Mojo: bindings connector

mojo/public/bindings/lib/connector.cc

+// Copyright 2013 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 "mojo/public/bindings/lib/connector.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include <algorithm>
+
+namespace mojo {
+
+// ----------------------------------------------------------------------------
+
+Connector::Connector(Handle message_pipe)
+    : message_pipe_(message_pipe),
+      incoming_receiver_(NULL),
+      error_(false) {
+}
+
+Connector::~Connector() {
+  if (read_callback_.IsPending())
+    read_callback_.Cancel();
+  if (write_callback_.IsPending())
+    write_callback_.Cancel();
+}
+
+void Connector::SetIncomingReceiver(MessageReceiver* receiver) {
+  assert(!incoming_receiver_);
+  incoming_receiver_ = receiver;
+  if (incoming_receiver_)
+    WaitToReadMore();
+}
+
+bool Connector::Accept(Message* message) {
+  if (error_)
+    return false;
+
+  write_queue_.push(Message());
+  write_queue_.back().Swap(message);
+  WriteMore();
+  return !error_;
+}
+
+void Connector::OnHandleReady(Callback* callback, MojoResult result) {
+  if (callback == &read_callback_)
+    ReadMore();
+  if (callback == &write_callback_)
+    WriteMore();
+}
+
+void Connector::WaitToReadMore() {
+  read_callback_.SetOwnerToNotify(this);
+
+  bool ok = BindingsSupport::Get()->AsyncWait(message_pipe_,
+                                              MOJO_WAIT_FLAG_READABLE,
+                                              MOJO_DEADLINE_INDEFINITE,
+                                              &read_callback_);
+  if (!ok)
+    error_ = true;
+}
+
+void Connector::WaitToWriteMore() {
+  write_callback_.SetOwnerToNotify(this);
+
+  bool ok = BindingsSupport::Get()->AsyncWait(message_pipe_,
+                                              MOJO_WAIT_FLAG_WRITABLE,
+                                              MOJO_DEADLINE_INDEFINITE,
+                                              &write_callback_);
+  if (!ok)
+    error_ = true;
+}
+
+void Connector::ReadMore() {
+  for (;;) {
+    MojoResult rv;
+
+    uint32_t num_bytes = 0, num_handles = 0;
+    rv = ReadMessage(message_pipe_,

[viettrungluu, 2013/11/05 22:45:29]

I wonder if it wouldn't be better (mostly for performance) to start off with a
default size (# of bytes and handles) and possibly complete the read
immediately. (It'd waste some memory, but then we wouldn't need to make two
"system calls". For further optimization, we could preallocate default-size
chunks, and even return them to that pool when done with them. In that case,
probably Accept() should be made to take ownership of the message.)

+                     NULL,
+                     &num_bytes,
+                     NULL,
+                     &num_handles,
+                     MOJO_READ_MESSAGE_FLAG_NONE);
+    if (rv == MOJO_RESULT_NOT_FOUND) {
+      WaitToReadMore();
+      break;
+    }
+    if (rv != MOJO_RESULT_RESOURCE_EXHAUSTED) {
+      error_ = true;
+      break;
+    }
+
+    Message message;
+    message.data = static_cast<MessageData*>(malloc(num_bytes));
+    message.handles.resize(num_handles);
+
+    rv = ReadMessage(message_pipe_,
+                     message.data,
+                     &num_bytes,
+                     &message.handles[0],
+                     &num_handles,
+                     MOJO_READ_MESSAGE_FLAG_NONE);
+    if (rv != MOJO_RESULT_OK) {
+      error_ = true;
+      break;
+    }
+
+    incoming_receiver_->Accept(&message);
+  }
+}
+
+void Connector::WriteMore() {
+  while (!write_queue_.empty()) {
+    const Message& message = write_queue_.back();
+
+    MojoResult rv = WriteMessage(message_pipe_,
+                                 message.data,
+                                 message.data->header.num_bytes,
+                                 message.handles.data(),
+                                 message.handles.size(),
+                                 MOJO_WRITE_MESSAGE_FLAG_NONE);
+    if (rv == MOJO_RESULT_OK) {
+      write_queue_.pop();
+      continue;  // Write another message.
+    }
+
+    error_ = true;
+    break;
+  }
+}
+
+// ----------------------------------------------------------------------------
+
+Connector::Callback::Callback()
+    : owner_(NULL) {
+}
+
+void Connector::Callback::Cancel() {
+  owner_ = NULL;
+  BindingsSupport::Get()->CancelWait(this);
+}
+
+void Connector::Callback::SetOwnerToNotify(Connector* owner) {
+  assert(!owner_);
+  owner_ = owner;
+}
+
+bool Connector::Callback::IsPending() const {
+  return owner_ != NULL;
+}
+
+void Connector::Callback::OnHandleReady(MojoResult result) {
+  assert(owner_);
+  Connector* owner = NULL;
+  std::swap(owner, owner_);
+  owner->OnHandleReady(this, result);
+}
+
+}  // namespace mojo