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/*
* memmem.c
*
* Find a byte string inside a longer byte string
*
* 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)
{
const unsigned char *y = (const unsigned char *)haystack;
const unsigned char *x = (const unsigned char *)needle;
size_t j, k, l;
if (!m)
return (void *)haystack;
if (m > n)
return NULL;
if (1 != m) {
if (x[0] == x[1]) {
k = 2;
l = 1;
} else {
k = 1;
l = 2;
}
j = 0;
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
do {
if (*y == *x)
return (void *)y;
y++;
} while (--n);
return NULL;
}
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