--- a/lib/Protobuf-PHP/library/DrSlump/Protobuf/Registry.php
+++ b/lib/Protobuf-PHP/library/DrSlump/Protobuf/Registry.php
@@ -1,1 +1,75 @@
+<?php
 
+namespace DrSlump\Protobuf;
+
+use DrSlump\Protobuf;
+
+/**
+ * Keeps instances of the different message descriptors used.
+ *
+ */
+class Registry
+{
+    /** @var array */
+    protected $descriptors = array();
+
+    /**
+     * @param string|\DrSlump\Protobuf\Message $message
+     * @param \DrSlump\Protobuf\Descriptor $descriptor
+     */
+    public function setDescriptor($message, Descriptor $descriptor)
+    {
+        $message = is_object($message) ? get_class($message) : $message;
+        $message = ltrim($message, '\\');
+
+        $this->descriptors[$message] = $descriptor;
+    }
+
+    /**
+     * Obtains the descriptor for the given message class, obtaining
+     * it if not yet loaded.
+     *
+     * @param string|\DrSlump\Protobuf\Message $message
+     * @return \DrSlump\Protobuf\Descriptor
+     */
+    public function getDescriptor($message)
+    {
+        $message = is_object($message) ? get_class($message) : $message;
+        $message = ltrim($message, '\\');
+
+        // Build a descriptor for the message
+        if (!isset($this->descriptors[$message])) {
+            $class = '\\' . $message;
+            if (!class_exists($class)) {
+                throw Protobuf\Exception('Message class "' . $class . '" not available');
+            }
+
+            $this->descriptors[$message] = $class::descriptor();
+        }
+
+        return $this->descriptors[$message];
+    }
+
+    /**
+     * @param string|\DrSlump\Protobuf\Message $message
+     * @return bool
+     */
+    public function hasDescriptor($message)
+    {
+        $message = is_object($message) ? get_class($message) : $message;
+        $message = ltrim($message, '\\');
+
+        return isset($this->descriptors[$message]);
+    }
+
+    /**
+     * @param string|\DrSlump\Protobuf\Message $message
+     */
+    public function unsetDescriptor($message)
+    {
+        $message = is_object($message) ? get_class($message) : $message;
+        $message = ltrim($message, '\\');
+
+        unset($this->descriptors[$message]);
+    }
+}