1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
/*
* 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 > n )
return NULL;
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;
}
}
return NULL;
}
|
