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<?php
/**
* This file is part of the ramsey/uuid library
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*
* @copyright Copyright (c) Ben Ramsey <ben@benramsey.com>
* @license http://opensource.org/licenses/MIT MIT
*/
declare(strict_types=1);
namespace Ramsey\Uuid\Generator;
use Brick\Math\BigInteger;
use DateTimeImmutable;
use DateTimeInterface;
use Ramsey\Uuid\Type\Hexadecimal;
use function hash;
use function pack;
use function str_pad;
use function strlen;
use function substr;
use function substr_replace;
use function unpack;
use const PHP_INT_SIZE;
use const STR_PAD_LEFT;
/**
* UnixTimeGenerator generates bytes that combine a 48-bit timestamp in
* milliseconds since the Unix Epoch with 80 random bits
*
* Code and concepts within this class are borrowed from the symfony/uid package
* and are used under the terms of the MIT license distributed with symfony/uid.
*
* symfony/uid is copyright (c) Fabien Potencier.
*
* @link https://symfony.com/components/Uid Symfony Uid component
* @link https://github.com/symfony/uid/blob/4f9f537e57261519808a7ce1d941490736522bbc/UuidV7.php Symfony UuidV7 class
* @link https://github.com/symfony/uid/blob/6.2/LICENSE MIT License
*/
class UnixTimeGenerator implements TimeGeneratorInterface
{
private static string $time = '';
private static ?string $seed = null;
private static int $seedIndex = 0;
/** @var int[] */
private static array $rand = [];
/** @var int[] */
private static array $seedParts;
public function __construct(
private RandomGeneratorInterface $randomGenerator,
private int $intSize = PHP_INT_SIZE
) {
}
/**
* @param Hexadecimal|int|string|null $node Unused in this generator
* @param int|null $clockSeq Unused in this generator
* @param DateTimeInterface $dateTime A date-time instance to use when
* generating bytes
*
* @inheritDoc
*/
public function generate($node = null, ?int $clockSeq = null, ?DateTimeInterface $dateTime = null): string
{
$time = ($dateTime ?? new DateTimeImmutable('now'))->format('Uv');
if ($time > self::$time || ($dateTime !== null && $time !== self::$time)) {
$this->randomize($time);
} else {
$time = $this->increment();
}
if ($this->intSize >= 8) {
$time = substr(pack('J', (int) $time), -6);
} else {
$time = str_pad(BigInteger::of($time)->toBytes(false), 6, "\x00", STR_PAD_LEFT);
}
/** @var non-empty-string */
return $time . pack('n*', self::$rand[1], self::$rand[2], self::$rand[3], self::$rand[4], self::$rand[5]);
}
private function randomize(string $time): void
{
if (self::$seed === null) {
$seed = $this->randomGenerator->generate(16);
self::$seed = $seed;
} else {
$seed = $this->randomGenerator->generate(10);
}
/** @var int[] $rand */
$rand = unpack('n*', $seed);
$rand[1] &= 0x03ff;
self::$rand = $rand;
self::$time = $time;
}
/**
* Special thanks to Nicolas Grekas for sharing the following information:
*
* Within the same ms, we increment the rand part by a random 24-bit number.
*
* Instead of getting this number from random_bytes(), which is slow, we get
* it by sha512-hashing self::$seed. This produces 64 bytes of entropy,
* which we need to split in a list of 24-bit numbers. unpack() first splits
* them into 16 x 32-bit numbers; we take the first byte of each of these
* numbers to get 5 extra 24-bit numbers. Then, we consume those numbers
* one-by-one and run this logic every 21 iterations.
*
* self::$rand holds the random part of the UUID, split into 5 x 16-bit
* numbers for x86 portability. We increment this random part by the next
* 24-bit number in the self::$seedParts list and decrement
* self::$seedIndex.
*
* @link https://twitter.com/nicolasgrekas/status/1583356938825261061 Tweet from Nicolas Grekas
*/
private function increment(): string
{
if (self::$seedIndex === 0 && self::$seed !== null) {
self::$seed = hash('sha512', self::$seed, true);
/** @var int[] $s */
$s = unpack('l*', self::$seed);
$s[] = ($s[1] >> 8 & 0xff0000) | ($s[2] >> 16 & 0xff00) | ($s[3] >> 24 & 0xff);
$s[] = ($s[4] >> 8 & 0xff0000) | ($s[5] >> 16 & 0xff00) | ($s[6] >> 24 & 0xff);
$s[] = ($s[7] >> 8 & 0xff0000) | ($s[8] >> 16 & 0xff00) | ($s[9] >> 24 & 0xff);
$s[] = ($s[10] >> 8 & 0xff0000) | ($s[11] >> 16 & 0xff00) | ($s[12] >> 24 & 0xff);
$s[] = ($s[13] >> 8 & 0xff0000) | ($s[14] >> 16 & 0xff00) | ($s[15] >> 24 & 0xff);
self::$seedParts = $s;
self::$seedIndex = 21;
}
self::$rand[5] = 0xffff & $carry = self::$rand[5] + (self::$seedParts[self::$seedIndex--] & 0xffffff);
self::$rand[4] = 0xffff & $carry = self::$rand[4] + ($carry >> 16);
self::$rand[3] = 0xffff & $carry = self::$rand[3] + ($carry >> 16);
self::$rand[2] = 0xffff & $carry = self::$rand[2] + ($carry >> 16);
self::$rand[1] += $carry >> 16;
if (0xfc00 & self::$rand[1]) {
$time = self::$time;
$mtime = (int) substr($time, -9);
if ($this->intSize >= 8 || strlen($time) < 10) {
$time = (string) ((int) $time + 1);
} elseif ($mtime === 999999999) {
$time = (1 + (int) substr($time, 0, -9)) . '000000000';
} else {
$mtime++;
$time = substr_replace($time, str_pad((string) $mtime, 9, '0', STR_PAD_LEFT), -9);
}
$this->randomize($time);
}
return self::$time;
}
}
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