Introduce nvim namespace: Move files.

Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

1 files changed, 2880 insertions, 0 deletions

diff --git a/src/nvim/undo.c b/src/nvim/undo.c
new file mode 100644
index 0000000000..47ce8ee8da
--- /dev/null
+++ b/src/nvim/undo.c
@@ -0,0 +1,2880 @@
+/*
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * undo.c: multi level undo facility
+ *
+ * The saved lines are stored in a list of lists (one for each buffer):
+ *
+ * b_u_oldhead------------------------------------------------+
+ *							      |
+ *							      V
+ *		  +--------------+    +--------------+	  +--------------+
+ * b_u_newhead--->| u_header	 |    | u_header     |	  | u_header	 |
+ *		  |	uh_next------>|     uh_next------>|	uh_next---->NULL
+ *	   NULL<--------uh_prev  |<---------uh_prev  |<---------uh_prev  |
+ *		  |	uh_entry |    |     uh_entry |	  |	uh_entry |
+ *		  +--------|-----+    +--------|-----+	  +--------|-----+
+ *			   |		       |		   |
+ *			   V		       V		   V
+ *		  +--------------+    +--------------+	  +--------------+
+ *		  | u_entry	 |    | u_entry      |	  | u_entry	 |
+ *		  |	ue_next  |    |     ue_next  |	  |	ue_next  |
+ *		  +--------|-----+    +--------|-----+	  +--------|-----+
+ *			   |		       |		   |
+ *			   V		       V		   V
+ *		  +--------------+	      NULL		  NULL
+ *		  | u_entry	 |
+ *		  |	ue_next  |
+ *		  +--------|-----+
+ *			   |
+ *			   V
+ *			  etc.
+ *
+ * Each u_entry list contains the information for one undo or redo.
+ * curbuf->b_u_curhead points to the header of the last undo (the next redo),
+ * or is NULL if nothing has been undone (end of the branch).
+ *
+ * For keeping alternate undo/redo branches the uh_alt field is used.  Thus at
+ * each point in the list a branch may appear for an alternate to redo.  The
+ * uh_seq field is numbered sequentially to be able to find a newer or older
+ * branch.
+ *
+ *		   +---------------+	+---------------+
+ * b_u_oldhead --->| u_header	   |	| u_header	|
+ *		   |   uh_alt_next ---->|   uh_alt_next ----> NULL
+ *	   NULL <----- uh_alt_prev |<------ uh_alt_prev |
+ *		   |   uh_prev	   |	|   uh_prev	|
+ *		   +-----|---------+	+-----|---------+
+ *			 |		      |
+ *			 V		      V
+ *		   +---------------+	+---------------+
+ *		   | u_header	   |	| u_header	|
+ *		   |   uh_alt_next |	|   uh_alt_next |
+ * b_u_newhead --->|   uh_alt_prev |	|   uh_alt_prev |
+ *		   |   uh_prev	   |	|   uh_prev	|
+ *		   +-----|---------+	+-----|---------+
+ *			 |		      |
+ *			 V		      V
+ *		       NULL		+---------------+    +---------------+
+ *					| u_header	|    | u_header      |
+ *					|   uh_alt_next ---->|	 uh_alt_next |
+ *					|   uh_alt_prev |<------ uh_alt_prev |
+ *					|   uh_prev	|    |	 uh_prev     |
+ *					+-----|---------+    +-----|---------+
+ *					      |			   |
+ *					     etc.		  etc.
+ *
+ *
+ * All data is allocated and will all be freed when the buffer is unloaded.
+ */
+
+/* Uncomment the next line for including the u_check() function.  This warns
+ * for errors in the debug information. */
+/* #define U_DEBUG 1 */
+#define UH_MAGIC 0x18dade       /* value for uh_magic when in use */
+#define UE_MAGIC 0xabc123       /* value for ue_magic when in use */
+
+#include <string.h>
+
+#include "vim.h"
+#include "undo.h"
+#include "edit.h"
+#include "eval.h"
+#include "fileio.h"
+#include "fold.h"
+#include "mark.h"
+#include "memline.h"
+#include "message.h"
+#include "misc1.h"
+#include "misc2.h"
+#include "memory.h"
+#include "crypt.h"
+#include "garray.h"
+#include "option.h"
+#include "os_unix.h"
+#include "path.h"
+#include "quickfix.h"
+#include "screen.h"
+#include "sha256.h"
+#include "os/os.h"
+#include "os/time.h"
+
+static long get_undolevel(void);
+static void u_unch_branch(u_header_T *uhp);
+static u_entry_T *u_get_headentry(void);
+static void u_getbot(void);
+static void u_doit(int count);
+static void u_undoredo(int undo);
+static void u_undo_end(int did_undo, int absolute);
+static void u_add_time(char_u *buf, size_t buflen, time_t tt);
+static void u_freeheader(buf_T *buf, u_header_T *uhp, u_header_T **uhpp);
+static void u_freebranch(buf_T *buf, u_header_T *uhp, u_header_T **uhpp);
+static void u_freeentries(buf_T *buf, u_header_T *uhp,
+                          u_header_T **uhpp);
+static void u_freeentry(u_entry_T *, long);
+static void corruption_error(char *mesg, char_u *file_name);
+static void u_free_uhp(u_header_T *uhp);
+static size_t fwrite_crypt(buf_T *buf, char_u *ptr, size_t len,
+                           FILE *fp);
+static char_u *read_string_decrypt(buf_T *buf, FILE *fd, int len);
+static int serialize_header(FILE *fp, buf_T *buf, char_u *hash);
+static int serialize_uhp(FILE *fp, buf_T *buf, u_header_T *uhp);
+static u_header_T *unserialize_uhp(FILE *fp, char_u *file_name);
+static int serialize_uep(FILE *fp, buf_T *buf, u_entry_T *uep);
+static u_entry_T *unserialize_uep(FILE *fp, int *error,
+                                  char_u *file_name);
+static void serialize_pos(pos_T pos, FILE *fp);
+static void unserialize_pos(pos_T *pos, FILE *fp);
+static void serialize_visualinfo(visualinfo_T *info, FILE *fp);
+static void unserialize_visualinfo(visualinfo_T *info, FILE *fp);
+static void put_header_ptr(FILE *fp, u_header_T *uhp);
+
+static char_u *u_save_line(linenr_T);
+
+/* used in undo_end() to report number of added and deleted lines */
+static long u_newcount, u_oldcount;
+
+/*
+ * When 'u' flag included in 'cpoptions', we behave like vi.  Need to remember
+ * the action that "u" should do.
+ */
+static int undo_undoes = FALSE;
+
+static int lastmark = 0;
+
+#if defined(U_DEBUG) || defined(PROTO)
+/*
+ * Check the undo structures for being valid.  Print a warning when something
+ * looks wrong.
+ */
+static int seen_b_u_curhead;
+static int seen_b_u_newhead;
+static int header_count;
+
+static void u_check_tree(u_header_T *uhp,
+    u_header_T *exp_uh_next,
+    u_header_T *exp_uh_alt_prev) {
+  u_entry_T *uep;
+
+  if (uhp == NULL)
+    return;
+  ++header_count;
+  if (uhp == curbuf->b_u_curhead && ++seen_b_u_curhead > 1) {
+    EMSG("b_u_curhead found twice (looping?)");
+    return;
+  }
+  if (uhp == curbuf->b_u_newhead && ++seen_b_u_newhead > 1) {
+    EMSG("b_u_newhead found twice (looping?)");
+    return;
+  }
+
+  if (uhp->uh_magic != UH_MAGIC)
+    EMSG("uh_magic wrong (may be using freed memory)");
+  else {
+    /* Check pointers back are correct. */
+    if (uhp->uh_next.ptr != exp_uh_next) {
+      EMSG("uh_next wrong");
+      smsg((char_u *)"expected: 0x%x, actual: 0x%x",
+          exp_uh_next, uhp->uh_next.ptr);
+    }
+    if (uhp->uh_alt_prev.ptr != exp_uh_alt_prev) {
+      EMSG("uh_alt_prev wrong");
+      smsg((char_u *)"expected: 0x%x, actual: 0x%x",
+          exp_uh_alt_prev, uhp->uh_alt_prev.ptr);
+    }
+
+    /* Check the undo tree at this header. */
+    for (uep = uhp->uh_entry; uep != NULL; uep = uep->ue_next) {
+      if (uep->ue_magic != UE_MAGIC) {
+        EMSG("ue_magic wrong (may be using freed memory)");
+        break;
+      }
+    }
+
+    /* Check the next alt tree. */
+    u_check_tree(uhp->uh_alt_next.ptr, uhp->uh_next.ptr, uhp);
+
+    /* Check the next header in this branch. */
+    u_check_tree(uhp->uh_prev.ptr, uhp, NULL);
+  }
+}
+
+static void u_check(int newhead_may_be_NULL)                 {
+  seen_b_u_newhead = 0;
+  seen_b_u_curhead = 0;
+  header_count = 0;
+
+  u_check_tree(curbuf->b_u_oldhead, NULL, NULL);
+
+  if (seen_b_u_newhead == 0 && curbuf->b_u_oldhead != NULL
+      && !(newhead_may_be_NULL && curbuf->b_u_newhead == NULL))
+    EMSGN("b_u_newhead invalid: 0x%x", curbuf->b_u_newhead);
+  if (curbuf->b_u_curhead != NULL && seen_b_u_curhead == 0)
+    EMSGN("b_u_curhead invalid: 0x%x", curbuf->b_u_curhead);
+  if (header_count != curbuf->b_u_numhead) {
+    EMSG("b_u_numhead invalid");
+    smsg((char_u *)"expected: %" PRId64 ", actual: %" PRId64,
+        (int64_t)header_count, (int64_t)curbuf->b_u_numhead);
+  }
+}
+
+#endif
+
+/*
+ * Save the current line for both the "u" and "U" command.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns OK or FAIL.
+ */
+int u_save_cursor(void)
+{
+  return u_save((linenr_T)(curwin->w_cursor.lnum - 1),
+      (linenr_T)(curwin->w_cursor.lnum + 1));
+}
+
+/*
+ * Save the lines between "top" and "bot" for both the "u" and "U" command.
+ * "top" may be 0 and bot may be curbuf->b_ml.ml_line_count + 1.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns FAIL when lines could not be saved, OK otherwise.
+ */
+int u_save(linenr_T top, linenr_T bot)
+{
+  if (undo_off)
+    return OK;
+
+  if (top > curbuf->b_ml.ml_line_count
+      || top >= bot
+      || bot > curbuf->b_ml.ml_line_count + 1)
+    return FALSE;       /* rely on caller to do error messages */
+
+  if (top + 2 == bot)
+    u_saveline((linenr_T)(top + 1));
+
+  return u_savecommon(top, bot, (linenr_T)0, FALSE);
+}
+
+/*
+ * Save the line "lnum" (used by ":s" and "~" command).
+ * The line is replaced, so the new bottom line is lnum + 1.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns FAIL when lines could not be saved, OK otherwise.
+ */
+int u_savesub(linenr_T lnum)
+{
+  if (undo_off)
+    return OK;
+
+  return u_savecommon(lnum - 1, lnum + 1, lnum + 1, FALSE);
+}
+
+/*
+ * A new line is inserted before line "lnum" (used by :s command).
+ * The line is inserted, so the new bottom line is lnum + 1.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns FAIL when lines could not be saved, OK otherwise.
+ */
+int u_inssub(linenr_T lnum)
+{
+  if (undo_off)
+    return OK;
+
+  return u_savecommon(lnum - 1, lnum, lnum + 1, FALSE);
+}
+
+/*
+ * Save the lines "lnum" - "lnum" + nlines (used by delete command).
+ * The lines are deleted, so the new bottom line is lnum, unless the buffer
+ * becomes empty.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns FAIL when lines could not be saved, OK otherwise.
+ */
+int u_savedel(linenr_T lnum, long nlines)
+{
+  if (undo_off)
+    return OK;
+
+  return u_savecommon(lnum - 1, lnum + nlines,
+      nlines == curbuf->b_ml.ml_line_count ? 2 : lnum, FALSE);
+}
+
+/*
+ * Return TRUE when undo is allowed.  Otherwise give an error message and
+ * return FALSE.
+ */
+int undo_allowed(void)
+{
+  /* Don't allow changes when 'modifiable' is off.  */
+  if (!curbuf->b_p_ma) {
+    EMSG(_(e_modifiable));
+    return FALSE;
+  }
+
+#ifdef HAVE_SANDBOX
+  /* In the sandbox it's not allowed to change the text. */
+  if (sandbox != 0) {
+    EMSG(_(e_sandbox));
+    return FALSE;
+  }
+#endif
+
+  /* Don't allow changes in the buffer while editing the cmdline.  The
+   * caller of getcmdline() may get confused. */
+  if (textlock != 0) {
+    EMSG(_(e_secure));
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
+/*
+ * Get the undolevle value for the current buffer.
+ */
+static long get_undolevel(void)
+{
+  if (curbuf->b_p_ul == NO_LOCAL_UNDOLEVEL)
+    return p_ul;
+  return curbuf->b_p_ul;
+}
+
+/*
+ * Common code for various ways to save text before a change.
+ * "top" is the line above the first changed line.
+ * "bot" is the line below the last changed line.
+ * "newbot" is the new bottom line.  Use zero when not known.
+ * "reload" is TRUE when saving for a buffer reload.
+ * Careful: may trigger autocommands that reload the buffer.
+ * Returns FAIL when lines could not be saved, OK otherwise.
+ */
+int u_savecommon(linenr_T top, linenr_T bot, linenr_T newbot, int reload)
+{
+  linenr_T lnum;
+  long i;
+  u_header_T  *uhp;
+  u_header_T  *old_curhead;
+  u_entry_T   *uep;
+  u_entry_T   *prev_uep;
+  long size;
+
+  if (!reload) {
+    /* When making changes is not allowed return FAIL.  It's a crude way
+     * to make all change commands fail. */
+    if (!undo_allowed())
+      return FAIL;
+
+
+    /*
+     * Saving text for undo means we are going to make a change.  Give a
+     * warning for a read-only file before making the change, so that the
+     * FileChangedRO event can replace the buffer with a read-write version
+     * (e.g., obtained from a source control system).
+     */
+    change_warning(0);
+    if (bot > curbuf->b_ml.ml_line_count + 1) {
+      /* This happens when the FileChangedRO autocommand changes the
+       * file in a way it becomes shorter. */
+      EMSG(_("E881: Line count changed unexpectedly"));
+      return FAIL;
+    }
+  }
+
+#ifdef U_DEBUG
+  u_check(FALSE);
+#endif
+
+  size = bot - top - 1;
+
+  /*
+   * If curbuf->b_u_synced == TRUE make a new header.
+   */
+  if (curbuf->b_u_synced) {
+    /* Need to create new entry in b_changelist. */
+    curbuf->b_new_change = TRUE;
+
+    if (get_undolevel() >= 0) {
+      /*
+       * Make a new header entry.  Do this first so that we don't mess
+       * up the undo info when out of memory.
+       */
+      uhp = xmalloc(sizeof(u_header_T));
+#ifdef U_DEBUG
+      uhp->uh_magic = UH_MAGIC;
+#endif
+    } else
+      uhp = NULL;
+
+    /*
+     * If we undid more than we redid, move the entry lists before and
+     * including curbuf->b_u_curhead to an alternate branch.
+     */
+    old_curhead = curbuf->b_u_curhead;
+    if (old_curhead != NULL) {
+      curbuf->b_u_newhead = old_curhead->uh_next.ptr;
+      curbuf->b_u_curhead = NULL;
+    }
+
+    /*
+     * free headers to keep the size right
+     */
+    while (curbuf->b_u_numhead > get_undolevel()
+           && curbuf->b_u_oldhead != NULL) {
+      u_header_T      *uhfree = curbuf->b_u_oldhead;
+
+      if (uhfree == old_curhead)
+        /* Can't reconnect the branch, delete all of it. */
+        u_freebranch(curbuf, uhfree, &old_curhead);
+      else if (uhfree->uh_alt_next.ptr == NULL)
+        /* There is no branch, only free one header. */
+        u_freeheader(curbuf, uhfree, &old_curhead);
+      else {
+        /* Free the oldest alternate branch as a whole. */
+        while (uhfree->uh_alt_next.ptr != NULL)
+          uhfree = uhfree->uh_alt_next.ptr;
+        u_freebranch(curbuf, uhfree, &old_curhead);
+      }
+#ifdef U_DEBUG
+      u_check(TRUE);
+#endif
+    }
+
+    if (uhp == NULL) {                  /* no undo at all */
+      if (old_curhead != NULL)
+        u_freebranch(curbuf, old_curhead, NULL);
+      curbuf->b_u_synced = FALSE;
+      return OK;
+    }
+
+    uhp->uh_prev.ptr = NULL;
+    uhp->uh_next.ptr = curbuf->b_u_newhead;
+    uhp->uh_alt_next.ptr = old_curhead;
+    if (old_curhead != NULL) {
+      uhp->uh_alt_prev.ptr = old_curhead->uh_alt_prev.ptr;
+      if (uhp->uh_alt_prev.ptr != NULL)
+        uhp->uh_alt_prev.ptr->uh_alt_next.ptr = uhp;
+      old_curhead->uh_alt_prev.ptr = uhp;
+      if (curbuf->b_u_oldhead == old_curhead)
+        curbuf->b_u_oldhead = uhp;
+    } else
+      uhp->uh_alt_prev.ptr = NULL;
+    if (curbuf->b_u_newhead != NULL)
+      curbuf->b_u_newhead->uh_prev.ptr = uhp;
+
+    uhp->uh_seq = ++curbuf->b_u_seq_last;
+    curbuf->b_u_seq_cur = uhp->uh_seq;
+    uhp->uh_time = time(NULL);
+    uhp->uh_save_nr = 0;
+    curbuf->b_u_time_cur = uhp->uh_time + 1;
+
+    uhp->uh_walk = 0;
+    uhp->uh_entry = NULL;
+    uhp->uh_getbot_entry = NULL;
+    uhp->uh_cursor = curwin->w_cursor;          /* save cursor pos. for undo */
+    if (virtual_active() && curwin->w_cursor.coladd > 0)
+      uhp->uh_cursor_vcol = getviscol();
+    else
+      uhp->uh_cursor_vcol = -1;
+
+    /* save changed and buffer empty flag for undo */
+    uhp->uh_flags = (curbuf->b_changed ? UH_CHANGED : 0) +
+                    ((curbuf->b_ml.ml_flags & ML_EMPTY) ? UH_EMPTYBUF : 0);
+
+    /* save named marks and Visual marks for undo */
+    memmove(uhp->uh_namedm, curbuf->b_namedm, sizeof(pos_T) * NMARKS);
+    uhp->uh_visual = curbuf->b_visual;
+
+    curbuf->b_u_newhead = uhp;
+    if (curbuf->b_u_oldhead == NULL)
+      curbuf->b_u_oldhead = uhp;
+    ++curbuf->b_u_numhead;
+  } else {
+    if (get_undolevel() < 0)            /* no undo at all */
+      return OK;
+
+    /*
+     * When saving a single line, and it has been saved just before, it
+     * doesn't make sense saving it again.  Saves a lot of memory when
+     * making lots of changes inside the same line.
+     * This is only possible if the previous change didn't increase or
+     * decrease the number of lines.
+     * Check the ten last changes.  More doesn't make sense and takes too
+     * long.
+     */
+    if (size == 1) {
+      uep = u_get_headentry();
+      prev_uep = NULL;
+      for (i = 0; i < 10; ++i) {
+        if (uep == NULL)
+          break;
+
+        /* If lines have been inserted/deleted we give up.
+         * Also when the line was included in a multi-line save. */
+        if ((curbuf->b_u_newhead->uh_getbot_entry != uep
+             ? (uep->ue_top + uep->ue_size + 1
+                != (uep->ue_bot == 0
+                    ? curbuf->b_ml.ml_line_count + 1
+                    : uep->ue_bot))
+             : uep->ue_lcount != curbuf->b_ml.ml_line_count)
+            || (uep->ue_size > 1
+                && top >= uep->ue_top
+                && top + 2 <= uep->ue_top + uep->ue_size + 1))
+          break;
+
+        /* If it's the same line we can skip saving it again. */
+        if (uep->ue_size == 1 && uep->ue_top == top) {
+          if (i > 0) {
+            /* It's not the last entry: get ue_bot for the last
+             * entry now.  Following deleted/inserted lines go to
+             * the re-used entry. */
+            u_getbot();
+            curbuf->b_u_synced = FALSE;
+
+            /* Move the found entry to become the last entry.  The
+             * order of undo/redo doesn't matter for the entries
+             * we move it over, since they don't change the line
+             * count and don't include this line.  It does matter
+             * for the found entry if the line count is changed by
+             * the executed command. */
+            prev_uep->ue_next = uep->ue_next;
+            uep->ue_next = curbuf->b_u_newhead->uh_entry;
+            curbuf->b_u_newhead->uh_entry = uep;
+          }
+
+          /* The executed command may change the line count. */
+          if (newbot != 0)
+            uep->ue_bot = newbot;
+          else if (bot > curbuf->b_ml.ml_line_count)
+            uep->ue_bot = 0;
+          else {
+            uep->ue_lcount = curbuf->b_ml.ml_line_count;
+            curbuf->b_u_newhead->uh_getbot_entry = uep;
+          }
+          return OK;
+        }
+        prev_uep = uep;
+        uep = uep->ue_next;
+      }
+    }
+
+    /* find line number for ue_bot for previous u_save() */
+    u_getbot();
+  }
+
+  /*
+   * add lines in front of entry list
+   */
+  uep = xmalloc(sizeof(u_entry_T));
+  memset(uep, 0, sizeof(u_entry_T));
+#ifdef U_DEBUG
+  uep->ue_magic = UE_MAGIC;
+#endif
+
+  uep->ue_size = size;
+  uep->ue_top = top;
+  if (newbot != 0)
+    uep->ue_bot = newbot;
+  /*
+   * Use 0 for ue_bot if bot is below last line.
+   * Otherwise we have to compute ue_bot later.
+   */
+  else if (bot > curbuf->b_ml.ml_line_count)
+    uep->ue_bot = 0;
+  else {
+    uep->ue_lcount = curbuf->b_ml.ml_line_count;
+    curbuf->b_u_newhead->uh_getbot_entry = uep;
+  }
+
+  if (size > 0) {
+    uep->ue_array = xmalloc(sizeof(char_u *) * size);
+    for (i = 0, lnum = top + 1; i < size; ++i) {
+      fast_breakcheck();
+      if (got_int) {
+        u_freeentry(uep, i);
+        return FAIL;
+      }
+      if ((uep->ue_array[i] = u_save_line(lnum++)) == NULL) {
+        u_freeentry(uep, i);
+        goto nomem;
+      }
+    }
+  } else
+    uep->ue_array = NULL;
+  uep->ue_next = curbuf->b_u_newhead->uh_entry;
+  curbuf->b_u_newhead->uh_entry = uep;
+  curbuf->b_u_synced = FALSE;
+  undo_undoes = FALSE;
+
+#ifdef U_DEBUG
+  u_check(FALSE);
+#endif
+  return OK;
+
+nomem:
+  msg_silent = 0;       /* must display the prompt */
+  if (ask_yesno((char_u *)_("No undo possible; continue anyway"), TRUE)
+      == 'y') {
+    undo_off = TRUE;                /* will be reset when character typed */
+    return OK;
+  }
+  do_outofmem_msg((long_u)0);
+  return FAIL;
+}
+
+
+# define UF_START_MAGIC     "Vim\237UnDo\345"  /* magic at start of undofile */
+# define UF_START_MAGIC_LEN     9
+# define UF_HEADER_MAGIC        0x5fd0  /* magic at start of header */
+# define UF_HEADER_END_MAGIC    0xe7aa  /* magic after last header */
+# define UF_ENTRY_MAGIC         0xf518  /* magic at start of entry */
+# define UF_ENTRY_END_MAGIC     0x3581  /* magic after last entry */
+# define UF_VERSION             2       /* 2-byte undofile version number */
+# define UF_VERSION_CRYPT       0x8002  /* idem, encrypted */
+
+/* extra fields for header */
+# define UF_LAST_SAVE_NR        1
+
+/* extra fields for uhp */
+# define UHP_SAVE_NR            1
+
+static char_u e_not_open[] = N_("E828: Cannot open undo file for writing: %s");
+
+/*
+ * Compute the hash for the current buffer text into hash[UNDO_HASH_SIZE].
+ */
+void u_compute_hash(char_u *hash)
+{
+  context_sha256_T ctx;
+  linenr_T lnum;
+  char_u              *p;
+
+  sha256_start(&ctx);
+  for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum) {
+    p = ml_get(lnum);
+    sha256_update(&ctx, p, (uint32_t)(STRLEN(p) + 1));
+  }
+  sha256_finish(&ctx, hash);
+}
+
+/*
+ * Return an allocated string of the full path of the target undofile.
+ * When "reading" is TRUE find the file to read, go over all directories in
+ * 'undodir'.
+ * When "reading" is FALSE use the first name where the directory exists.
+ * Returns NULL when there is no place to write or no file to read.
+ */
+char_u *u_get_undo_file_name(char_u *buf_ffname, int reading)
+{
+  char_u      *dirp;
+  char_u dir_name[IOSIZE + 1];
+  char_u      *munged_name = NULL;
+  char_u      *undo_file_name = NULL;
+  int dir_len;
+  char_u      *p;
+  char_u      *ffname = buf_ffname;
+#ifdef HAVE_READLINK
+  char_u fname_buf[MAXPATHL];
+#endif
+
+  if (ffname == NULL)
+    return NULL;
+
+#ifdef HAVE_READLINK
+  /* Expand symlink in the file name, so that we put the undo file with the
+   * actual file instead of with the symlink. */
+  if (resolve_symlink(ffname, fname_buf) == OK)
+    ffname = fname_buf;
+#endif
+
+  /* Loop over 'undodir'.  When reading find the first file that exists.
+   * When not reading use the first directory that exists or ".". */
+  dirp = p_udir;
+  while (*dirp != NUL) {
+    dir_len = copy_option_part(&dirp, dir_name, IOSIZE, ",");
+    if (dir_len == 1 && dir_name[0] == '.') {
+      /* Use same directory as the ffname,
+       * "dir/name" -> "dir/.name.un~" */
+      undo_file_name = vim_strnsave(ffname, (int)(STRLEN(ffname) + 5));
+      if (undo_file_name == NULL)
+        break;
+      p = path_tail(undo_file_name);
+      memmove(p + 1, p, STRLEN(p) + 1);
+      *p = '.';
+      STRCAT(p, ".un~");
+    } else {
+      dir_name[dir_len] = NUL;
+      if (os_isdir(dir_name)) {
+        if (munged_name == NULL) {
+          munged_name = vim_strsave(ffname);
+          if (munged_name == NULL)
+            return NULL;
+          for (p = munged_name; *p != NUL; mb_ptr_adv(p))
+            if (vim_ispathsep(*p))
+              *p = '%';
+        }
+        undo_file_name = concat_fnames(dir_name, munged_name, TRUE);
+      }
+    }
+
+    // When reading check if the file exists.
+    if (undo_file_name != NULL &&
+        (!reading || os_file_exists(undo_file_name))) {
+      break;
+    }
+    free(undo_file_name);
+    undo_file_name = NULL;
+  }
+
+  free(munged_name);
+  return undo_file_name;
+}
+
+static void corruption_error(char *mesg, char_u *file_name)
+{
+  EMSG3(_("E825: Corrupted undo file (%s): %s"), mesg, file_name);
+}
+
+static void u_free_uhp(u_header_T *uhp)
+{
+  u_entry_T   *nuep;
+  u_entry_T   *uep;
+
+  uep = uhp->uh_entry;
+  while (uep != NULL) {
+    nuep = uep->ue_next;
+    u_freeentry(uep, uep->ue_size);
+    uep = nuep;
+  }
+  free(uhp);
+}
+
+/*
+ * Like fwrite() but crypt the bytes when 'key' is set.
+ * Returns 1 if successful.
+ */
+static size_t fwrite_crypt(buf_T *buf, char_u *ptr, size_t len, FILE *fp)
+{
+  char_u  *copy;
+  char_u small_buf[100];
+  size_t i;
+
+  if (*buf->b_p_key == NUL)
+    return fwrite(ptr, len, (size_t)1, fp);
+  if (len < 100)
+    copy = small_buf;      /* no malloc()/free() for short strings */
+  else {
+    copy = xmalloc(len);
+  }
+  crypt_encode(ptr, len, copy);
+  i = fwrite(copy, len, (size_t)1, fp);
+  if (copy != small_buf)
+    free(copy);
+  return i;
+}
+
+/*
+ * Read a string of length "len" from "fd".
+ * When 'key' is set decrypt the bytes.
+ */
+static char_u *read_string_decrypt(buf_T *buf, FILE *fd, int len)
+{
+  char_u  *ptr;
+
+  ptr = read_string(fd, len);
+  if (ptr != NULL && *buf->b_p_key != NUL)
+    crypt_decode(ptr, len);
+  return ptr;
+}
+
+static int serialize_header(FILE *fp, buf_T *buf, char_u *hash)
+{
+  int len;
+
+  /* Start writing, first the magic marker and undo info version. */
+  if (fwrite(UF_START_MAGIC, (size_t)UF_START_MAGIC_LEN, (size_t)1, fp) != 1)
+    return FAIL;
+
+  /* If the buffer is encrypted then all text bytes following will be
+   * encrypted.  Numbers and other info is not crypted. */
+  if (*buf->b_p_key != NUL) {
+    char_u *header;
+    int header_len;
+
+    put_bytes(fp, (long_u)UF_VERSION_CRYPT, 2);
+    header = prepare_crypt_write(buf, &header_len);
+    if (header == NULL)
+      return FAIL;
+    len = (int)fwrite(header, (size_t)header_len, (size_t)1, fp);
+    free(header);
+    if (len != 1) {
+      crypt_pop_state();
+      return FAIL;
+    }
+  } else
+    put_bytes(fp, (long_u)UF_VERSION, 2);
+
+
+  /* Write a hash of the buffer text, so that we can verify it is still the
+   * same when reading the buffer text. */
+  if (fwrite(hash, (size_t)UNDO_HASH_SIZE, (size_t)1, fp) != 1)
+    return FAIL;
+
+  /* buffer-specific data */
+  put_bytes(fp, (long_u)buf->b_ml.ml_line_count, 4);
+  len = buf->b_u_line_ptr != NULL ? (int)STRLEN(buf->b_u_line_ptr) : 0;
+  put_bytes(fp, (long_u)len, 4);
+  if (len > 0 && fwrite_crypt(buf, buf->b_u_line_ptr, (size_t)len, fp) != 1)
+    return FAIL;
+  put_bytes(fp, (long_u)buf->b_u_line_lnum, 4);
+  put_bytes(fp, (long_u)buf->b_u_line_colnr, 4);
+
+  /* Undo structures header data */
+  put_header_ptr(fp, buf->b_u_oldhead);
+  put_header_ptr(fp, buf->b_u_newhead);
+  put_header_ptr(fp, buf->b_u_curhead);
+
+  put_bytes(fp, (long_u)buf->b_u_numhead, 4);
+  put_bytes(fp, (long_u)buf->b_u_seq_last, 4);
+  put_bytes(fp, (long_u)buf->b_u_seq_cur, 4);
+  put_time(fp, buf->b_u_time_cur);
+
+  /* Optional fields. */
+  putc(4, fp);
+  putc(UF_LAST_SAVE_NR, fp);
+  put_bytes(fp, (long_u)buf->b_u_save_nr_last, 4);
+
+  putc(0, fp);    /* end marker */
+
+  return OK;
+}
+
+static int serialize_uhp(FILE *fp, buf_T *buf, u_header_T *uhp)
+{
+  int i;
+  u_entry_T   *uep;
+
+  if (put_bytes(fp, (long_u)UF_HEADER_MAGIC, 2) == FAIL)
+    return FAIL;
+
+  put_header_ptr(fp, uhp->uh_next.ptr);
+  put_header_ptr(fp, uhp->uh_prev.ptr);
+  put_header_ptr(fp, uhp->uh_alt_next.ptr);
+  put_header_ptr(fp, uhp->uh_alt_prev.ptr);
+  put_bytes(fp, uhp->uh_seq, 4);
+  serialize_pos(uhp->uh_cursor, fp);
+  put_bytes(fp, (long_u)uhp->uh_cursor_vcol, 4);
+  put_bytes(fp, (long_u)uhp->uh_flags, 2);
+  /* Assume NMARKS will stay the same. */
+  for (i = 0; i < NMARKS; ++i)
+    serialize_pos(uhp->uh_namedm[i], fp);
+  serialize_visualinfo(&uhp->uh_visual, fp);
+  put_time(fp, uhp->uh_time);
+
+  /* Optional fields. */
+  putc(4, fp);
+  putc(UHP_SAVE_NR, fp);
+  put_bytes(fp, (long_u)uhp->uh_save_nr, 4);
+
+  putc(0, fp);    /* end marker */
+
+  /* Write all the entries. */
+  for (uep = uhp->uh_entry; uep != NULL; uep = uep->ue_next) {
+    put_bytes(fp, (long_u)UF_ENTRY_MAGIC, 2);
+    if (serialize_uep(fp, buf, uep) == FAIL)
+      return FAIL;
+  }
+  put_bytes(fp, (long_u)UF_ENTRY_END_MAGIC, 2);
+  return OK;
+}
+
+static u_header_T *unserialize_uhp(FILE *fp, char_u *file_name)
+{
+  u_header_T  *uhp;
+  int i;
+  u_entry_T   *uep, *last_uep;
+  int c;
+  int error;
+
+  uhp = xmalloc(sizeof(u_header_T));
+  memset(uhp, 0, sizeof(u_header_T));
+#ifdef U_DEBUG
+  uhp->uh_magic = UH_MAGIC;
+#endif
+  uhp->uh_next.seq = get4c(fp);
+  uhp->uh_prev.seq = get4c(fp);
+  uhp->uh_alt_next.seq = get4c(fp);
+  uhp->uh_alt_prev.seq = get4c(fp);
+  uhp->uh_seq = get4c(fp);
+  if (uhp->uh_seq <= 0) {
+    corruption_error("uh_seq", file_name);
+    free(uhp);
+    return NULL;
+  }
+  unserialize_pos(&uhp->uh_cursor, fp);
+  uhp->uh_cursor_vcol = get4c(fp);
+  uhp->uh_flags = get2c(fp);
+  for (i = 0; i < NMARKS; ++i)
+    unserialize_pos(&uhp->uh_namedm[i], fp);
+  unserialize_visualinfo(&uhp->uh_visual, fp);
+  uhp->uh_time = get8ctime(fp);
+
+  /* Optional fields. */
+  for (;; ) {
+    int len = getc(fp);
+    int what;
+
+    if (len == 0)
+      break;
+    what = getc(fp);
+    switch (what) {
+    case UHP_SAVE_NR:
+      uhp->uh_save_nr = get4c(fp);
+      break;
+    default:
+      /* field not supported, skip */
+      while (--len >= 0)
+        (void)getc(fp);
+    }
+  }
+
+  /* Unserialize the uep list. */
+  last_uep = NULL;
+  while ((c = get2c(fp)) == UF_ENTRY_MAGIC) {
+    error = FALSE;
+    uep = unserialize_uep(fp, &error, file_name);
+    if (last_uep == NULL)
+      uhp->uh_entry = uep;
+    else
+      last_uep->ue_next = uep;
+    last_uep = uep;
+    if (uep == NULL || error) {
+      u_free_uhp(uhp);
+      return NULL;
+    }
+  }
+  if (c != UF_ENTRY_END_MAGIC) {
+    corruption_error("entry end", file_name);
+    u_free_uhp(uhp);
+    return NULL;
+  }
+
+  return uhp;
+}
+
+/*
+ * Serialize "uep" to "fp".
+ */
+static int serialize_uep(FILE *fp, buf_T *buf, u_entry_T *uep)
+{
+  int i;
+  size_t len;
+
+  put_bytes(fp, (long_u)uep->ue_top, 4);
+  put_bytes(fp, (long_u)uep->ue_bot, 4);
+  put_bytes(fp, (long_u)uep->ue_lcount, 4);
+  put_bytes(fp, (long_u)uep->ue_size, 4);
+  for (i = 0; i < uep->ue_size; ++i) {
+    len = STRLEN(uep->ue_array[i]);
+    if (put_bytes(fp, (long_u)len, 4) == FAIL)
+      return FAIL;
+    if (len > 0 && fwrite_crypt(buf, uep->ue_array[i], len, fp) != 1)
+      return FAIL;
+  }
+  return OK;
+}
+
+static u_entry_T *unserialize_uep(FILE *fp, int *error, char_u *file_name)
+{
+  int i;
+  u_entry_T   *uep;
+  char_u      **array;
+  char_u      *line;
+  int line_len;
+
+  uep = xmalloc(sizeof(u_entry_T));
+  memset(uep, 0, sizeof(u_entry_T));
+#ifdef U_DEBUG
+  uep->ue_magic = UE_MAGIC;
+#endif
+  uep->ue_top = get4c(fp);
+  uep->ue_bot = get4c(fp);
+  uep->ue_lcount = get4c(fp);
+  uep->ue_size = get4c(fp);
+  if (uep->ue_size > 0) {
+    array = xmalloc(sizeof(char_u *) * uep->ue_size);
+    memset(array, 0, sizeof(char_u *) * uep->ue_size);
+  } else
+    array = NULL;
+  uep->ue_array = array;
+
+  for (i = 0; i < uep->ue_size; ++i) {
+    line_len = get4c(fp);
+    if (line_len >= 0)
+      line = read_string_decrypt(curbuf, fp, line_len);
+    else {
+      line = NULL;
+      corruption_error("line length", file_name);
+    }
+    if (line == NULL) {
+      *error = TRUE;
+      return uep;
+    }
+    array[i] = line;
+  }
+  return uep;
+}
+
+/*
+ * Serialize "pos" to "fp".
+ */
+static void serialize_pos(pos_T pos, FILE *fp)
+{
+  put_bytes(fp, (long_u)pos.lnum, 4);
+  put_bytes(fp, (long_u)pos.col, 4);
+  put_bytes(fp, (long_u)pos.coladd, 4);
+}
+
+/*
+ * Unserialize the pos_T at the current position in fp.
+ */
+static void unserialize_pos(pos_T *pos, FILE *fp)
+{
+  pos->lnum = get4c(fp);
+  if (pos->lnum < 0)
+    pos->lnum = 0;
+  pos->col = get4c(fp);
+  if (pos->col < 0)
+    pos->col = 0;
+  pos->coladd = get4c(fp);
+  if (pos->coladd < 0)
+    pos->coladd = 0;
+}
+
+/*
+ * Serialize "info" to "fp".
+ */
+static void serialize_visualinfo(visualinfo_T *info, FILE *fp)
+{
+  serialize_pos(info->vi_start, fp);
+  serialize_pos(info->vi_end, fp);
+  put_bytes(fp, (long_u)info->vi_mode, 4);
+  put_bytes(fp, (long_u)info->vi_curswant, 4);
+}
+
+/*
+ * Unserialize the visualinfo_T at the current position in fp.
+ */
+static void unserialize_visualinfo(visualinfo_T *info, FILE *fp)
+{
+  unserialize_pos(&info->vi_start, fp);
+  unserialize_pos(&info->vi_end, fp);
+  info->vi_mode = get4c(fp);
+  info->vi_curswant = get4c(fp);
+}
+
+/*
+ * Write the pointer to an undo header.  Instead of writing the pointer itself
+ * we use the sequence number of the header.  This is converted back to
+ * pointers when reading. */
+static void put_header_ptr(FIL