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//
// Copyright 2016 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// signal_utils:
// Helper classes for tracking dependent state changes between objects.
// These changes are signaled to the dependent class via channels.
// See design document:
// https://docs.google.com/document/d/15Edfotqg6_l1skTEL8ADQudF_oIdNa7i8Po43k6jMd4/
#ifndef LIBANGLE_SIGNAL_UTILS_H_
#define LIBANGLE_SIGNAL_UTILS_H_
#include <set>
#include "common/angleutils.h"
#include "common/debug.h"
namespace angle
{
// Interface that the depending class inherits from.
template <typename ChannelID = uint32_t, typename... MessageT>
class SignalReceiver
{
public:
virtual ~SignalReceiver() = default;
virtual void signal(ChannelID channelID, MessageT... message) = 0;
};
template <typename ChannelID, typename... MessageT>
class ChannelBinding;
// The host class owns the channel. It uses the channel to fire signals to the receiver.
template <typename ChannelID = uint32_t, typename... MessageT>
class BroadcastChannel final : NonCopyable
{
public:
BroadcastChannel();
~BroadcastChannel();
void signal(MessageT... message) const;
void reset();
bool empty() const;
private:
// Only the ChannelBinding class should add or remove receivers.
friend class ChannelBinding<ChannelID, MessageT...>;
void addReceiver(ChannelBinding<ChannelID, MessageT...> *receiver);
void removeReceiver(ChannelBinding<ChannelID, MessageT...> *receiver);
std::vector<ChannelBinding<ChannelID, MessageT...> *> mReceivers;
};
template <typename ChannelID, typename... MessageT>
BroadcastChannel<ChannelID, MessageT...>::BroadcastChannel()
{
}
template <typename ChannelID, typename... MessageT>
BroadcastChannel<ChannelID, MessageT...>::~BroadcastChannel()
{
reset();
}
template <typename ChannelID, typename... MessageT>
void BroadcastChannel<ChannelID, MessageT...>::addReceiver(
ChannelBinding<ChannelID, MessageT...> *receiver)
{
ASSERT(std::find(mReceivers.begin(), mReceivers.end(), receiver) == mReceivers.end());
mReceivers.push_back(receiver);
}
template <typename ChannelID, typename... MessageT>
void BroadcastChannel<ChannelID, MessageT...>::removeReceiver(
ChannelBinding<ChannelID, MessageT...> *receiver)
{
auto iter = std::find(mReceivers.begin(), mReceivers.end(), receiver);
ASSERT(iter != mReceivers.end());
mReceivers.erase(iter);
}
template <typename ChannelID, typename... MessageT>
void BroadcastChannel<ChannelID, MessageT...>::signal(MessageT... message) const
{
if (mReceivers.empty())
return;
for (const auto *receiver : mReceivers)
{
receiver->signal(message...);
}
}
template <typename ChannelID, typename... MessageT>
void BroadcastChannel<ChannelID, MessageT...>::reset()
{
for (auto receiver : mReceivers)
{
receiver->onChannelClosed();
}
mReceivers.clear();
}
template <typename ChannelID, typename... MessageT>
bool BroadcastChannel<ChannelID, MessageT...>::empty() const
{
return mReceivers.empty();
}
// The dependent class keeps bindings to the host's BroadcastChannel.
template <typename ChannelID = uint32_t, typename... MessageT>
class ChannelBinding final
{
public:
ChannelBinding(SignalReceiver<ChannelID, MessageT...> *receiver, ChannelID channelID);
~ChannelBinding();
ChannelBinding(const ChannelBinding &other) = default;
ChannelBinding &operator=(const ChannelBinding &other) = default;
void bind(BroadcastChannel<ChannelID, MessageT...> *channel);
void reset();
void signal(MessageT... message) const;
void onChannelClosed();
private:
BroadcastChannel<ChannelID, MessageT...> *mChannel;
SignalReceiver<ChannelID, MessageT...> *mReceiver;
ChannelID mChannelID;
};
template <typename ChannelID, typename... MessageT>
ChannelBinding<ChannelID, MessageT...>::ChannelBinding(
SignalReceiver<ChannelID, MessageT...> *receiver,
ChannelID channelID)
: mChannel(nullptr), mReceiver(receiver), mChannelID(channelID)
{
ASSERT(receiver);
}
template <typename ChannelID, typename... MessageT>
ChannelBinding<ChannelID, MessageT...>::~ChannelBinding()
{
reset();
}
template <typename ChannelID, typename... MessageT>
void ChannelBinding<ChannelID, MessageT...>::bind(BroadcastChannel<ChannelID, MessageT...> *channel)
{
ASSERT(mReceiver);
if (mChannel)
{
mChannel->removeReceiver(this);
}
mChannel = channel;
if (mChannel)
{
mChannel->addReceiver(this);
}
}
template <typename ChannelID, typename... MessageT>
void ChannelBinding<ChannelID, MessageT...>::reset()
{
bind(nullptr);
}
template <typename ChannelID, typename... MessageT>
void ChannelBinding<ChannelID, MessageT...>::signal(MessageT... message) const
{
mReceiver->signal(mChannelID, message...);
}
template <typename ChannelID, typename... MessageT>
void ChannelBinding<ChannelID, MessageT...>::onChannelClosed()
{
mChannel = nullptr;
}
} // namespace angle
#endif // LIBANGLE_SIGNAL_UTILS_H_
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