lib/unistr/u8-strrchr.c

   1 /* Search character in UTF-8 string.
   2    Copyright (C) 1999, 2002, 2006-2007, 2009-2021 Free Software Foundation,
   3    Inc.
   4    Written by Bruno Haible <bruno@clisp.org>, 2002.
   5
   6    This program is free software: you can redistribute it and/or modify it
   7    under the terms of the GNU Lesser General Public License as published
   8    by the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include "unistr.h"
  23
  24 uint8_t *
  25 u8_strrchr (const uint8_t *s, ucs4_t uc)
  26 {
  27   /* Calling u8_strlen and then searching from the other end would cause more
  28      memory accesses. Avoid that, at the cost of a few more comparisons.  */
  29   uint8_t *result = NULL;
  30   uint8_t c[6];
  31
  32   if (uc < 0x80)
  33     {
  34       uint8_t c0 = uc;
  35
  36       for (;; s++)
  37         {
  38           if (*s == c0)
  39             result = (uint8_t *) s;
  40           if (*s == 0)
  41             break;
  42         }
  43     }
  44   else
  45     switch (u8_uctomb_aux (c, uc, 6))
  46       {
  47       case 2:
  48         if (*s)
  49           {
  50             uint8_t c0 = c[0];
  51             uint8_t c1 = c[1];
  52
  53             /* FIXME: Maybe walking the string via u8_mblen is a win?  */
  54             for (;; s++)
  55               {
  56                 if (s[1] == 0)
  57                   break;
  58                 if (*s == c0 && s[1] == c1)
  59                   result = (uint8_t *) s;
  60               }
  61           }
  62         break;
  63
  64       case 3:
  65         if (*s && s[1])
  66           {
  67             uint8_t c0 = c[0];
  68             uint8_t c1 = c[1];
  69             uint8_t c2 = c[2];
  70
  71             /* FIXME: Maybe walking the string via u8_mblen is a win?  */
  72             for (;; s++)
  73               {
  74                 if (s[2] == 0)
  75                   break;
  76                 if (*s == c0 && s[1] == c1 && s[2] == c2)
  77                   result = (uint8_t *) s;
  78               }
  79           }
  80         break;
  81
  82       case 4:
  83         if (*s && s[1] && s[2])
  84           {
  85             uint8_t c0 = c[0];
  86             uint8_t c1 = c[1];
  87             uint8_t c2 = c[2];
  88             uint8_t c3 = c[3];
  89
  90             /* FIXME: Maybe walking the string via u8_mblen is a win?  */
  91             for (;; s++)
  92               {
  93                 if (s[3] == 0)
  94                   break;
  95                 if (*s == c0 && s[1] == c1 && s[2] == c2 && s[3] == c3)
  96                   result = (uint8_t *) s;
  97               }
  98           }
  99         break;
 100       }
 101   return result;
 102 }