#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>

void* calloc(size_t nmemb, size_t size)
{
    size_t bytes = nmemb * size;
    void* ptr;
    
    /* Test for overflow.
     * See http://stackoverflow.com/questions/1815367/multiplication-of-large-numbers-how-to-catch-overflow
     */

    if ((nmemb == 0) || (size == 0) || (nmemb > (SIZE_MAX / size)))
        return NULL;
    
    ptr = malloc(bytes);
    if (!ptr)
        return NULL;

    memset(ptr, 0, bytes);
    return ptr;
}