mirror of
https://sourceware.org/git/glibc.git
synced 2025-10-30 10:45:40 +03:00
2a8867a17f
New algorithm read the first aligned address and mask off the unwanted bytes (this strategy is similar to arch-specific implementations used on powerpc, sparc, and sh). The loop now read word-aligned address and check using the has_eq macro. Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu, and powerpc64-linux-gnu by removing the arch-specific assembly implementation and disabling multi-arch (it covers both LE and BE for 64 and 32 bits). Co-authored-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
89 lines
2.6 KiB
C
89 lines
2.6 KiB
C
/* Scan memory for a character. Generic version
|
|
Copyright (C) 1991-2023 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
|