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#include "my_base.h"
/*
my_memmem, port of a GNU extension.
Returns a pointer to the beginning of the substring, needle, or NULL if the
substring is not found in haystack.
*/
void *my_memmem(const void *haystack, size_t haystacklen,
const void *needle, size_t needlelen)
{
const unsigned char *cursor;
const unsigned char *last_possible_needle_location =
(unsigned char *)haystack + haystacklen - needlelen;
/* Easy answers */
if (needlelen > haystacklen) return(NULL);
if (needle == NULL) return(NULL);
if (haystack == NULL) return(NULL);
if (needlelen == 0) return(NULL);
if (haystacklen == 0) return(NULL);
for (cursor = haystack; cursor <= last_possible_needle_location; cursor++) {
if (memcmp(needle, cursor, needlelen) == 0) {
return((void *) cursor);
}
}
return(NULL);
}
#ifdef MAIN
#include <assert.h>
int main(int argc, char *argv[]) {
char haystack[10], needle[3];
memmove(haystack, "0123456789", 10);
memmove(needle, "no", 2);
assert(my_memmem(haystack, 10, needle, 2) == NULL);
memmove(needle, "345", 3);
assert(my_memmem(haystack, 10, needle, 3) != NULL);
memmove(needle, "789", 3);
assert(my_memmem(haystack, 10, needle, 3) != NULL);
assert(my_memmem(haystack, 9, needle, 3) == NULL);
memmove(needle, "012", 3);
assert(my_memmem(haystack, 10, needle, 3) != NULL);
assert(my_memmem(NULL, 10, needle, 3) == NULL);
assert(my_memmem(NULL, 10, needle, 3) == NULL);
assert(my_memmem(haystack, 0, needle, 3) == NULL);
assert(my_memmem(haystack, 10, NULL, 3) == NULL);
assert(my_memmem(haystack, 10, needle, 0) == NULL);
assert(my_memmem(haystack, 1, needle, 3) == NULL);
printf("success\n");
return(0);
}
#endif
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