string/strchrnul.c

   1 /* Copyright (C) 1991-2025 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 <libc-pointer-arith.h>
  19 #include <string-fzb.h>
  20 #include <string-fzc.h>
  21 #include <string-fzi.h>
  22 #include <string-shift.h>
  23 #include <string.h>
  24
  25 #undef __strchrnul
  26 #undef strchrnul
  27
  28 #ifdef STRCHRNUL
  29 # define __strchrnul STRCHRNUL
  30 #endif
  31
  32 /* Find the first occurrence of C in S or the final NUL byte.  */
  33 char *
  34 __strchrnul (const char *str, int c_in)
  35 {
  36   /* Align pointer to sizeof op_t.  */
  37   uintptr_t s_int = (uintptr_t) str;
  38   const op_t *word_ptr = (const op_t *) PTR_ALIGN_DOWN (str, sizeof (op_t));
  39
  40   op_t repeated_c = repeat_bytes (c_in);
  41
  42   op_t word = *word_ptr;
  43   find_t mask = shift_find (find_zero_eq_all (word, repeated_c), s_int);
  44   if (mask != 0)
  45     return (char *) str + index_first (mask);
  46
  47   do
  48     word = *++word_ptr;
  49   while (! has_zero_eq (word, repeated_c));
  50
  51   return (char *) word_ptr + index_first_zero_eq (word, repeated_c);
  52 }
  53 #ifndef STRCHRNUL
  54 libc_hidden_def (__strchrnul)
  55 weak_alias (__strchrnul, strchrnul)
  56 #endif