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/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMessageBus_DEFINED
#define SkMessageBus_DEFINED
#include "../private/SkNoncopyable.h"
#include "SkMutex.h"
#include "SkOnce.h"
#include "SkTArray.h"
#include "SkTDArray.h"
#include "SkTypes.h"
/**
* Message must implement bool Message::shouldSend(uint32_t inboxID) const. Perhaps someday we
* can use std::experimental::is_detected to avoid this requirement by sending to all inboxes when
* the method is not detected on Message.
*/
template <typename Message>
class SkMessageBus : SkNoncopyable {
public:
// Post a message to be received by Inboxes for this Message type. Checks
// Message::shouldSend() for each inbox. Threadsafe.
static void Post(const Message& m);
class Inbox {
public:
Inbox(uint32_t uniqueID = SK_InvalidUniqueID);
~Inbox();
// Overwrite out with all the messages we've received since the last call. Threadsafe.
void poll(SkTArray<Message>* out);
private:
SkTArray<Message> fMessages;
SkMutex fMessagesMutex;
uint32_t fUniqueID;
friend class SkMessageBus;
void receive(const Message& m); // SkMessageBus is a friend only to call this.
};
private:
SkMessageBus();
static SkMessageBus* Get();
SkTDArray<Inbox*> fInboxes;
SkMutex fInboxesMutex;
};
// This must go in a single .cpp file, not some .h, or we risk creating more than one global
// SkMessageBus per type when using shared libraries. NOTE: at most one per file will compile.
#define DECLARE_SKMESSAGEBUS_MESSAGE(Message) \
template <> \
SkMessageBus<Message>* SkMessageBus<Message>::Get() { \
static SkOnce once; \
static SkMessageBus<Message>* bus; \
once([] { bus = new SkMessageBus<Message>(); }); \
return bus; \
}
// ----------------------- Implementation of SkMessageBus::Inbox -----------------------
template<typename Message>
SkMessageBus<Message>::Inbox::Inbox(uint32_t uniqueID) : fUniqueID(uniqueID) {
// Register ourselves with the corresponding message bus.
SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
SkAutoMutexAcquire lock(bus->fInboxesMutex);
bus->fInboxes.push(this);
}
template<typename Message>
SkMessageBus<Message>::Inbox::~Inbox() {
// Remove ourselves from the corresponding message bus.
SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
SkAutoMutexAcquire lock(bus->fInboxesMutex);
// This is a cheaper fInboxes.remove(fInboxes.find(this)) when order doesn't matter.
for (int i = 0; i < bus->fInboxes.count(); i++) {
if (this == bus->fInboxes[i]) {
bus->fInboxes.removeShuffle(i);
break;
}
}
}
template<typename Message>
void SkMessageBus<Message>::Inbox::receive(const Message& m) {
SkAutoMutexAcquire lock(fMessagesMutex);
fMessages.push_back(m);
}
template<typename Message>
void SkMessageBus<Message>::Inbox::poll(SkTArray<Message>* messages) {
SkASSERT(messages);
messages->reset();
SkAutoMutexAcquire lock(fMessagesMutex);
fMessages.swap(*messages);
}
// ----------------------- Implementation of SkMessageBus -----------------------
template <typename Message>
SkMessageBus<Message>::SkMessageBus() {}
template <typename Message>
/*static*/ void SkMessageBus<Message>::Post(const Message& m) {
SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
SkAutoMutexAcquire lock(bus->fInboxesMutex);
for (int i = 0; i < bus->fInboxes.count(); i++) {
if (m.shouldSend(bus->fInboxes[i]->fUniqueID)) {
bus->fInboxes[i]->receive(m);
}
}
}
#endif // SkMessageBus_DEFINED
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