70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
|
/*
|
||
|
|
* Copyright 2011 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>
|
||
|
|
#include "string-endian.h"
|
||
|
|
|
||
|
|
void *memchr(const void *s, int c, size_t n)
|
||
|
|
{
|
||
|
|
const uint64_t *last_word_ptr;
|
||
|
|
const uint64_t *p;
|
||
|
|
const char *last_byte_ptr;
|
||
|
|
uintptr_t s_int;
|
||
|
|
uint64_t goal, before_mask, v, bits;
|
||
|
|
char *ret;
|
||
|
|
|
||
|
|
if (__builtin_expect(n == 0, 0)) {
|
||
|
|
/* Don't dereference any memory if the array is empty. */
|
||
|
|
return NULL;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Get an aligned pointer. */
|
||
|
|
s_int = (uintptr_t) s;
|
||
|
|
p = (const uint64_t *)(s_int & -8);
|
||
|
|
|
||
|
|
/* Create eight copies of the byte for which we are looking. */
|
||
|
|
goal = copy_byte(c);
|
||
|
|
|
||
|
|
/* Read the first word, but munge it so that bytes before the array
|
||
|
|
* will not match goal.
|
||
|
|
*/
|
||
|
|
before_mask = MASK(s_int);
|
||
|
|
v = (*p | before_mask) ^ (goal & before_mask);
|
||
|
|
|
||
|
|
/* Compute the address of the last byte. */
|
||
|
|
last_byte_ptr = (const char *)s + n - 1;
|
||
|
|
|
||
|
|
/* Compute the address of the word containing the last byte. */
|
||
|
|
last_word_ptr = (const uint64_t *)((uintptr_t) last_byte_ptr & -8);
|
||
|
|
|
||
|
|
while ((bits = __insn_v1cmpeq(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) + (CFZ(bits) >> 3);
|
||
|
|
return (ret <= last_byte_ptr) ? ret : NULL;
|
||
|
|
}
|
||
|
|
EXPORT_SYMBOL(memchr);
|