gecko/ipc/glue/SyncChannel.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
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 *
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 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Plugin App.
 *
 * The Initial Developer of the Original Code is
 *   Chris Jones <jones.chris.g@gmail.com>
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
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 *
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#include "mozilla/ipc/SyncChannel.h"
#include "mozilla/ipc/GeckoThread.h"

#include "nsDebug.h"

using mozilla::MutexAutoLock;

template<>
struct RunnableMethodTraits<mozilla::ipc::SyncChannel>
{
    static void RetainCallee(mozilla::ipc::SyncChannel* obj) { }
    static void ReleaseCallee(mozilla::ipc::SyncChannel* obj) { }
};

namespace mozilla {
namespace ipc {

bool
SyncChannel::Send(Message* msg, Message* reply)
{
    AssertWorkerThread();
    NS_ABORT_IF_FALSE(!ProcessingSyncMessage(),
                      "violation of sync handler invariant");
    NS_ABORT_IF_FALSE(msg->is_sync(), "can only Send() sync messages here");

    MutexAutoLock lock(mMutex);

    if (!Connected())
        // trying to Send() to a closed or error'd channel
        return false;

    mPendingReply = msg->type() + 1;
    mIOLoop->PostTask(
        FROM_HERE,
        NewRunnableMethod(this, &SyncChannel::OnSend, msg));

    // wait for the next sync message to arrive
    WaitForNotify();

    if (!Connected())
        // FIXME more sophisticated error handling
        return false;

    // we just received a synchronous message from the other side.
    // If it's not the reply we were awaiting, there's a serious
    // error: either a mistimed/malformed message or a sync in-message
    // that raced with our sync out-message.
    // (NB: IPDL prevents the latter from occuring in actor code)

    // FIXME/cjones: real error handling
    NS_ABORT_IF_FALSE(mRecvd.is_sync() && mRecvd.is_reply() &&
                      (mPendingReply == mRecvd.type() || mRecvd.is_reply_error()),
                      "unexpected sync message");

    mPendingReply = 0;
    *reply = mRecvd;

    return true;
}

void
SyncChannel::OnDispatchMessage(const Message& msg)
{
    AssertWorkerThread();
    NS_ABORT_IF_FALSE(msg.is_sync(), "only sync messages here");
    NS_ABORT_IF_FALSE(!msg.is_reply(), "wasn't awaiting reply");

    Message* reply = 0;

    mProcessingSyncMessage = true;
    Result rv =
        static_cast<SyncListener*>(mListener)->OnMessageReceived(msg, reply);
    mProcessingSyncMessage = false;

    switch (rv) {
    case MsgProcessed:
        break;

    case MsgNotKnown:
    case MsgNotAllowed:
    case MsgPayloadError:
    case MsgRouteError:
    case MsgValueError:
        // FIXME/cjones: error handling; OnError()?
        delete reply;
        reply = new Message();
        reply->set_sync();
        reply->set_reply();
        reply->set_reply_error();
        break;

    default:
        NOTREACHED();
        return;
    }

    mIOLoop->PostTask(
        FROM_HERE,
        NewRunnableMethod(this, &SyncChannel::OnSend, reply));
}

//
// The methods below run in the context of the IO thread, and can proxy
// back to the methods above
//

void
SyncChannel::OnMessageReceived(const Message& msg)
{
    AssertIOThread();
    if (!msg.is_sync()) {
        return AsyncChannel::OnMessageReceived(msg);
    }

    MutexAutoLock lock(mMutex);

    if (!AwaitingSyncReply()) {
        // wake up the worker, there's work to do
        mWorkerLoop->PostTask(
            FROM_HERE,
            NewRunnableMethod(this, &SyncChannel::OnDispatchMessage, msg));
    }
    else {
        // let the worker know a new sync message has arrived
        mRecvd = msg;
        NotifyWorkerThread();
    }
}

void
SyncChannel::OnChannelError()
{
    AssertIOThread();
    {
        MutexAutoLock lock(mMutex);

        mChannelState = ChannelError;

        if (AwaitingSyncReply()) {
            NotifyWorkerThread();
        }
    }

    return AsyncChannel::OnChannelError();
}

//
// Synchronization between worker and IO threads
//

void
SyncChannel::WaitForNotify()
{
    mCvar.Wait();
}

void
SyncChannel::NotifyWorkerThread()
{
    mCvar.Notify();
}


} // namespace ipc
} // namespace mozilla