lib/mbsrchr.c

   1 /* Searching a string for the last occurrence of a character.
   2    Copyright (C) 2007-2024 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2007.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation, either version 3 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <string.h>
  22
  23 #include <stdlib.h>
  24
  25 #if GNULIB_MCEL_PREFER
  26 # include "mcel.h"
  27 #else
  28 # include "mbuiterf.h"
  29 #endif
  30
  31 /* Locate the last single-byte character C in the character string STRING,
  32    and return a pointer to it.  Return NULL if C is not found in STRING.  */
  33 char *
  34 mbsrchr (const char *string, int c)
  35 {
  36   if (MB_CUR_MAX > 1
  37       /* Optimization: We know that ASCII characters < 0x30 don't occur as
  38          part of multibyte characters longer than 1 byte.  Hence, if c < 0x30,
  39          the faster unibyte loop can be used.  */
  40       && (unsigned char) c >= 0x30)
  41     {
  42       const char *result = NULL;
  43
  44 #if GNULIB_MCEL_PREFER
  45       while (*string)
  46         {
  47           mcel_t g = mcel_scanz (string);
  48           if (g.len == 1 && (unsigned char) *string == (unsigned char) c)
  49             result = string;
  50           string += g.len;
  51         }
  52 #else
  53       mbuif_state_t state;
  54       const char *iter;
  55       for (mbuif_init (state), iter = string; mbuif_avail (state, iter); )
  56         {
  57           mbchar_t cur = mbuif_next (state, iter);
  58           if (mb_len (cur) == 1 && (unsigned char) *iter == (unsigned char) c)
  59             result = iter;
  60           iter += mb_len (cur);
  61         }
  62 #endif
  63
  64       return (char *) result;
  65     }
  66   else
  67     return strrchr (string, c);
  68 }