<?php
/**
 * Random_* Compatibility Library 
 * for using the new PHP 7 random_* API in PHP 5 projects
 * 
 * The MIT License (MIT)
 * 
 * Copyright (c) 2015 - 2018 Paragon Initiative Enterprises
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

if (!is_callable('random_bytes')) {
    /**
     * Windows with PHP < 5.3.0 will not have the function
     * openssl_random_pseudo_bytes() available, so let's use
     * CAPICOM to work around this deficiency.
     *
     * @param int $bytes
     *
     * @throws Exception
     *
     * @return string
     */
    function random_bytes($bytes)
    {
        try {
            /** @var int $bytes */
            $bytes = RandomCompat_intval($bytes);
        } catch (TypeError $ex) {
            throw new TypeError(
                'random_bytes(): $bytes must be an integer'
            );
        }

        if ($bytes < 1) {
            throw new Error(
                'Length must be greater than 0'
            );
        }

        /** @var string $buf */
        $buf = '';
        if (!class_exists('COM')) {
            throw new Error(
                'COM does not exist'
            );
        }
        /** @var COM $util */
        $util = new COM('CAPICOM.Utilities.1');
        $execCount = 0;

        /**
         * Let's not let it loop forever. If we run N times and fail to
         * get N bytes of random data, then CAPICOM has failed us.
         */
        do {
            $buf .= base64_decode((string) $util->GetRandom($bytes, 0));
            if (RandomCompat_strlen($buf) >= $bytes) {
                /**
                 * Return our random entropy buffer here:
                 */
                return (string) RandomCompat_substr($buf, 0, $bytes);
            }
            ++$execCount;
        } while ($execCount < $bytes);

        /**
         * If we reach here, PHP has failed us.
         */
        throw new Exception(
            'Could not gather sufficient random data'
        );
    }
}