<?php
  
  /**
   * UUID Utility
   *
   * This class has static methods to generate and validate UUID's.
   * UUIDs are used a decent amount within various *DAV standards, so it made
   * sense to include it.
   *
   * @package Sabre
   * @subpackage DAV
   * @copyright Copyright (C) 2007-2013 Rooftop Solutions. All rights reserved.
   * @author Evert Pot (http://www.rooftopsolutions.nl/)
   * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
   */
  class Sabre_DAV_UUIDUtil {
  
      /**
       * Returns a pseudo-random v4 UUID
       *
       * This function is based on a comment by Andrew Moore on php.net
       *
       * @see http://www.php.net/manual/en/function.uniqid.php#94959
       * @return string
       */
      static function getUUID() {
  
          return sprintf( '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
              // 32 bits for "time_low"
              mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ),
  
              // 16 bits for "time_mid"
              mt_rand( 0, 0xffff ),
  
              // 16 bits for "time_hi_and_version",
              // four most significant bits holds version number 4
              mt_rand( 0, 0x0fff ) | 0x4000,
  
              // 16 bits, 8 bits for "clk_seq_hi_res",
              // 8 bits for "clk_seq_low",
              // two most significant bits holds zero and one for variant DCE1.1
              mt_rand( 0, 0x3fff ) | 0x8000,
  
              // 48 bits for "node"
              mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff )
          );
      }
  
      /**
       * Checks if a string is a valid UUID.
       *
       * @param string $uuid
       * @return bool
       */
      static function validateUUID($uuid) {
  
          return preg_match(
              '/^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}$/i',
              $uuid
          ) == true;
  
      }
  
  }