Source/core/dom/default/PlatformMessagePortChannel.cpp

/*
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 * Copyright (C) 2013 Apple Inc. All rights reserved.
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#include "config.h"
#include "core/dom/default/PlatformMessagePortChannel.h"

#include "core/dom/MessagePort.h"
#include "core/dom/ScriptExecutionContext.h"

namespace WebCore {

PassOwnPtr<PlatformMessagePortChannel::EventData> PlatformMessagePortChannel::EventData::create(PassRefPtr<SerializedScriptValue> message, PassOwnPtr<MessagePortChannelArray> channels)
{
    return adoptPtr(new EventData(message, channels));
}

PlatformMessagePortChannel::EventData::EventData(PassRefPtr<SerializedScriptValue> message, PassOwnPtr<MessagePortChannelArray> channels)
    : m_message(message)
    , m_channels(channels)
{
}

void MessagePortChannel::createChannel(PassRefPtr<MessagePort> port1, PassRefPtr<MessagePort> port2)
{
    RefPtr<PlatformMessagePortChannel::MessagePortQueue> queue1 = PlatformMessagePortChannel::MessagePortQueue::create();
    RefPtr<PlatformMessagePortChannel::MessagePortQueue> queue2 = PlatformMessagePortChannel::MessagePortQueue::create();

    OwnPtr<MessagePortChannel> channel1 = adoptPtr(new MessagePortChannel(PlatformMessagePortChannel::create(queue1, queue2)));
    OwnPtr<MessagePortChannel> channel2 = adoptPtr(new MessagePortChannel(PlatformMessagePortChannel::create(queue2, queue1)));

    channel1->m_channel->m_entangledChannel = channel2->m_channel;
    channel2->m_channel->m_entangledChannel = channel1->m_channel;

    port1->entangle(channel2.release());
    port2->entangle(channel1.release());
}

MessagePortChannel::MessagePortChannel(PassRefPtr<PlatformMessagePortChannel> channel)
    : m_channel(channel)
{
}

MessagePortChannel::~MessagePortChannel()
{
    close();
}

bool MessagePortChannel::entangleIfOpen(MessagePort* port)
{
    // We can't call member functions on our remote pair while holding our mutex or we'll deadlock,
    // but we need to guard against the remote port getting closed/freed, so create a standalone reference.
    RefPtr<PlatformMessagePortChannel> remote = m_channel->entangledChannel();
    if (!remote)
        return false;
    remote->setRemotePort(port);
    return true;
}

void MessagePortChannel::disentangle()
{
    RefPtr<PlatformMessagePortChannel> remote = m_channel->entangledChannel();
    if (remote)
        remote->setRemotePort(0);
}

void MessagePortChannel::postMessageToRemote(PassRefPtr<SerializedScriptValue> message, PassOwnPtr<MessagePortChannelArray> channels)
{
    MutexLocker lock(m_channel->m_mutex);
    if (!m_channel->m_outgoingQueue)
        return;
    bool wasEmpty = m_channel->m_outgoingQueue->appendAndCheckEmpty(PlatformMessagePortChannel::EventData::create(message, channels));
    if (wasEmpty && m_channel->m_remotePort)
        m_channel->m_remotePort->messageAvailable();
}

bool MessagePortChannel::tryGetMessageFromRemote(RefPtr<SerializedScriptValue>& message, OwnPtr<MessagePortChannelArray>& channels)
{
    MutexLocker lock(m_channel->m_mutex);
    OwnPtr<PlatformMessagePortChannel::EventData> result = m_channel->m_incomingQueue->tryGetMessage();
    if (!result)
        return false;

    message = result->message();
    channels = result->channels();

    return true;
}

void MessagePortChannel::close()
{
    RefPtr<PlatformMessagePortChannel> remote = m_channel->entangledChannel();
    if (!remote)
        return;
    m_channel->closeInternal();
    remote->closeInternal();
}

bool MessagePortChannel::isConnectedTo(MessagePort* port)
{
    // FIXME: What guarantees that the result remains the same after we release the lock?
    MutexLocker lock(m_channel->m_mutex);
    return m_channel->m_remotePort == port;
}

bool MessagePortChannel::hasPendingActivity()
{
    // FIXME: What guarantees that the result remains the same after we release the lock?
    MutexLocker lock(m_channel->m_mutex);
    return !m_channel->m_incomingQueue->isEmpty();
}

MessagePort* MessagePortChannel::locallyEntangledPort(const ScriptExecutionContext* context)
{
    MutexLocker lock(m_channel->m_mutex);
    // See if both contexts are run by the same thread (are the same context, or are both documents).
    if (m_channel->m_remotePort) {
        // The remote port's ScriptExecutionContext is guaranteed not to change here - MessagePort::contextDestroyed()
        // will close the port before the context goes away, and close() will block because we are holding the mutex.
        ScriptExecutionContext* remoteContext = m_channel->m_remotePort->scriptExecutionContext();
        if (remoteContext == context || (remoteContext && remoteContext->isDocument() && context->isDocument()))
            return m_channel->m_remotePort;
    }
    return 0;
}

PassRefPtr<PlatformMessagePortChannel> PlatformMessagePortChannel::create(PassRefPtr<MessagePortQueue> incoming, PassRefPtr<MessagePortQueue> outgoing)
{
    return adoptRef(new PlatformMessagePortChannel(incoming, outgoing));
}

PlatformMessagePortChannel::PlatformMessagePortChannel(PassRefPtr<MessagePortQueue> incoming, PassRefPtr<MessagePortQueue> outgoing)
    : m_incomingQueue(incoming)
    , m_outgoingQueue(outgoing)
    , m_remotePort(0)
{
}

PlatformMessagePortChannel::~PlatformMessagePortChannel()
{
}

void PlatformMessagePortChannel::setRemotePort(MessagePort* port)
{
    MutexLocker lock(m_mutex);
    // Should never set port if it is already set.
    ASSERT(!port || !m_remotePort);
    m_remotePort = port;
}

PassRefPtr<PlatformMessagePortChannel> PlatformMessagePortChannel::entangledChannel()
{
    // FIXME: What guarantees that the result remains the same after we release the lock?
    // This lock only guarantees that the returned pointer will not be pointing to released memory,
    // but not that it will still be pointing to this object's entangled port channel.
    MutexLocker lock(m_mutex);
    return m_entangledChannel;
}

void PlatformMessagePortChannel::closeInternal()
{
    MutexLocker lock(m_mutex);
    // Disentangle ourselves from the other end. We still maintain a reference to our incoming queue, since previously-existing messages should still be delivered.
    m_remotePort = 0;
    m_entangledChannel = 0;
    m_outgoingQueue = 0;
}

} // namespace WebCore