MDL-61038 setuplib: Fixed PECL UUID extension support

lib/setuplib.php

@@ -610,25 +610,25 @@ function get_exception_info($ex) {
 }
 
 /**
- * Generate a uuid.
+ * Generate a V4 UUID.
  *
- * Unique is hard. Very hard. Attempt to use the PECL UUID functions if available, and if not then revert to
+ * Unique is hard. Very hard. Attempt to use the PECL UUID function if available, and if not then revert to
  * constructing the uuid using mt_rand.
  *
  * It is important that this token is not solely based on time as this could lead
  * to duplicates in a clustered environment (especially on VMs due to poor time precision).
  *
+ * @see https://tools.ietf.org/html/rfc4122
+ *
  * @return string The uuid.
  */
 function generate_uuid() {
     $uuid = '';
 
-    if (function_exists("uuid_create")) {
-        $context = null;
-        uuid_create($context);
-
-        uuid_make($context, UUID_MAKE_V4);
-        uuid_export($context, UUID_FMT_STR, $uuid);
+    // Check if PECL UUID extension is available.
+    if (function_exists('uuid_time')) {
+        // Create a V4 UUID.
+        $uuid = uuid_create(UUID_TYPE_RANDOM);
     } else {
         // Fallback uuid generation based on:
         // "http://www.php.net/manual/en/function.uniqid.php#94959".

lib/tests/setuplib_test.php

@@ -476,4 +476,30 @@ class core_setuplib_testcase extends advanced_testcase {
     public function test_get_real_size($input, $expectedbytes) {
         $this->assertEquals($expectedbytes, get_real_size($input));
     }
+
+    /**
+     * Validate the given V4 UUID.
+     *
+     * @param string $value The candidate V4 UUID
+     * @return bool True if valid; otherwise, false.
+     */
+    protected static function is_valid_uuid_v4($value) {
+        // Version 4 UUIDs have the form xxxxxxxx-xxxx-4xxx-Yxxx-xxxxxxxxxxxx
+        // where x is any hexadecimal digit and Y is one of 8, 9, aA, or bB.
+        // First, the size is 36 (32 + 4 dashes).
+        if (strlen($value) != 36) {
+            return false;
+        }
+        // Finally, check the format.
+        $uuidv4pattern = '/^[0-9A-F]{8}-[0-9A-F]{4}-4[0-9A-F]{3}-[89AB][0-9A-F]{3}-[0-9A-F]{12}$/i';
+        return (preg_match($uuidv4pattern, $value) === 1);
+    }
+
+    /**
+     * Test the generate_uuid() function.
+     */
+    public function test_generate_uuid() {
+        $uuid = generate_uuid();
+        $this->assertTrue(self::is_valid_uuid_v4($uuid), "Invalid v4 UUID: '$uuid'");
+    }
 }