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/* Scan memory for a character. Generic version
Copyright (C) 1991-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <libc-pointer-arith.h>
#include <string-fzb.h>
#include <string-fzc.h>
#include <string-fzi.h>
#include <string-shift.h>
#include <string.h>
#undef memchr
#ifdef MEMCHR
# define __memchr MEMCHR
#endif
static __always_inline const char *
sadd (uintptr_t x, uintptr_t y)
{
return (const char *)(y > UINTPTR_MAX - x ? UINTPTR_MAX : x + y);
}
/* Search no more than N bytes of S for C. */
void *
__memchr (void const *s, int c_in, size_t n)
{
if (__glibc_unlikely (n == 0))
return NULL;
/* Read the first word, but munge it so that bytes before the array
will not match goal. */
const op_t *word_ptr = PTR_ALIGN_DOWN (s, sizeof (op_t));
uintptr_t s_int = (uintptr_t) s;
op_t word = *word_ptr;
op_t repeated_c = repeat_bytes (c_in);
/* Compute the address of the last byte taking in consideration possible
overflow. */
const char *lbyte = sadd (s_int, n - 1);
/* And also the address of the word containing the last byte. */
const op_t *lword = (const op_t *) PTR_ALIGN_DOWN (lbyte, sizeof (op_t));
find_t mask = shift_find (find_eq_all (word, repeated_c), s_int);
if (mask != 0)
{
char *ret = (char *) s + index_first (mask);
return (ret <= lbyte) ? ret : NULL;
}
if (word_ptr == lword)
return NULL;
word = *++word_ptr;
while (word_ptr != lword)
{
if (has_eq (word, repeated_c))
return (char *) word_ptr + index_first_eq (word, repeated_c);
word = *++word_ptr;
}
if (has_eq (word, repeated_c))
{
/* We found a match, but it might be in a byte past the end of the
array. */
char *ret = (char *) word_ptr + index_first_eq (word, repeated_c);
if (ret <= lbyte)
return ret;
}
return NULL;
}
#ifndef MEMCHR
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
#endif
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