random.c

#include "random.h"
#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <time.h>

void init()
{
    static bool seeded = false;
    if (seeded)
        return;
    srand(time(NULL));

    // See: http://stackoverflow.com/a/7867148/1104531
    rand();

    seeded = true;
}

int randomInt()
{
    init();
    return rand();
}

int randomMax(int max)
{
    if (max - 1 == RAND_MAX)
        return randomInt();

    long end = RAND_MAX / max;
    assert(end > 0L);
    end *= max;

    int r;
    while ((r = randomInt()) >= end);

    return r % max;
}

int randomRange(int min, int max)
{
    //return (rand() / ((double)RAND_MAX + 1.0)) * (max - min + 1) + min;
    return randomMax(max) + min;
}