memmem.c File Reference

#include <string.h>

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Functions
void *	memmem (const void *l, size_t l_len, const void *s, size_t s_len)
	Find substring s in memory area l. More...

Function Documentation

memmem()

void* memmem	(	const void *	l,
		size_t	l_len,
		const void *	s,
		size_t	s_len
	)

Find substring s in memory area l.

Finds the start of the first occurrence of the substring s of length s_len in the memory area l of length l_len.

The behavior is undefined if access occurs beyond the end of the array (s) searched. The behavior is undefined if s is a null pointer.

Parameters

l	pointer to the object to be examined
l_len	number of characters to examine
s	the substring to search for
s_len	number of characters to examine

Returns

a pointer to the beginning of the substring, or NULL if the substring is not found.

Definition at line 34 of file memmem.c.

{
    const register char *cur, *last;
    const char* cl = (const char*)l;
    const char* cs = (const char*)s;

    /* we need something to compare */
    if(l_len == 0 || s_len == 0)
    {
        return NULL;
    }

    /* "s" must be smaller or equal to "l" */
    if(l_len < s_len)
    {
        return NULL;
    }

    /* special case where s_len == 1 */
    if(s_len == 1)
    {
        return memchr(l, (int)*cs, l_len);
    }

    /* the last position where its possible to find "s" in "l" */
    last = cl + l_len - s_len;

    for(cur = cl; cur <= last; cur++)
    {
        if(cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
        {
            return (void*)(uintptr_t)cur;
        }
    }

    return NULL;
}

References memchr(), memcmp(), and NULL.