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   1  <?php
   2  /**
   3   * This file is part of the ramsey/uuid library
   4   *
   5   * For the full copyright and license information, please view the LICENSE
   6   * file that was distributed with this source code.
   7   *
   8   * @copyright Copyright (c) Ben Ramsey <[email protected]>
   9   * @license http://opensource.org/licenses/MIT MIT
  10   * @link https://benramsey.com/projects/ramsey-uuid/ Documentation
  11   * @link https://packagist.org/packages/ramsey/uuid Packagist
  12   * @link https://github.com/ramsey/uuid GitHub
  13   */
  14  
  15  namespace Ramsey\Uuid\Generator;
  16  
  17  use Exception;
  18  use InvalidArgumentException;
  19  use Ramsey\Uuid\Converter\NumberConverterInterface;
  20  use Ramsey\Uuid\Exception\UnsatisfiedDependencyException;
  21  
  22  /**
  23   * CombGenerator provides functionality to generate COMB (combined GUID/timestamp)
  24   * sequential UUIDs
  25   *
  26   * @link https://en.wikipedia.org/wiki/Globally_unique_identifier#Sequential_algorithms
  27   */
  28  class CombGenerator implements RandomGeneratorInterface
  29  {
  30      const TIMESTAMP_BYTES = 6;
  31  
  32      /**
  33       * @var RandomGeneratorInterface
  34       */
  35      private $randomGenerator;
  36  
  37      /**
  38       * @var NumberConverterInterface
  39       */
  40      private $converter;
  41  
  42      /**
  43       * Constructs a `CombGenerator` using a random-number generator and a number converter
  44       *
  45       * @param RandomGeneratorInterface $generator Random-number generator for the non-time part.
  46       * @param NumberConverterInterface $numberConverter Instance of number converter.
  47       */
  48      public function __construct(RandomGeneratorInterface $generator, NumberConverterInterface $numberConverter)
  49      {
  50          $this->converter = $numberConverter;
  51          $this->randomGenerator = $generator;
  52      }
  53  
  54      /**
  55       * Generates a string of binary data of the specified length
  56       *
  57       * @param integer $length The number of bytes of random binary data to generate
  58       * @return string A binary string
  59       * @throws UnsatisfiedDependencyException if `Moontoast\Math\BigNumber` is not present
  60       * @throws InvalidArgumentException if length is not a positive integer
  61       * @throws Exception
  62       */
  63      public function generate($length)
  64      {
  65          if ($length < self::TIMESTAMP_BYTES || $length < 0) {
  66              throw new InvalidArgumentException('Length must be a positive integer.');
  67          }
  68  
  69          $hash = '';
  70  
  71          if (self::TIMESTAMP_BYTES > 0 && $length > self::TIMESTAMP_BYTES) {
  72              $hash = $this->randomGenerator->generate($length - self::TIMESTAMP_BYTES);
  73          }
  74  
  75          $lsbTime = str_pad($this->converter->toHex($this->timestamp()), self::TIMESTAMP_BYTES * 2, '0', STR_PAD_LEFT);
  76  
  77          return hex2bin(str_pad(bin2hex($hash), $length - self::TIMESTAMP_BYTES, '0') . $lsbTime);
  78      }
  79  
  80      /**
  81       * Returns current timestamp as integer, precise to 0.00001 seconds
  82       *
  83       * @return string
  84       */
  85      private function timestamp()
  86      {
  87          $time = explode(' ', microtime(false));
  88  
  89          return $time[1] . substr($time[0], 2, 5);
  90      }
  91  }