#include <stddef.h>

const void *memchr(const void *ptr, int value, size_t num) {
    const unsigned char *buf = ptr;
    unsigned char val = value;

    for (size_t i = 0; i < num; i++) {
        if (buf[i] == val) {
            return (void *)(buf + i);
        }
    }

    return NULL;
}