metaforce/hecl/lib/winsupport.cpp

#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <string>
#include "hecl/winsupport.hpp"

/*
* The memmem() function finds the start of the first occurrence of the
* substring 'needle' of length 'nlen' in the memory area 'haystack' of
* length 'hlen'.
*
* The return value is a pointer to the beginning of the sub-string, or
* NULL if the substring is not found.
*/
void *memmem(const void *haystack, size_t hlen, const void *needle, size_t nlen)
{
    int needle_first;
    const uint8_t *p = static_cast<const uint8_t*>(haystack);
    size_t plen = hlen;

    if (!nlen)
        return NULL;

    needle_first = *(unsigned char *)needle;

    while (plen >= nlen && (p = static_cast<const uint8_t*>(memchr(p, needle_first, plen - nlen + 1))))
    {
        if (!memcmp(p, needle, nlen))
            return (void *)p;

        p++;
        plen = hlen - (p - static_cast<const uint8_t*>(haystack));
    }

    return NULL;
}