strings: Remove vim_strbyte

Ref #1476

src/nvim/ex_cmds.c

@@ -5087,14 +5087,13 @@ static void helptags_one(char_u *dir, char_u *ext, char_u *tagfname,
       }
       p1 = vim_strchr(IObuff, '*');             /* find first '*' */
       while (p1 != NULL) {
-        /* Use vim_strbyte() instead of vim_strchr() so that when
-         * 'encoding' is dbcs it still works, don't find '*' in the
-         * second byte. */
-        p2 = vim_strbyte(p1 + 1, '*');          /* find second '*' */
-        if (p2 != NULL && p2 > p1 + 1) {        /* skip "*" and "**" */
-          for (s = p1 + 1; s < p2; ++s)
-            if (*s == ' ' || *s == '\t' || *s == '|')
+        p2 = (char_u *)strchr((const char *)p1 + 1, '*');  // Find second '*'.
+        if (p2 != NULL && p2 > p1 + 1) {  // Skip "*" and "**".
+          for (s = p1 + 1; s < p2; s++) {
+            if (*s == ' ' || *s == '\t' || *s == '|') {
               break;
+            }
+          }
 
           /*
            * Only accept a *tag* when it consists of valid

src/nvim/getchar.c

@@ -3588,8 +3588,8 @@ int check_abbr(int c, char_u *ptr, int col, int mincol)
       char_u *q = mp->m_keys;
       int match;
 
-      if (vim_strbyte(mp->m_keys, K_SPECIAL) != NULL) {
-        /* might have CSI escaped mp->m_keys */
+      if (strchr((const char *)mp->m_keys, K_SPECIAL) != NULL) {
+        // Might have CSI escaped mp->m_keys.
         q = vim_strsave(mp->m_keys);
         vim_unescape_csi(q);
         qlen = (int)STRLEN(q);

src/nvim/mbyte.c

@@ -356,10 +356,10 @@ int bomb_size(void)
  */
 void remove_bom(char_u *s)
 {
-  char_u *p = s;
+  char *p = (char *)s;
 
-  while ((p = vim_strbyte(p, 0xef)) != NULL) {
-    if (p[1] == 0xbb && p[2] == 0xbf) {
+  while ((p = strchr(p, 0xef)) != NULL) {
+    if ((uint8_t)p[1] == 0xbb && (uint8_t)p[2] == 0xbf) {
       STRMOVE(p, p + 3);
     } else {
       p++;

src/nvim/regexp.c

@@ -3429,32 +3429,26 @@ static long bt_regexec_both(char_u *line,
       c = *prog->regmust;
     s = line + col;
 
-    /*
-     * This is used very often, esp. for ":global".  Use three versions of
-     * the loop to avoid overhead of conditions.
-     */
-    if (!ireg_ic
-        && !has_mbyte
-        )
-      while ((s = vim_strbyte(s, c)) != NULL) {
-        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
-          break;                        /* Found it. */
-        ++s;
-      }
-    else if (!ireg_ic || (!enc_utf8 && mb_char2len(c) > 1))
+    // This is used very often, esp. for ":global".  Use two versions of
+    // the loop to avoid overhead of conditions.
+    if (!ireg_ic) {
       while ((s = vim_strchr(s, c)) != NULL) {
-        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
-          break;                        /* Found it. */
+        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0) {
+          break;  // Found it.
+        }
         mb_ptr_adv(s);
       }
-    else
+    } else {
       while ((s = cstrchr(s, c)) != NULL) {
-        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
-          break;                        /* Found it. */
+        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0) {
+          break;  // Found it.
+        }
         mb_ptr_adv(s);
       }
-    if (s == NULL)              /* Not present. */
+    }
+    if (s == NULL) {  // Not present.
       goto theend;
+    }
   }
 
   regline = line;
@@ -3484,14 +3478,8 @@ static long bt_regexec_both(char_u *line,
     /* Messy cases:  unanchored match. */
     while (!got_int) {
       if (prog->regstart != NUL) {
-        /* Skip until the char we know it must start with.
-         * Used often, do some work to avoid call overhead. */
-        if (!ireg_ic
-            && !has_mbyte
-            )
-          s = vim_strbyte(regline + col, prog->regstart);
-        else
-          s = cstrchr(regline + col, prog->regstart);
+        // Skip until the char we know it must start with.
+        s = cstrchr(regline + col, prog->regstart);
         if (s == NULL) {
           retval = 0;
           break;

src/nvim/regexp_nfa.c

@@ -4855,17 +4855,10 @@ static int failure_chance(nfa_state_T *state, int depth)
  */
 static int skip_to_start(int c, colnr_T *colp)
 {
-  char_u *s;
-
-  /* Used often, do some work to avoid call overhead. */
-  if (!ireg_ic
-      && !has_mbyte
-      )
-    s = vim_strbyte(regline + *colp, c);
-  else
-    s = cstrchr(regline + *colp, c);
-  if (s == NULL)
+  const char_u *const s = cstrchr(regline + *colp, c);
+  if (s == NULL) {
     return FAIL;
+  }
   *colp = (int)(s - regline);
   return OK;
 }

src/nvim/strings.c

@@ -425,24 +425,6 @@ char_u *vim_strchr(const char_u *const string, const int c)
   }
 }
 
-/*
- * Version of strchr() that only works for bytes and handles unsigned char
- * strings with characters above 128 correctly. It also doesn't return a
- * pointer to the NUL at the end of the string.
- */
-char_u *vim_strbyte(const char_u *string, int c)
-  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
-{
-  const char_u *p = string;
-
-  while (*p != NUL) {
-    if (*p == c)
-      return (char_u *) p;
-    ++p;
-  }
-  return NULL;
-}
-
 /*
  * Search for last occurrence of "c" in "string".
  * Return NULL if not found.