- Patch #1252486 by dixon_, skwashd, heyrocker, Rob Loach: low level UUID API in core.

includes/uuid.inc

+<?php
+
+/**
+ * @file
+ * Handling of universally unique identifiers.
+ */
+
+/**
+ * Interface that defines a UUID backend.
+ */
+interface UuidInterface {
+
+  /**
+   * Generates a Universally Unique IDentifier (UUID).
+   *
+   * @return
+   *   A 32 byte integer represented as a hex string formatted with 4 hypens.
+   */
+  public function generate();
+
+}
+
+/**
+ * Factory class for UUIDs.
+ *
+ * Determines which UUID implementation to use, and uses that to generate
+ * and validate UUIDs.
+ */
+class Uuid {
+
+  /**
+   * Holds the UUID implementation.
+   */
+  protected $plugin;
+
+  /**
+   * This constructor instantiates the correct UUID object.
+   */
+  public function __construct() {
+    $class = $this->determinePlugin();
+    $this->plugin = new $class();
+  }
+
+  /**
+   * Generates an universally unique identifier.
+   *
+   * @see UuidInterface::generate()
+   */
+  public function generate() {
+    return $this->plugin->generate();
+  }
+
+  /**
+   * Check that a string appears to be in the format of a UUID.
+   *
+   * Plugins should not implement validation, since UUIDs should be in a
+   * consistent format across all plugins.
+   *
+   * @param $uuid
+   *   The string to test.
+   *
+   * @return
+   *   TRUE if the string is well formed.
+   */
+  public function isValid($uuid) {
+    return preg_match("/^[0-9a-f]{8}-([0-9a-f]{4}-){3}[0-9a-f]{12}$/", $uuid);
+  }
+
+  /**
+   * Determines the optimal implementation to use for generating UUIDs.
+   *
+   * The selection is made based on the enabled PHP extensions with the
+   * most performant available option chosen.
+   *
+   * @return
+   *  The class name for the optimal UUID generator.
+   */
+  protected function determinePlugin() {
+    static $plugin;
+    if (!empty($plugin)) {
+      return $plugin;
+    }
+
+    $plugin = 'UuidPhp';
+
+    // Debian/Ubuntu uses the (broken) OSSP extension as their UUID
+    // implementation. The OSSP implementation is not compatible with the
+    // PECL functions.
+    if (function_exists('uuid_create') && !function_exists('uuid_make')) {
+      $plugin = 'UuidPecl';
+    }
+    // Try to use the COM implementation for Windows users.
+    elseif (function_exists('com_create_guid')) {
+      $plugin = 'UuidCom';
+    }
+    return $plugin;
+  }
+}
+
+/**
+ * UUID implementation using the PECL extension.
+ */
+class UuidPecl implements UuidInterface {
+  public function generate() {
+    return uuid_create(UUID_TYPE_DEFAULT);
+  }
+}
+
+/**
+ * UUID implementation using the Windows internal GUID extension.
+ *
+ * @see http://php.net/com_create_guid
+ */
+class UuidCom implements UuidInterface {
+  public function generate() {
+    // Remove {} wrapper and make lower case to keep result consistent.
+    return drupal_strtolower(trim(com_create_guid(), '{}'));
+  }
+}
+
+/**
+ * Generates an UUID v4 using PHP code.
+ *
+ * Loosely based on Ruby's UUIDTools generate_random logic.
+ *
+ * @see http://uuidtools.rubyforge.org/api/classes/UUIDTools/UUID.html
+ */
+class UuidPhp implements UuidInterface {
+  public function generate() {
+    $hex = substr(hash('sha256', drupal_random_bytes(16)), 0, 32);
+
+    // The field names refer to RFC 4122 section 4.1.2.
+    $time_low = substr($hex, 0, 8);
+    $time_mid = substr($hex, 8, 4);
+
+    $time_hi_and_version = base_convert(substr($hex, 12, 4), 16, 10);
+    $time_hi_and_version &= 0x0FFF;
+    $time_hi_and_version |= (4 << 12);
+
+    $clock_seq_hi_and_reserved = base_convert(substr($hex, 16, 4), 16, 10);
+    $clock_seq_hi_and_reserved &= 0x3F;
+    $clock_seq_hi_and_reserved |= 0x80;
+
+    $clock_seq_low = substr($hex, 20, 2);
+    $nodes = substr($hex, 20);
+
+    $uuid = sprintf('%s-%s-%04x-%02x%02x-%s',
+      $time_low, $time_mid,
+      $time_hi_and_version, $clock_seq_hi_and_reserved,
+      $clock_seq_low, $nodes);
+
+    return $uuid;
+  }
+}