/*
 *  Copyright (c) 2019, The OpenThread Authors.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the copyright holder nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 *   This file implements an entropy source based on /dev/urandom or pseudo-random generator.
 */

#include "openthread-posix-config.h"
#include "platform-posix.h"

#include <assert.h>
#include <stdio.h>

#include <openthread/error.h>
#include <openthread/platform/entropy.h>

#include "common/code_utils.hpp"

void platformRandomInit(void)
{
    // Do nothing.
}

otError otPlatEntropyGet(uint8_t *aOutput, uint16_t aOutputLength)
{
    otError error = OT_ERROR_NONE;

    FILE  *file = nullptr;
    size_t readLength;

    VerifyOrExit(aOutput && aOutputLength, error = OT_ERROR_INVALID_ARGS);

    file = fopen("/dev/urandom", "rb");
    VerifyOrExit(file != nullptr, error = OT_ERROR_FAILED);

    readLength = fread(aOutput, 1, aOutputLength, file);
    VerifyOrExit(readLength == aOutputLength, error = OT_ERROR_FAILED);

exit:

    if (file != nullptr)
    {
        fclose(file);
    }
    return error;
}
