Mojo JS Bindings: add support for associative arrays (Mojo map type)

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 623cca71b66ff334e41f72173997199cbd410e52..529c2a65aed2f8ee32d2f49a7dc22c30312b69d1 100644
--- a/mojo/public/js/bindings/codec.js
+++ b/mojo/public/js/bindings/codec.js
@@ -4,8 +4,8 @@
 
 define("mojo/public/js/bindings/codec", [
   "mojo/public/js/bindings/unicode",
-  "mojo/public/js/bindings/buffer"
-  ], function(unicode, buffer) {
+  "mojo/public/js/bindings/buffer",
+], function(unicode, buffer) {
 
   var kErrorUnsigned = "Passing negative value to unsigned";
 
@@ -27,6 +27,7 @@ define("mojo/public/js/bindings/codec", [
   var kStructHeaderSize = 8;
   var kMessageHeaderSize = 16;
   var kMessageWithRequestIDHeaderSize = 24;
+  var kMapStructSize = 16;

[yzshen1, 2014/10/15 05:58:02]

It doesn't include the struct header itself, right? It seems
kMapStructPayloadSize is more suitable.

[hansmuller, 2014/10/15 21:45:46]

Done.

 
   var kStructHeaderNumBytesOffset = 0;
   var kStructHeaderNumFieldsOffset = 4;
@@ -180,6 +181,26 @@ define("mojo/public/js/bindings/codec", [
     return this.decodeAndCreateDecoder(pointer).decodeString();
   };
 
+  Decoder.prototype.decodeMap = function(keyClass, valueClass) {
+    this.skip(4); // numberOfBytes
+    this.skip(4); // numberOfFields

[qsr, 2014/10/15 13:03:40]

Don't you want to check that the header is the one you expect?

[hansmuller, 2014/10/15 21:45:46]

Yes. That will happen when the incoming message is validated.

+    var keys = this.decodeArrayPointer(keyClass);
+    var values = this.decodeArrayPointer(valueClass);
+    var val = new Map();
+    for (var i = 0; i < keys.length; i++)
+      val.set(keys[i], values[i]);
+    return val;
+  };
+
+  Decoder.prototype.decodeMapPointer = function(keyClass, valueClass) {
+    var pointer = this.decodePointer();
+    if (!pointer) {
+      return null;
+    }
+    var decoder = this.decodeAndCreateDecoder(pointer);
+    return decoder.decodeMap(keyClass, valueClass);
+  };
+
   // Encoder ------------------------------------------------------------------
 
   function Encoder(buffer, handles, base) {
@@ -349,6 +370,31 @@ define("mojo/public/js/bindings/codec", [
     encoder.encodeString(val);
   };
 
+  Encoder.prototype.encodeMap = function(keyClass, valueClass, val) {
+    var keys = new Array(val.size);
+    var values = new Array(val.size);
+    var i = 0;
+    val.forEach(function(value, key) {
+      values[i] = value;
+      keys[i++] = key;
+    });

[abarth-chromium, 2014/10/15 04:53:26]

for (var [key, value] of val) {
  ...
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Obje...

Not sure if that works in V8, but it's worth a try.  :)

[hansmuller, 2014/10/15 21:45:46]

That would be nicer. I gave it a try; it doesn't appear to supported yet.

+    this.writeUint32(kMapStructSize);

[yzshen1, 2014/10/15 05:58:02]

num_bytes should also include the header size.

[hansmuller, 2014/10/15 21:45:46]

Yes it should! Sorry about that.

+    this.writeUint32(2);
+    this.encodeArrayPointer(keyClass, keys);
+    this.encodeArrayPointer(valueClass, values);
+  }
+
+  Encoder.prototype.encodeMapPointer = function(keyClass, valueClass, val) {
+    if (val == null) {
+      // Also handles undefined, since undefined == null.
+      this.encodePointer(val);
+      return;
+    }
+    var encodedSize = kStructHeaderSize + kMapStructSize;
+    var encoder = this.createAndEncodeEncoder(encodedSize);
+    encoder.encodeMap(keyClass, valueClass, val);
+  };
+
   // Message ------------------------------------------------------------------
 
   var kMessageNameOffset = kStructHeaderSize;