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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 Ramsey\Uuid\Converter\NumberConverterInterface;
use Ramsey\Uuid\Exception\InvalidArgumentException;
use function bin2hex;
use function explode;
use function hex2bin;
use function microtime;
use function str_pad;
use function substr;
use const STR_PAD_LEFT;
/**
* CombGenerator generates COMBs (combined UUID/timestamp)
*
* The CombGenerator, when used with the StringCodec (and, by proxy, the
* TimestampLastCombCodec) or the TimestampFirstCombCodec, combines the current
* timestamp with a UUID (hence the name "COMB"). The timestamp either appears
* as the first or last 48 bits of the COMB, depending on the codec used.
*
* By default, COMBs will have the timestamp set as the last 48 bits of the
* identifier.
*
* ``` php
* $factory = new UuidFactory();
*
* $factory->setRandomGenerator(new CombGenerator(
* $factory->getRandomGenerator(),
* $factory->getNumberConverter()
* ));
*
* $comb = $factory->uuid4();
* ```
*
* To generate a COMB with the timestamp as the first 48 bits, set the
* TimestampFirstCombCodec as the codec.
*
* ``` php
* $factory->setCodec(new TimestampFirstCombCodec($factory->getUuidBuilder()));
* ```
*
* @link https://www.informit.com/articles/printerfriendly/25862 The Cost of GUIDs as Primary Keys
*/
class CombGenerator implements RandomGeneratorInterface
{
public const TIMESTAMP_BYTES = 6;
public function __construct(
private RandomGeneratorInterface $generator,
private NumberConverterInterface $numberConverter
) {
}
/**
* @throws InvalidArgumentException if $length is not a positive integer
* greater than or equal to CombGenerator::TIMESTAMP_BYTES
*
* @inheritDoc
*/
public function generate(int $length): string
{
if ($length < self::TIMESTAMP_BYTES) {
throw new InvalidArgumentException(
'Length must be a positive integer greater than or equal to ' . self::TIMESTAMP_BYTES
);
}
$hash = '';
if (self::TIMESTAMP_BYTES > 0 && $length > self::TIMESTAMP_BYTES) {
$hash = $this->generator->generate($length - self::TIMESTAMP_BYTES);
}
$lsbTime = str_pad(
$this->numberConverter->toHex($this->timestamp()),
self::TIMESTAMP_BYTES * 2,
'0',
STR_PAD_LEFT
);
return (string) hex2bin(
str_pad(
bin2hex($hash),
$length - self::TIMESTAMP_BYTES,
'0'
)
. $lsbTime
);
}
/**
* Returns current timestamp a string integer, precise to 0.00001 seconds
*/
private function timestamp(): string
{
$time = explode(' ', microtime(false));
return $time[1] . substr($time[0], 2, 5);
}
}
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