Basic Mojo message header validation for JavaScript.

mojo/public/js/bindings/codec.js

Index: mojo/public/js/bindings/codec.js
diff --git a/mojo/public/js/bindings/codec.js b/mojo/public/js/bindings/codec.js
index dca6009071d01a724845d27d8f2dfa9b3f969bc5..45feef2bb1b0ad7fc86f382a9da0be58a21a4974 100644
--- a/mojo/public/js/bindings/codec.js
+++ b/mojo/public/js/bindings/codec.js
@@ -17,6 +17,10 @@ define("mojo/public/js/bindings/codec", [
     return size + (kAlignment - (size % kAlignment)) % kAlignment;
   }
 
+  function isAligned(offset) {
+    return offset >= 0 && (offset % kAlignment) == 0;
+  }
+
   // Constants ----------------------------------------------------------------
 
   var kArrayHeaderSize = 8;
@@ -355,6 +359,10 @@ define("mojo/public/js/bindings/codec", [
   var kMessageExpectsResponse = 1 << 0;
   var kMessageIsResponse      = 1 << 1;
 
+  // Message header is a struct, begins with a struct header.
+  var kNumBytesOffset = 0;
+  var kNumFieldsOffset = 4;
+
   // Skip over num_bytes, num_fields, and message_name.
   var kFlagsOffset = 4 + 4 + 4;
 
@@ -366,15 +374,32 @@ define("mojo/public/js/bindings/codec", [
     this.handles = handles;
   }
 
-  Message.prototype.setRequestID = function(requestID) {
-    // TODO(darin): Verify that space was reserved for this field!
-    this.buffer.setUint64(kRequestIDOffset, requestID);
+  Message.prototype.getHeaderNumBytes = function() {
+    return this.buffer.getUint32(kNumBytesOffset);
+  };
+
+  Message.prototype.getHeaderNumFields = function() {
+    return this.buffer.getUint32(kNumFieldsOffset);
   };
 
   Message.prototype.getFlags = function() {
     return this.buffer.getUint32(kFlagsOffset);
   };
 
+  Message.prototype.isResponse = function() {
+    return (this.getFlags() & kMessageIsResponse) != 0;
+  };
+
+  Message.prototype.expectsResponse = function() {
+    return (this.getFlags() & kMessageExpectsResponse) != 0;
+  };
+
+  Message.prototype.setRequestID = function(requestID) {
+    // TODO(darin): Verify that space was reserved for this field!
+    this.buffer.setUint64(kRequestIDOffset, requestID);
+  };
+
+
   // MessageBuilder -----------------------------------------------------------
 
   function MessageBuilder(messageName, payloadSize) {
@@ -666,6 +691,7 @@ define("mojo/public/js/bindings/codec", [
 
   var exports = {};
   exports.align = align;
+  exports.isAligned = isAligned;
   exports.Message = Message;
   exports.MessageBuilder = MessageBuilder;
   exports.MessageWithRequestIDBuilder = MessageWithRequestIDBuilder;
@@ -673,6 +699,7 @@ define("mojo/public/js/bindings/codec", [
   exports.kArrayHeaderSize = kArrayHeaderSize;
   exports.kStructHeaderSize = kStructHeaderSize;
   exports.kMessageHeaderSize = kMessageHeaderSize;
+  exports.kMessageWithRequestIDHeaderSize = kMessageWithRequestIDHeaderSize;
   exports.kMessageExpectsResponse = kMessageExpectsResponse;
   exports.kMessageIsResponse = kMessageIsResponse;
   exports.Int8 = Int8;