Binary.php

<?php
declare(strict_types=1);
namespace ParagonIE\ConstantTime;

use TypeError;

/**
 *  Copyright (c) 2016 - 2022 Paragon Initiative Enterprises.
 *  Copyright (c) 2014 Steve "Sc00bz" Thomas (steve at tobtu dot com)
 *
 *  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.
 */

/**
 * Class Binary
 *
 * Binary string operators that don't choke on
 * mbstring.func_overload
 *
 * @package ParagonIE\ConstantTime
 */
abstract class Binary
{
    /**
     * Safe string length
     *
     * @ref mbstring.func_overload
     *
     * @param string $str
     * @return int
     */
    public static function safeStrlen(
        #[\SensitiveParameter]
        string $str
    ): int {
        if (\function_exists('mb_strlen')) {
            // mb_strlen in PHP 7.x can return false.
            /** @psalm-suppress RedundantCast */
            return (int) \mb_strlen($str, '8bit');
        } else {
            return \strlen($str);
        }
    }

    /**
     * Safe substring
     *
     * @ref mbstring.func_overload
     *
     * @staticvar boolean $exists
     * @param string $str
     * @param int $start
     * @param ?int $length
     * @return string
     *
     * @throws TypeError
     */
    public static function safeSubstr(
        #[\SensitiveParameter]
        string $str,
        int $start = 0,
        $length = null
    ): string {
        if ($length === 0) {
            return '';
        }
        if (\function_exists('mb_substr')) {
            return \mb_substr($str, $start, $length, '8bit');
        }
        // Unlike mb_substr(), substr() doesn't accept NULL for length
        if ($length !== null) {
            return \substr($str, $start, $length);
        } else {
            return \substr($str, $start);
        }
    }
}