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// Copyright (c) 2010 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.
#pragma once
#include <string>
#include <deque>
#include "base/basictypes.h"
#include "base/lock.h"
#include "base/ref_counted.h"
#include "base/waitable_event_watcher.h"
#include "ipc/ipc_channel_proxy.h"
#include "ipc/ipc_sync_message.h"
namespace base {
class WaitableEvent;
namespace IPC {
class SyncMessage;
class MessageReplyDeserializer;
// This is similar to ChannelProxy, with the added feature of supporting sending
// synchronous messages.
// Note that care must be taken that the lifetime of the ipc_thread argument
// is more than this object. If the message loop goes away while this object
// is running and it's used to send a message, then it will use the invalid
// message loop pointer to proxy it to the ipc thread.
class SyncChannel : public ChannelProxy,
public base::WaitableEventWatcher::Delegate {
SyncChannel(const std::string& channel_id, Channel::Mode mode,
Channel::Listener* listener, MessageFilter* filter,
MessageLoop* ipc_message_loop, bool create_pipe_now,
base::WaitableEvent* shutdown_event);
virtual ~SyncChannel();
virtual bool Send(Message* message);
virtual bool SendWithTimeout(Message* message, int timeout_ms);
// Whether we allow sending messages with no time-out.
void set_sync_messages_with_no_timeout_allowed(bool value) {
sync_messages_with_no_timeout_allowed_ = value;
class ReceivedSyncMsgQueue;
friend class ReceivedSyncMsgQueue;
// SyncContext holds the per object data for SyncChannel, so that SyncChannel
// can be deleted while it's being used in a different thread. See
// ChannelProxy::Context for more information.
class SyncContext : public Context,
public base::WaitableEventWatcher::Delegate {
SyncContext(Channel::Listener* listener,
MessageFilter* filter,
MessageLoop* ipc_thread,
base::WaitableEvent* shutdown_event);
// Adds information about an outgoing sync message to the context so that
// we know how to deserialize the reply.
void Push(SyncMessage* sync_msg);
// Cleanly remove the top deserializer (and throw it away). Returns the
// result of the Send call for that message.
bool Pop();
// Returns an event that's set when the send is complete, timed out or the
// process shut down.
base::WaitableEvent* GetSendDoneEvent();
// Returns an event that's set when an incoming message that's not the reply
// needs to get dispatched (by calling SyncContext::DispatchMessages).
base::WaitableEvent* GetDispatchEvent();
void DispatchMessages();
// Checks if the given message is blocking the listener thread because of a
// synchronous send. If it is, the thread is unblocked and true is
// returned. Otherwise the function returns false.
bool TryToUnblockListener(const Message* msg);
// Called on the IPC thread when a sync send that runs a nested message loop
// times out.
void OnSendTimeout(int message_id);
base::WaitableEvent* shutdown_event() { return shutdown_event_; }
ReceivedSyncMsgQueue* received_sync_msgs() {
return received_sync_msgs_;
// ChannelProxy methods that we override.
// Called on the listener thread.
virtual void Clear();
// Called on the IPC thread.
virtual void OnMessageReceived(const Message& msg);
virtual void OnChannelError();
virtual void OnChannelOpened();
virtual void OnChannelClosed();
// Cancels all pending Send calls.
void CancelPendingSends();
// WaitableEventWatcher::Delegate implementation.
virtual void OnWaitableEventSignaled(base::WaitableEvent* arg);
typedef std::deque<PendingSyncMsg> PendingSyncMessageQueue;
PendingSyncMessageQueue deserializers_;
Lock deserializers_lock_;
scoped_refptr<ReceivedSyncMsgQueue> received_sync_msgs_;
base::WaitableEvent* shutdown_event_;
base::WaitableEventWatcher shutdown_watcher_;
// WaitableEventWatcher::Delegate implementation.
virtual void OnWaitableEventSignaled(base::WaitableEvent* arg);
SyncContext* sync_context() {
return reinterpret_cast<SyncContext*>(context());
// Both these functions wait for a reply, timeout or process shutdown. The
// latter one also runs a nested message loop in the meantime.
static void WaitForReply(
SyncContext* context, base::WaitableEvent* pump_messages_event);
// Runs a nested message loop until a reply arrives, times out, or the process
// shuts down.
static void WaitForReplyWithNestedMessageLoop(SyncContext* context);
bool sync_messages_with_no_timeout_allowed_;
// Used to signal events between the IPC and listener threads.
base::WaitableEventWatcher dispatch_watcher_;
} // namespace IPC