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/*
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, version 2.
*
* This program 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, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/module.h>
void *memchr(const void *s, int c, size_t n)
{
/* Get an aligned pointer. */
const uintptr_t s_int = (uintptr_t) s;
const uint32_t *p = (const uint32_t *)(s_int & -4);
/* Create four copies of the byte for which we are looking. */
const uint32_t goal = 0x01010101 * (uint8_t) c;
/* Read the first word, but munge it so that bytes before the array
* will not match goal.
*
* Note that this shift count expression works because we know
* shift counts are taken mod 32.
*/
const uint32_t before_mask = (1 << (s_int << 3)) - 1;
uint32_t v = (*p | before_mask) ^ (goal & before_mask);
/* Compute the address of the last byte. */
const char *const last_byte_ptr = (const char *)s + n - 1;
/* Compute the address of the word containing the last byte. */
const uint32_t *const last_word_ptr =
(const uint32_t *)((uintptr_t) last_byte_ptr & -4);
uint32_t bits;
char *ret;
if (__builtin_expect(n == 0, 0)) {
/* Don't dereference any memory if the array is empty. */
return NULL;
}
while ((bits = __insn_seqb(v, goal)) == 0) {
if (__builtin_expect(p == last_word_ptr, 0)) {
/* We already read the last word in the array,
* so give up.
*/
return NULL;
}
v = *++p;
}
/* We found a match, but it might be in a byte past the end
* of the array.
*/
ret = ((char *)p) + (__insn_ctz(bits) >> 3);
return (ret <= last_byte_ptr) ? ret : NULL;
}
EXPORT_SYMBOL(memchr);
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