qsort

void __qswap(void *a, int offseta, void *b, int offsetb, size_t size) {
    void *tmp = malloc(size);
    memcpy(tmp, (char*)a + (offseta * size), size);
    memcpy((char*)a + (offseta * size), (char*)b + (offsetb * size), size);
    memcpy((char*)b + (offsetb * size), tmp, size);
    free(tmp);
}

void qs(void *arr, unsigned n, size_t size, int (*comp)(const void*, const void*)) {
    if (n <= 1)
        return;
    int pivot = (n - 1) >> 1;
    int left = 0, right = n - 1;
    void *a = malloc(size), *b = malloc(size);
    while (left < right) {
        memcpy(a, (char*)arr + (left * size), size);
        memcpy(b, (char*)arr + (pivot * size), size);
        while (left < pivot && comp(a, b) < 1) { // while (left < pivot && arr[left] <= arr[pivot])
            ++ left;
            memcpy(a, (char*)arr + (left * size), size);
        }
        memcpy(a, (char*)arr + (right * size), size);
        memcpy(b, (char*)arr + (pivot * size), size);
        while (right > pivot && comp(a, b) > -1) { // while (right > pivot && arr[right] >= arr[pivot])
            -- right;
            memcpy(a, (char*)arr + (right * size), size);
        }
        memcpy(a, (char*)arr + (left * size), size);
        memcpy(b, (char*)arr + (right * size), size);
        if (comp(a, b) == 1) { // if (arr[left] > arr[right])
            if (left == pivot) {
                __qswap(arr, left, arr, right, size);
                pivot = right;
            }
            else if (right == pivot) {
                __qswap(arr, right, arr, left, size);
                pivot = left;
            }
            else {
                __qswap(arr, left, arr, right, size);
            }
        }
        memcpy(a, (char*)arr + (left * size), size);
        memcpy(b, (char*)arr + (right * size), size);
        if (comp(a, b) == 0) // if (arr[left] == arr[right])
            break;
    }
    if (n == 2) {
        memcpy(a, (char*)arr + (0 * size), size);
        memcpy(b, (char*)arr + (1 * size), size);
        if (comp(a, b) == 1) // if (arr[0] > arr[1])
            __qswap(arr, 0, arr, 1, size);
        free(a);
        free(b);
        return;
    }
    free(a);
    free(b);
    qs(arr, pivot, size, comp);
    qs((char*)arr + (pivot * size), n - pivot, size, comp);
}