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// Copyright (c) 2006-2008 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.
#define WIN32_LEAN_AND_MEAN 1
#include <windows.h>
#include "chrome/common/ipc_sync_sender.h"
#include "chrome/common/ipc_sync_message.h"
#include "base/logging.h"
namespace IPC {
SyncSender::SyncSender(HANDLE shutdown_event) :
shutdown_event_(shutdown_event),
reply_deserialize_result_(false),
reply_event_(CreateEvent(NULL, FALSE, FALSE, NULL)),
blocking_event_(CreateEvent(NULL, FALSE, FALSE, NULL)) {
DCHECK(shutdown_event != NULL);
}
SyncSender::~SyncSender() {
CloseHandle(reply_event_);
CloseHandle(blocking_event_);
DCHECK(deserializers_.empty());
}
bool SyncSender::SendSync(IPC::Message* message) {
bool message_is_sync = false;
message_is_sync = message->is_sync();
if (message_is_sync) {
IPC::SyncMessage* sync_msg = static_cast<IPC::SyncMessage*>(message);
PendingSyncMsg pending(IPC::SyncMessage::GetMessageId(*sync_msg),
sync_msg->GetReplyDeserializer());
deserializers_.push(pending);
}
// Get the derived class to send the message.
bool send_result = SendPrivate(message);
if (!message_is_sync)
return send_result;
if (!send_result) {
delete deserializers_.top().deserializer;
deserializers_.pop();
return false;
}
do {
// wait for reply
HANDLE objects[] = { reply_event_, blocking_event_, shutdown_event_ };
DWORD result = WaitForMultipleObjects(3, objects, FALSE, INFINITE);
if (result == WAIT_OBJECT_0 + 2) {
// Process shut down before we can get a reply to a synchronous message.
// Unblock the thread.
return false;
}
if (result == WAIT_OBJECT_0 + 1) {
// We're waiting for a reply, but the replier is making a synchronous
// request that we must service or else we deadlock. Or in case this
// process supports processing of any synchronous messages while it's
// blocked waiting for a reply (i.e. because it communicates with
// multiple processes).
while (true) {
blocking_messages_lock_.Acquire();
size_t size = blocking_messages_.size();
Message* blocking_message;
if (size) {
blocking_message = blocking_messages_.front();
blocking_messages_.pop();
}
blocking_messages_lock_.Release();
if (!size)
break;
OnDispatchMessage(*blocking_message);
delete blocking_message;
}
// Continue looping until we get the reply to our synchronous message.
} else {
// We got the reply to our synchronous message.
return reply_deserialize_result_;
}
} while (true);
}
bool SyncSender::OnFilterMessage(const Message& msg) {
if (deserializers_.empty())
return false;
if (IPC::SyncMessage::IsMessageReplyTo(msg, deserializers_.top().id)) {
reply_deserialize_result_ =
deserializers_.top().deserializer->SerializeOutputParameters(msg);
delete deserializers_.top().deserializer;
deserializers_.pop();
SetEvent(reply_event_);
return true;
}
if (msg.is_sync()) {
// When we're blocked waiting for a reply we have to respond to other
// synchronous messages as they might be blocking our reply. We also don't
// want to block other processes because one is blocked.
// Create a copy of this message, as it can be deleted from under us
// if there are more than two synchronous messages in parallel.
// (i.e. A->B, B->A, A->B all synchronous)
blocking_messages_lock_.Acquire();
blocking_messages_.push(new Message(msg));
blocking_messages_lock_.Release();
SetEvent(blocking_event_);
return true;
}
return false;
}
} // namespace IPC
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