/***********************************************************************************
 * FourQlib: a high-performance crypto library based on the elliptic curve FourQ
 *
 *    Copyright (c) Microsoft Corporation. All rights reserved.
 *
 * Abstract: pseudo-random function
 ************************************************************************************/

#include "fourq/random.h"
#include <stdbool.h>
#include <stdlib.h>
#if defined(__WINDOWS__)
#include <windows.h>
#include <bcrypt.h>
#define RTL_GENRANDOM "SystemFunction036"
NTSTATUS last_bcrypt_error = 0;
#elif defined(__LINUX__)
#include <fcntl.h>
#include <unistd.h>
static int lock = -1;
#endif

#ifdef __LINUX__
static __inline void delay(unsigned int count)
{
    while (count--) {
    }
}
#endif

int random_bytes(unsigned char *random_array, unsigned int nbytes)
{ // Generation of "nbytes" of random values

#if defined(__WINDOWS__)
    if (BCRYPT_SUCCESS(last_bcrypt_error)) {
        NTSTATUS status =
            BCryptGenRandom(NULL, random_array, nbytes, BCRYPT_USE_SYSTEM_PREFERRED_RNG);

        if (BCRYPT_SUCCESS(status)) {
            return true;
        }
        last_bcrypt_error = status;
    }

    HMODULE hAdvApi = LoadLibraryA("ADVAPI32.DLL");
    if (!hAdvApi) {
        return false;
    }

    BOOLEAN(APIENTRY * RtlGenRandom)
    (void *, ULONG) = (BOOLEAN(APIENTRY *)(void *, ULONG))GetProcAddress(hAdvApi, RTL_GENRANDOM);

    BOOLEAN genrand_result = FALSE;
    if (RtlGenRandom) {
        genrand_result = RtlGenRandom(random_array, nbytes);
    }

    FreeLibrary(hAdvApi);

    if (!genrand_result) {
        return false;
    }

#elif defined(__LINUX__)
    int r, n = nbytes, count = 0;

    if (lock == -1) {
        do {
            lock = open("/dev/urandom", O_RDONLY);
            if (lock == -1) {
                delay(0xFFFFF);
            }
        } while (lock == -1);
    }

    while (n > 0) {
        do {
            r = read(lock, random_array + count, n);
            if (r == -1) {
                delay(0xFFFF);
            }
        } while (r == -1);
        count += r;
        n -= r;
    }
#endif

    return true;
}