start.lnum != oap->end.lnum && !got_int) {
    // Auto-indenting may have changed the indent.  If the cursor was past
    // the indent, exclude that indent change from the inserted text.
    firstline = ml_get(oap->start.lnum);
    if (bd.textcol > (colnr_T)pre_indent) {
      long new_indent = (long)getwhitecols(firstline);

      pre_textlen += new_indent - pre_indent;
      bd.textcol += (colnr_T)(new_indent - pre_indent);
    }

    ins_len = (long)STRLEN(firstline) - pre_textlen;
    if (ins_len > 0) {
      /* Subsequent calls to ml_get() flush the firstline data - take a
       * copy of the inserted text.  */
      ins_text = (char_u *)xmalloc((size_t)(ins_len + 1));
      STRLCPY(ins_text, firstline + bd.textcol, ins_len + 1);
      for (linenr = oap->start.lnum + 1; linenr <= oap->end.lnum;
           linenr++) {
        block_prep(oap, &bd, linenr, true);
        if (!bd.is_short || virtual_op) {
          pos_T vpos;

          /* If the block starts in virtual space, count the
           * initial coladd offset as part of "startspaces" */
          if (bd.is_short) {
            vpos.lnum = linenr;
            (void)getvpos(&vpos, oap->start_vcol);
          } else {
            vpos.coladd = 0;
          }
          oldp = ml_get(linenr);
          newp = xmalloc(STRLEN(oldp) + (size_t)vpos.coladd
                         + (size_t)ins_len + 1);
          // copy up to block start
          memmove(newp, oldp, (size_t)bd.textcol);
          offset = bd.textcol;
          memset(newp + offset, ' ', (size_t)vpos.coladd);
          offset += vpos.coladd;
          memmove(newp + offset, ins_text, (size_t)ins_len);
          offset += ins_len;
          oldp += bd.textcol;
          STRMOVE(newp + offset, oldp);
          ml_replace(linenr, newp, false);
          extmark_splice_cols(curbuf, (int)linenr-1, bd.textcol,
                              0, vpos.coladd+(int)ins_len, kExtmarkUndo);
        }
      }
      check_cursor();
      changed_lines(oap->start.lnum + 1, 0, oap->end.lnum + 1, 0L, true);
      xfree(ins_text);
    }
  }

  return retval;
}

/*
 * set all the yank registers to empty (called from main())
 */
void init_yank(void)
{
  memset(&(y_regs[0]), 0, sizeof(y_regs));
}

#if defined(EXITFREE)
void clear_registers(void)
{
  int i;

  for (i = 0; i < NUM_REGISTERS; i++) {
    free_register(&y_regs[i]);
  }
}

#endif


 /// Free contents of yankreg `reg`.
 /// Called for normal freeing and in case of error.
 /// `reg` must not be NULL (but `reg->y_array` might be)
void free_register(yankreg_T *reg)
  FUNC_ATTR_NONNULL_ALL
{
  set_yreg_additional_data(reg, NULL);
  if (reg->y_array != NULL) {
    for (size_t i = reg->y_size; i-- > 0;) {  // from y_size - 1 to 0 included
      xfree(reg->y_array[i]);
    }
    XFREE_CLEAR(reg->y_array);
  }
}

/// Yanks the text between "oap->start" and "oap->end" into a yank register.
/// If we are to append (uppercase register), we first yank into a new yank
/// register and then concatenate the old and the new one.
///
/// @param oap operator arguments
/// @param message show message when more than `&report` lines are yanked.
/// @param deleting whether the function was called from a delete operation.
/// @returns whether the operation register was writable.
bool op_yank(oparg_T *oap, bool message, int deleting)
  FUNC_ATTR_NONNULL_ALL
{
  // check for read-only register
  if (oap->regname != 0 && !valid_yank_reg(oap->regname, true)) {
    beep_flush();
    return false;
  }
  if (oap->regname == '_') {
    return true; // black hole: nothing to do
  }

  yankreg_T *reg = get_yank_register(oap->regname, YREG_YANK);
  op_yank_reg(oap, message, reg, is_append_register(oap->regname));
  // op_delete will set_clipboard and do_autocmd
  if (!deleting) {
    set_clipboard(oap->regname, reg);
    do_autocmd_textyankpost(oap, reg);
  }

  return true;
}

static void op_yank_reg(oparg_T *oap, bool message, yankreg_T *reg, bool append)
{
  yankreg_T newreg;  // new yank register when appending
  char_u **new_ptr;
  linenr_T lnum;     // current line number
  size_t j;
  MotionType yank_type = oap->motion_type;
  size_t yanklines = (size_t)oap->line_count;
  linenr_T yankendlnum = oap->end.lnum;
  char_u *p;
  char_u *pnew;
  struct block_def bd;

  yankreg_T *curr = reg;  // copy of current register
  // append to existing contents
  if (append && reg->y_array != NULL) {
    reg = &newreg;
  } else {
    free_register(reg);  // free previously yanked lines
  }

  // If the cursor was in column 1 before and after the movement, and the
  // operator is not inclusive, the yank is always linewise.
  if (oap->motion_type == kMTCharWise
      && oap->start.col == 0
      && !oap->inclusive
      && (!oap->is_VIsual || *p_sel == 'o')
      && oap->end.col == 0
      && yanklines > 1) {
    yank_type = kMTLineWise;
    yankendlnum--;
    yanklines--;
  }

  reg->y_size = yanklines;
  reg->y_type = yank_type;  // set the yank register type
  reg->y_width = 0;
  reg->y_array = xcalloc(yanklines, sizeof(char_u *));
  reg->additional_data = NULL;
  reg->timestamp = os_time();

  size_t y_idx = 0;  // index in y_array[]
  lnum = oap->start.lnum;

  if (yank_type == kMTBlockWise) {
    // Visual block mode
    reg->y_width = oap->end_vcol - oap->start_vcol;

    if (curwin->w_curswant == MAXCOL && reg->y_width > 0)
      reg->y_width--;
  }

  for (; lnum <= yankendlnum; lnum++, y_idx++) {
    switch (reg->y_type) {
    case kMTBlockWise:
      block_prep(oap, &bd, lnum, false);
      yank_copy_line(reg, &bd, y_idx, oap->excl_tr_ws);
      break;

    case kMTLineWise:
      reg->y_array[y_idx] = vim_strsave(ml_get(lnum));
      break;

    case kMTCharWise:
    {
      colnr_T startcol = 0, endcol = MAXCOL;
      int is_oneChar = false;
      colnr_T cs, ce;
      p = ml_get(lnum);
      bd.startspaces = 0;
      bd.endspaces = 0;

      if (lnum == oap->start.lnum) {
        startcol = oap->start.col;
        if (virtual_op) {
          getvcol(curwin, &oap->start, &cs, NULL, &ce);
          if (ce != cs && oap->start.coladd > 0) {
            /* Part of a tab selected -- but don't
             * double-count it. */
            bd.startspaces = (ce - cs + 1)
                             - oap->start.coladd;
            startcol++;
          }
        }
      }

      if (lnum == oap->end.lnum) {
        endcol = oap->end.col;
        if (virtual_op) {
          getvcol(curwin, &oap->end, &cs, NULL, &ce);
          if (p[endcol] == NUL || (cs + oap->end.coladd < ce
                                   // Don't add space for double-wide
                                   // char; endcol will be on last byte
                                   // of multi-byte char.
                                   && utf_head_off(p, p + endcol) == 0)) {
            if (oap->start.lnum == oap->end.lnum
                && oap->start.col == oap->end.col) {
              // Special case: inside a single char
              is_oneChar = true;
              bd.startspaces = oap->end.coladd
                               - oap->start.coladd + oap->inclusive;
              endcol = startcol;
            } else {
              bd.endspaces = oap->end.coladd
                             + oap->inclusive;
              endcol -= oap->inclusive;
            }
          }
        }
      }
      if (endcol == MAXCOL)
        endcol = (colnr_T)STRLEN(p);
      if (startcol > endcol
          || is_oneChar
          ) {
        bd.textlen = 0;
      } else {
        bd.textlen = endcol - startcol + oap->inclusive;
      }
      bd.textstart = p + startcol;
      yank_copy_line(reg, &bd, y_idx, false);
      break;
    }
    // NOTREACHED
    case kMTUnknown:
        abort();
    }
  }

  if (curr != reg) {      /* append the new block to the old block */
    new_ptr = xmalloc(sizeof(char_u *) * (curr->y_size + reg->y_size));
    for (j = 0; j < curr->y_size; ++j)
      new_ptr[j] = curr->y_array[j];
    xfree(curr->y_array);
    curr->y_array = new_ptr;

    if (yank_type == kMTLineWise) {
      // kMTLineWise overrides kMTCharWise and kMTBlockWise
      curr->y_type = kMTLineWise;
    }

    // Concatenate the last line of the old block with the first line of
    // the new block, unless being Vi compatible.
    if (curr->y_type == kMTCharWise
        && vim_strchr(p_cpo, CPO_REGAPPEND) == NULL) {
      pnew = xmalloc(STRLEN(curr->y_array[curr->y_size - 1])
                     + STRLEN(reg->y_array[0]) + 1);
      STRCPY(pnew, curr->y_array[--j]);
      STRCAT(pnew, reg->y_array[0]);
      xfree(curr->y_array[j]);
      xfree(reg->y_array[0]);
      curr->y_array[j++] = pnew;
      y_idx = 1;
    } else
      y_idx = 0;
    while (y_idx < reg->y_size)
      curr->y_array[j++] = reg->y_array[y_idx++];
    curr->y_size = j;
    xfree(reg->y_array);
  }
  if (curwin->w_p_rnu) {
    redraw_later(curwin, SOME_VALID);  // cursor moved to start
  }
  if (message) {  // Display message about yank?
    if (yank_type == kMTCharWise && yanklines == 1) {
      yanklines = 0;
    }
    // Some versions of Vi use ">=" here, some don't...
    if (yanklines > (size_t)p_report) {
      char namebuf[100];

      if (oap->regname == NUL) {
        *namebuf = NUL;
      } else {
        vim_snprintf(namebuf, sizeof(namebuf), _(" into \"%c"), oap->regname);
      }

      // redisplay now, so message is not deleted
      update_topline_redraw();
      if (yanklines == 1) {
        if (yank_type == kMTBlockWise) {
          smsg(_("block of 1 line yanked%s"), namebuf);
        } else {
          smsg(_("1 line yanked%s"), namebuf);
        }
      } else if (yank_type == kMTBlockWise) {
        smsg(_("block of %" PRId64 " lines yanked%s"),
             (int64_t)yanklines, namebuf);
      } else {
        smsg(_("%" PRId64 " lines yanked%s"), (int64_t)yanklines, namebuf);
      }
    }
  }

  /*
   * Set "'[" and "']" marks.
   */
  curbuf->b_op_start = oap->start;
  curbuf->b_op_end = oap->end;
  if (yank_type == kMTLineWise) {
    curbuf->b_op_start.col = 0;
    curbuf->b_op_end.col = MAXCOL;
  }

  return;
}

// Copy a block range into a register.
// If "exclude_trailing_space" is set, do not copy trailing whitespaces.
static void yank_copy_line(yankreg_T *reg, struct block_def *bd,
                           size_t y_idx, bool exclude_trailing_space)
  FUNC_ATTR_NONNULL_ALL
{
  if (exclude_trailing_space) {
    bd->endspaces = 0;
  }
  int size = bd->startspaces + bd->endspaces + bd->textlen;
  assert(size >= 0);
  char_u *pnew = xmallocz((size_t)size);
  reg->y_array[y_idx] = pnew;
  memset(pnew, ' ', (size_t)bd->startspaces);
  pnew += bd->startspaces;
  memmove(pnew, bd->textstart, (size_t)bd->textlen);
  pnew += bd->textlen;
  memset(pnew, ' ', (size_t)bd->endspaces);
  pnew += bd->endspaces;
  if (exclude_trailing_space) {
    int s = bd->textlen + bd->endspaces;

    while (ascii_iswhite(*(bd->textstart + s - 1)) && s > 0) {
      s = s - utf_head_off(bd->textstart, bd->textstart + s - 1) - 1;
      pnew--;
    }
  }
  *pnew = NUL;
}

/// Execute autocommands for TextYankPost.
///
/// @param oap Operator arguments.
/// @param reg The yank register used.
static void do_autocmd_textyankpost(oparg_T *oap, yankreg_T *reg)
  FUNC_ATTR_NONNULL_ALL
{
  static bool recursive = false;

  if (recursive || !has_event(EVENT_TEXTYANKPOST)) {
    // No autocommand was defined, or we yanked from this autocommand.
    return;
  }

  recursive = true;

  // Set the v:event dictionary with information about the yank.
  dict_T *dict = get_vim_var_dict(VV_EVENT);

  // The yanked text contents.
  list_T *const list = tv_list_alloc((ptrdiff_t)reg->y_size);
  for (size_t i = 0; i < reg->y_size; i++) {
    tv_list_append_string(list, (const char *)reg->y_array[i], -1);
  }
  tv_list_set_lock(list, VAR_FIXED);
  tv_dict_add_list(dict, S_LEN("regcontents"), list);

  // Register type.
  char buf[NUMBUFLEN+2];
  format_reg_type(reg->y_type, reg->y_width, buf, ARRAY_SIZE(buf));
  tv_dict_add_str(dict, S_LEN("regtype"), buf);

  // Name of requested register, or empty string for unnamed operation.
  buf[0] = (char)oap->regname;
  buf[1] = NUL;
  tv_dict_add_str(dict, S_LEN("regname"), buf);

  // Motion type: inclusive or exclusive.
  tv_dict_add_bool(dict, S_LEN("inclusive"),
                   oap->inclusive ? kBoolVarTrue : kBoolVarFalse);

  // Kind of operation: yank, delete, change).
  buf[0] = (char)get_op_char(oap->op_type);
  buf[1] = NUL;
  tv_dict_add_str(dict, S_LEN("operator"), buf);

  // Selection type: visual or not.
  tv_dict_add_bool(dict, S_LEN("visual"),
                   oap->is_VIsual ? kBoolVarTrue : kBoolVarFalse);

  tv_dict_set_keys_readonly(dict);
  textlock++;
  apply_autocmds(EVENT_TEXTYANKPOST, NULL, NULL, false, curbuf);
  textlock--;
  tv_dict_clear(dict);

  recursive = false;
}

// Put contents of register "regname" into the text.
// Caller must check "regname" to be valid!
// "flags": PUT_FIXINDENT     make indent look nice
//          PUT_CURSEND       leave cursor after end of new text
//          PUT_LINE          force linewise put (":put")
//          PUT_BLOCK_INNER   in block mode, do not add trailing spaces
// dir: BACKWARD for 'P', FORWARD for 'p'
void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
{
  char_u *ptr;
  char_u *newp;
  char_u *oldp;
  int yanklen;
  size_t totlen = 0;  // init for gcc
  linenr_T lnum = 0;
  colnr_T col = 0;
  size_t i;  // index in y_array[]
  MotionType y_type;
  size_t y_size;
  size_t oldlen;
  int y_width = 0;
  colnr_T vcol = 0;
  int delcount;
  int incr = 0;
  struct block_def bd;
  char_u      **y_array = NULL;
  long nr_lines = 0;
  pos_T new_cursor;
  int indent;
  int orig_indent = 0;                  /* init for gcc */
  int indent_diff = 0;                  /* init for gcc */
  int first_indent = TRUE;
  int lendiff = 0;
  pos_T old_pos;
  char_u      *insert_string = NULL;
  bool allocated = false;
  long cnt;

  if (flags & PUT_FIXINDENT)
    orig_indent = get_indent();

  curbuf->b_op_start = curwin->w_cursor;        /* default for '[ mark */
  curbuf->b_op_end = curwin->w_cursor;          /* default for '] mark */

  /*
   * Using inserted text works differently, because the register includes
   * special characters (newlines, etc.).
   */
  if (regname == '.' && !reg) {
    bool non_linewise_vis = (VIsual_active && VIsual_mode != 'V');

    // PUT_LINE has special handling below which means we use 'i' to start.
    char command_start_char = non_linewise_vis ? 'c' :
      (flags & PUT_LINE ? 'i' : (dir == FORWARD ? 'a' : 'i'));

    // To avoid 'autoindent' on linewise puts, create a new line with `:put _`.
    if (flags & PUT_LINE) {
      do_put('_', NULL, dir, 1, PUT_LINE);
    }

    // If given a count when putting linewise, we stuff the readbuf with the
    // dot register 'count' times split by newlines.
    if (flags & PUT_LINE) {
      stuffcharReadbuff(command_start_char);
      for (; count > 0; count--) {
        (void)stuff_inserted(NUL, 1, count != 1);
        if (count != 1) {
          // To avoid 'autoindent' affecting the text, use Ctrl_U to remove any
          // whitespace. Can't just insert Ctrl_U into readbuf1, this would go
          // back to the previous line in the case of 'noautoindent' and
          // 'backspace' includes "eol". So we insert a dummy space for Ctrl_U
          // to consume.
          stuffReadbuff("\n ");
          stuffcharReadbuff(Ctrl_U);
        }
      }
    } else {
      (void)stuff_inserted(command_start_char, count, false);
    }

    // Putting the text is done later, so can't move the cursor to the next
    // character.  Simulate it with motion commands after the insert.
    if (flags & PUT_CURSEND) {
      if (flags & PUT_LINE) {
        stuffReadbuff("j0");
      } else {
        // Avoid ringing the bell from attempting to move into the space after
        // the current line. We can stuff the readbuffer with "l" if:
        // 1) 'virtualedit' is "all" or "onemore"
        // 2) We are not at the end of the line
        // 3) We are not  (one past the end of the line && on the last line)
        //    This allows a visual put over a selection one past the end of the
        //    line joining the current line with the one below.

        // curwin->w_cursor.col marks the byte position of the cursor in the
        // currunt line. It increases up to a max of
        // STRLEN(ml_get(curwin->w_cursor.lnum)). With 'virtualedit' and the
        // cursor past the end of the line, curwin->w_cursor.coladd is
        // incremented instead of curwin->w_cursor.col.
        char_u *cursor_pos = get_cursor_pos_ptr();
        bool one_past_line = (*cursor_pos == NUL);
        bool eol = false;
        if (!one_past_line) {
          eol = (*(cursor_pos + mb_ptr2len(cursor_pos)) == NUL);
        }

        bool ve_allows = (ve_flags == VE_ALL || ve_flags == VE_ONEMORE);
        bool eof = curbuf->b_ml.ml_line_count == curwin->w_cursor.lnum
                   && one_past_line;
        if (ve_allows || !(eol || eof)) {
          stuffcharReadbuff('l');
        }
      }
    } else if (flags & PUT_LINE) {
      stuffReadbuff("g'[");
    }

    // So the 'u' command restores cursor position after ".p, save the cursor
    // position now (though not saving any text).
    if (command_start_char == 'a') {
      if (u_save(curwin->w_cursor.lnum, curwin->w_cursor.lnum + 1) == FAIL) {
        return;
      }
    }
    return;
  }

  /*
   * For special registers '%' (file name), '#' (alternate file name) and
   * ':' (last command line), etc. we have to create a fake yank register.
   */
  if (!reg && get_spec_reg(regname, &insert_string, &allocated, true)) {
    if (insert_string == NULL) {
      return;
    }
  }

  if (!curbuf->terminal) {
    // Autocommands may be executed when saving lines for undo.  This might
    // make y_array invalid, so we start undo now to avoid that.
    if (u_save(curwin->w_cursor.lnum, curwin->w_cursor.lnum + 1) == FAIL) {
      return;
    }
  }

  if (insert_string != NULL) {
    y_type = kMTCharWise;
    if (regname == '=') {
      /* For the = register we need to split the string at NL
       * characters.
       * Loop twice: count the number of lines and save them. */
      for (;; ) {
        y_size = 0;
        ptr = insert_string;
        while (ptr != NULL) {
          if (y_array != NULL)
            y_array[y_size] = ptr;
          ++y_size;
          ptr = vim_strchr(ptr, '\n');
          if (ptr != NULL) {
            if (y_array != NULL)
              *ptr = NUL;
            ++ptr;
            /* A trailing '\n' makes the register linewise. */
            if (*ptr == NUL) {
              y_type = kMTLineWise;
              break;
            }
          }
        }
        if (y_array != NULL)
          break;
        y_array = (char_u **)xmalloc(y_size * sizeof(char_u *));
      }
    } else {
      y_size = 1;               /* use fake one-line yank register */
      y_array = &insert_string;
    }
  } else {
    // in case of replacing visually selected text
    // the yankreg might already have been saved to avoid
    // just restoring the deleted text.
    if (reg == NULL) {
      reg = get_yank_register(regname, YREG_PASTE);
    }

    y_type = reg->y_type;
    y_width = reg->y_width;
    y_size = reg->y_size;
    y_array = reg->y_array;
  }

  if (curbuf->terminal) {
    terminal_paste(count, y_array, y_size);
    return;
  }

  if (y_type == kMTLineWise) {
    if (flags & PUT_LINE_SPLIT) {
      // "p" or "P" in Visual mode: split the lines to put the text in
      // between.
      if (u_save_cursor() == FAIL) {
        goto end;
      }
      char_u *p = get_cursor_pos_ptr();
      if (dir == FORWARD && *p != NUL) {
        MB_PTR_ADV(p);
      }
      ptr = vim_strsave(p);
      ml_append(curwin->w_cursor.lnum, ptr, (colnr_T)0, false);
      xfree(ptr);

      oldp = get_cursor_line_ptr();
      p = oldp + curwin->w_cursor.col;
      if (dir == FORWARD && *p != NUL) {
        MB_PTR_ADV(p);
      }
      ptr = vim_strnsave(oldp, (size_t)(p - oldp));
      ml_replace(curwin->w_cursor.lnum, ptr, false);
      nr_lines++;
      dir = FORWARD;
    }
    if (flags & PUT_LINE_FORWARD) {
      /* Must be "p" for a Visual block, put lines below the block. */
      curwin->w_cursor = curbuf->b_visual.vi_end;
      dir = FORWARD;
    }
    curbuf->b_op_start = curwin->w_cursor;      /* default for '[ mark */
    curbuf->b_op_end = curwin->w_cursor;        /* default for '] mark */
  }

  if (flags & PUT_LINE) {  // :put command or "p" in Visual line mode.
    y_type = kMTLineWise;
  }

  if (y_size == 0 || y_array == NULL) {
    EMSG2(_("E353: Nothing in register %s"),
        regname == 0 ? (char_u *)"\"" : transchar(regname));
    goto end;
  }

  if (y_type == kMTBlockWise) {
    lnum = curwin->w_cursor.lnum + (linenr_T)y_size + 1;
    if (lnum > curbuf->b_ml.ml_line_count) {
      lnum = curbuf->b_ml.ml_line_count + 1;
    }
    if (u_save(curwin->w_cursor.lnum - 1, lnum) == FAIL) {
      goto end;
    }
  } else if (y_type == kMTLineWise) {
    lnum = curwin->w_cursor.lnum;
    // Correct line number for closed fold.  Don't move the cursor yet,
    // u_save() uses it.
    if (dir == BACKWARD) {
      (void)hasFolding(lnum, &lnum, NULL);
    } else {
      (void)hasFolding(lnum, NULL, &lnum);
    }
    if (dir == FORWARD) {
      lnum++;
    }
    // In an empty buffer the empty line is going to be replaced, include
    // it in the saved lines.
    if ((BUFEMPTY() ? u_save(0, 2) : u_save(lnum - 1, lnum)) == FAIL) {
      goto end;
    }
    if (dir == FORWARD) {
      curwin->w_cursor.lnum = lnum - 1;
    } else {
      curwin->w_cursor.lnum = lnum;
    }
    curbuf->b_op_start = curwin->w_cursor;      // for mark_adjust()
  } else if (u_save_cursor() == FAIL) {
    goto end;
  }

  yanklen = (int)STRLEN(y_array[0]);

  if (ve_flags == VE_ALL && y_type == kMTCharWise) {
    if (gchar_cursor() == TAB) {
      /* Don't need to insert spaces when "p" on the last position of a
       * tab or "P" on the first position. */
      int viscol = getviscol();
      if (dir == FORWARD
          ? tabstop_padding(viscol, curbuf->b_p_ts, curbuf->b_p_vts_array) != 1
          : curwin->w_cursor.coladd > 0) {
        coladvance_force(viscol);
      } else {
        curwin->w_cursor.coladd = 0;
      }
    } else if (curwin->w_cursor.coladd > 0 || gchar_cursor() == NUL) {
      coladvance_force(getviscol() + (dir == FORWARD));
    }
  }

  lnum = curwin->w_cursor.lnum;
  col = curwin->w_cursor.col;

  /*
   * Block mode
   */
  if (y_type == kMTBlockWise) {
    int c = gchar_cursor();
    colnr_T endcol2 = 0;

    if (dir == FORWARD && c != NUL) {
      if (ve_flags == VE_ALL)
        getvcol(curwin, &curwin->w_cursor, &col, NULL, &endcol2);
      else
        getvcol(curwin, &curwin->w_cursor, NULL, NULL, &col);

      // move to start of next multi-byte character
      curwin->w_cursor.col += utfc_ptr2len(get_cursor_pos_ptr());
      col++;
    } else {
      getvcol(curwin, &curwin->w_cursor, &col, NULL, &endcol2);
    }

    col += curwin->w_cursor.coladd;
    if (ve_flags == VE_ALL
        && (curwin->w_cursor.coladd > 0
            || endcol2 == curwin->w_cursor.col)) {
      if (dir == FORWARD && c == NUL) {
        col++;
      }
      if (dir != FORWARD && c != NUL && curwin->w_cursor.coladd > 0) {
        curwin->w_cursor.col++;
      }
      if (c == TAB) {
        if (dir == BACKWARD && curwin->w_cursor.col)
          curwin->w_cursor.col--;
        if (dir == FORWARD && col - 1 == endcol2)
          curwin->w_cursor.col++;
      }
    }
    curwin->w_cursor.coladd = 0;
    bd.textcol = 0;
    for (i = 0; i < y_size; i++) {
      int spaces = 0;
      char shortline;
      // can just be 0 or 1, needed for blockwise paste beyond the current
      // buffer end
      int lines_appended = 0;

      bd.startspaces = 0;
      bd.endspaces = 0;
      vcol = 0;
      delcount = 0;

      /* add a new line */
      if (curwin->w_cursor.lnum > curbuf->b_ml.ml_line_count) {
        if (ml_append(curbuf->b_ml.ml_line_count, (char_u *)"",
                      (colnr_T)1, false) == FAIL) {
          break;
        }
        nr_lines++;
        lines_appended = 1;
      }
      /* get the old line and advance to the position to insert at */
      oldp = get_cursor_line_ptr();
      oldlen = STRLEN(oldp);
      for (ptr = oldp; vcol < col && *ptr; ) {
        /* Count a tab for what it's worth (if list mode not on) */
        incr = lbr_chartabsize_adv(oldp, &ptr, (colnr_T)vcol);
        vcol += incr;
      }
      bd.textcol = (colnr_T)(ptr - oldp);

      shortline = (vcol < col) || (vcol == col && !*ptr);

      if (vcol < col)       /* line too short, padd with spaces */
        bd.startspaces = col - vcol;
      else if (vcol > col) {
        bd.endspaces = vcol - col;
        bd.startspaces = incr - bd.endspaces;
        --bd.textcol;
        delcount = 1;
        bd.textcol -= utf_head_off(oldp, oldp + bd.textcol);
        if (oldp[bd.textcol] != TAB) {
          /* Only a Tab can be split into spaces.  Other
           * characters will have to be moved to after the
           * block, causing misalignment. */
          delcount = 0;
          bd.endspaces = 0;
        }
      }

      yanklen = (int)STRLEN(y_array[i]);

      if ((flags & PUT_BLOCK_INNER) == 0) {
        // calculate number of spaces required to fill right side of
        // block
        spaces = y_width + 1;
        for (int j = 0; j < yanklen; j++) {
          spaces -= lbr_chartabsize(NULL, &y_array[i][j], 0);
        }
        if (spaces < 0) {
          spaces = 0;
        }
      }

      // insert the new text
      totlen = (size_t)(count * (yanklen + spaces)
                        + bd.startspaces + bd.endspaces);
      int addcount = (int)totlen + lines_appended;
      newp = (char_u *)xmalloc(totlen + oldlen + 1);
      // copy part up to cursor to new line
      ptr = newp;
      memmove(ptr, oldp, (size_t)bd.textcol);
      ptr += bd.textcol;
      // may insert some spaces before the new text
      memset(ptr, ' ', (size_t)bd.startspaces);
      ptr += bd.startspaces;
      // insert the new text
      for (long j = 0; j < count; j++) {
        memmove(ptr, y_array[i], (size_t)yanklen);
        ptr += yanklen;

        // insert block's trailing spaces only if there's text behind
        if ((j < count - 1 || !shortline) && spaces) {
          memset(ptr, ' ', (size_t)spaces);
          ptr += spaces;
        } else {
          addcount -= spaces;
        }
      }
      // may insert some spaces after the new text
      memset(ptr, ' ', (size_t)bd.endspaces);
      ptr += bd.endspaces;
      // move the text after the cursor to the end of the line.
      int columns = (int)oldlen - bd.textcol - delcount + 1;
      assert(columns >= 0);
      memmove(ptr, oldp + bd.textcol + delcount, (size_t)columns);
      ml_replace(curwin->w_cursor.lnum, newp, false);
      extmark_splice_cols(curbuf, (int)curwin->w_cursor.lnum-1, bd.textcol,
                          delcount, addcount, kExtmarkUndo);

      ++curwin->w_cursor.lnum;
      if (i == 0)
        curwin->w_cursor.col += bd.startspaces;
    }

    changed_lines(lnum, 0, curbuf->b_op_start.lnum + (linenr_T)y_size
                  - (linenr_T)nr_lines , nr_lines, true);

    /* Set '[ mark. */
    curbuf->b_op_start = curwin->w_cursor;
    curbuf->b_op_start.lnum = lnum;

    /* adjust '] mark */
    curbuf->b_op_end.lnum = curwin->w_cursor.lnum - 1;
    curbuf->b_op_end.col = bd.textcol + (colnr_T)totlen - 1;
    curbuf->b_op_end.coladd = 0;
    if (flags & PUT_CURSEND) {
      colnr_T len;

      curwin->w_cursor = curbuf->b_op_end;
      curwin->w_cursor.col++;

      /* in Insert mode we might be after the NUL, correct for that */
      len = (colnr_T)STRLEN(get_cursor_line_ptr());
      if (curwin->w_cursor.col > len)
        curwin->w_cursor.col = len;
    } else
      curwin->w_cursor.lnum = lnum;
  } else {
    // Character or Line mode
    if (y_type == kMTCharWise) {
      // if type is kMTCharWise, FORWARD is the same as BACKWARD on the next
      // char
      if (dir == FORWARD && gchar_cursor() != NUL) {
        int bytelen = (*mb_ptr2len)(get_cursor_pos_ptr());

        // put it on the next of the multi-byte character.
        col += bytelen;
        if (yanklen) {
          curwin->w_cursor.col += bytelen;
          curbuf->b_op_end.col += bytelen;
        }
      }
      curbuf->b_op_start = curwin->w_cursor;
    }
    /*
     * Line mode: BACKWARD is the same as FORWARD on the previous line
     */
    else if (dir == BACKWARD)
      --lnum;
    new_cursor = curwin->w_cursor;

    // simple case: insert into one line at a time
    if (y_type == kMTCharWise && y_size == 1) {
      linenr_T end_lnum = 0;  // init for gcc
      linenr_T start_lnum = lnum;

      if (VIsual_active) {
        end_lnum = curbuf->b_visual.vi_end.lnum;
        if (end_lnum < curbuf->b_visual.vi_start.lnum) {
            end_lnum = curbuf->b_visual.vi_start.lnum;
        }
        if (end_lnum > start_lnum) {
          // "col" is valid for the first line, in following lines
          // the virtual column needs to be used.  Matters for
          // multi-byte characters.
          pos_T pos = {
            .lnum = lnum,
            .col = col,
            .coladd = 0,
          };
          getvcol(curwin, &pos, NULL, &vcol, NULL);
        }
      }

      do {
        totlen = (size_t)(count * yanklen);
        if (totlen > 0) {
          oldp = ml_get(lnum);
          if (lnum > start_lnum) {
            pos_T pos = {
              .lnum = lnum,
            };
            if (getvpos(&pos, vcol) == OK) {
              col = pos.col;
            } else {
              col = MAXCOL;
            }
          }
          if (VIsual_active && col > (int)STRLEN(oldp)) {
            lnum++;
            continue;
          }
          newp = (char_u *)xmalloc((size_t)(STRLEN(oldp) + totlen + 1));
          memmove(newp, oldp, (size_t)col);
          ptr = newp + col;
          for (i = 0; i < (size_t)count; i++) {
            memmove(ptr, y_array[0], (size_t)yanklen);
            ptr += yanklen;
          }
          STRMOVE(ptr, oldp + col);
          ml_replace(lnum, newp, false);
          // Place cursor on last putted char.
          if (lnum == curwin->w_cursor.lnum) {
            // make sure curwin->w_virtcol is updated
            changed_cline_bef_curs();
            curwin->w_cursor.col += (colnr_T)(totlen - 1);
          }
          changed_bytes(lnum, col);
          extmark_splice_cols(curbuf, (int)lnum-1, col,
                              0, (int)totlen, kExtmarkUndo);
        }
        if (VIsual_active) {
          lnum++;
        }
      } while (VIsual_active && lnum <= end_lnum);

      if (VIsual_active) {  /* reset lnum to the last visual line */
        lnum--;
      }

      curbuf->b_op_end = curwin->w_cursor;
      // For "CTRL-O p" in Insert mode, put cursor after last char
      if (totlen && (restart_edit != 0 || (flags & PUT_CURSEND))) {
        curwin->w_cursor.col++;
      }
    } else {
      // Insert at least one line.  When y_type is kMTCharWise, break the first
      // line in two.
      for (cnt = 1; cnt <= count; cnt++) {
        i = 0;
        if (y_type == kMTCharWise) {
          // Split the current line in two at the insert position.
          // First insert y_array[size - 1] in front of second line.
          // Then append y_array[0] to first line.
          lnum = new_cursor.lnum;
          ptr = ml_get(lnum) + col;
          totlen = STRLEN(y_array[y_size - 1]);
          newp = (char_u *) xmalloc((size_t)(STRLEN(ptr) + totlen + 1));
          STRCPY(newp, y_array[y_size - 1]);
          STRCAT(newp, ptr);
          // insert second line
          ml_append(lnum, newp, (colnr_T)0, false);
          xfree(newp);

          oldp = ml_get(lnum);
          newp = (char_u *)xmalloc((size_t)col + (size_t)yanklen + 1);
          // copy first part of line
          memmove(newp, oldp, (size_t)col);
          // append to first line
          memmove(newp + col, y_array[0], (size_t)yanklen + 1);
          ml_replace(lnum, newp, false);

          curwin->w_cursor.lnum = lnum;
          i = 1;
        }

        for (; i < y_size; i++) {
          if ((y_type != kMTCharWise || i < y_size - 1)
              && ml_append(lnum, y_array[i], (colnr_T)0, false)
              == FAIL) {
            goto error;
          }
          lnum++;
          ++nr_lines;
          if (flags & PUT_FIXINDENT) {
            old_pos = curwin->w_cursor;
            curwin->w_cursor.lnum = lnum;
            ptr = ml_get(lnum);
            if (cnt == count && i == y_size - 1)
              lendiff = (int)STRLEN(ptr);
            if (*ptr == '#' && preprocs_left())
              indent = 0;                   /* Leave # lines at start */
            else if (*ptr == NUL)
              indent = 0;                   /* Ignore empty lines */
            else if (first_indent) {
              indent_diff = orig_indent - get_indent();
              indent = orig_indent;
              first_indent = FALSE;
            } else if ((indent = get_indent() + indent_diff) < 0)
              indent = 0;
            (void)set_indent(indent, SIN_NOMARK);
            curwin->w_cursor = old_pos;
            /* remember how many chars were removed */
            if (cnt == count && i == y_size - 1)
              lendiff -= (int)STRLEN(ml_get(lnum));
          }
        }

        bcount_t totsize = 0;
        int lastsize = 0;
        if (y_type == kMTCharWise
            || (y_type == kMTLineWise && flags & PUT_LINE_SPLIT)) {
          for (i = 0; i < y_size-1; i++) {
            totsize += (bcount_t)STRLEN(y_array[i]) + 1;
          }
          lastsize = (int)STRLEN(y_array[y_size-1]);
          totsize += lastsize;
        }
        if (y_type == kMTCharWise) {
          extmark_splice(curbuf, (int)new_cursor.lnum-1, col, 0, 0, 0,
                         (int)y_size-1, lastsize, totsize,
                         kExtmarkUndo);
        } else if (y_type == kMTLineWise && flags & PUT_LINE_SPLIT) {
          extmark_splice(curbuf, (int)new_cursor.lnum-1, col, 0, 0, 0,
                         (int)y_size+1, 0, totsize+1, kExtmarkUndo);
        }
      }

error:
      // Adjust marks.
      if (y_type == kMTLineWise) {
        curbuf->b_op_start.col = 0;
        if (dir == FORWARD)
          curbuf->b_op_start.lnum++;
      }

      ExtmarkOp kind = (y_type == kMTLineWise && !(flags & PUT_LINE_SPLIT))
                       ? kExtmarkUndo : kExtmarkNOOP;
      mark_adjust(curbuf->b_op_start.lnum + (y_type == kMTCharWise),
                  (linenr_T)MAXLNUM, nr_lines, 0L, kind);

      // note changed text for displaying and folding
      if (y_type == kMTCharWise) {
        changed_lines(curwin->w_cursor.lnum, col,
                      curwin->w_cursor.lnum + 1, nr_lines, true);
      } else {
        changed_lines(curbuf->b_op_start.lnum, 0,
                      curbuf->b_op_start.lnum, nr_lines, true);
      }

      /* put '] mark at last inserted character */
      curbuf->b_op_end.lnum = lnum;
      /* correct length for change in indent */
      col = (colnr_T)STRLEN(y_array[y_size - 1]) - lendiff;
      if (col > 1)
        curbuf->b_op_end.col = col - 1;
      else
        curbuf->b_op_end.col = 0;

      if (flags & PUT_CURSLINE) {
        /* ":put": put cursor on last inserted line */
        curwin->w_cursor.lnum = lnum;
        beginline(BL_WHITE | BL_FIX);
      } else if (flags & PUT_CURSEND) {
        // put cursor after inserted text
        if (y_type == kMTLineWise) {
          if (lnum >= curbuf->b_ml.ml_line_count) {
            curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
          } else {
            curwin->w_cursor.lnum = lnum + 1;
          }
          curwin->w_cursor.col = 0;
        } else {
          curwin->w_cursor.lnum = lnum;
          curwin->w_cursor.col = col;
        }
      } else if (y_type == kMTLineWise) {
        // put cursor on first non-blank in first inserted line
        curwin->w_cursor.col = 0;
        if (dir == FORWARD)
          ++curwin->w_cursor.lnum;
        beginline(BL_WHITE | BL_FIX);
      } else            /* put cursor on first inserted character */
        curwin->w_cursor = new_cursor;
    }
  }

  msgmore(nr_lines);
  curwin->w_set_curswant = TRUE;

end:
  if (allocated)
    xfree(insert_string);
  if (regname == '=')
    xfree(y_array);

  VIsual_active = FALSE;

  /* If the cursor is past the end of the line put it at the end. */
  adjust_cursor_eol();
}  // NOLINT(readability/fn_size)

/*
 * When the cursor is on the NUL past the end of the line and it should not be
 * there move it left.
 */
void adjust_cursor_eol(void)
{
  if (curwin->w_cursor.col > 0
      && gchar_cursor() == NUL
      && (ve_flags & VE_ONEMORE) == 0
      && !(restart_edit || (State & INSERT))) {
    /* Put the cursor on the last character in the line. */
    dec_cursor();

    if (ve_flags == VE_ALL) {
      colnr_T scol, ecol;

      /* Coladd is set to the width of the last character. */
      getvcol(curwin, &curwin->w_cursor, &scol, NULL, &ecol);
      curwin->w_cursor.coladd = ecol - scol + 1;
    }
  }
}

/*
 * Return TRUE if lines starting with '#' should be left aligned.
 */
int preprocs_left(void)
{
  return ((curbuf->b_p_si && !curbuf->b_p_cin)
          || (curbuf->b_p_cin && in_cinkeys('#', ' ', true)
              && curbuf->b_ind_hash_comment == 0));
}

/* Return the character name of the register with the given number */
int get_register_name(int num)
{
  if (num == -1)
    return '"';
  else if (num < 10)
    return num + '0';
  else if (num == DELETION_REGISTER)
    return '-';
  else if (num == STAR_REGISTER)
    return '*';
  else if (num == PLUS_REGISTER)
    return '+';
  else {
    return num + 'a' - 10;
  }
}

/*
 * ":dis" and ":registers": Display the contents of the yank registers.
 */
void ex_display(exarg_T *eap)
{
  char_u *p;
  yankreg_T *yb;
  int name;
  char_u *arg = eap->arg;
  int clen;
  char_u type[2];

  if (arg != NULL && *arg == NUL)
    arg = NULL;
  int attr = HL_ATTR(HLF_8);

  // Highlight title
  msg_puts_title(_("\nType Name Content"));
  for (int i = -1; i < NUM_REGISTERS && !got_int; i++) {
    name = get_register_name(i);
    switch (get_reg_type(name, NULL)) {
      case kMTLineWise: type[0] = 'l'; break;
      case kMTCharWise: type[0] = 'c'; break;
      default: type[0] = 'b'; break;
    }

    if (arg != NULL && vim_strchr(arg, name) == NULL) {
      continue;             /* did not ask for this register */
    }


    if (i == -1) {
      if (y_previous != NULL)
        yb = y_previous;
      else
        yb = &(y_regs[0]);
    } else
      yb = &(y_regs[i]);

    get_clipboard(name, &yb, true);

    if (name == mb_tolower(redir_reg)
        || (redir_reg == '"' && yb == y_previous)) {
      continue;  // do not list register being written to, the
                 // pointer can be freed
    }

    if (yb->y_array != NULL) {
      msg_putchar('\n');
      msg_puts("  ");
      msg_putchar(type[0]);
      msg_puts("  ");
      msg_putchar('"');
      msg_putchar(name);
      MSG_PUTS("   ");

      int n = Columns - 11;
      for (size_t j = 0; j < yb->y_size && n > 1; j++) {
        if (j) {
          MSG_PUTS_ATTR("^J", attr);
          n -= 2;
        }
        for (p = yb->y_array[j]; *p && (n -= ptr2cells(p)) >= 0; p++) {  // -V1019 NOLINT(whitespace/line_length)
          clen = (*mb_ptr2len)(p);
          msg_outtrans_len(p, clen);
          p += clen - 1;
        }
      }
      if (n > 1 && yb->y_type == kMTLineWise) {
        MSG_PUTS_ATTR("^J", attr);
      }
      ui_flush();  // show one line at a time
    }
    os_breakcheck();
  }

  /*
   * display last inserted text
   */
  if ((p = get_last_insert()) != NULL
      && (arg == NULL || vim_strchr(arg, '.') != NULL) && !got_int) {
    msg_puts("\n  c  \".   ");
    dis_msg(p, true);
  }

  /*
   * display last command line
   */
  if (last_cmdline != NULL && (arg == NULL || vim_strchr(arg, ':') != NULL)
      && !got_int) {
    msg_puts("\n  c  \":   ");
    dis_msg(last_cmdline, false);
  }

  /*
   * display current file name
   */
  if (curbuf->b_fname != NULL
      && (arg == NULL || vim_strchr(arg, '%') != NULL) && !got_int) {
    msg_puts("\n  c  \"%   ");
    dis_msg(curbuf->b_fname, false);
  }

  /*
   * display alternate file name
   */
  if ((arg == NULL || vim_strchr(arg, '%') != NULL) && !got_int) {
    char_u      *fname;
    linenr_T dummy;

    if (buflist_name_nr(0, &fname, &dummy) != FAIL) {
      msg_puts("\n  c  \"#   ");
      dis_msg(fname, false);
    }
  }

  /*
   * display last search pattern
   */
  if (last_search_pat() != NULL
      && (arg == NULL || vim_strchr(arg, '/') != NULL) && !got_int) {
    msg_puts("\n  c  \"/   ");
    dis_msg(last_search_pat(), false);
  }

  /*
   * display last used expression
   */
  if (expr_line != NULL && (arg == NULL || vim_strchr(arg, '=') != NULL)
      && !got_int) {
    msg_puts("\n  c  \"=   ");
    dis_msg(expr_line, false);
  }
}

/*
 * display a string for do_dis()
 * truncate at end of screen line
 */
static void
dis_msg(
    const char_u *p,
    bool skip_esc     // if true, ignore trailing ESC
)
  FUNC_ATTR_NONNULL_ALL
{
  int n;
  int l;

  n = Columns - 6;
  while (*p != NUL
         && !(*p == ESC && skip_esc && *(p + 1) == NUL)
         && (n -= ptr2cells(p)) >= 0) {
    if ((l = utfc_ptr2len(p)) > 1) {
      msg_outtrans_len(p, l);
      p += l;
    } else
      msg_outtrans_len(p++, 1);
  }
  os_breakcheck();
}

/// If \p "process" is true and the line begins with a comment leader (possibly
/// after some white space), return a pointer to the text after it.
/// Put a boolean value indicating whether the line ends with an unclosed
/// comment in "is_comment".
///
/// @param line - line to be processed
/// @param process - if false, will only check whether the line ends
///         with an unclosed comment,
/// @param include_space - whether to skip space following the comment leader
/// @param[out] is_comment - whether the current line ends with an unclosed
///  comment.
char_u *skip_comment(
    char_u *line, bool process, bool include_space, bool *is_comment
)
{
  char_u *comment_flags = NULL;
  int lead_len;
  int leader_offset = get_last_leader_offset(line, &comment_flags);

  *is_comment = false;
  if (leader_offset != -1) {
    /* Let's check whether the line ends with an unclosed comment.
     * If the last comment leader has COM_END in flags, there's no comment.
     */
    while (*comment_flags) {
      if (*comment_flags == COM_END
          || *comment_flags == ':') {
        break;
      }
      comment_flags++;
    }
    if (*comment_flags != COM_END) {
      *is_comment = true;
    }
  }

  if (process == false) {
    return line;
  }

  lead_len = get_leader_len(line, &comment_flags, false, include_space);

  if (lead_len == 0)
    return line;

  /* Find:
   * - COM_END,
   * - colon,
   * whichever comes first.
   */
  while (*comment_flags) {
    if (*comment_flags == COM_END
        || *comment_flags == ':') {
      break;
    }
    ++comment_flags;
  }

  /* If we found a colon, it means that we are not processing a line
   * starting with a closing part of a three-part comment. That's good,
   * because we don't want to remove those as this would be annoying.
   */
  if (*comment_flags == ':' || *comment_flags == NUL) {
    line += lead_len;
  }

  return line;
}

// Join 'count' lines (minimal 2) at cursor position.
// When "save_undo" is TRUE save lines for undo first.
// Set "use_formatoptions" to FALSE when e.g. processing backspace and comment
// leaders should not be removed.
// When setmark is true, sets the '[ and '] mark, else, the caller is expected
// to set those marks.
//
// return FAIL for failure, OK otherwise
int do_join(size_t count,
            int insert_space,
            int save_undo,
            int use_formatoptions,
            bool setmark)
{
  char_u      *curr = NULL;
  char_u      *curr_start = NULL;
  char_u      *cend;
  char_u      *newp;
  char_u      *spaces;          /* number of spaces inserted before a line */
  int endcurr1 = NUL;
  int endcurr2 = NUL;
  int currsize = 0;             /* size of the current line */
  int sumsize = 0;              /* size of the long new line */
  linenr_T t;
  colnr_T col = 0;
  int ret = OK;
  int         *comments = NULL;
  int remove_comments = (use_formatoptions == TRUE)
                        && has_format_option(FO_REMOVE_COMS);
  bool prev_was_comment = false;
  assert(count >= 1);

  if (save_undo && u_save(curwin->w_cursor.lnum - 1,
                          curwin->w_cursor.lnum + (linenr_T)count) == FAIL) {
    return FAIL;
  }
  // Allocate an array to store the number of spaces inserted before each
  // line.  We will use it to pre-compute the length of the new line and the
  // proper placement of each original line in the new one.
  spaces = xcalloc(count, 1);
  if (remove_comments) {
    comments = xcalloc(count, sizeof(*comments));
  }

  // Don't move anything, just compute the final line length
  // and setup the array of space strings lengths
  for (t = 0; t < (linenr_T)count; t++) {
    curr = curr_start = ml_get((linenr_T)(curwin->w_cursor.lnum + t));
    if (t == 0 && setmark) {
      // Set the '[ mark.
      curwin->w_buffer->b_op_start.lnum = curwin->w_cursor.lnum;
      curwin->w_buffer->b_op_start.col = (colnr_T)STRLEN(curr);
    }
    if (remove_comments) {
      // We don't want to remove the comment leader if the
      // previous line is not a comment.
      if (t > 0 && prev_was_comment) {
        char_u *new_curr = skip_comment(curr, true, insert_space,
                                        &prev_was_comment);
        comments[t] = (int)(new_curr - curr);
        curr = new_curr;
      } else {
        curr = skip_comment(curr, false, insert_space, &prev_was_comment);
      }
    }

    if (insert_space && t > 0) {
      curr = skipwhite(curr);
      if (*curr != NUL
          && *curr != ')'
          && sumsize != 0
          && endcurr1 != TAB
          && (!has_format_option(FO_MBYTE_JOIN)
              || (utf_ptr2char(curr) < 0x100 && endcurr1 < 0x100))
          && (!has_format_option(FO_MBYTE_JOIN2)
              || (utf_ptr2char(curr) < 0x100 && !utf_eat_space(endcurr1))
              || (endcurr1 < 0x100 && !utf_eat_space(utf_ptr2char(curr))))
          ) {
        /* don't add a space if the line is ending in a space */
        if (endcurr1 == ' ')
          endcurr1 = endcurr2;
        else
          ++spaces[t];
        // Extra space when 'joinspaces' set and line ends in '.', '?', or '!'.
        if (p_js && (endcurr1 == '.' || endcurr1 == '?' || endcurr1 == '!')) {
          ++spaces[t];
        }
      }
    }

    if (t > 0 && curbuf_splice_pending == 0) {
      colnr_T removed = (int)(curr- curr_start);
      extmark_splice(curbuf, (int)curwin->w_cursor.lnum-1, sumsize,
                     1, removed, removed + 1,
                     0, spaces[t], spaces[t],
                     kExtmarkUndo);
    }
    currsize = (int)STRLEN(curr);
    sumsize += currsize + spaces[t];
    endcurr1 = endcurr2 = NUL;
    if (insert_space && currsize > 0) {
      cend = curr + currsize;
      MB_PTR_BACK(curr, cend);
      endcurr1 = utf_ptr2char(cend);
      if (cend > curr) {
        MB_PTR_BACK(curr, cend);
        endcurr2 = utf_ptr2char(cend);
      }
    }
    line_breakcheck();
    if (got_int) {
      ret = FAIL;
      goto theend;
    }
  }

  // store the column position before last line
  col = sumsize - currsize - spaces[count - 1];

  // allocate the space for the new line
  newp = (char_u *)xmalloc((size_t)sumsize + 1);
  cend = newp + sumsize;
  *cend = 0;

  /*
   * Move affected lines to the new long one.
   *
   * Move marks from each deleted line to the joined line, adjusting the
   * column.  This is not Vi compatible, but Vi deletes the marks, thus that
   * should not really be a problem.
   */

  curbuf_splice_pending++;

  for (t = (linenr_T)count - 1;; t--) {
    cend -= currsize;
    memmove(cend, curr, (size_t)currsize);
    if (spaces[t] > 0) {
      cend -= spaces[t];
      memset(cend, ' ', (size_t)(spaces[t]));
    }

    // If deleting more spaces than adding, the cursor moves no more than
    // what is added if it is inside these spaces.
    const int spaces_removed = (int)((curr - curr_start) - spaces[t]);
    linenr_T lnum = curwin->w_cursor.lnum + t;
    colnr_T mincol = (colnr_T)0;
    long lnum_amount = (linenr_T)-t;
    long col_amount = (long)(cend - newp - spaces_removed);

    mark_col_adjust(lnum, mincol, lnum_amount, col_amount, spaces_removed);

    if (t == 0) {
      break;
    }

    curr = curr_start = ml_get((linenr_T)(curwin->w_cursor.lnum + t - 1));
    if (remove_comments)
      curr += comments[t - 1];
    if (insert_space && t > 1)
      curr = skipwhite(curr);
    currsize = (int)STRLEN(curr);
  }

  ml_replace(curwin->w_cursor.lnum, newp, false);

  if (setmark) {
    // Set the '] mark.
    curwin->w_buffer->b_op_end.lnum = curwin->w_cursor.lnum;
    curwin->w_buffer->b_op_end.col = sumsize;
  }

  /* Only report the change in the first line here, del_lines() will report
   * the deleted line. */
  changed_lines(curwin->w_cursor.lnum, currsize,
                curwin->w_cursor.lnum + 1, 0L, true);

  /*
   * Delete following lines. To do this we move the cursor there
   * briefly, and then move it back. After del_lines() the cursor may
   * have moved up (last line deleted), so the current lnum is kept in t.
   */
  t = curwin->w_cursor.lnum;
  curwin->w_cursor.lnum++;
  del_lines((long)count - 1, false);
  curwin->w_cursor.lnum = t;
  curbuf_splice_pending--;
  curbuf->deleted_bytes2 = 0;

  /*
   * Set the cursor column:
   * Vi compatible: use the column of the first join
   * vim:	      use the column of the last join
   */
  curwin->w_cursor.col =
    (vim_strchr(p_cpo, CPO_JOINCOL) != NULL ? currsize : col);
  check_cursor_col();

  curwin->w_cursor.coladd = 0;
  curwin->w_set_curswant = TRUE;

theend:
  xfree(spaces);
  if (remove_comments)
    xfree(comments);
  return ret;
}

/*
 * Return TRUE if the two comment leaders given are the same.  "lnum" is
 * the first line.  White-space is ignored.  Note that the whole of
 * 'leader1' must match 'leader2_len' characters from 'leader2' -- webb
 */
static int same_leader(linenr_T lnum, int leader1_len, char_u *leader1_flags, int leader2_len, char_u *leader2_flags)
{
  int idx1 = 0, idx2 = 0;
  char_u  *p;
  char_u  *line1;
  char_u  *line2;

  if (leader1_len == 0)
    return leader2_len == 0;

  /*
   * If first leader has 'f' flag, the lines can be joined only if the
   * second line does not have a leader.
   * If first leader has 'e' flag, the lines can never be joined.
   * If fist leader has 's' flag, the lines can only be joined if there is
   * some text after it and the second line has the 'm' flag.
   */
  if (leader1_flags != NULL) {
    for (p = leader1_flags; *p && *p != ':'; ++p) {
      if (*p == COM_FIRST)
        return leader2_len == 0;
      if (*p == COM_END)
        return FALSE;
      if (*p == COM_START) {
        if (*(ml_get(lnum) + leader1_len) == NUL)
          return FALSE;
        if (leader2_flags == NULL || leader2_len == 0)
          return FALSE;
        for (p = leader2_flags; *p && *p != ':'; ++p)
          if (*p == COM_MIDDLE)
            return TRUE;
        return FALSE;
      }
    }
  }

  /*
   * Get current line and next line, compare the leaders.
   * The first line has to be saved, only one line can be locked at a time.
   */
  line1 = vim_strsave(ml_get(lnum));
  for (idx1 = 0; ascii_iswhite(line1[idx1]); ++idx1)
    ;
  line2 = ml_get(lnum + 1);
  for (idx2 = 0; idx2 < leader2_len; ++idx2) {
    if (!ascii_iswhite(line2[idx2])) {
      if (line1[idx1++] != line2[idx2])
        break;
    } else
      while (ascii_iswhite(line1[idx1]))
        ++idx1;
  }
  xfree(line1);

  return idx2 == leader2_len && idx1 == leader1_len;
}

/*
 * Implementation of the format operator 'gq'.
 */
void
op_format(
    oparg_T *oap,
    int keep_cursor                        /* keep cursor on same text char */
)
{
  long old_line_count = curbuf->b_ml.ml_line_count;

  /* Place the cursor where the "gq" or "gw" command was given, so that "u"
   * can put it back there. */
  curwin->w_cursor = oap->cursor_start;

  if (u_save((linenr_T)(oap->start.lnum - 1),
          (linenr_T)(oap->end.lnum + 1)) == FAIL)
    return;
  curwin->w_cursor = oap->start;

  if (oap->is_VIsual)
    /* When there is no change: need to remove the Visual selection */
    redraw_curbuf_later(INVERTED);

  /* Set '[ mark at the start of the formatted area */
  curbuf->b_op_start = oap->start;

  /* For "gw" remember the cursor position and put it back below (adjusted
   * for joined and split lines). */
  if (keep_cursor)
    saved_cursor = oap->cursor_start;

  format_lines(oap->line_count, keep_cursor);

  /*
   * Leave the cursor at the first non-blank of the last formatted line.
   * If the cursor was moved one line back (e.g. with "Q}") go to the next
   * line, so "." will do the next lines.
   */
  if (oap->end_adjusted && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
    ++curwin->w_cursor.lnum;
  beginline(BL_WHITE | BL_FIX);
  old_line_count = curbuf->b_ml.ml_line_count - old_line_count;
  msgmore(old_line_count);

  /* put '] mark on the end of the formatted area */
  curbuf->b_op_end = curwin->w_cursor;

  if (keep_cursor) {
    curwin->w_cursor = saved_cursor;
    saved_cursor.lnum = 0;
  }

  if (oap->is_VIsual) {
    FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
      if (wp->w_old_cursor_lnum != 0) {
        /* When lines have been inserted or deleted, adjust the end of
         * the Visual area to be redrawn. */
        if (wp->w_old_cursor_lnum > wp->w_old_visual_lnum) {
          wp->w_old_cursor_lnum += old_line_count;
        } else {
          wp->w_old_visual_lnum += old_line_count;
        }
      }
    }
  }
}

/*
 * Implementation of the format operator 'gq' for when using 'formatexpr'.
 */
void op_formatexpr(oparg_T *oap)
{
  if (oap->is_VIsual)
    /* When there is no change: need to remove the Visual selection */
    redraw_curbuf_later(INVERTED);

  if (fex_format(oap->start.lnum, oap->line_count, NUL) != 0)
    /* As documented: when 'formatexpr' returns non-zero fall back to
     * internal formatting. */
    op_format(oap, FALSE);
}

int
fex_format(
    linenr_T lnum,
    long count,
    int c                  /* character to be inserted */
)
{
  int use_sandbox = was_set_insecurely(
      curwin, (char_u *)"formatexpr", OPT_LOCAL);
  int r;
  char_u *fex;

  /*
   * Set v:lnum to the first line number and v:count to the number of lines.
   * Set v:char to the character to be inserted (can be NUL).
   */
  set_vim_var_nr(VV_LNUM, (varnumber_T)lnum);
  set_vim_var_nr(VV_COUNT, (varnumber_T)count);
  set_vim_var_char(c);

  // Make a copy, the option could be changed while calling it.
  fex = vim_strsave(curbuf->b_p_fex);
  // Evaluate the function.
  if (use_sandbox) {
    sandbox++;
  }
  r = (int)eval_to_number(fex);
  if (use_sandbox) {
    sandbox--;
  }

  set_vim_var_string(VV_CHAR, NULL, -1);
  xfree(fex);

  return r;
}

/*
 * Format "line_count" lines, starting at the cursor position.
 * When "line_count" is negative, format until the end of the paragraph.
 * Lines after the cursor line are saved for undo, caller must have saved the
 * first line.
 */
void
format_lines(
    linenr_T line_count,
    int avoid_fex                          /* don't use 'formatexpr' */
)
{
  bool is_not_par;                  // current line not part of parag.
  bool next_is_not_par;             // next line not part of paragraph
  bool is_end_par;                  // at end of paragraph
  bool prev_is_end_par = false;     // prev. line not part of parag.
  bool next_is_start_par = false;
  int leader_len = 0;               // leader len of current line
  int next_leader_len;              // leader len of next line
  char_u *leader_flags = NULL;      // flags for leader of current line
  char_u *next_leader_flags;        // flags for leader of next line
  bool advance = true;
  int second_indent = -1;           // indent for second line (comment aware)
  bool first_par_line = true;
  int smd_save;
  long count;
  bool need_set_indent = true;      // set indent of next paragraph
  bool force_format = false;
  const int old_State = State;

  // length of a line to force formatting: 3 * 'tw'
  const int max_len = comp_textwidth(true) * 3;

  // check for 'q', '2' and '1' in 'formatoptions'
  const bool do_comments = has_format_option(FO_Q_COMS);  // format comments
  int do_comments_list = 0;  // format comments with 'n' or '2'
  const bool do_second_indent = has_format_option(FO_Q_SECOND);
  const bool do_number_indent = has_format_option(FO_Q_NUMBER);
  const bool do_trail_white = has_format_option(FO_WHITE_PAR);

  // Get info about the previous and current line.
  if (curwin->w_cursor.lnum > 1) {
    is_not_par = fmt_check_par(curwin->w_cursor.lnum - 1,
                               &leader_len, &leader_flags, do_comments);
  } else {
    is_not_par = true;
  }
  next_is_not_par = fmt_check_par(curwin->w_cursor.lnum
      , &next_leader_len, &next_leader_flags, do_comments
      );
  is_end_par = (is_not_par || next_is_not_par);
  if (!is_end_par && do_trail_white)
    is_end_par = !ends_in_white(curwin->w_cursor.lnum - 1);

  curwin->w_cursor.lnum--;
  for (count = line_count; count != 0 && !got_int; --count) {
    /*
     * Advance to next paragraph.
     */
    if (advance) {
      curwin->w_cursor.lnum++;
      prev_is_end_par = is_end_par;
      is_not_par = next_is_not_par;
      leader_len = next_leader_len;
      leader_flags = next_leader_flags;
    }

    /*
     * The last line to be formatted.
     */
    if (count == 1 || curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count) {
      next_is_not_par = true;
      next_leader_len = 0;
      next_leader_flags = NULL;
    } else {
      next_is_not_par = fmt_check_par(curwin->w_cursor.lnum + 1
          , &next_leader_len, &next_leader_flags, do_comments
          );
      if (do_number_indent)
        next_is_start_par =
          (get_number_indent(curwin->w_cursor.lnum + 1) > 0);
    }
    advance = true;
    is_end_par = (is_not_par || next_is_not_par || next_is_start_par);
    if (!is_end_par && do_trail_white)
      is_end_par = !ends_in_white(curwin->w_cursor.lnum);

    /*
     * Skip lines that are not in a paragraph.
     */
    if (is_not_par) {
      if (line_count < 0)
        break;
    } else {
      /*
       * For the first line of a paragraph, check indent of second line.
       * Don't do this for comments and empty lines.
       */
      if (first_par_line
          && (do_second_indent || do_number_indent)
          && prev_is_end_par
          && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
        if (do_second_indent && !LINEEMPTY(curwin->w_cursor.lnum + 1)) {
          if (leader_len == 0 && next_leader_len == 0) {
            /* no comment found */
            second_indent =
              get_indent_lnum(curwin->w_cursor.lnum + 1);
          } else {
            second_indent = next_leader_len;
            do_comments_list = 1;
          }
        } else if (do_number_indent) {
          if (leader_len == 0 && next_leader_len == 0) {
            /* no comment found */
            second_indent =
              get_number_indent(curwin->w_cursor.lnum);
          } else {
            /* get_number_indent() is now "comment aware"... */
            second_indent =
              get_number_indent(curwin->w_cursor.lnum);
            do_comments_list = 1;
          }
        }
      }

      /*
       * When the comment leader changes, it's the end of the paragraph.
       */
      if (curwin->w_cursor.lnum >= curbuf->b_ml.ml_line_count
          || !same_leader(curwin->w_cursor.lnum,
              leader_len, leader_flags,
              next_leader_len, next_leader_flags)
          )
        is_end_par = true;

      /*
       * If we have got to the end of a paragraph, or the line is
       * getting long, format it.
       */
      if (is_end_par || force_format) {
        if (need_set_indent)
          /* replace indent in first line with minimal number of
           * tabs and spaces, according to current options */
          (void)set_indent(get_indent(), SIN_CHANGED);

        // put cursor on last non-space
        State = NORMAL;  // don't go past end-of-line
        coladvance(MAXCOL);
        while (curwin->w_cursor.col && ascii_isspace(gchar_cursor())) {
          dec_cursor();
        }

        /* do the formatting, without 'showmode' */
        State = INSERT;         /* for open_line() */
        smd_save = p_smd;
        p_smd = FALSE;
        insertchar(NUL, INSCHAR_FORMAT
            + (do_comments ? INSCHAR_DO_COM : 0)
            + (do_comments && do_comments_list
               ? INSCHAR_COM_LIST : 0)
            + (avoid_fex ? INSCHAR_NO_FEX : 0), second_indent);
        State = old_State;
        p_smd = smd_save;
        second_indent = -1;
        /* at end of par.: need to set indent of next par. */
        need_set_indent = is_end_par;
        if (is_end_par) {
          /* When called with a negative line count, break at the
           * end of the paragraph. */
          if (line_count < 0)
            break;
          first_par_line = true;
        }
        force_format = false;
      }

      /*
       * When still in same paragraph, join the lines together.  But
       * first delete the leader from the second line.
       */
      if (!is_end_par) {
        advance = false;
        curwin->w_cursor.lnum++;
        curwin->w_cursor.col = 0;
        if (line_count < 0 && u_save_cursor() == FAIL)
          break;
        if (next_leader_len > 0) {
          (void)del_bytes(next_leader_len, false, false);
          mark_col_adjust(curwin->w_cursor.lnum, (colnr_T)0, 0L,
                          (long)-next_leader_len, 0);
        } else if (second_indent > 0) {   // the "leader" for FO_Q_SECOND
          int indent = (int)getwhitecols_curline();

          if (indent > 0) {
            (void)del_bytes(indent, false, false);
            mark_col_adjust(curwin->w_cursor.lnum,
                            (colnr_T)0, 0L, (long)-indent, 0);
          }
        }
        curwin->w_cursor.lnum--;
        if (do_join(2, TRUE, FALSE, FALSE, false) == FAIL) {
          beep_flush();
          break;
        }
        first_par_line = false;
        // If the line is getting long, format it next time
        if (STRLEN(get_cursor_line_ptr()) > (size_t)max_len) {
          force_format = true;
        } else {
          force_format = false;
        }
      }
    }
    line_breakcheck();
  }
}

/*
 * Return TRUE if line "lnum" ends in a white character.
 */
static int ends_in_white(linenr_T lnum)
{
  char_u      *s = ml_get(lnum);
  size_t l;

  if (*s == NUL)
    return FALSE;
  l = STRLEN(s) - 1;
  return ascii_iswhite(s[l]);
}

/*
 * Blank lines, and lines containing only the comment leader, are left
 * untouched by the formatting.  The function returns TRUE in this
 * case.  It also returns TRUE when a line starts with the end of a comment
 * ('e' in comment flags), so that this line is skipped, and not joined to the
 * previous line.  A new paragraph starts after a blank line, or when the
 * comment leader changes -- webb.
 */
static int fmt_check_par(linenr_T lnum, int *leader_len, char_u **leader_flags, int do_comments)
{
  char_u      *flags = NULL;        /* init for GCC */
  char_u      *ptr;

  ptr = ml_get(lnum);
  if (do_comments)
    *leader_len = get_leader_len(ptr, leader_flags, FALSE, TRUE);
  else
    *leader_len = 0;

  if (*leader_len > 0) {
    /*
     * Search for 'e' flag in comment leader flags.
     */
    flags = *leader_flags;
    while (*flags && *flags != ':' && *flags != COM_END)
      ++flags;
  }

  return *skipwhite(ptr + *leader_len) == NUL
         || (*leader_len > 0 && *flags == COM_END)
         || startPS(lnum, NUL, FALSE);
}

/*
 * Return TRUE when a paragraph starts in line "lnum".  Return FALSE when the
 * previous line is in the same paragraph.  Used for auto-formatting.
 */
int paragraph_start(linenr_T lnum)
{
  char_u *p;
  int leader_len = 0;                // leader len of current line
  char_u *leader_flags = NULL;       // flags for leader of current line
  int next_leader_len = 0;           // leader len of next line
  char_u *next_leader_flags = NULL;  // flags for leader of next line

  if (lnum <= 1)
    return TRUE;                /* start of the file */

  p = ml_get(lnum - 1);
  if (*p == NUL)
    return TRUE;                /* after empty line */

  const bool do_comments = has_format_option(FO_Q_COMS);  // format comments
  if (fmt_check_par(lnum - 1, &leader_len, &leader_flags, do_comments)) {
    return true;  // after non-paragraph line
  }

  if (fmt_check_par(lnum, &next_leader_len, &next_leader_flags, do_comments)) {
    return true;  // "lnum" is not a paragraph line
  }

  if (has_format_option(FO_WHITE_PAR) && !ends_in_white(lnum - 1))
    return TRUE;                /* missing trailing space in previous line. */

  if (has_format_option(FO_Q_NUMBER) && (get_number_indent(lnum) > 0))
    return TRUE;                /* numbered item starts in "lnum". */

  if (!same_leader(lnum - 1, leader_len, leader_flags,
          next_leader_len, next_leader_flags))
    return TRUE;                /* change of comment leader. */

  return FALSE;
}

/*
 * prepare a few things for block mode yank/delete/tilde
 *
 * for delete:
 * - textlen includes the first/last char to be (partly) deleted
 * - start/endspaces is the number of columns that are taken by the
 *   first/last deleted char minus the number of columns that have to be
 *   deleted.
 * for yank and tilde:
 * - textlen includes the first/last char to be wholly yanked
 * - start/endspaces is the number of columns of the first/last yanked char
 *   that are to be yanked.
 */
static void block_prep(oparg_T *oap, struct block_def *bdp, linenr_T lnum,
                       bool is_del)
{
  int incr = 0;
  char_u      *pend;
  char_u      *pstart;
  char_u      *line;
  char_u      *prev_pstart;
  char_u      *prev_pend;
  const int lbr_saved = curwin->w_p_lbr;

  // Avoid a problem with unwanted linebreaks in block mode.
  curwin->w_p_lbr = false;
  bdp->startspaces = 0;
  bdp->endspaces = 0;
  bdp->textlen = 0;
  bdp->start_vcol = 0;
  bdp->end_vcol = 0;
  bdp->is_short = false;
  bdp->is_oneChar = false;
  bdp->pre_whitesp = 0;
  bdp->pre_whitesp_c = 0;
  bdp->end_char_vcols = 0;
  bdp->start_char_vcols = 0;

  line = ml_get(lnum);
  pstart = line;
  prev_pstart = line;
  while (bdp->start_vcol < oap->start_vcol && *pstart) {
    /* Count a tab for what it's worth (if list mode not on) */
    incr = lbr_chartabsize(line, pstart, (colnr_T)bdp->start_vcol);
    bdp->start_vcol += incr;
    if (ascii_iswhite(*pstart)) {
      bdp->pre_whitesp += incr;
      bdp->pre_whitesp_c++;
    } else {
      bdp->pre_whitesp = 0;
      bdp->pre_whitesp_c = 0;
    }
    prev_pstart = pstart;
    MB_PTR_ADV(pstart);
  }
  bdp->start_char_vcols = incr;
  if (bdp->start_vcol < oap->start_vcol) {      /* line too short */
    bdp->end_vcol = bdp->start_vcol;
    bdp->is_short = true;
    if (!is_del || oap->op_type == OP_APPEND) {
      bdp->endspaces = oap->end_vcol - oap->start_vcol + 1;
    }
  } else {
    /* notice: this converts partly selected Multibyte characters to
     * spaces, too. */
    bdp->startspaces = bdp->start_vcol - oap->start_vcol;
    if (is_del && bdp->startspaces)
      bdp->startspaces = bdp->start_char_vcols - bdp->startspaces;
    pend = pstart;
    bdp->end_vcol = bdp->start_vcol;
    if (bdp->end_vcol > oap->end_vcol) {  // it's all in one character
      bdp->is_oneChar = true;
      if (oap->op_type == OP_INSERT) {
        bdp->endspaces = bdp->start_char_vcols - bdp->startspaces;
      } else if (oap->op_type == OP_APPEND) {
        bdp->startspaces += oap->end_vcol - oap->start_vcol + 1;
        bdp->endspaces = bdp->start_char_vcols - bdp->startspaces;
      } else {
        bdp->startspaces = oap->end_vcol - oap->start_vcol + 1;
        if (is_del && oap->op_type != OP_LSHIFT) {
          /* just putting the sum of those two into
           * bdp->startspaces doesn't work for Visual replace,
           * so we have to split the tab in two */
          bdp->startspaces = bdp->start_char_vcols
                             - (bdp->start_vcol - oap->start_vcol);
          bdp->endspaces = bdp->end_vcol - oap->end_vcol - 1;
        }
      }
    } else {
      prev_pend = pend;
      while (bdp->end_vcol <= oap->end_vcol && *pend != NUL) {
        /* Count a tab for what it's worth (if list mode not on) */
        prev_pend = pend;
        incr = lbr_chartabsize_adv(line, &pend, (colnr_T)bdp->end_vcol);
        bdp->end_vcol += incr;
      }
      if (bdp->end_vcol <= oap->end_vcol
          && (!is_del
              || oap->op_type == OP_APPEND
              || oap->op_type == OP_REPLACE)) {  // line too short
        bdp->is_short = true;
        // Alternative: include spaces to fill up the block.
        // Disadvantage: can lead to trailing spaces when the line is
        // short where the text is put
        // if (!is_del || oap->op_type == OP_APPEND)
        if (oap->op_type == OP_APPEND || virtual_op) {
          bdp->endspaces = oap->end_vcol - bdp->end_vcol
                           + oap->inclusive;
        }
      } else if (bdp->end_vcol > oap->end_vcol) {
        bdp->endspaces = bdp->end_vcol - oap->end_vcol - 1;
        if (!is_del && bdp->endspaces) {
          bdp->endspaces = incr - bdp->endspaces;
          if (pend != pstart)
            pend = prev_pend;
        }
      }
    }
    bdp->end_char_vcols = incr;
    if (is_del && bdp->startspaces)
      pstart = prev_pstart;
    bdp->textlen = (int)(pend - pstart);
  }
  bdp->textcol = (colnr_T) (pstart - line);
  bdp->textstart = pstart;
  curwin->w_p_lbr = lbr_saved;
}

/// Handle the add/subtract operator.
///
/// @param[in]  oap      Arguments of operator.
/// @param[in]  Prenum1  Amount of addition or subtraction.
/// @param[in]  g_cmd    Prefixed with `g`.
void op_addsub(oparg_T *oap, linenr_T Prenum1, bool g_cmd)
{
  pos_T pos;
  struct block_def bd;
  ssize_t change_cnt = 0;
  linenr_T amount = Prenum1;

  if (!VIsual_active) {
    pos = curwin->w_cursor;
    if (u_save_cursor() == FAIL) {
      return;
    }
    change_cnt = do_addsub(oap->op_type, &pos, 0, amount);
    if (change_cnt) {
      changed_lines(pos.lnum, 0, pos.lnum + 1, 0L, true);
    }
  } else {
    int one_change;
    int length;
    pos_T startpos;

    if (u_save((linenr_T)(oap->start.lnum - 1),
               (linenr_T)(oap->end.lnum + 1)) == FAIL) {
      return;
    }

    pos = oap->start;
    for (; pos.lnum <= oap->end.lnum; pos.lnum++) {
      if (oap->motion_type == kMTBlockWise) {
        // Visual block mode
        block_prep(oap, &bd, pos.lnum, false);
        pos.col = bd.textcol;
        length = bd.textlen;
      } else if (oap->motion_type == kMTLineWise) {
        curwin->w_cursor.col = 0;
        pos.col = 0;
        length = (colnr_T)STRLEN(ml_get(pos.lnum));
      } else {
        // oap->motion_type == kMTCharWise
        if (pos.lnum == oap->start.lnum && !oap->inclusive) {
          dec(&(oap->end));
        }
        length = (colnr_T)STRLEN(ml_get(pos.lnum));
        pos.col = 0;
        if (pos.lnum == oap->start.lnum) {
          pos.col += oap->start.col;
          length -= oap->start.col;
        }
        if (pos.lnum == oap->end.lnum) {
          length = (int)STRLEN(ml_get(oap->end.lnum));
          if (oap->end.col >= length) {
            oap->end.col = length - 1;
          }
          length = oap->end.col - pos.col + 1;
        }
      }
      one_change = do_addsub(oap->op_type, &pos, length, amount);
      if (one_change) {
        // Remember the start position of the first change.
        if (change_cnt == 0) {
          startpos = curbuf->b_op_start;
        }
        change_cnt++;
      }

      if (g_cmd && one_change) {
        amount += Prenum1;
      }
    }
    if (change_cnt) {
      changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
    }

    if (!change_cnt && oap->is_VIsual) {
      // No change: need to remove the Visual selection
      redraw_curbuf_later(INVERTED);
    }

    // Set '[ mark if something changed. Keep the last end
    // position from do_addsub().
    if (change_cnt > 0) {
      curbuf->b_op_start = startpos;
    }

    if (change_cnt > p_report) {
      if (change_cnt == 1) {
        MSG(_("1 line changed"));
      } else {
        smsg((char *)_("%" PRId64 " lines changed"), (int64_t)change_cnt);
      }
    }
  }
}

/// Add or subtract from a number in a line.
///
/// @param op_type OP_NR_ADD or OP_NR_SUB.
/// @param pos     Cursor position.
/// @param length  Target number length.
/// @param Prenum1 Amount of addition or subtraction.
///
/// @return true if some character was changed.
int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
{
  int col;
  char_u      *buf1 = NULL;
  char_u buf2[NUMBUFLEN];
  int pre;  // 'X' or 'x': hex; '0': octal; 'B' or 'b': bin
  static bool hexupper = false;  // 0xABC
  uvarnumber_T n;
  uvarnumber_T oldn;
  char_u      *ptr;
  int c;
  int todel;
  int firstdigit;
  bool negative = false;
  bool was_positive = true;
  bool visual = VIsual_active;
  bool did_change = false;
  pos_T save_cursor = curwin->w_cursor;
  int maxlen = 0;
  pos_T startpos;
  pos_T endpos;
  colnr_T save_coladd = 0;

  const bool do_hex = vim_strchr(curbuf->b_p_nf, 'x') != NULL;    // "heX"
  const bool do_oct = vim_strchr(curbuf->b_p_nf, 'o') != NULL;    // "Octal"
  const bool do_bin = vim_strchr(curbuf->b_p_nf, 'b') != NULL;    // "Bin"
  const bool do_alpha = vim_strchr(curbuf->b_p_nf, 'p') != NULL;  // "alPha"
  // "Unsigned"
  const bool do_unsigned = vim_strchr(curbuf->b_p_nf, 'u') != NULL;

  if (virtual_active()) {
    save_coladd = pos->coladd;
    pos->coladd = 0;
  }

  curwin->w_cursor = *pos;
  ptr = ml_get(pos->lnum);
  col = pos->col;

  if (*ptr == NUL || col + !!save_coladd >= (int)STRLEN(ptr)) {
    goto theend;
  }

  // First check if we are on a hexadecimal number, after the "0x".
  if (!VIsual_active) {
    if (do_bin) {
      while (col > 0 && ascii_isbdigit(ptr[col])) {
        col--;
        col -= utf_head_off(ptr, ptr + col);
      }
    }

    if (do_hex) {
      while (col > 0 && ascii_isxdigit(ptr[col])) {
        col--;
        col -= utf_head_off(ptr, ptr + col);
      }
    }
    if (do_bin
        && do_hex
        && !((col > 0
              && (ptr[col] == 'X' || ptr[col] == 'x')
              && ptr[col - 1] == '0'
              && !utf_head_off(ptr, ptr + col - 1)
              && ascii_isxdigit(ptr[col + 1])))) {
        // In case of binary/hexadecimal pattern overlap match, rescan

        col = curwin->w_cursor.col;

        while (col > 0 && ascii_isdigit(ptr[col])) {
          col--;
          col -= utf_head_off(ptr, ptr + col);
        }
    }

    if ((do_hex
         && col > 0
         && (ptr[col] == 'X' || ptr[col] == 'x')
         && ptr[col - 1] == '0'
         && !utf_head_off(ptr, ptr + col - 1)
         && ascii_isxdigit(ptr[col + 1]))
        || (do_bin
            && col > 0
            && (ptr[col] == 'B' || ptr[col] == 'b')
            && ptr[col - 1] == '0'
            && !utf_head_off(ptr, ptr + col - 1)
            && ascii_isbdigit(ptr[col + 1]))) {
      // Found hexadecimal or binary number, move to its start.
        col--;
        col -= utf_head_off(ptr, ptr + col);
    } else {
      // Search forward and then backward to find the start of number.
      col = pos->col;

      while (ptr[col] != NUL
             && !ascii_isdigit(ptr[col])
             && !(do_alpha && ASCII_ISALPHA(ptr[col]))) {
        col++;
      }

      while (col > 0
             && ascii_isdigit(ptr[col - 1])
             && !(do_alpha && ASCII_ISALPHA(ptr[col]))) {
        col--;
      }
    }
  }

  if (visual) {
    while (ptr[col] != NUL && length > 0 && !ascii_isdigit(ptr[col])
           && !(do_alpha && ASCII_ISALPHA(ptr[col]))) {
      int mb_len = utfc_ptr2len(ptr + col);

      col += mb_len;
      length -= mb_len;
    }

    if (length == 0) {
      goto theend;
    }

    if (col > pos->col && ptr[col - 1] == '-'
        && !utf_head_off(ptr, ptr + col - 1)
        && !do_unsigned) {
      negative = true;
      was_positive = false;
    }
  }

  // If a number was found, and saving for undo works, replace the number.
  firstdigit = ptr[col];
  if (!ascii_isdigit(firstdigit) && !(do_alpha && ASCII_ISALPHA(firstdigit))) {
    beep_flush();
    goto theend;
  }

  if (do_alpha && ASCII_ISALPHA(firstdigit)) {
    // decrement or increment alphabetic character
    if (op_type == OP_NR_SUB) {
      if (CharOrd(firstdigit) < Prenum1) {
        if (isupper(firstdigit)) {
          firstdigit = 'A';
        } else {
          firstdigit = 'a';
        }
      } else {
        firstdigit -= (int)Prenum1;
      }
    } else {
      if (26 - CharOrd(firstdigit) - 1 < Prenum1) {
        if (isupper(firstdigit)) {
          firstdigit = 'Z';
        } else {
          firstdigit = 'z';
        }
      } else {
        firstdigit += (int)Prenum1;
      }
    }
    curwin->w_cursor.col = col;
    startpos = curwin->w_cursor;
    did_change = true;
    (void)del_char(false);
    ins_char(firstdigit);
    endpos = curwin->w_cursor;
    curwin->w_cursor.col = col;
  } else {
    if (col > 0 && ptr[col - 1] == '-'
        && !utf_head_off(ptr, ptr + col - 1)
        && !visual
        && !do_unsigned) {
      // negative number
      col--;
      negative = true;
    }

    // get the number value (unsigned)
    if (visual && VIsual_mode != 'V') {
      maxlen = (curbuf->b_visual.vi_curswant == MAXCOL
                ? (int)STRLEN(ptr) - col
                : length);
    }

    vim_str2nr(ptr + col, &pre, &length,
               0 + (do_bin ? STR2NR_BIN : 0)
               + (do_oct ? STR2NR_OCT : 0)
               + (do_hex ? STR2NR_HEX : 0),
               NULL, &n, maxlen);

    // ignore leading '-' for hex, octal and bin numbers
    if (pre && negative) {
      col++;
      length--;
      negative = false;
    }

    // add or subtract
    bool subtract = false;
    if (op_type == OP_NR_SUB) {
      subtract ^= true;
    }
    if (negative) {
      subtract ^= true;
    }

    oldn = n;

    n = subtract ? n - (uvarnumber_T)Prenum1
                 : n + (uvarnumber_T)Prenum1;

    // handle wraparound for decimal numbers
    if (!pre) {
      if (subtract) {
        if (n > oldn) {
          n = 1 + (n ^ (uvarnumber_T)-1);
          negative ^= true;
        }
      } else {
        // add
        if (n < oldn) {
          n = (n ^ (uvarnumber_T)-1);
          negative ^= true;
        }
      }
      if (n == 0) {
        negative = false;
      }
    }

    if (do_unsigned && negative) {
      if (subtract) {
        // sticking at zero.
        n = (uvarnumber_T)0;
      } else {
        // sticking at 2^64 - 1.
        n = (uvarnumber_T)(-1);
      }
      negative = false;
    }

    if (visual && !was_positive && !negative && col > 0) {
      // need to remove the '-'
      col--;
      length++;
    }

    // Delete the old number.
    curwin->w_cursor.col = col;
    startpos = curwin->w_cursor;
    did_change = true;
    todel = length;
    c = gchar_cursor();

    // Don't include the '-' in the length, only the length of the part
    // after it is kept the same.
    if (c == '-') {
      length--;
    }
    while (todel-- > 0) {
      if (c < 0x100 && isalpha(c)) {
        if (isupper(c)) {
          hexupper = true;
        } else {
          hexupper = false;
        }
      }
      // del_char() will mark line needing displaying
      (void)del_char(false);
      c = gchar_cursor();
    }

    // Prepare the leading characters in buf1[].
    // When there are many leading zeros it could be very long.
    // Allocate a bit too much.
    buf1 = xmalloc((size_t)length + NUMBUFLEN);
    ptr = buf1;
    if (negative && (!visual || was_positive)) {
      *ptr++ = '-';
    }
    if (pre) {
      *ptr++ = '0';
      length--;
    }
    if (pre == 'b' || pre == 'B' || pre == 'x' || pre == 'X') {
      *ptr++ = (char_u)pre;
      length--;
    }

    // Put the number characters in buf2[].
    if (pre == 'b' || pre == 'B') {
      size_t bits = 0;
      size_t i = 0;

      // leading zeros
      for (bits = 8 * sizeof(n); bits > 0; bits--) {
          if ((n >> (bits - 1)) & 0x1) {
            break;
          }
      }

      while (bits > 0) {
          buf2[i++] = ((n >> --bits) & 0x1) ? '1' : '0';
      }

      buf2[i] = '\0';

    } else if (pre == 0) {
      vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIu64, (uint64_t)n);
    } else if (pre == '0') {
      vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIo64, (uint64_t)n);
    } else if (hexupper) {
      vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIX64, (uint64_t)n);
    } else {
      vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIx64, (uint64_t)n);
    }
    length -= (int)STRLEN(buf2);

    // Adjust number of zeros to the new number of digits, so the
    // total length of the number remains the same.
    // Don't do this when
    // the result may look like an octal number.
    if (firstdigit == '0' && !(do_oct && pre == 0)) {
      while (length-- > 0) {
        *ptr++ = '0';
      }
    }
    *ptr = NUL;
    STRCAT(buf1, buf2);
    ins_str(buf1);              // insert the new number
    endpos = curwin->w_cursor;
    if (curwin->w_cursor.col) {
      curwin->w_cursor.col--;
    }
  }

  // set the '[ and '] marks
  curbuf->b_op_start = startpos;
  curbuf->b_op_end = endpos;
  if (curbuf->b_op_end.col > 0) {
    curbuf->b_op_end.col--;
  }

theend:
  xfree(buf1);
  if (visual) {
    curwin->w_cursor = save_cursor;
  } else if (did_change) {
    curwin->w_set_curswant = true;
  } else if (virtual_active()) {
    curwin->w_cursor.coladd = save_coladd;
  }

  return did_change;
}

/*
 * Return the type of a register.
 * Used for getregtype()
 * Returns kMTUnknown for error.
 */
MotionType get_reg_type(int regname, colnr_T *reg_width)
{
  switch (regname) {
    case '%':     // file name
    case '#':     // alternate file name
    case '=':     // expression
    case ':':     // last command line
    case '/':     // last search-pattern
    case '.':     // last inserted text
    case Ctrl_F:  // Filename under cursor
    case Ctrl_P:  // Path under cursor, expand via "path"
    case Ctrl_W:  // word under cursor
    case Ctrl_A:  // WORD (mnemonic All) under cursor
    case '_':     // black hole: always empty
      return kMTCharWise;
  }

  if (regname != NUL && !valid_yank_reg(regname, false)) {
    return kMTUnknown;
  }

  yankreg_T *reg = get_yank_register(regname, YREG_PASTE);

  if (reg->y_array != NULL) {
    if (reg_width != NULL && reg->y_type == kMTBlockWise) {
      *reg_width = reg->y_width;
    }
    return reg->y_type;
  }
  return kMTUnknown;
}

/// Format the register type as a string.
///
/// @param reg_type The register type.
/// @param reg_width The width, only used if "reg_type" is kMTBlockWise.
/// @param[out] buf Buffer to store formatted string. The allocated size should
///                 be at least NUMBUFLEN+2 to always fit the value.
/// @param buf_len The allocated size of the buffer.
void format_reg_type(MotionType reg_type, colnr_T reg_width,
                     char *buf, size_t buf_len)
  FUNC_ATTR_NONNULL_ALL
{
  assert(buf_len > 1);
  switch (reg_type) {
    case kMTLineWise:
      buf[0] = 'V';
      buf[1] = NUL;
      break;
    case kMTCharWise:
      buf[0] = 'v';
      buf[1] = NUL;
      break;
    case kMTBlockWise:
      snprintf(buf, buf_len, CTRL_V_STR "%" PRIdCOLNR, reg_width + 1);
      break;
    case kMTUnknown:
      buf[0] = NUL;
      break;
  }
}


/// When `flags` has `kGRegList` return a list with text `s`.
/// Otherwise just return `s`.
///
/// Returns a void * for use in get_reg_contents().
static void *get_reg_wrap_one_line(char_u *s, int flags)
{
  if (!(flags & kGRegList)) {
    return s;
  }
  list_T *const list = tv_list_alloc(1);
  tv_list_append_allocated_string(list, (char *)s);
  return list;
}

/// Gets the contents of a register.
/// @remark Used for `@r` in expressions and for `getreg()`.
///
/// @param regname  The register.
/// @param flags    see @ref GRegFlags
///
/// @returns The contents of the register as an allocated string.
/// @returns A linked list when `flags` contains @ref kGRegList.
/// @returns NULL for error.
void *get_reg_contents(int regname, int flags)
{
  // Don't allow using an expression register inside an expression.
  if (regname == '=') {
    if (flags & kGRegNoExpr) {
      return NULL;
    }
    if (flags & kGRegExprSrc) {
      return get_reg_wrap_one_line(get_expr_line_src(), flags);
    }
    return get_reg_wrap_one_line(get_expr_line(), flags);
  }

  if (regname == '@')       /* "@@" is used for unnamed register */
    regname = '"';

  /* check for valid regname */
  if (regname != NUL && !valid_yank_reg(regname, false))
    return NULL;

  char_u *retval;
  bool allocated;
  if (get_spec_reg(regname, &retval, &allocated, false)) {
    if (retval == NULL) {
      return NULL;
    }
    if (allocated) {
      return get_reg_wrap_one_line(retval, flags);
    }
    return get_reg_wrap_one_line(vim_strsave(retval), flags);
  }

  yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
  if (reg->y_array == NULL)
    return NULL;

  if (flags & kGRegList) {
    list_T *const list = tv_list_alloc((ptrdiff_t)reg->y_size);
    for (size_t i = 0; i < reg->y_size; i++) {
      tv_list_append_string(list, (const char *)reg->y_array[i], -1);
    }

    return list;
  }

  /*
   * Compute length of resulting string.
   */
  size_t len = 0;
  for (size_t i = 0; i < reg->y_size; i++) {
    len += STRLEN(reg->y_array[i]);
    /*
     * Insert a newline between lines and after last line if
     * y_type is kMTLineWise.
     */
    if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
      len++;
    }
  }

  retval = xmalloc(len + 1);

  /*
   * Copy the lines of the yank register into the string.
   */
  len = 0;
  for (size_t i = 0; i < reg->y_size; i++) {
    STRCPY(retval + len, reg->y_array[i]);
    len += STRLEN(retval + len);

    /*
     * Insert a NL between lines and after the last line if y_type is
     * kMTLineWise.
     */
    if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
      retval[len++] = '\n';
    }
  }
  retval[len] = NUL;

  return retval;
}

static yankreg_T *init_write_reg(int name, yankreg_T **old_y_previous, bool must_append)
{
  if (!valid_yank_reg(name, true)) {  // check for valid reg name
    emsg_invreg(name);
    return NULL;
  }

  // Don't want to change the current (unnamed) register.
  *old_y_previous = y_previous;

  yankreg_T *reg = get_yank_register(name, YREG_YANK);
  if (!is_append_register(name) && !must_append) {
      free_register(reg);
  }
  return reg;
}

static void finish_write_reg(int name, yankreg_T *reg, yankreg_T *old_y_previous)
{
  // Send text of clipboard register to the clipboard.
  set_clipboard(name, reg);

  // ':let @" = "val"' should change the meaning of the "" register
  if (name != '"') {
    y_previous = old_y_previous;
  }
}

/// write_reg_contents - store `str` in register `name`
///
/// @see write_reg_contents_ex
void write_reg_contents(int name, const char_u *str, ssize_t len,
                        int must_append)
{
  write_reg_contents_ex(name, str, len, must_append, kMTUnknown, 0L);
}

void write_reg_contents_lst(int name, char_u **strings,
                            bool must_append, MotionType yank_type,
                            colnr_T block_len)
{
  if (name == '/' || name == '=') {
    char_u  *s = strings[0];
    if (strings[0] == NULL) {
      s = (char_u *)"";
    } else if (strings[1] != NULL) {
      EMSG(_("E883: search pattern and expression register may not "
             "contain two or more lines"));
      return;
    }
    write_reg_contents_ex(name, s, -1, must_append, yank_type, block_len);
    return;
  }

  // black hole: nothing to do
  if (name == '_') {
    return;
  }

  yankreg_T  *old_y_previous, *reg;
  if (!(reg = init_write_reg(name, &old_y_previous, must_append))) {
    return;
  }

  str_to_reg(reg, yank_type, (char_u *)strings, STRLEN((char_u *)strings),
             block_len, true);
  finish_write_reg(name, reg, old_y_previous);
}

/// write_reg_contents_ex - store `str` in register `name`
///
/// If `str` ends in '\n' or '\r', use linewise, otherwise use charwise.
///
/// @warning when `name` is '/', `len` and `must_append` are ignored. This
///          means that `str` MUST be NUL-terminated.
///
/// @param name The name of the register
/// @param str The contents to write
/// @param len If >= 0, write `len` bytes of `str`. Otherwise, write
///               `strlen(str)` bytes. If `len` is larger than the
///               allocated size of `src`, the behaviour is undefined.
/// @param must_append If true, append the contents of `str` to the current
///                    contents of the register. Note that regardless of
///                    `must_append`, this function will append when `name`
///                    is an uppercase letter.
/// @param yank_type The motion type (kMTUnknown to auto detect)
/// @param block_len width of visual block
void write_reg_contents_ex(int name,
                           const char_u *str,
                           ssize_t len,
                           bool must_append,
                           MotionType yank_type,
                           colnr_T block_len)
{
  if (len < 0) {
    len = (ssize_t) STRLEN(str);
  }

  /* Special case: '/' search pattern */
  if (name == '/') {
    set_last_search_pat(str, RE_SEARCH, TRUE, TRUE);
    return;
  }

  if (name == '#') {
    buf_T *buf;

    if (ascii_isdigit(*str)) {
      int num = atoi((char *)str);

      buf = buflist_findnr(num);
      if (buf == NULL) {
        EMSGN(_(e_nobufnr), (long)num);
      }
    } else {
      buf = buflist_findnr(buflist_findpat(str, str + STRLEN(str),
                                           true, false, false));
    }
    if (buf == NULL) {
      return;
    }
    curwin->w_alt_fnum = buf->b_fnum;
    return;
  }

  if (name == '=') {
    size_t offset = 0;
    size_t totlen = (size_t) len;

    if (must_append && expr_line) {
      // append has been specified and expr_line already exists, so we'll
      // append the new string to expr_line.
      size_t exprlen = STRLEN(expr_line);

      totlen += exprlen;
      offset = exprlen;
    }

    // modify the global expr_line, extend/shrink it if necessary (realloc).
    // Copy the input string into the adjusted memory at the specified
    // offset.
    expr_line = xrealloc(expr_line, totlen + 1);
    memcpy(expr_line + offset, str, (size_t)len);
    expr_line[totlen] = NUL;

    return;
  }

  if (name == '_') {        // black hole: nothing to do
    return;
  }

  yankreg_T  *old_y_previous, *reg;
  if (!(reg = init_write_reg(name, &old_y_previous, must_append))) {
    return;
  }
  str_to_reg(reg, yank_type, str, (size_t)len, block_len, false);
  finish_write_reg(name, reg, old_y_previous);
}

/// str_to_reg - Put a string into a register.
///
/// When the register is not empty, the string is appended.
///
/// @param y_ptr pointer to yank register
/// @param yank_type The motion type (kMTUnknown to auto detect)
/// @param str string or list of strings to put in register
/// @param len length of the string (Ignored when str_list=true.)
/// @param blocklen width of visual block, or -1 for "I don't know."
/// @param str_list True if str is `char_u **`.
static void str_to_reg(yankreg_T *y_ptr, MotionType yank_type,
                       const char_u *str, size_t len, colnr_T blocklen,
                       bool str_list)
  FUNC_ATTR_NONNULL_ALL
{
  if (y_ptr->y_array == NULL) {  // NULL means empty register
    y_ptr->y_size = 0;
  }

  if (yank_type == kMTUnknown) {
    yank_type = ((str_list
                  || (len > 0 && (str[len - 1] == NL || str[len - 1] == CAR)))
                 ? kMTLineWise : kMTCharWise);
  }

  size_t newlines = 0;
  bool extraline = false;  // extra line at the end
  bool append = false;     // append to last line in register

  // Count the number of lines within the string
  if (str_list) {
    for (char_u **ss = (char_u **) str; *ss != NULL; ++ss) {
      newlines++;
    }
  } else {
    newlines = memcnt(str, '\n', len);
    if (yank_type == kMTCharWise || len == 0 || str[len - 1] != '\n') {
      extraline = 1;
      ++newlines;         // count extra newline at the end
    }
    if (y_ptr->y_size > 0 && y_ptr->y_type == kMTCharWise) {
      append = true;
      --newlines;         // uncount newline when appending first line
    }
  }


  // Grow the register array to hold the pointers to the new lines.
  char_u **pp = xrealloc(y_ptr->y_array,
                         (y_ptr->y_size + newlines) * sizeof(char_u *));
  y_ptr->y_array = pp;

  size_t lnum = y_ptr->y_size;  // The current line number.

  // If called with `blocklen < 0`, we have to update the yank reg's width.
  size_t maxlen = 0;

  // Find the end of each line and save it into the array.
  if (str_list) {
    for (char_u **ss = (char_u **) str; *ss != NULL; ++ss, ++lnum) {
      size_t ss_len = STRLEN(*ss);
      pp[lnum] = xmemdupz(*ss, ss_len);
      if (ss_len > maxlen) {
        maxlen = ss_len;
      }
    }
  } else {
    size_t line_len;
    for (const char_u *start = str, *end = str + len;
         start < end + extraline;
         start += line_len + 1, lnum++) {
      assert(end - start >= 0);
      line_len = (size_t)((char_u *)xmemscan(start, '\n',
                                             (size_t)(end - start)) - start);
      if (line_len > maxlen) {
        maxlen = line_len;
      }

      // When appending, copy the previous line and free it after.
      size_t extra = append ? STRLEN(pp[--lnum]) : 0;
      char_u *s = xmallocz(line_len + extra);
      memcpy(s, pp[lnum], extra);
      memcpy(s + extra, start, line_len);
      size_t s_len = extra + line_len;

      if (append) {
        xfree(pp[lnum]);
        append = false;  // only first line is appended
      }
      pp[lnum] = s;

      // Convert NULs to '\n' to prevent truncation.
      memchrsub(pp[lnum], NUL, '\n', s_len);
    }
  }
  y_ptr->y_type = yank_type;
  y_ptr->y_size = lnum;
  set_yreg_additional_data(y_ptr, NULL);
  y_ptr->timestamp = os_time();
  if (yank_type == kMTBlockWise) {
    y_ptr->y_width = (blocklen == -1 ? (colnr_T) maxlen - 1 : blocklen);
  } else {
    y_ptr->y_width = 0;
  }
}

void clear_oparg(oparg_T *oap)
{
  memset(oap, 0, sizeof(oparg_T));
}


/*
 *  Count the number of bytes, characters and "words" in a line.
 *
 *  "Words" are counted by looking for boundaries between non-space and
 *  space characters.  (it seems to produce results that match 'wc'.)
 *
 *  Return value is byte count; word count for the line is added to "*wc".
 *  Char count is added to "*cc".
 *
 *  The function will only examine the first "limit" characters in the
 *  line, stopping if it encounters an end-of-line (NUL byte).  In that
 *  case, eol_size will be added to the character count to account for
 *  the size of the EOL character.
 */
static varnumber_T line_count_info(char_u *line, varnumber_T *wc,
                                   varnumber_T *cc, varnumber_T limit,
                                   int eol_size)
{
  varnumber_T i;
  varnumber_T words = 0;
  varnumber_T chars = 0;
  int is_word = 0;

  for (i = 0; i < limit && line[i] != NUL; ) {
    if (is_word) {
      if (ascii_isspace(line[i])) {
        words++;
        is_word = 0;
      }
    } else if (!ascii_isspace(line[i]))
      is_word = 1;
    ++chars;
    i += (*mb_ptr2len)(line + i);
  }

  if (is_word)
    words++;
  *wc += words;

  /* Add eol_size if the end of line was reached before hitting limit. */
  if (i < limit && line[i] == NUL) {
    i += eol_size;
    chars += eol_size;
  }
  *cc += chars;
  return i;
}

/// Give some info about the position of the cursor (for "g CTRL-G").
/// In Visual mode, give some info about the selected region.  (In this case,
/// the *_count_cursor variables store running totals for the selection.)
/// When "dict" is not NULL store the info there instead of showing it.
void cursor_pos_info(dict_T *dict)
{
  char_u      *p;
  char_u buf1[50];
  char_u buf2[40];
  linenr_T lnum;
  varnumber_T byte_count = 0;
  varnumber_T bom_count = 0;
  varnumber_T byte_count_cursor = 0;
  varnumber_T char_count = 0;
  varnumber_T char_count_cursor = 0;
  varnumber_T word_count = 0;
  varnumber_T word_count_cursor = 0;
  int eol_size;
  varnumber_T last_check = 100000L;
  long line_count_selected = 0;
  pos_T min_pos, max_pos;
  oparg_T oparg;
  struct block_def bd;
  const int l_VIsual_active = VIsual_active;
  const int l_VIsual_mode = VIsual_mode;

  // Compute the length of the file in characters.
  if (curbuf->b_ml.ml_flags & ML_EMPTY) {
    if (dict == NULL) {
      MSG(_(no_lines_msg));
      return;
    }
  } else {
    if (get_fileformat(curbuf) == EOL_DOS)
      eol_size = 2;
    else
      eol_size = 1;

    if (l_VIsual_active) {
      if (lt(VIsual, curwin->w_cursor)) {
        min_pos = VIsual;
        max_pos = curwin->w_cursor;
      } else {
        min_pos = curwin->w_cursor;
        max_pos = VIsual;
      }
      if (*p_sel == 'e' && max_pos.col > 0)
        --max_pos.col;

      if (l_VIsual_mode == Ctrl_V) {
        char_u * saved_sbr = p_sbr;

        /* Make 'sbr' empty for a moment to get the correct size. */
        p_sbr = empty_option;
        oparg.is_VIsual = true;
        oparg.motion_type = kMTBlockWise;
        oparg.op_type = OP_NOP;
        getvcols(curwin, &min_pos, &max_pos,
            &oparg.start_vcol, &oparg.end_vcol);
        p_sbr = saved_sbr;
        if (curwin->w_curswant == MAXCOL)
          oparg.end_vcol = MAXCOL;
        /* Swap the start, end vcol if needed */
        if (oparg.end_vcol < oparg.start_vcol) {
          oparg.end_vcol += oparg.start_vcol;
          oparg.start_vcol = oparg.end_vcol - oparg.start_vcol;
          oparg.end_vcol -= oparg.start_vcol;
        }
      }
      line_count_selected = max_pos.lnum - min_pos.lnum + 1;
    }

    for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum) {
      /* Check for a CTRL-C every 100000 characters. */
      if (byte_count > last_check) {
        os_breakcheck();
        if (got_int)
          return;
        last_check = byte_count + 100000L;
      }

      /* Do extra processing for VIsual mode. */
      if (l_VIsual_active
          && lnum >= min_pos.lnum && lnum <= max_pos.lnum) {
        char_u      *s = NULL;
        long len = 0L;

        switch (l_VIsual_mode) {
        case Ctrl_V:
          virtual_op = virtual_active();
          block_prep(&oparg, &bd, lnum, false);
          virtual_op = kNone;
          s = bd.textstart;
          len = (long)bd.textlen;
          break;
        case 'V':
          s = ml_get(lnum);
          len = MAXCOL;
          break;
        case 'v':
        {
          colnr_T start_col = (lnum == min_pos.lnum)
                              ? min_pos.col : 0;
          colnr_T end_col = (lnum == max_pos.lnum)
                            ? max_pos.col - start_col + 1 : MAXCOL;

          s = ml_get(lnum) + start_col;
          len = end_col;
        }
        break;
        }
        if (s != NULL) {
          byte_count_cursor += line_count_info(s, &word_count_cursor,
              &char_count_cursor, len, eol_size);
          if (lnum == curbuf->b_ml.ml_line_count
              && !curbuf->b_p_eol
              && (curbuf->b_p_bin || !curbuf->b_p_fixeol)
              && (long)STRLEN(s) < len)
            byte_count_cursor -= eol_size;
        }
      } else {
        /* In non-visual mode, check for the line the cursor is on */
        if (lnum == curwin->w_cursor.lnum) {
          word_count_cursor += word_count;
          char_count_cursor += char_count;
          byte_count_cursor = byte_count
            + line_count_info(ml_get(lnum), &word_count_cursor,
                              &char_count_cursor,
                              (varnumber_T)curwin->w_cursor.col + 1,
                              eol_size);
        }
      }
      // Add to the running totals
      byte_count += line_count_info(ml_get(lnum), &word_count, &char_count,
                                    (varnumber_T)MAXCOL, eol_size);
    }

    // Correction for when last line doesn't have an EOL.
    if (!curbuf->b_p_eol && (curbuf->b_p_bin || !curbuf->b_p_fixeol)) {
      byte_count -= eol_size;
    }

    if (dict == NULL) {
      if (l_VIsual_active) {
        if (l_VIsual_mode == Ctrl_V && curwin->w_curswant < MAXCOL) {
          getvcols(curwin, &min_pos, &max_pos, &min_pos.col, &max_pos.col);
          int64_t cols;
          STRICT_SUB(oparg.end_vcol + 1, oparg.start_vcol, &cols, int64_t);
          vim_snprintf((char *)buf1, sizeof(buf1), _("%" PRId64 " Cols; "),
                       cols);
        } else {
          buf1[0] = NUL;
        }

        if (char_count_cursor == byte_count_cursor
            && char_count == byte_count) {
          vim_snprintf((char *)IObuff, IOSIZE,
                       _("Selected %s%" PRId64 " of %" PRId64 " Lines;"
                         " %" PRId64 " of %" PRId64 " Words;"
                         " %" PRId64 " of %" PRId64 " Bytes"),
                       buf1, (int64_t)line_count_selected,
                       (int64_t)curbuf->b_ml.ml_line_count,
                       (int64_t)word_count_cursor, (int64_t)word_count,
                       (int64_t)byte_count_cursor, (int64_t)byte_count);
        } else {
          vim_snprintf((char *)IObuff, IOSIZE,
                       _("Selected %s%" PRId64 " of %" PRId64 " Lines;"
                         " %" PRId64 " of %" PRId64 " Words;"
                         " %" PRId64 " of %" PRId64 " Chars;"
                         " %" PRId64 " of %" PRId64 " Bytes"),
                       buf1, (int64_t)line_count_selected,
                       (int64_t)curbuf->b_ml.ml_line_count,
                       (int64_t)word_count_cursor, (int64_t)word_count,
                       (int64_t)char_count_cursor, (int64_t)char_count,
                       (int64_t)byte_count_cursor, (int64_t)byte_count);
        }
      } else {
        p = get_cursor_line_ptr();
        validate_virtcol();
        col_print(buf1, sizeof(buf1), (int)curwin->w_cursor.col + 1,
                  (int)curwin->w_virtcol + 1);
        col_print(buf2, sizeof(buf2), (int)STRLEN(p), linetabsize(p));

        if (char_count_cursor == byte_count_cursor
            && char_count == byte_count) {
          vim_snprintf((char *)IObuff, IOSIZE,
                       _("Col %s of %s; Line %" PRId64 " of %" PRId64 ";"
                         " Word %" PRId64 " of %" PRId64 ";"
                         " Byte %" PRId64 " of %" PRId64 ""),
                       (char *)buf1, (char *)buf2,
                       (int64_t)curwin->w_cursor.lnum,
                       (int64_t)curbuf->b_ml.ml_line_count,
                       (int64_t)word_count_cursor, (int64_t)word_count,
                       (int64_t)byte_count_cursor, (int64_t)byte_count);
        } else {
          vim_snprintf((char *)IObuff, IOSIZE,
                       _("Col %s of %s; Line %" PRId64 " of %" PRId64 ";"
                         " Word %" PRId64 " of %" PRId64 ";"
                         " Char %" PRId64 " of %" PRId64 ";"
                         " Byte %" PRId64 " of %" PRId64 ""),
                       (char *)buf1, (char *)buf2,
                       (int64_t)curwin->w_cursor.lnum,
                       (int64_t)curbuf->b_ml.ml_line_count,
                       (int64_t)word_count_cursor, (int64_t)word_count,
                       (int64_t)char_count_cursor, (int64_t)char_count,
                       (int64_t)byte_count_cursor, (int64_t)byte_count);
        }
      }
    }

    bom_count = bomb_size();
    if (dict == NULL && bom_count > 0) {
      const size_t len = STRLEN(IObuff);
      vim_snprintf((char *)IObuff + len, IOSIZE - len,
                   _("(+%" PRId64 " for BOM)"), (int64_t)bom_count);
    }
    if (dict == NULL) {
      // Don't shorten this message, the user asked for it.
      p = p_shm;
      p_shm = (char_u *)"";
      msg(IObuff);
      p_shm = p;
    }
  }

  if (dict != NULL) {
    // Don't shorten this message, the user asked for it.
    tv_dict_add_nr(dict, S_LEN("words"), (varnumber_T)word_count);
    tv_dict_add_nr(dict, S_LEN("chars"), (varnumber_T)char_count);
    tv_dict_add_nr(dict, S_LEN("bytes"), (varnumber_T)(byte_count + bom_count));

    STATIC_ASSERT(sizeof("visual") == sizeof("cursor"),
                  "key_len argument in tv_dict_add_nr is wrong");
    tv_dict_add_nr(dict, l_VIsual_active ? "visual_bytes" : "cursor_bytes",
                   sizeof("visual_bytes") - 1, (varnumber_T)byte_count_cursor);
    tv_dict_add_nr(dict, l_VIsual_active ? "visual_chars" : "cursor_chars",
                   sizeof("visual_chars") - 1, (varnumber_T)char_count_cursor);
    tv_dict_add_nr(dict, l_VIsual_active ? "visual_words" : "cursor_words",
                   sizeof("visual_words") - 1, (varnumber_T)word_count_cursor);
  }
}

/// Check if the default register (used in an unnamed paste) should be a
/// clipboard register. This happens when `clipboard=unnamed[plus]` is set
/// and a provider is available.
///
/// @returns the name of of a clipboard register that should be used, or `NUL` if none.
int get_default_register_name(void)
{
  int name = NUL;
  adjust_clipboard_name(&name, true, false);
  return name;
}

/// Determine if register `*name` should be used as a clipboard.
/// In an unnamed operation, `*name` is `NUL` and will be adjusted to */+ if
/// `clipboard=unnamed[plus]` is set.
///
/// @param name The name of register, or `NUL` if unnamed.
/// @param quiet Suppress error messages
/// @param writing if we're setting the contents of the clipboard
///
/// @returns the yankreg that should be written into, or `NULL`
/// if the register isn't a clipboard or provider isn't available.
static yankreg_T *adjust_clipboard_name(int *name, bool quiet, bool writing)
{
#define MSG_NO_CLIP "clipboard: No provider. " \
  "Try \":checkhealth\" or \":h clipboard\"."

  yankreg_T *target = NULL;
  bool explicit_cb_reg = (*name == '*' || *name == '+');
  bool implicit_cb_reg = (*name == NUL) && (cb_flags & CB_UNNAMEDMASK);
  if (!explicit_cb_reg && !implicit_cb_reg) {
    goto end;
  }

  if (!eval_has_provider("clipboard")) {
    if (batch_change_count == 1 && !quiet
        && (!clipboard_didwarn || (explicit_cb_reg && !redirecting()))) {
      clipboard_didwarn = true;
      // Do NOT error (emsg()) here--if it interrupts :redir we get into
      // a weird state, stuck in "redirect mode".
      msg((char_u *)MSG_NO_CLIP);
    }
    // ... else, be silent (don't flood during :while, :redir, etc.).
    goto end;
  }

  if (explicit_cb_reg) {
    target = &y_regs[*name == '*' ? STAR_REGISTER : PLUS_REGISTER];
    if (writing && (cb_flags & (*name == '*' ? CB_UNNAMED : CB_UNNAMEDPLUS))) {
      clipboard_needs_update = false;
    }
    goto end;
  } else {  // unnamed register: "implicit" clipboard
    if (writing && clipboard_delay_update) {
      // For "set" (copy), defer the clipboard call.
      clipboard_needs_update = true;
      goto end;
    } else if (!writing && clipboard_needs_update) {
      // For "get" (paste), use the internal value.
      goto end;
    }

    if (cb_flags & CB_UNNAMEDPLUS) {
      *name = (cb_flags & CB_UNNAMED && writing) ? '"': '+';
      target = &y_regs[PLUS_REGISTER];
    } else {
      *name = '*';
      target = &y_regs[STAR_REGISTER];
    }
    goto end;
  }

end:
  return target;
}

/// @param[out] reg Expected to be empty
bool prepare_yankreg_from_object(yankreg_T *reg, String regtype, size_t lines)
{
  char type = regtype.data ? regtype.data[0] : NUL;

  switch (type) {
  case 0:
    reg->y_type = kMTUnknown;
    break;
  case 'v': case 'c':
    reg->y_type = kMTCharWise;
    break;
  case 'V': case 'l':
    reg->y_type = kMTLineWise;
    break;
  case 'b': case Ctrl_V:
    reg->y_type = kMTBlockWise;
    break;
  default:
    return false;
  }

  reg->y_width = 0;
  if (regtype.size > 1) {
    if (reg->y_type != kMTBlockWise) {
      return false;
    }

    // allow "b7" for a block at least 7 spaces wide
    if (!ascii_isdigit(regtype.data[1])) {
      return false;
    }
    const char *p = regtype.data+1;
    reg->y_width = getdigits_int((char_u **)&p, false, 1) - 1;
    if (regtype.size > (size_t)(p-regtype.data)) {
      return false;
    }
  }

  reg->y_array = xcalloc(lines, sizeof(uint8_t *));
  reg->y_size = lines;
  reg->additional_data = NULL;
  reg->timestamp = 0;
  return true;
}

void finish_yankreg_from_object(yankreg_T *reg, bool clipboard_adjust)
{
  if (reg->y_size > 0 && strlen((char *)reg->y_array[reg->y_size-1]) == 0) {
    // a known-to-be charwise yank might have a final linebreak
    // but otherwise there is no line after the final newline
    if (reg->y_type != kMTCharWise) {
      if (reg->y_type == kMTUnknown || clipboard_adjust) {
        xfree(reg->y_array[reg->y_size-1]);
        reg->y_size--;
      }
      if (reg->y_type == kMTUnknown) {
        reg->y_type = kMTLineWise;
      }
    }
  } else {
    if (reg->y_type == kMTUnknown) {
      reg->y_type = kMTCharWise;
    }
  }

  if (reg->y_type == kMTBlockWise) {
    size_t maxlen = 0;
    for (size_t i = 0; i < reg->y_size; i++) {
      size_t rowlen = STRLEN(reg->y_array[i]);
      if (rowlen > maxlen) {
        maxlen = rowlen;
      }
    }
    assert(maxlen <= INT_MAX);
    reg->y_width = MAX(reg->y_width, (int)maxlen - 1);
  }
}

static bool get_clipboard(int name, yankreg_T **target, bool quiet)
{
  // show message on error
  bool errmsg = true;

  yankreg_T *reg = adjust_clipboard_name(&name, quiet, false);
  if (reg == NULL) {
    return false;
  }
  free_register(reg);

  list_T *const args = tv_list_alloc(1);
  const char regname = (char)name;
  tv_list_append_string(args, &regname, 1);

  typval_T result = eval_call_provider("clipboard", "get", args, false);

  if (result.v_type != VAR_LIST) {
    if (result.v_type == VAR_NUMBER && result.vval.v_number == 0) {
      // failure has already been indicated by provider
      errmsg = false;
    }
    goto err;
  }

  list_T *res = result.vval.v_list;
  list_T *lines = NULL;
  if (tv_list_len(res) == 2
      && TV_LIST_ITEM_TV(tv_list_first(res))->v_type == VAR_LIST) {
    lines = TV_LIST_ITEM_TV(tv_list_first(res))->vval.v_list;
    if (TV_LIST_ITEM_TV(tv_list_last(res))->v_type != VAR_STRING) {
      goto err;
    }
    char_u *regtype = TV_LIST_ITEM_TV(tv_list_last(res))->vval.v_string;
    if (regtype == NULL || strlen((char *)regtype) > 1) {
      goto err;
    }
    switch (regtype[0]) {
    case 0:
      reg->y_type = kMTUnknown;
      break;
    case 'v': case 'c':
      reg->y_type = kMTCharWise;
      break;
    case 'V': case 'l':
      reg->y_type = kMTLineWise;
      break;
    case 'b': case Ctrl_V:
      reg->y_type = kMTBlockWise;
      break;
    default:
      goto err;
    }
  } else {
    lines = res;
    // provider did not specify regtype, calculate it below
    reg->y_type = kMTUnknown;
  }

  reg->y_array = xcalloc((size_t)tv_list_len(lines), sizeof(char_u *));
  reg->y_size = (size_t)tv_list_len(lines);
  reg->additional_data = NULL;
  reg->timestamp = 0;
  // Timestamp is not saved for clipboard registers because clipboard registers
  // are not saved in the ShaDa file.

  size_t tv_idx = 0;
  TV_LIST_ITER_CONST(lines, li, {
    if (TV_LIST_ITEM_TV(li)->v_type != VAR_STRING) {
      goto err;
    }
    reg->y_array[tv_idx++] = (char_u *)xstrdupnul(
        (const char *)TV_LIST_ITEM_TV(li)->vval.v_string);
  });

  if (reg->y_size > 0 && strlen((char*)reg->y_array[reg->y_size-1]) == 0) {
    // a known-to-be charwise yank might have a final linebreak
    // but otherwise there is no line after the final newline
    if (reg->y_type != kMTCharWise) {
      xfree(reg->y_array[reg->y_size-1]);
      reg->y_size--;
      if (reg->y_type == kMTUnknown) {
        reg->y_type = kMTLineWise;
      }
    }
  } else {
    if (reg->y_type == kMTUnknown) {
      reg->y_type = kMTCharWise;
    }
  }

  if (reg->y_type == kMTBlockWise) {
    size_t maxlen = 0;
    for (size_t i = 0; i < reg->y_size; i++) {
      size_t rowlen = STRLEN(reg->y_array[i]);
      if (rowlen > maxlen) {
        maxlen = rowlen;
      }
    }
    assert(maxlen <= INT_MAX);
    reg->y_width = (int)maxlen - 1;
  }

  *target = reg;
  return true;

err:
  if (reg->y_array) {
    for (size_t i = 0; i < reg->y_size; i++) {
      xfree(reg->y_array[i]);
    }
    xfree(reg->y_array);
  }
  reg->y_array = NULL;
  reg->y_size = 0;
  reg->additional_data = NULL;
  reg->timestamp = 0;
  if (errmsg) {
    EMSG("clipboard: provider returned invalid data");
  }
  *target = reg;
  return false;
}

static void set_clipboard(int name, yankreg_T *reg)
{
  if (!adjust_clipboard_name(&name, false, true)) {
    return;
  }

  list_T *const lines = tv_list_alloc(
      (ptrdiff_t)reg->y_size + (reg->y_type != kMTCharWise));

  for (size_t i = 0; i < reg->y_size; i++) {
    tv_list_append_string(lines, (const char *)reg->y_array[i], -1);
  }

  char regtype;
  switch (reg->y_type) {
    case kMTLineWise: {
      regtype = 'V';
      tv_list_append_string(lines, NULL, 0);
      break;
    }
    case kMTCharWise: {
      regtype = 'v';
      break;
    }
    case kMTBlockWise: {
      regtype = 'b';
      tv_list_append_string(lines, NULL, 0);
      break;
    }
    case kMTUnknown: {
      abort();
    }
  }

  list_T *args = tv_list_alloc(3);
  tv_list_append_list(args, lines);
  tv_list_append_string(args, &regtype, 1);  // -V614
  tv_list_append_string(args, ((char[]) { (char)name }), 1);

  (void)eval_call_provider("clipboard", "set", args, true);
}

/// Avoid slow things (clipboard) during batch operations (while/for-loops).
void start_batch_changes(void)
{
  if (++batch_change_count > 1) {
    return;
  }
  clipboard_delay_update = true;
}

/// Counterpart to start_batch_changes().
void end_batch_changes(void)
{
  if (--batch_change_count > 0) {
    // recursive
    return;
  }
  clipboard_delay_update = false;
  if (clipboard_needs_update) {
    // must be before, as set_clipboard will invoke
    // start/end_batch_changes recursively
    clipboard_needs_update = false;
    // unnamed ("implicit" clipboard)
    set_clipboard(NUL, y_previous);
  }
}

int save_batch_count(void)
{
  int save_count = batch_change_count;
  batch_change_count = 0;
  clipboard_delay_update = false;
  if (clipboard_needs_update) {
    clipboard_needs_update = false;
    // unnamed ("implicit" clipboard)
    set_clipboard(NUL, y_previous);
  }
  return save_count;
}

void restore_batch_count(int save_count)
{
  assert(batch_change_count == 0);
  batch_change_count = save_count;
  if (batch_change_count > 0) {
    clipboard_delay_update = true;
  }
}


/// Check whether register is empty
static inline bool reg_empty(const yankreg_T *const reg)
  FUNC_ATTR_PURE
{
  return (reg->y_array == NULL
          || reg->y_size == 0
          || (reg->y_size == 1
              && reg->y_type == kMTCharWise
              && *(reg->y_array[0]) == NUL));
}

/// Iterate over global registers.
///
/// @see op_register_iter
const void *op_global_reg_iter(const void *const iter, char *const name,
                               yankreg_T *const reg, bool *is_unnamed)
  FUNC_ATTR_NONNULL_ARG(2, 3, 4) FUNC_ATTR_WARN_UNUSED_RESULT
{
  return op_reg_iter(iter, y_regs, name, reg, is_unnamed);
}

/// Iterate over registers `regs`.
///
/// @param[in]   iter      Iterator. Pass NULL to start iteration.
/// @param[in]   regs      Registers list to be iterated.
/// @param[out]  name      Register name.
/// @param[out]  reg       Register contents.
///
/// @return Pointer that must be passed to next `op_register_iter` call or
///         NULL if iteration is over.
const void *op_reg_iter(const void *const iter, const yankreg_T *const regs,
                        char *const name, yankreg_T *const reg,
                        bool *is_unnamed)
  FUNC_ATTR_NONNULL_ARG(3, 4, 5) FUNC_ATTR_WARN_UNUSED_RESULT
{
  *name = NUL;
  const yankreg_T *iter_reg = (iter == NULL
                               ? &(regs[0])
                               : (const yankreg_T *const)iter);
  while (iter_reg - &(regs[0]) < NUM_SAVED_REGISTERS && reg_empty(iter_reg)) {
    iter_reg++;
  }
  if (iter_reg - &(regs[0]) == NUM_SAVED_REGISTERS || reg_empty(iter_reg)) {
    return NULL;
  }
  int iter_off = (int)(iter_reg - &(regs[0]));
  *name = (char)get_register_name(iter_off);
  *reg = *iter_reg;
  *is_unnamed = (iter_reg == y_previous);
  while (++iter_reg - &(regs[0]) < NUM_SAVED_REGISTERS) {
    if (!reg_empty(iter_reg)) {
      return (void *) iter_reg;
    }
  }
  return NULL;
}

/// Get a number of non-empty registers
size_t op_reg_amount(void)
  FUNC_ATTR_WARN_UNUSED_RESULT
{
  size_t ret = 0;
  for (size_t i = 0; i < NUM_SAVED_REGISTERS; i++) {
    if (!reg_empty(y_regs + i)) {
      ret++;
    }
  }
  return ret;
}

/// Set register to a given value
///
/// @param[in]  name  Register name.
/// @param[in]  reg  Register value.
/// @param[in]  is_unnamed  Whether to set the unnamed regiseter to reg
///
/// @return true on success, false on failure.
bool op_reg_set(const char name, const yankreg_T reg, bool is_unnamed)
{
  int i = op_reg_index(name);
  if (i == -1) {
    return false;
  }
  free_register(&y_regs[i]);
  y_regs[i] = reg;

  if (is_unnamed) {
    y_previous = &y_regs[i];
  }
  return true;
}

/// Get register with the given name
///
/// @param[in]  name  Register name.
///
/// @return Pointer to the register contents or NULL.
const yankreg_T *op_reg_get(const char name)
{
  int i = op_reg_index(name);
  if (i == -1) {
    return NULL;
  }
  return &y_regs[i];
}

/// Set the previous yank register
///
/// @param[in]  name  Register name.
///
/// @return true on success, false on failure.
bool op_reg_set_previous(const char name)
  FUNC_ATTR_WARN_UNUSED_RESULT
{
  int i = op_reg_index(name);
  if (i == -1) {
    return false;
  }

  y_previous = &y_regs[i];
  return true;
}

/// Get the byte count of buffer region. End-exclusive.
///
/// @return number of bytes
bcount_t get_region_bytecount(buf_T *buf, linenr_T start_lnum,
                              linenr_T end_lnum, colnr_T start_col,
                              colnr_T end_col)
{
  linenr_T max_lnum = buf->b_ml.ml_line_count;
  if (start_lnum > max_lnum) {
    return 0;
  }
  if (start_lnum == end_lnum) {
    return end_col - start_col;
  }
  const char *first = (const char *)ml_get_buf(buf, start_lnum, false);
  bcount_t deleted_bytes = (bcount_t)STRLEN(first) - start_col + 1;

  for (linenr_T i = 1; i <= end_lnum-start_lnum-1; i++) {
    if (start_lnum + i > max_lnum) {
      return deleted_bytes;
    }
    deleted_bytes += (bcount_t)STRLEN(
        ml_get_buf(buf, start_lnum + i, false)) + 1;
  }
  if (end_lnum > max_lnum) {
    return deleted_bytes;
  }
  return deleted_bytes + end_col;
}