Adds Mojo IDL.

third_party/WebKit/Source/core/mojo/Mojo.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/mojo/Mojo.h"
+
+#include "bindings/core/v8/ArrayBufferOrArrayBufferView.h"
+#include "core/dom/DOMArrayBuffer.h"
+#include "core/dom/DOMArrayBufferView.h"
+#include "core/mojo/MojoCreateMessagePipeOptions.h"
+#include "core/mojo/MojoCreateMessagePipeResult.h"
+#include "core/mojo/MojoHandle.h"
+#include "core/mojo/MojoReadMessageResult.h"
+#include "core/mojo/MojoWatcher.h"
+
+namespace blink {
+
+Mojo* Mojo::create() {
+  return new Mojo();
+}
+
+MojoWatcher* Mojo::watch(ScriptState* scriptState,
+                         MojoHandle* handle,
+                         MojoHandleSignals signals,
+                         MojoWatchCallback* callback) {
+  return MojoWatcher::create(handle->get(), signals, scriptState, callback);
+}
+
+void Mojo::createMessagePipe(const MojoCreateMessagePipeOptions& optionsDict,
+                             MojoCreateMessagePipeResult& resultDict) {
+  ::MojoCreateMessagePipeOptions options = {0};
+  options.struct_size = sizeof(::MojoCreateMessagePipeOptions);
+  options.flags = optionsDict.flags();
+
+  mojo::ScopedMessagePipeHandle handle0, handle1;
+  MojoResult result = mojo::CreateMessagePipe(&options, &handle0, &handle1);
+
+  resultDict.setResult(result);
+  if (result == MOJO_RESULT_OK) {
+    resultDict.setHandle0(
+        MojoHandle::create(mojo::ScopedHandle::From(std::move(handle0))));
+    resultDict.setHandle1(
+        MojoHandle::create(mojo::ScopedHandle::From(std::move(handle1))));
+  }
+}
+
+MojoResult Mojo::writeMessage(MojoHandle* pipe,
+                              ArrayBufferOrArrayBufferView& buffer,
+                              const HeapVector<Member<MojoHandle>>& handles,
+                              MojoWriteMessageFlags flags) {
+  // MojoWriteMessage takes ownership of the handles, so release them here.
+  std::vector<::MojoHandle> rawHandles(handles.size());

[esprehn, 2016/10/25 03:34:06]

Use Vector, I'd also suggest using inline capacity here since you can totally
avoid the heap allocation.

Vector<::MojoHandle, 32> rawHandles(handles.size());

or something, how many handles is typical?

[alokp, 2016/10/25 05:01:37]

Used WTF::Vector. The number of handle really depends on the interface, but most
messages do not have any handle. Do you still recommend using a non-zero inline
capacity?

[Ken Rockot(use gerrit already), 2016/10/25 18:11:11]

I don't think there's any harm in having some non-zero inline capacity. Even 4
or 8 would avoid heap allocation in the vast majority of cases.

[alokp, 2016/10/25 20:33:36]

OK. Used an inline capacity of 4.

+  for (size_t i = 0; i < handles.size(); ++i)

[esprehn, 2016/10/25 03:34:06]

for (auto& handle : handles)
  rawHandles.append(handle.release().value))

?

[alokp, 2016/10/25 05:01:37]

Done.

+    rawHandles[i] = handles[i]->release().value();
+
+  const void* bytes = nullptr;
+  uint32_t numBytes = 0;
+  if (buffer.isArrayBuffer()) {
+    DOMArrayBuffer* array = buffer.getAsArrayBuffer();
+    bytes = array->data();
+    numBytes = array->byteLength();
+  } else {

[esprehn, 2016/10/25 03:34:06]

We should really add an abstraction over this for you :/

+    DCHECK(buffer.isArrayBufferView());
+    DOMArrayBufferView* view = buffer.getAsArrayBufferView();
+    bytes = view->baseAddress();
+    numBytes = view->byteLength();
+  }
+
+  return MojoWriteMessage(pipe->value(), bytes, numBytes, rawHandles.data(),
+                          rawHandles.size(), flags);
+}
+
+void Mojo::readMessage(MojoHandle* pipe,
+                       MojoReadMessageFlags flags,
+                       MojoReadMessageResult& resultDict) {
+  uint32_t numBytes = 0, numHandles = 0;
+  MojoResult result = MojoReadMessage(pipe->value(), nullptr, &numBytes,
+                                      nullptr, &numHandles, flags);
+  if (result != MOJO_RESULT_RESOURCE_EXHAUSTED) {
+    resultDict.setResult(result);
+    return;
+  }
+
+  DCHECK_GT(numBytes, 0u);
+  DOMArrayBuffer* buffer = DOMArrayBuffer::createUninitialized(numBytes, 1);
+  std::vector<::MojoHandle> rawHandles(numHandles);

[esprehn, 2016/10/25 03:34:06]

Vector<> again, you probably also want inline capacity since this vector is
wasted below when we convert to a HeapVector for making the objects.

[alokp, 2016/10/25 05:01:37]

Used Vector. Since most messages would not have any handle, wouldn't using a
non-zero inline-capacity be more expensive on average?

[Ken Rockot(use gerrit already), 2016/10/25 18:11:11]

Only marginally, just consumes a little extra stack space.

+  result = MojoReadMessage(pipe->value(), buffer->data(), &numBytes,
+                           rawHandles.data(), &numHandles, flags);
+
+  HeapVector<Member<MojoHandle>> handles(numHandles);
+  for (size_t i = 0; i < numHandles; ++i) {
+    handles[i] =
+        MojoHandle::create(mojo::MakeScopedHandle(mojo::Handle(rawHandles[i])));
+  }
+
+  resultDict.setResult(result);
+  resultDict.setBuffer(buffer);
+  resultDict.setHandles(handles);
+}
+
+}  // namespace blink