/*
 * Portable C interface for the system uniform pseudo random
 * generator.
 *
 * Copyright (c) 2009 Manlio Perillo (manlio.perillo@gmail.com)
 *
 */


#if defined (HAVE_URANDOM)
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

/*
 * NOTE: this file descriptor is never explicitly closed.
 * Instead, the operating system will close it when the process
 * terminates.
 */

static int fdUrandom = 0;

int hsUrandom(unsigned char* buf, int num) {
    int n = 0;

    if (fdUrandom == 0) {
        fdUrandom = open("/dev/urandom", O_RDONLY);
        if (fdUrandom == -1) {
            return -1;
        }
    }

    n = read(fdUrandom, buf, num);

    /*
     * TODO: handle the case when less data then requested is read.
     * TODO: handle EINTR.
     */

    if (n != num) {
        return -1;
    }

    return 0;
}

#elif defined (HAVE_SSL)
#include <openssl/rand.h>

int hsUrandom(unsigned char* buf, int num) {
    return RAND_pseudo_bytes(buf, num);
}

#elif defined (HAVE_WIN32_CRYPT)
#include <windows.h>
#include <wincrypt.h>

/*
 * This handle is never explicitly released.
 * Instead, the operating system will release it when the process
 * terminates.
 */

static HCRYPTPROV hCryptProv = 0;

int hsUrandom(unsigned char* buf, int num) {
    if (hCryptProv == 0) {
        if (!CryptAcquireContext(&hCryptProv, NULL, NULL,
                                 PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) {
            return -1;
        }
    }

    if (!CryptGenRandom(hCryptProv, num, buf)) {
        return -1;
    }

    return 0;
}

#else
#error "no suitable source of random data available"
#endif