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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* This uses the "Not So Naive" algorithm, a very simple but
* usually effective algorithm, see:
* http://www-igm.univ-mlv.fr/~lecroq/string/
*/
#include <string.h>
void *memmem(const void *haystack, size_t n, const void *needle, size_t m)
{
if (m > n || !m || !n)
return NULL;
if (__builtin_expect((m > 1), 1)) {
const unsigned char* y = (const unsigned char*) haystack;
const unsigned char* x = (const unsigned char*) needle;
size_t j = 0;
size_t k = 1, l = 2;
if (x[0] == x[1]) {
k = 2;
l = 1;
}
while (j <= n-m) {
if (x[1] != y[j+1]) {
j += k;
} else {
if (!memcmp(x+2, y+j+2, m-2) && x[0] == y[j])
return (void*) &y[j];
j += l;
}
}
} else {
/* degenerate case */
return memchr(haystack, ((unsigned char*)needle)[0], n);
}
return NULL;
}
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