michael@0: /*
michael@0:  * Copyright 2013 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef SkMessageBus_DEFINED
michael@0: #define SkMessageBus_DEFINED
michael@0: 
michael@0: #include "SkOnce.h"
michael@0: #include "SkTDArray.h"
michael@0: #include "SkThread.h"
michael@0: #include "SkTypes.h"
michael@0: 
michael@0: template <typename Message>
michael@0: class SkMessageBus : SkNoncopyable {
michael@0: public:
michael@0:     // Post a message to be received by all Inboxes for this Message type.  Threadsafe.
michael@0:     static void Post(const Message& m);
michael@0: 
michael@0:     class Inbox {
michael@0:     public:
michael@0:         Inbox();
michael@0:         ~Inbox();
michael@0: 
michael@0:         // Overwrite out with all the messages we've received since the last call.  Threadsafe.
michael@0:         void poll(SkTDArray<Message>* out);
michael@0: 
michael@0:     private:
michael@0:         SkTDArray<Message> fMessages;
michael@0:         SkMutex            fMessagesMutex;
michael@0: 
michael@0:         friend class SkMessageBus;
michael@0:         void receive(const Message& m);  // SkMessageBus is a friend only to call this.
michael@0:     };
michael@0: 
michael@0: private:
michael@0:     SkMessageBus();
michael@0:     static SkMessageBus* Get();
michael@0:     static void New(SkMessageBus**);
michael@0: 
michael@0:     SkTDArray<Inbox*> fInboxes;
michael@0:     SkMutex           fInboxesMutex;
michael@0: };
michael@0: 
michael@0: // This must go in a single .cpp file, not some .h, or we risk creating more than one global
michael@0: // SkMessageBus per type when using shared libraries.
michael@0: #define DECLARE_SKMESSAGEBUS_MESSAGE(Message)             \
michael@0:     template <>                                           \
michael@0:     SkMessageBus<Message>* SkMessageBus<Message>::Get() { \
michael@0:         static SkMessageBus<Message>* bus = NULL;         \
michael@0:         SK_DECLARE_STATIC_ONCE(once);                     \
michael@0:         SkOnce(&once, &New, &bus);                        \
michael@0:         SkASSERT(bus != NULL);                            \
michael@0:         return bus;                                       \
michael@0:     }
michael@0: 
michael@0: //   ----------------------- Implementation of SkMessageBus::Inbox -----------------------
michael@0: 
michael@0: template<typename Message>
michael@0: SkMessageBus<Message>::Inbox::Inbox() {
michael@0:     // Register ourselves with the corresponding message bus.
michael@0:     SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
michael@0:     SkAutoMutexAcquire lock(bus->fInboxesMutex);
michael@0:     bus->fInboxes.push(this);
michael@0: }
michael@0: 
michael@0: template<typename Message>
michael@0: SkMessageBus<Message>::Inbox::~Inbox() {
michael@0:     // Remove ourselves from the corresponding message bus.
michael@0:     SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
michael@0:     SkAutoMutexAcquire lock(bus->fInboxesMutex);
michael@0:     // This is a cheaper fInboxes.remove(fInboxes.find(this)) when order doesn't matter.
michael@0:     for (int i = 0; i < bus->fInboxes.count(); i++) {
michael@0:         if (this == bus->fInboxes[i]) {
michael@0:             bus->fInboxes.removeShuffle(i);
michael@0:             break;
michael@0:         }
michael@0:     }
michael@0: }
michael@0: 
michael@0: template<typename Message>
michael@0: void SkMessageBus<Message>::Inbox::receive(const Message& m) {
michael@0:     SkAutoMutexAcquire lock(fMessagesMutex);
michael@0:     fMessages.push(m);
michael@0: }
michael@0: 
michael@0: template<typename Message>
michael@0: void SkMessageBus<Message>::Inbox::poll(SkTDArray<Message>* messages) {
michael@0:     SkASSERT(NULL != messages);
michael@0:     messages->reset();
michael@0:     SkAutoMutexAcquire lock(fMessagesMutex);
michael@0:     messages->swap(fMessages);
michael@0: }
michael@0: 
michael@0: //   ----------------------- Implementation of SkMessageBus -----------------------
michael@0: 
michael@0: template <typename Message>
michael@0: SkMessageBus<Message>::SkMessageBus() {}
michael@0: 
michael@0: template <typename Message>
michael@0: /*static*/ void SkMessageBus<Message>::New(SkMessageBus<Message>** bus) {
michael@0:     *bus = new SkMessageBus<Message>();
michael@0: }
michael@0: 
michael@0: template <typename Message>
michael@0: /*static*/ void SkMessageBus<Message>::Post(const Message& m) {
michael@0:     SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
michael@0:     SkAutoMutexAcquire lock(bus->fInboxesMutex);
michael@0:     for (int i = 0; i < bus->fInboxes.count(); i++) {
michael@0:         bus->fInboxes[i]->receive(m);
michael@0:     }
michael@0: }
michael@0: 
michael@0: #endif  // SkMessageBus_DEFINED