HTML MessagePort as mojo::MessagePipeHandle

content/public/common/message_port.cc

+// Copyright (c) 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 "content/public/common/message_port.h"
+
+#include "base/logging.h"
+
+namespace content {
+
+MessagePort::~MessagePort() {
+}
+
+MessagePort::MessagePort() : state_(new State()) {
+}
+
+MessagePort::MessagePort(const MessagePort& other) : state_(other.state_) {
+}
+
+MessagePort& MessagePort::operator=(const MessagePort& other) {
+  state_ = other.state_;
+  return *this;
+}
+
+MessagePort::MessagePort(mojo::ScopedMessagePipeHandle handle)
+    : state_(new State(std::move(handle))) {
+}
+
+const mojo::ScopedMessagePipeHandle& MessagePort::GetHandle() const {
+  return state_->handle_;
+}
+
+mojo::ScopedMessagePipeHandle MessagePort::ReleaseHandle() const {
+  state_->CancelWatch();
+  return std::move(state_->handle_);
+}
+
+// static
+std::vector<mojo::ScopedMessagePipeHandle> MessagePort::ReleaseHandles(
+    const std::vector<MessagePort>& ports) {
+  std::vector<mojo::ScopedMessagePipeHandle> handles(ports.size());
+  for (size_t i = 0; i < ports.size(); ++i)
+    handles[i] = ports[i].ReleaseHandle();
+  return handles;
+}
+
+void MessagePort::PostMessage(const base::string16& encoded_message,
+                              std::vector<MessagePort> ports) {
+  DCHECK(state_->handle_.is_valid());
+
+  uint32_t num_bytes = encoded_message.size() * sizeof(base::char16);
+
+  // NOTE: It is OK to ignore the return value of MojoWriteMessage here. HTML
+  // MessagePorts have no way of reporting when the peer is gone.
+
+  if (ports.empty()) {
+    MojoWriteMessage(state_->handle_.get().value(),
+                     encoded_message.data(),
+                     num_bytes,
+                     nullptr,
+                     0,
+                     MOJO_WRITE_MESSAGE_FLAG_NONE);
+  } else {
+    uint32_t num_handles = static_cast<uint32_t>(ports.size());
+    std::unique_ptr<MojoHandle[]> handles(new MojoHandle[num_handles]);
+    for (uint32_t i = 0; i < num_handles; ++i)
+      handles[i] = ports[i].ReleaseHandle().release().value();
+    MojoWriteMessage(state_->handle_.get().value(),
+                     encoded_message.data(),
+                     num_bytes,
+                     handles.get(),
+                     num_handles,
+                     MOJO_WRITE_MESSAGE_FLAG_NONE);
+  }
+}
+
+bool MessagePort::GetMessage(base::string16* encoded_message,
+                             std::vector<MessagePort>* ports) {
+  DCHECK(state_->handle_.is_valid());
+
+  uint32_t num_bytes = 0;
+  uint32_t num_handles = 0;
+
+  MojoResult rv = MojoReadMessage(state_->handle_.get().value(),
+                                  nullptr,
+                                  &num_bytes,
+                                  nullptr,
+                                  &num_handles,
+                                  MOJO_READ_MESSAGE_FLAG_NONE);
+  if (rv == MOJO_RESULT_OK) {
+    encoded_message->clear();
+    ports->clear();
+    return true;
+  }
+  if (rv != MOJO_RESULT_RESOURCE_EXHAUSTED)
+    return false;
+
+  // XXX ensure num_bytes is a multiple of 2!

[jam, 2017/01/23 18:08:56]

is this an old comment that can be removed?

+  CHECK(num_bytes % 2 == 0);
+
+  base::string16 buffer;
+  buffer.resize(num_bytes / sizeof(base::char16));
+
+  std::unique_ptr<MojoHandle[]> handles;
+  if (num_handles)
+    handles.reset(new MojoHandle[num_handles]);
+
+  rv = MojoReadMessage(state_->handle_.get().value(),
+                       num_bytes ? &buffer[0] : nullptr,
+                       &num_bytes,
+                       handles.get(),
+                       &num_handles,
+                       MOJO_READ_MESSAGE_FLAG_NONE);
+  if (rv != MOJO_RESULT_OK)
+    return false;
+
+  buffer.swap(*encoded_message);
+
+  if (num_handles) {
+    ports->resize(static_cast<size_t>(num_handles));
+    for (uint32_t i = 0; i < num_handles; ++i) {
+      ports->at(i) = MessagePort(
+          mojo::ScopedMessagePipeHandle(mojo::MessagePipeHandle(handles[i])));
+    }
+  }
+  return true;
+}
+
+void MessagePort::SetCallback(const base::Closure& callback) {
+  state_->CancelWatch();
+  state_->callback_ = callback;
+  state_->AddWatch();
+}
+
+void MessagePort::ClearCallback() {
+  state_->CancelWatch();
+  state_->callback_.Reset();
+}
+
+MessagePort::State::State() {
+}
+
+MessagePort::State::State(mojo::ScopedMessagePipeHandle handle)
+    : handle_(std::move(handle)) {
+}
+
+void MessagePort::State::AddWatch() {
+  if (!callback_)
+    return;
+
+  // NOTE: An HTML MessagePort does not receive an event to tell it when the
+  // peer has gone away, so we only watch for readability here.
+  MojoResult rv = MojoWatch(handle_.get().value(),
+                            MOJO_HANDLE_SIGNAL_READABLE,
+                            &MessagePort::State::OnHandleReady,
+                            reinterpret_cast<uintptr_t>(this));
+  if (rv != MOJO_RESULT_OK)
+    DVLOG(1) << this << " MojoWatch failed: " << rv;
+}
+
+void MessagePort::State::CancelWatch() {
+  if (!callback_)
+    return;
+
+  // NOTE: This synchronizes with the thread where OnHandleReady runs so we are
+  // sure to not be racing with it.
+  MojoCancelWatch(handle_.get().value(), reinterpret_cast<uintptr_t>(this));
+}
+
+// static
+void MessagePort::State::OnHandleReady(
+    uintptr_t context,
+    MojoResult result,
+    MojoHandleSignalsState signals_state,
+    MojoWatchNotificationFlags flags) {
+  if (result == MOJO_RESULT_OK) {
+    reinterpret_cast<MessagePort::State*>(context)->callback_.Run();
+  } else {
+    // And now his watch is ended.
+  }
+}
+
+MessagePort::State::~State() {
+  CancelWatch();
+}
+
+}  // namespace content