d8 Worker test of SharedArrayBuffer transferring

test/mjsunit/d8-worker-sharedarraybuffer.js

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+// Flags: --harmony-sharedarraybuffer --harmony-atomics
+
 if (this.Worker) {
   function f() {

[Jarin, 2015/06/30 17:42:43]

I do not think this is doing what you think it's doing. E.g.

var x = false;
if (x) function f() { print("f"); }
f();

still happily prints f.

You really have to say 
var f = function () { ... }

Even then I am not entirely sure why this has to be conditioned on this.Worker
being defined?

[binji, 2015/06/30 18:11:04]

Oh, I wasn't trying to prevent the definition of f, it's just that sometimes
Worker isn't defined, so I was wrapping the whole test in the Worker check. I'll
move f out to make that clearer.

-    var g = function () {
-      postMessage(42);
-    };
+    onmessage = function(m) {
+      var sab = m;
+      var ta = new Uint32Array(sab);
+      if (sab.byteLength !== 16)
+        throw new Error("SharedArrayBuffer transfer byteLength");

[Jarin, 2015/06/30 17:42:43]

Nit: Could we get the braces here and below? (In general, we like braces if the
body is not on the same line.)

[binji, 2015/06/30 18:11:04]

Done.

+      for (var i = 0; i < 4; ++i)
+        if (ta[i] !== i)
+          throw new Error("SharedArrayBuffer transfer value " + i);
 
-    var w = new Worker(g);
-
-    onmessage = function(parentMsg) {
-      w.postMessage(parentMsg);
-      var childMsg = w.getMessage();
-      postMessage(childMsg);
+      // Atomically update ta[0]
+      Atomics.store(ta, 0, 100);
     };
   }
 
   var w = new Worker(f);
-  w.postMessage(9);
-  assertEquals(42, w.getMessage());
+
+  var sab = new SharedArrayBuffer(16);
+  var ta = new Uint32Array(sab);
+  for (var i = 0; i < 4; ++i)
+    ta[i] = i;
+
+  // Transfer SharedArrayBuffer
+  w.postMessage(sab, [sab]);
+  assertEquals(16, sab.byteLength);  // ArrayBuffer should not neutered.

[Jarin, 2015/06/30 17:42:43]

In the comment: ... should not *be* neutered.

[binji, 2015/06/30 18:11:04]

Done.

+
+  // Spinwait for the worker to update ta[0]
+  var ta0;
+  while ((ta0 = Atomics.load(ta, 0)) == 0);

[Jarin, 2015/06/30 17:42:43]

"while (<condition>);" is not recommended by the Chromium C++ style guide (and
we are trying to stick to the C++ style guide even for JS).

Either do "while (<condition>) continue;" or "while (<condition>) {}".

+
+  assertEquals(100, ta0);
+
+  w.terminate();

[Jarin, 2015/06/30 17:42:43]

Could we also check that the array has not been neutered after termination? 

[binji, 2015/06/30 18:11:04]

Done.

 }