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#include <string.h>
#include "_assert.h"
/** search for substring **/
char * strstr(const char *s1, const char *s2)
{
size_t l1 = 0;
size_t l2 = 0;
char *p = (char*)s1;
ASSERT_NONNULL(s1);
ASSERT_NONNULL(s2);
l2 = strlen(s2);
if (l2 == 0) {
return p;
}
l1 = strlen(s1);
do {
p = memchr(p, *s2, l1);
if (p == NULL || strcmp(p + 1, s2 + 1) == 0) {
break;
}
p++;
} while (p < s1 + l2);
/*
RETURN_FAILURE(CONSTANT(NULL));
RETURN_SUCCESS(a pointer to the located string);
*/
return p;
}
/***
finds the first occurrence of the string ARGUMENT(s2) in the string
ARGUMENT(s1). Specifying the empty string for ARGUMENT(s2) matches the first
character of ARGUMENT(s1).
***/
/*
STDC(1)
*/
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