Other: Initial descriptor.proto extension for reflection interoperabi…

…lity, see #757

ext/descriptor.js

@@ -0,0 +1,108 @@
+// Extension for reflection interoperability with descriptor.proto types
+// var protobuf   = require("protobufjs"),
+//     descriptor = require("protobufjs/ext/descriptor");
+// ...
+"use strict";
+
+/**
+ * Descriptor extension.
+ * @namespace
+ */
+var descriptor = exports;
+
+var protobuf = require("..");
+
+var root  = protobuf.Root.fromJSON(require("../google/protobuf/descriptor.json")).resolveAll(),
+    Root  = protobuf.Root,
+    Type  = protobuf.Type,
+    Field = protobuf.Field;
+
+// Root
+
+/**
+ * FileDescriptorSet describing a root.
+ * @type {Type}
+ */
+descriptor.FileDescriptorSet = root.lookupType(".google.protobuf.FileDescriptorSet");
+
+/**
+ * Creates a root from a descriptor set.
+ * @param {FileDescriptorSet|Reader|Uint8Array} descriptor Descriptor
+ * @returns {Root} Root instance
+ */
+protobuf.Root.fromDescriptor = function fromDescriptorSet(descriptor) {
+    throw Error("not implemented");
+};
+
+/**
+ * Converts a root to a descriptor set.
+ * @returns {FileDescriptorSet} Descriptor
+ */
+protobuf.Root.prototype.toDescriptor = function toDescriptorSet() {
+    throw Error("not implemented");
+};
+
+// Type
+
+/**
+ * DescriptorProto describing a type.
+ * @type {Type}
+ */
+descriptor.DescriptorProto = root.lookupType(".google.protobuf.DescriptorProto");
+
+/**
+ * Creates a type from a descriptor.
+ * @param {DescriptorProto|Reader|Uint8Array} descriptor Descriptor
+ * @returns {Type} Type instance
+ */
+protobuf.Type.fromDescriptor = function fromDescriptor(descriptor) {
+
+    // Decode the descriptor message if specified as a buffer:
+    if (typeof descriptor.length === "number")
+        descriptor = DescriptorProto.decode(reader);
+
+    // Create the message type
+    var type = new protobuf.Type(descriptor.name);
+
+    // Add fields
+    descriptor.field.map(protobuf.Field.fromDescriptor).forEach(protobuf.Type.prototype.add.bind(type));
+
+    // etc.
+
+    return type;
+};
+
+/**
+ * Converts a type to a descriptor.
+ * @returns {DescriptorProto}
+ */
+protobuf.Type.prototype.toDescriptor = function toDescriptor() {
+    throw Error("not implemented");
+};
+
+// Field
+
+/**
+ * FieldDescriptorProto describing a field.
+ * @type {Type}
+ */
+descriptor.FieldDescriptorProto = root.lookupType(".google.protobuf.FieldDescriptorProto");
+
+/**
+ * Creates a field from a descriptor.
+ * @param {FieldDescriptorProto|Reader|Uint8Array} descriptor Descriptor
+ * @returns {Field} Field instance
+ */
+protobuf.Field.fromDescriptor = function fromDescriptor(descriptor) {
+    throw Error("not implemented");
+};
+
+/**
+ * Converts a field to a descriptor.
+ * @returns {FieldDescriptorProto} Descriptor
+ */
+protobuf.Field.prototype.toDescriptor = function toDescriptor() {
+    throw Error("not implemented");
+};
+
+// etc.