string/strcspn.c

   1 /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <stdint.h>
  20 #include <libc-pointer-arith.h>
  21
  22 #undef strcspn
  23
  24 #ifndef STRCSPN
  25 # define STRCSPN strcspn
  26 #endif
  27
  28 /* Return the length of the maximum initial segment of S
  29    which contains no characters from REJECT.  */
  30 size_t
  31 STRCSPN (const char *str, const char *reject)
  32 {
  33   if (__glibc_unlikely (reject[0] == '\0')
  34       || __glibc_unlikely (reject[1] == '\0'))
  35     return __strchrnul (str, reject [0]) - str;
  36
  37   /* Use multiple small memsets to enable inlining on most targets.  */
  38   unsigned char table[256];
  39   unsigned char *p = memset (table, 0, 64);
  40   memset (p + 64, 0, 64);
  41   memset (p + 128, 0, 64);
  42   memset (p + 192, 0, 64);
  43
  44   unsigned char *s = (unsigned char*) reject;
  45   unsigned char tmp;
  46   do
  47     p[tmp = *s++] = 1;
  48   while (tmp);
  49
  50   s = (unsigned char*) str;
  51   if (p[s[0]]) return 0;
  52   if (p[s[1]]) return 1;
  53   if (p[s[2]]) return 2;
  54   if (p[s[3]]) return 3;
  55
  56   s = (unsigned char *) PTR_ALIGN_DOWN (s, 4);
  57
  58   unsigned int c0, c1, c2, c3;
  59   do
  60     {
  61       s += 4;
  62       c0 = p[s[0]];
  63       c1 = p[s[1]];
  64       c2 = p[s[2]];
  65       c3 = p[s[3]];
  66     }
  67   while ((c0 | c1 | c2 | c3) == 0);
  68
  69   size_t count = s - (unsigned char *) str;
  70   return (c0 | c1) != 0 ? count - c0 + 1 : count - c2 + 3;
  71 }
  72 libc_hidden_builtin_def (strcspn)