vim-patch:8.2.3139: functions for string manipulation are spread out (#23316)

Problem:    Functions for string manipulation are spread out.
Solution:   Move string related functions to a new source file. (Yegappan
            Lakshmanan, closes vim/vim#8470)

https://github.com/vim/vim/commit/a2438132a675be4dde3acbdf03ba1fdb2f09427c

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

5 files changed, 623 insertions, 621 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index afb8d841a4..5c9d39b91f 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -149,8 +149,6 @@ PRAGMA_DIAG_POP
 static const char *e_listblobarg = N_("E899: Argument of %s must be a List or Blob");
 static const char *e_invalwindow = N_("E957: Invalid window number");
 static const char *e_reduceempty = N_("E998: Reduce of an empty %s with no initial value");
-static const char e_using_number_as_bool_nr[]
-  = N_("E1023: Using a Number as a Bool: %d");
 static const char e_missing_function_argument[]
   = N_("E1132: Missing function argument");
 
@@ -529,41 +527,6 @@ static void f_byte2line(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   }
 }
 
-static void byteidx(typval_T *argvars, typval_T *rettv, int comp)
-{
-  const char *const str = tv_get_string_chk(&argvars[0]);
-  varnumber_T idx = tv_get_number_chk(&argvars[1], NULL);
-  rettv->vval.v_number = -1;
-  if (str == NULL || idx < 0) {
-    return;
-  }
-
-  const char *t = str;
-  for (; idx > 0; idx--) {
-    if (*t == NUL) {  // EOL reached.
-      return;
-    }
-    if (comp) {
-      t += utf_ptr2len(t);
-    } else {
-      t += utfc_ptr2len(t);
-    }
-  }
-  rettv->vval.v_number = (varnumber_T)(t - str);
-}
-
-/// "byteidx()" function
-static void f_byteidx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  byteidx(argvars, rettv, false);
-}
-
-/// "byteidxcomp()" function
-static void f_byteidxcomp(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  byteidx(argvars, rettv, true);
-}
-
 /// "call(func, arglist [, dict])" function
 static void f_call(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -788,50 +751,6 @@ static void f_charcol(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   get_col(argvars, rettv, true);
 }
 
-/// "charidx()" function
-static void f_charidx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->vval.v_number = -1;
-
-  if ((tv_check_for_string_arg(argvars, 0) == FAIL
-       || tv_check_for_number_arg(argvars, 1) == FAIL
-       || tv_check_for_opt_bool_arg(argvars, 2) == FAIL)) {
-    return;
-  }
-
-  const char *str = tv_get_string_chk(&argvars[0]);
-  varnumber_T idx = tv_get_number_chk(&argvars[1], NULL);
-  if (str == NULL || idx < 0) {
-    return;
-  }
-  int countcc = 0;
-  if (argvars[2].v_type != VAR_UNKNOWN) {
-    countcc = (int)tv_get_number(&argvars[2]);
-  }
-  if (countcc < 0 || countcc > 1) {
-    semsg(_(e_using_number_as_bool_nr), countcc);
-    return;
-  }
-
-  int (*ptr2len)(const char *);
-  if (countcc) {
-    ptr2len = utf_ptr2len;
-  } else {
-    ptr2len = utfc_ptr2len;
-  }
-
-  const char *p;
-  int len;
-  for (p = str, len = 0; p <= str + idx; len++) {
-    if (*p == NUL) {
-      return;
-    }
-    p += ptr2len(p);
-  }
-
-  rettv->vval.v_number = len > 0 ? len - 1 : 0;
-}
-
 /// "chdir(dir)" function
 static void f_chdir(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -3447,34 +3366,6 @@ static void f_hostname(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   rettv->vval.v_string = xstrdup(hostname);
 }
 
-/// iconv() function
-static void f_iconv(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  vimconv_T vimconv;
-
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = NULL;
-
-  const char *const str = tv_get_string(&argvars[0]);
-  char buf1[NUMBUFLEN];
-  char *const from = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[1], buf1)));
-  char buf2[NUMBUFLEN];
-  char *const to = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[2], buf2)));
-  vimconv.vc_type = CONV_NONE;
-  convert_setup(&vimconv, from, to);
-
-  // If the encodings are equal, no conversion needed.
-  if (vimconv.vc_type == CONV_NONE) {
-    rettv->vval.v_string = xstrdup(str);
-  } else {
-    rettv->vval.v_string = string_convert(&vimconv, (char *)str, NULL);
-  }
-
-  convert_setup(&vimconv, NULL, NULL);
-  xfree(from);
-  xfree(to);
-}
-
 /// "indent()" function
 static void f_indent(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -8041,60 +7932,6 @@ static void f_str2float(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   rettv->v_type = VAR_FLOAT;
 }
 
-/// "str2list()" function
-static void f_str2list(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  tv_list_alloc_ret(rettv, kListLenUnknown);
-  const char *p = tv_get_string(&argvars[0]);
-
-  for (; *p != NUL; p += utf_ptr2len(p)) {
-    tv_list_append_number(rettv->vval.v_list, utf_ptr2char(p));
-  }
-}
-
-/// "str2nr()" function
-static void f_str2nr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  int base = 10;
-  int what = 0;
-
-  if (argvars[1].v_type != VAR_UNKNOWN) {
-    base = (int)tv_get_number(&argvars[1]);
-    if (base != 2 && base != 8 && base != 10 && base != 16) {
-      emsg(_(e_invarg));
-      return;
-    }
-    if (argvars[2].v_type != VAR_UNKNOWN && tv_get_bool(&argvars[2])) {
-      what |= STR2NR_QUOTE;
-    }
-  }
-
-  char *p = skipwhite(tv_get_string(&argvars[0]));
-  bool isneg = (*p == '-');
-  if (*p == '+' || *p == '-') {
-    p = skipwhite(p + 1);
-  }
-  switch (base) {
-  case 2:
-    what |= STR2NR_BIN | STR2NR_FORCE;
-    break;
-  case 8:
-    what |= STR2NR_OCT | STR2NR_OOCT | STR2NR_FORCE;
-    break;
-  case 16:
-    what |= STR2NR_HEX | STR2NR_FORCE;
-    break;
-  }
-  varnumber_T n;
-  vim_str2nr(p, NULL, NULL, what, &n, NULL, 0, false, NULL);
-  // Text after the number is silently ignored.
-  if (isneg) {
-    rettv->vval.v_number = -n;
-  } else {
-    rettv->vval.v_number = n;
-  }
-}
-
 /// "strftime({format}[, {time}])" function
 static void f_strftime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -8145,235 +7982,6 @@ static void f_strftime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   xfree(enc);
 }
 
-/// "strgetchar()" function
-static void f_strgetchar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->vval.v_number = -1;
-
-  const char *const str = tv_get_string_chk(&argvars[0]);
-  if (str == NULL) {
-    return;
-  }
-  bool error = false;
-  varnumber_T charidx = tv_get_number_chk(&argvars[1], &error);
-  if (error) {
-    return;
-  }
-
-  const size_t len = strlen(str);
-  size_t byteidx = 0;
-
-  while (charidx >= 0 && byteidx < len) {
-    if (charidx == 0) {
-      rettv->vval.v_number = utf_ptr2char(str + byteidx);
-      break;
-    }
-    charidx--;
-    byteidx += (size_t)utf_ptr2len(str + byteidx);
-  }
-}
-
-/// "stridx()" function
-static void f_stridx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->vval.v_number = -1;
-
-  char buf[NUMBUFLEN];
-  const char *const needle = tv_get_string_chk(&argvars[1]);
-  const char *haystack = tv_get_string_buf_chk(&argvars[0], buf);
-  const char *const haystack_start = haystack;
-  if (needle == NULL || haystack == NULL) {
-    return;  // Type error; errmsg already given.
-  }
-
-  if (argvars[2].v_type != VAR_UNKNOWN) {
-    bool error = false;
-
-    const ptrdiff_t start_idx = (ptrdiff_t)tv_get_number_chk(&argvars[2],
-                                                             &error);
-    if (error || start_idx >= (ptrdiff_t)strlen(haystack)) {
-      return;
-    }
-    if (start_idx >= 0) {
-      haystack += start_idx;
-    }
-  }
-
-  const char *pos = strstr(haystack, needle);
-  if (pos != NULL) {
-    rettv->vval.v_number = (varnumber_T)(pos - haystack_start);
-  }
-}
-
-/// "string()" function
-static void f_string(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = encode_tv2string(&argvars[0], NULL);
-}
-
-/// "strlen()" function
-static void f_strlen(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->vval.v_number = (varnumber_T)strlen(tv_get_string(&argvars[0]));
-}
-
-static void strchar_common(typval_T *argvars, typval_T *rettv, bool skipcc)
-{
-  const char *s = tv_get_string(&argvars[0]);
-  varnumber_T len = 0;
-  int (*func_mb_ptr2char_adv)(const char **pp);
-
-  func_mb_ptr2char_adv = skipcc ? mb_ptr2char_adv : mb_cptr2char_adv;
-  while (*s != NUL) {
-    func_mb_ptr2char_adv(&s);
-    len++;
-  }
-  rettv->vval.v_number = len;
-}
-
-/// "strcharlen()" function
-static void f_strcharlen(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  strchar_common(argvars, rettv, true);
-}
-
-/// "strchars()" function
-static void f_strchars(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  int skipcc = false;
-
-  if (argvars[1].v_type != VAR_UNKNOWN) {
-    skipcc = (int)tv_get_bool(&argvars[1]);
-  }
-  if (skipcc < 0 || skipcc > 1) {
-    semsg(_(e_using_number_as_bool_nr), skipcc);
-  } else {
-    strchar_common(argvars, rettv, skipcc);
-  }
-}
-
-/// "strdisplaywidth()" function
-static void f_strdisplaywidth(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  const char *const s = tv_get_string(&argvars[0]);
-  int col = 0;
-
-  if (argvars[1].v_type != VAR_UNKNOWN) {
-    col = (int)tv_get_number(&argvars[1]);
-  }
-
-  rettv->vval.v_number = (varnumber_T)(linetabsize_col(col, (char *)s) - col);
-}
-
-/// "strwidth()" function
-static void f_strwidth(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  const char *const s = tv_get_string(&argvars[0]);
-
-  rettv->vval.v_number = (varnumber_T)mb_string2cells(s);
-}
-
-/// "strcharpart()" function
-static void f_strcharpart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  const char *const p = tv_get_string(&argvars[0]);
-  const size_t slen = strlen(p);
-
-  int nbyte = 0;
-  bool error = false;
-  varnumber_T nchar = tv_get_number_chk(&argvars[1], &error);
-  if (!error) {
-    if (nchar > 0) {
-      while (nchar > 0 && (size_t)nbyte < slen) {
-        nbyte += utf_ptr2len(p + nbyte);
-        nchar--;
-      }
-    } else {
-      nbyte = (int)nchar;
-    }
-  }
-  int len = 0;
-  if (argvars[2].v_type != VAR_UNKNOWN) {
-    int charlen = (int)tv_get_number(&argvars[2]);
-    while (charlen > 0 && nbyte + len < (int)slen) {
-      int off = nbyte + len;
-
-      if (off < 0) {
-        len += 1;
-      } else {
-        len += utf_ptr2len(p + off);
-      }
-      charlen--;
-    }
-  } else {
-    len = (int)slen - nbyte;    // default: all bytes that are available.
-  }
-
-  // Only return the overlap between the specified part and the actual
-  // string.
-  if (nbyte < 0) {
-    len += nbyte;
-    nbyte = 0;
-  } else if ((size_t)nbyte > slen) {
-    nbyte = (int)slen;
-  }
-  if (len < 0) {
-    len = 0;
-  } else if (nbyte + len > (int)slen) {
-    len = (int)slen - nbyte;
-  }
-
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = xstrndup(p + nbyte, (size_t)len);
-}
-
-/// "strpart()" function
-static void f_strpart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  bool error = false;
-
-  const char *const p = tv_get_string(&argvars[0]);
-  const size_t slen = strlen(p);
-
-  varnumber_T n = tv_get_number_chk(&argvars[1], &error);
-  varnumber_T len;
-  if (error) {
-    len = 0;
-  } else if (argvars[2].v_type != VAR_UNKNOWN) {
-    len = tv_get_number(&argvars[2]);
-  } else {
-    len = (varnumber_T)slen - n;  // Default len: all bytes that are available.
-  }
-
-  // Only return the overlap between the specified part and the actual
-  // string.
-  if (n < 0) {
-    len += n;
-    n = 0;
-  } else if (n > (varnumber_T)slen) {
-    n = (varnumber_T)slen;
-  }
-  if (len < 0) {
-    len = 0;
-  } else if (n + len > (varnumber_T)slen) {
-    len = (varnumber_T)slen - n;
-  }
-
-  if (argvars[2].v_type != VAR_UNKNOWN && argvars[3].v_type != VAR_UNKNOWN) {
-    int off;
-
-    // length in characters
-    for (off = (int)n; off < (int)slen && len > 0; len--) {
-      off += utfc_ptr2len(p + off);
-    }
-    len = off - n;
-  }
-
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = xmemdupz(p + n, (size_t)len);
-}
-
 /// "strptime({format}, {timestring})" function
 static void f_strptime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -8406,56 +8014,6 @@ static void f_strptime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   xfree(enc);
 }
 
-/// "strridx()" function
-static void f_strridx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  char buf[NUMBUFLEN];
-  const char *const needle = tv_get_string_chk(&argvars[1]);
-  const char *const haystack = tv_get_string_buf_chk(&argvars[0], buf);
-
-  rettv->vval.v_number = -1;
-  if (needle == NULL || haystack == NULL) {
-    return;  // Type error; errmsg already given.
-  }
-
-  const size_t haystack_len = strlen(haystack);
-  ptrdiff_t end_idx;
-  if (argvars[2].v_type != VAR_UNKNOWN) {
-    // Third argument: upper limit for index.
-    end_idx = (ptrdiff_t)tv_get_number_chk(&argvars[2], NULL);
-    if (end_idx < 0) {
-      return;  // Can never find a match.
-    }
-  } else {
-    end_idx = (ptrdiff_t)haystack_len;
-  }
-
-  const char *lastmatch = NULL;
-  if (*needle == NUL) {
-    // Empty string matches past the end.
-    lastmatch = haystack + end_idx;
-  } else {
-    for (const char *rest = haystack; *rest != NUL; rest++) {
-      rest = strstr(rest, needle);
-      if (rest == NULL || rest > haystack + end_idx) {
-        break;
-      }
-      lastmatch = rest;
-    }
-  }
-
-  if (lastmatch != NULL) {
-    rettv->vval.v_number = (varnumber_T)(lastmatch - haystack);
-  }
-}
-
-/// "strtrans()" function
-static void f_strtrans(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = transstr(tv_get_string(&argvars[0]), true);
-}
-
 /// "submatch()" function
 static void f_submatch(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -9020,185 +8578,6 @@ static void f_timer_stopall(typval_T *argvars, typval_T *unused, EvalFuncData fp
   timer_stop_all();
 }
 
-/// "tolower(string)" function
-static void f_tolower(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = strcase_save(tv_get_string(&argvars[0]), false);
-}
-
-/// "toupper(string)" function
-static void f_toupper(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = strcase_save(tv_get_string(&argvars[0]), true);
-}
-
-/// "tr(string, fromstr, tostr)" function
-static void f_tr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  char buf[NUMBUFLEN];
-  char buf2[NUMBUFLEN];
-
-  const char *in_str = tv_get_string(&argvars[0]);
-  const char *fromstr = tv_get_string_buf_chk(&argvars[1], buf);
-  const char *tostr = tv_get_string_buf_chk(&argvars[2], buf2);
-
-  // Default return value: empty string.
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = NULL;
-  if (fromstr == NULL || tostr == NULL) {
-    return;  // Type error; errmsg already given.
-  }
-  garray_T ga;
-  ga_init(&ga, (int)sizeof(char), 80);
-
-  // fromstr and tostr have to contain the same number of chars.
-  bool first = true;
-  while (*in_str != NUL) {
-    const char *cpstr = in_str;
-    const int inlen = utfc_ptr2len(in_str);
-    int cplen = inlen;
-    int idx = 0;
-    int fromlen;
-    for (const char *p = fromstr; *p != NUL; p += fromlen) {
-      fromlen = utfc_ptr2len(p);
-      if (fromlen == inlen && strncmp(in_str, p, (size_t)inlen) == 0) {
-        int tolen;
-        for (p = tostr; *p != NUL; p += tolen) {
-          tolen = utfc_ptr2len(p);
-          if (idx-- == 0) {
-            cplen = tolen;
-            cpstr = p;
-            break;
-          }
-        }
-        if (*p == NUL) {  // tostr is shorter than fromstr.
-          goto error;
-        }
-        break;
-      }
-      idx++;
-    }
-
-    if (first && cpstr == in_str) {
-      // Check that fromstr and tostr have the same number of
-      // (multi-byte) characters.  Done only once when a character
-      // of in_str doesn't appear in fromstr.
-      first = false;
-      int tolen;
-      for (const char *p = tostr; *p != NUL; p += tolen) {
-        tolen = utfc_ptr2len(p);
-        idx--;
-      }
-      if (idx != 0) {
-        goto error;
-      }
-    }
-
-    ga_grow(&ga, cplen);
-    memmove((char *)ga.ga_data + ga.ga_len, cpstr, (size_t)cplen);
-    ga.ga_len += cplen;
-
-    in_str += inlen;
-  }
-
-  // add a terminating NUL
-  ga_append(&ga, NUL);
-
-  rettv->vval.v_string = ga.ga_data;
-  return;
-error:
-  semsg(_(e_invarg2), fromstr);
-  ga_clear(&ga);
-}
-
-/// "trim({expr})" function
-static void f_trim(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
-{
-  char buf1[NUMBUFLEN];
-  char buf2[NUMBUFLEN];
-  const char *head = tv_get_string_buf_chk(&argvars[0], buf1);
-  const char *mask = NULL;
-  const char *prev;
-  const char *p;
-  int dir = 0;
-
-  rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = NULL;
-  if (head == NULL) {
-    return;
-  }
-
-  if (tv_check_for_opt_string_arg(argvars, 1) == FAIL) {
-    return;
-  }
-
-  if (argvars[1].v_type == VAR_STRING) {
-    mask = tv_get_string_buf_chk(&argvars[1], buf2);
-    if (argvars[2].v_type != VAR_UNKNOWN) {
-      bool error = false;
-      // leading or trailing characters to trim
-      dir = (int)tv_get_number_chk(&argvars[2], &error);
-      if (error) {
-        return;
-      }
-      if (dir < 0 || dir > 2) {
-        semsg(_(e_invarg2), tv_get_string(&argvars[2]));
-        return;
-      }
-    }
-  }
-
-  int c1;
-  if (dir == 0 || dir == 1) {
-    // Trim leading characters
-    while (*head != NUL) {
-      c1 = utf_ptr2char(head);
-      if (mask == NULL) {
-        if (c1 > ' ' && c1 != 0xa0) {
-          break;
-        }
-      } else {
-        for (p = mask; *p != NUL; MB_PTR_ADV(p)) {
-          if (c1 == utf_ptr2char(p)) {
-            break;
-          }
-        }
-        if (*p == NUL) {
-          break;
-        }
-      }
-      MB_PTR_ADV(head);
-    }
-  }
-
-  const char *tail = head + strlen(head);
-  if (dir == 0 || dir == 2) {
-    // Trim trailing characters
-    for (; tail > head; tail = prev) {
-      prev = tail;
-      MB_PTR_BACK(head, prev);
-      c1 = utf_ptr2char(prev);
-      if (mask == NULL) {
-        if (c1 > ' ' && c1 != 0xa0) {
-          break;
-        }
-      } else {
-        for (p = mask; *p != NUL; MB_PTR_ADV(p)) {
-          if (c1 == utf_ptr2char(p)) {
-            break;
-          }
-        }
-        if (*p == NUL) {
-          break;
-        }
-      }
-    }
-  }
-  rettv->vval.v_string = xstrnsave(head, (size_t)(tail - head));
-}
-
 /// "type(expr)" function
 static void f_type(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
diff --git a/src/nvim/generators/gen_eval.lua b/src/nvim/generators/gen_eval.lua
index e574efdf99..7d531bc228 100644
--- a/src/nvim/generators/gen_eval.lua
+++ b/src/nvim/generators/gen_eval.lua
@@ -35,6 +35,7 @@ hashpipe:write([[
 #include "nvim/quickfix.h"
 #include "nvim/runtime.h"
 #include "nvim/search.h"
+#include "nvim/strings.h"
 #include "nvim/sign.h"
 #include "nvim/testing.h"
 
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 0c7f55714c..159bfc202f 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -1003,6 +1003,7 @@ EXTERN const char e_fnametoolong[] INIT(= N_("E856: Filename too long"));
 EXTERN const char e_float_as_string[] INIT(= N_("E806: using Float as a String"));
 EXTERN const char e_inval_string[] INIT(= N_("E908: using an invalid value as a String"));
 EXTERN const char e_cannot_edit_other_buf[] INIT(= N_("E788: Not allowed to edit another buffer now"));
+EXTERN const char e_using_number_as_bool_nr[] INIT(= N_("E1023: Using a Number as a Bool: %d"));
 EXTERN const char e_not_callable_type_str[] INIT(= N_("E1085: Not a callable type: %s"));
 
 EXTERN const char e_cmdmap_err[] INIT(= N_("E5520: <Cmd> mapping must end with <CR>"));
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index ab787524a9..78204b22a8 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -2361,6 +2361,34 @@ static char *iconv_string(const vimconv_T *const vcp, const char *str, size_t sl
   return result;
 }
 
+/// iconv() function
+void f_iconv(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  vimconv_T vimconv;
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = NULL;
+
+  const char *const str = tv_get_string(&argvars[0]);
+  char buf1[NUMBUFLEN];
+  char *const from = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[1], buf1)));
+  char buf2[NUMBUFLEN];
+  char *const to = enc_canonize(enc_skip((char *)tv_get_string_buf(&argvars[2], buf2)));
+  vimconv.vc_type = CONV_NONE;
+  convert_setup(&vimconv, from, to);
+
+  // If the encodings are equal, no conversion needed.
+  if (vimconv.vc_type == CONV_NONE) {
+    rettv->vval.v_string = xstrdup(str);
+  } else {
+    rettv->vval.v_string = string_convert(&vimconv, (char *)str, NULL);
+  }
+
+  convert_setup(&vimconv, NULL, NULL);
+  xfree(from);
+  xfree(to);
+}
+
 /// Setup "vcp" for conversion from "from" to "to".
 /// The names must have been made canonical with enc_canonize().
 /// vcp->vc_type must have been initialized to CONV_NONE.
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index 14aa4ddc1a..d5d7d62c38 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -19,6 +19,7 @@
 #include "nvim/eval/typval.h"
 #include "nvim/eval/typval_defs.h"
 #include "nvim/ex_docmd.h"
+#include "nvim/garray.h"
 #include "nvim/gettext.h"
 #include "nvim/macros.h"
 #include "nvim/math.h"
@@ -26,6 +27,7 @@
 #include "nvim/memory.h"
 #include "nvim/message.h"
 #include "nvim/option.h"
+#include "nvim/plines.h"
 #include "nvim/strings.h"
 #include "nvim/types.h"
 #include "nvim/vim.h"
@@ -1499,3 +1501,594 @@ char *strrep(const char *src, const char *what, const char *rep)
 
   return ret;
 }
+
+static void byteidx(typval_T *argvars, typval_T *rettv, int comp)
+{
+  const char *const str = tv_get_string_chk(&argvars[0]);
+  varnumber_T idx = tv_get_number_chk(&argvars[1], NULL);
+  rettv->vval.v_number = -1;
+  if (str == NULL || idx < 0) {
+    return;
+  }
+
+  const char *t = str;
+  for (; idx > 0; idx--) {
+    if (*t == NUL) {  // EOL reached.
+      return;
+    }
+    if (comp) {
+      t += utf_ptr2len(t);
+    } else {
+      t += utfc_ptr2len(t);
+    }
+  }
+  rettv->vval.v_number = (varnumber_T)(t - str);
+}
+
+/// "byteidx()" function
+void f_byteidx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  byteidx(argvars, rettv, false);
+}
+
+/// "byteidxcomp()" function
+void f_byteidxcomp(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  byteidx(argvars, rettv, true);
+}
+
+/// "charidx()" function
+void f_charidx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->vval.v_number = -1;
+
+  if ((tv_check_for_string_arg(argvars, 0) == FAIL
+       || tv_check_for_number_arg(argvars, 1) == FAIL
+       || tv_check_for_opt_bool_arg(argvars, 2) == FAIL)) {
+    return;
+  }
+
+  const char *str = tv_get_string_chk(&argvars[0]);
+  varnumber_T idx = tv_get_number_chk(&argvars[1], NULL);
+  if (str == NULL || idx < 0) {
+    return;
+  }
+  int countcc = 0;
+  if (argvars[2].v_type != VAR_UNKNOWN) {
+    countcc = (int)tv_get_number(&argvars[2]);
+  }
+  if (countcc < 0 || countcc > 1) {
+    semsg(_(e_using_number_as_bool_nr), countcc);
+    return;
+  }
+
+  int (*ptr2len)(const char *);
+  if (countcc) {
+    ptr2len = utf_ptr2len;
+  } else {
+    ptr2len = utfc_ptr2len;
+  }
+
+  const char *p;
+  int len;
+  for (p = str, len = 0; p <= str + idx; len++) {
+    if (*p == NUL) {
+      return;
+    }
+    p += ptr2len(p);
+  }
+
+  rettv->vval.v_number = len > 0 ? len - 1 : 0;
+}
+
+/// "str2list()" function
+void f_str2list(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  tv_list_alloc_ret(rettv, kListLenUnknown);
+  const char *p = tv_get_string(&argvars[0]);
+
+  for (; *p != NUL; p += utf_ptr2len(p)) {
+    tv_list_append_number(rettv->vval.v_list, utf_ptr2char(p));
+  }
+}
+
+/// "str2nr()" function
+void f_str2nr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  int base = 10;
+  int what = 0;
+
+  if (argvars[1].v_type != VAR_UNKNOWN) {
+    base = (int)tv_get_number(&argvars[1]);
+    if (base != 2 && base != 8 && base != 10 && base != 16) {
+      emsg(_(e_invarg));
+      return;
+    }
+    if (argvars[2].v_type != VAR_UNKNOWN && tv_get_bool(&argvars[2])) {
+      what |= STR2NR_QUOTE;
+    }
+  }
+
+  char *p = skipwhite(tv_get_string(&argvars[0]));
+  bool isneg = (*p == '-');
+  if (*p == '+' || *p == '-') {
+    p = skipwhite(p + 1);
+  }
+  switch (base) {
+  case 2:
+    what |= STR2NR_BIN | STR2NR_FORCE;
+    break;
+  case 8:
+    what |= STR2NR_OCT | STR2NR_OOCT | STR2NR_FORCE;
+    break;
+  case 16:
+    what |= STR2NR_HEX | STR2NR_FORCE;
+    break;
+  }
+  varnumber_T n;
+  vim_str2nr(p, NULL, NULL, what, &n, NULL, 0, false, NULL);
+  // Text after the number is silently ignored.
+  if (isneg) {
+    rettv->vval.v_number = -n;
+  } else {
+    rettv->vval.v_number = n;
+  }
+}
+
+/// "strgetchar()" function
+void f_strgetchar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->vval.v_number = -1;
+
+  const char *const str = tv_get_string_chk(&argvars[0]);
+  if (str == NULL) {
+    return;
+  }
+  bool error = false;
+  varnumber_T charidx = tv_get_number_chk(&argvars[1], &error);
+  if (error) {
+    return;
+  }
+
+  const size_t len = strlen(str);
+  size_t byteidx = 0;
+
+  while (charidx >= 0 && byteidx < len) {
+    if (charidx == 0) {
+      rettv->vval.v_number = utf_ptr2char(str + byteidx);
+      break;
+    }
+    charidx--;
+    byteidx += (size_t)utf_ptr2len(str + byteidx);
+  }
+}
+
+/// "stridx()" function
+void f_stridx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->vval.v_number = -1;
+
+  char buf[NUMBUFLEN];
+  const char *const needle = tv_get_string_chk(&argvars[1]);
+  const char *haystack = tv_get_string_buf_chk(&argvars[0], buf);
+  const char *const haystack_start = haystack;
+  if (needle == NULL || haystack == NULL) {
+    return;  // Type error; errmsg already given.
+  }
+
+  if (argvars[2].v_type != VAR_UNKNOWN) {
+    bool error = false;
+
+    const ptrdiff_t start_idx = (ptrdiff_t)tv_get_number_chk(&argvars[2],
+                                                             &error);
+    if (error || start_idx >= (ptrdiff_t)strlen(haystack)) {
+      return;
+    }
+    if (start_idx >= 0) {
+      haystack += start_idx;
+    }
+  }
+
+  const char *pos = strstr(haystack, needle);
+  if (pos != NULL) {
+    rettv->vval.v_number = (varnumber_T)(pos - haystack_start);
+  }
+}
+
+/// "string()" function
+void f_string(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = encode_tv2string(&argvars[0], NULL);
+}
+
+/// "strlen()" function
+void f_strlen(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->vval.v_number = (varnumber_T)strlen(tv_get_string(&argvars[0]));
+}
+
+static void strchar_common(typval_T *argvars, typval_T *rettv, bool skipcc)
+{
+  const char *s = tv_get_string(&argvars[0]);
+  varnumber_T len = 0;
+  int (*func_mb_ptr2char_adv)(const char **pp);
+
+  func_mb_ptr2char_adv = skipcc ? mb_ptr2char_adv : mb_cptr2char_adv;
+  while (*s != NUL) {
+    func_mb_ptr2char_adv(&s);
+    len++;
+  }
+  rettv->vval.v_number = len;
+}
+
+/// "strcharlen()" function
+void f_strcharlen(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  strchar_common(argvars, rettv, true);
+}
+
+/// "strchars()" function
+void f_strchars(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  int skipcc = false;
+
+  if (argvars[1].v_type != VAR_UNKNOWN) {
+    skipcc = (int)tv_get_bool(&argvars[1]);
+  }
+  if (skipcc < 0 || skipcc > 1) {
+    semsg(_(e_using_number_as_bool_nr), skipcc);
+  } else {
+    strchar_common(argvars, rettv, skipcc);
+  }
+}
+
+/// "strdisplaywidth()" function
+void f_strdisplaywidth(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  const char *const s = tv_get_string(&argvars[0]);
+  int col = 0;
+
+  if (argvars[1].v_type != VAR_UNKNOWN) {
+    col = (int)tv_get_number(&argvars[1]);
+  }
+
+  rettv->vval.v_number = (varnumber_T)(linetabsize_col(col, (char *)s) - col);
+}
+
+/// "strwidth()" function
+void f_strwidth(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  const char *const s = tv_get_string(&argvars[0]);
+
+  rettv->vval.v_number = (varnumber_T)mb_string2cells(s);
+}
+
+/// "strcharpart()" function
+void f_strcharpart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  const char *const p = tv_get_string(&argvars[0]);
+  const size_t slen = strlen(p);
+
+  int nbyte = 0;
+  bool error = false;
+  varnumber_T nchar = tv_get_number_chk(&argvars[1], &error);
+  if (!error) {
+    if (nchar > 0) {
+      while (nchar > 0 && (size_t)nbyte < slen) {
+        nbyte += utf_ptr2len(p + nbyte);
+        nchar--;
+      }
+    } else {
+      nbyte = (int)nchar;
+    }
+  }
+  int len = 0;
+  if (argvars[2].v_type != VAR_UNKNOWN) {
+    int charlen = (int)tv_get_number(&argvars[2]);
+    while (charlen > 0 && nbyte + len < (int)slen) {
+      int off = nbyte + len;
+
+      if (off < 0) {
+        len += 1;
+      } else {
+        len += utf_ptr2len(p + off);
+      }
+      charlen--;
+    }
+  } else {
+    len = (int)slen - nbyte;    // default: all bytes that are available.
+  }
+
+  // Only return the overlap between the specified part and the actual
+  // string.
+  if (nbyte < 0) {
+    len += nbyte;
+    nbyte = 0;
+  } else if ((size_t)nbyte > slen) {
+    nbyte = (int)slen;
+  }
+  if (len < 0) {
+    len = 0;
+  } else if (nbyte + len > (int)slen) {
+    len = (int)slen - nbyte;
+  }
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = xstrndup(p + nbyte, (size_t)len);
+}
+
+/// "strpart()" function
+void f_strpart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  bool error = false;
+
+  const char *const p = tv_get_string(&argvars[0]);
+  const size_t slen = strlen(p);
+
+  varnumber_T n = tv_get_number_chk(&argvars[1], &error);
+  varnumber_T len;
+  if (error) {
+    len = 0;
+  } else if (argvars[2].v_type != VAR_UNKNOWN) {
+    len = tv_get_number(&argvars[2]);
+  } else {
+    len = (varnumber_T)slen - n;  // Default len: all bytes that are available.
+  }
+
+  // Only return the overlap between the specified part and the actual
+  // string.
+  if (n < 0) {
+    len += n;
+    n = 0;
+  } else if (n > (varnumber_T)slen) {
+    n = (varnumber_T)slen;
+  }
+  if (len < 0) {
+    len = 0;
+  } else if (n + len > (varnumber_T)slen) {
+    len = (varnumber_T)slen - n;
+  }
+
+  if (argvars[2].v_type != VAR_UNKNOWN && argvars[3].v_type != VAR_UNKNOWN) {
+    int off;
+
+    // length in characters
+    for (off = (int)n; off < (int)slen && len > 0; len--) {
+      off += utfc_ptr2len(p + off);
+    }
+    len = off - n;
+  }
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = xmemdupz(p + n, (size_t)len);
+}
+
+/// "strridx()" function
+void f_strridx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  char buf[NUMBUFLEN];
+  const char *const needle = tv_get_string_chk(&argvars[1]);
+  const char *const haystack = tv_get_string_buf_chk(&argvars[0], buf);
+
+  rettv->vval.v_number = -1;
+  if (needle == NULL || haystack == NULL) {
+    return;  // Type error; errmsg already given.
+  }
+
+  const size_t haystack_len = strlen(haystack);
+  ptrdiff_t end_idx;
+  if (argvars[2].v_type != VAR_UNKNOWN) {
+    // Third argument: upper limit for index.
+    end_idx = (ptrdiff_t)tv_get_number_chk(&argvars[2], NULL);
+    if (end_idx < 0) {
+      return;  // Can never find a match.
+    }
+  } else {
+    end_idx = (ptrdiff_t)haystack_len;
+  }
+
+  const char *lastmatch = NULL;
+  if (*needle == NUL) {
+    // Empty string matches past the end.
+    lastmatch = haystack + end_idx;
+  } else {
+    for (const char *rest = haystack; *rest != NUL; rest++) {
+      rest = strstr(rest, needle);
+      if (rest == NULL || rest > haystack + end_idx) {
+        break;
+      }
+      lastmatch = rest;
+    }
+  }
+
+  if (lastmatch != NULL) {
+    rettv->vval.v_number = (varnumber_T)(lastmatch - haystack);
+  }
+}
+
+/// "strtrans()" function
+void f_strtrans(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = transstr(tv_get_string(&argvars[0]), true);
+}
+
+/// "tolower(string)" function
+void f_tolower(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = strcase_save(tv_get_string(&argvars[0]), false);
+}
+
+/// "toupper(string)" function
+void f_toupper(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = strcase_save(tv_get_string(&argvars[0]), true);
+}
+
+/// "tr(string, fromstr, tostr)" function
+void f_tr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  char buf[NUMBUFLEN];
+  char buf2[NUMBUFLEN];
+
+  const char *in_str = tv_get_string(&argvars[0]);
+  const char *fromstr = tv_get_string_buf_chk(&argvars[1], buf);
+  const char *tostr = tv_get_string_buf_chk(&argvars[2], buf2);
+
+  // Default return value: empty string.
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = NULL;
+  if (fromstr == NULL || tostr == NULL) {
+    return;  // Type error; errmsg already given.
+  }
+  garray_T ga;
+  ga_init(&ga, (int)sizeof(char), 80);
+
+  // fromstr and tostr have to contain the same number of chars.
+  bool first = true;
+  while (*in_str != NUL) {
+    const char *cpstr = in_str;
+    const int inlen = utfc_ptr2len(in_str);
+    int cplen = inlen;
+    int idx = 0;
+    int fromlen;
+    for (const char *p = fromstr; *p != NUL; p += fromlen) {
+      fromlen = utfc_ptr2len(p);
+      if (fromlen == inlen && strncmp(in_str, p, (size_t)inlen) == 0) {
+        int tolen;
+        for (p = tostr; *p != NUL; p += tolen) {
+          tolen = utfc_ptr2len(p);
+          if (idx-- == 0) {
+            cplen = tolen;
+            cpstr = p;
+            break;
+          }
+        }
+        if (*p == NUL) {  // tostr is shorter than fromstr.
+          goto error;
+        }
+        break;
+      }
+      idx++;
+    }
+
+    if (first && cpstr == in_str) {
+      // Check that fromstr and tostr have the same number of
+      // (multi-byte) characters.  Done only once when a character
+      // of in_str doesn't appear in fromstr.
+      first = false;
+      int tolen;
+      for (const char *p = tostr; *p != NUL; p += tolen) {
+        tolen = utfc_ptr2len(p);
+        idx--;
+      }
+      if (idx != 0) {
+        goto error;
+      }
+    }
+
+    ga_grow(&ga, cplen);
+    memmove((char *)ga.ga_data + ga.ga_len, cpstr, (size_t)cplen);
+    ga.ga_len += cplen;
+
+    in_str += inlen;
+  }
+
+  // add a terminating NUL
+  ga_append(&ga, NUL);
+
+  rettv->vval.v_string = ga.ga_data;
+  return;
+error:
+  semsg(_(e_invarg2), fromstr);
+  ga_clear(&ga);
+}
+
+/// "trim({expr})" function
+void f_trim(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  char buf1[NUMBUFLEN];
+  char buf2[NUMBUFLEN];
+  const char *head = tv_get_string_buf_chk(&argvars[0], buf1);
+  const char *mask = NULL;
+  const char *prev;
+  const char *p;
+  int dir = 0;
+
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = NULL;
+  if (head == NULL) {
+    return;
+  }
+
+  if (tv_check_for_opt_string_arg(argvars, 1) == FAIL) {
+    return;
+  }
+
+  if (argvars[1].v_type == VAR_STRING) {
+    mask = tv_get_string_buf_chk(&argvars[1], buf2);
+    if (argvars[2].v_type != VAR_UNKNOWN) {
+      bool error = false;
+      // leading or trailing characters to trim
+      dir = (int)tv_get_number_chk(&argvars[2], &error);
+      if (error) {
+        return;
+      }
+      if (dir < 0 || dir > 2) {
+        semsg(_(e_invarg2), tv_get_string(&argvars[2]));
+        return;
+      }
+    }
+  }
+
+  int c1;
+  if (dir == 0 || dir == 1) {
+    // Trim leading characters
+    while (*head != NUL) {
+      c1 = utf_ptr2char(head);
+      if (mask == NULL) {
+        if (c1 > ' ' && c1 != 0xa0) {
+          break;
+        }
+      } else {
+        for (p = mask; *p != NUL; MB_PTR_ADV(p)) {
+          if (c1 == utf_ptr2char(p)) {
+            break;
+          }
+        }
+        if (*p == NUL) {
+          break;
+        }
+      }
+      MB_PTR_ADV(head);
+    }
+  }
+
+  const char *tail = head + strlen(head);
+  if (dir == 0 || dir == 2) {
+    // Trim trailing characters
+    for (; tail > head; tail = prev) {
+      prev = tail;
+      MB_PTR_BACK(head, prev);
+      c1 = utf_ptr2char(prev);
+      if (mask == NULL) {
+        if (c1 > ' ' && c1 != 0xa0) {
+          break;
+        }
+      } else {
+        for (p = mask; *p != NUL; MB_PTR_ADV(p)) {
+          if (c1 == utf_ptr2char(p)) {
+            break;
+          }
+        }
+        if (*p == NUL) {
+          break;
+        }
+      }
+    }
+  }
+  rettv->vval.v_string = xstrnsave(head, (size_t)(tail - head));
+}