Updated includes/utilities to includea get_uuid() function and an associated helper function. This functionality, for the time being, also resides as private functions in Repository.php file in the tuque library. Added it to utilities as there is need for it in the islandora_image_annotation module, so exposing the functionality for future use as well.

includes/utilities.inc

@@ -764,3 +764,63 @@ function islandora_get_content_models($ignore_system_namespace = TRUE) {
   }
   return $content_models;
 }
+
+/**
+ * This method will return a valid UUID based on V4 methods.
+ *
+ * @return string
+ *   A valid V4 UUID.
+ */
+function get_uuid() {
+  $bytes = openssl_random_pseudo_bytes(2);
+  $add_mask = convert_hex_to_bin('4000');
+  $negate_mask = convert_hex_to_bin('C000');
+  // Make start with 11.
+  $manipulated_bytes = $bytes | $negate_mask;
+  // Make start with 01.
+  $manipulated_bytes = $manipulated_bytes ^ $add_mask;
+  $hex_string_10 = bin2hex($manipulated_bytes);
+
+  return sprintf('%08s-%04s-4%03s-%s-%012s',
+      bin2hex(openssl_random_pseudo_bytes(4)),
+      bin2hex(openssl_random_pseudo_bytes(2)),
+      // Four most significant bits holds version number 4.
+      substr(bin2hex(openssl_random_pseudo_bytes(2)), 1),
+      // Two most significant bits holds zero and one for variant DCE1.1
+      $hex_string_10,
+      bin2hex(openssl_random_pseudo_bytes(6))
+  );
+}
+
+/**
+ * Will convert a hexadecimal string into a representative byte string.
+ *
+ * @note
+ *   This method can be eliminated in PHP >= 5.4.
+ *   http://php.net/manual/en/function.hex2bin.php#110973
+ *
+ * @param string $hex
+ *   A string representation of a hexadecimal number.
+ *
+ * @return string
+ *   A byte string holding the bits indicated by the hex string.
+ */
+function convert_hex_to_bin($hex) {
+  $length_of_hex = strlen($hex);
+  $byte_string = "";
+  $byte_counter = 0;
+  while ($byte_counter < $length_of_hex) {
+    $current_hex_byte = substr($hex, $byte_counter, 2);
+    $current_binary_byte = pack("H*", $current_hex_byte);
+
+    if ($byte_counter == 0) {
+      $byte_string = $current_binary_byte;
+    }
+    else {
+      $byte_string .= $current_binary_byte;
+    }
+    $byte_counter += 2;
+  }
+
+  return $byte_string;
+}