9a986cfd5f
Bug: skia: Change-Id: I87725b95761deb689333315ce681a4968d98190a Reviewed-on: https://skia-review.googlesource.com/c/163511 Reviewed-by: Brian Salomon <bsalomon@google.com> Commit-Queue: Chris Dalton <csmartdalton@google.com>
126 lines
4.1 KiB
C++
126 lines
4.1 KiB
C++
/*
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* Copyright 2013 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkMessageBus_DEFINED
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#define SkMessageBus_DEFINED
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#include "../private/SkNoncopyable.h"
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#include "SkMutex.h"
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#include "SkOnce.h"
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#include "SkTArray.h"
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#include "SkTDArray.h"
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#include "SkTypes.h"
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/**
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* The following method must have a specialization for type 'Message':
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*
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* bool SkShouldPostMessageToBus(const Message&, uint32_t msgBusUniqueID)
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*
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* We may want to consider providing a default template implementation, to avoid this requirement by
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* sending to all inboxes when the specialization for type 'Message' is not present.
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*/
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template <typename Message>
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class SkMessageBus : SkNoncopyable {
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public:
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// Post a message to be received by Inboxes for this Message type. Checks
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// SkShouldPostMessageToBus() for each inbox. Threadsafe.
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static void Post(const Message& m);
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class Inbox {
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public:
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Inbox(uint32_t uniqueID = SK_InvalidUniqueID);
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~Inbox();
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uint32_t uniqueID() const { return fUniqueID; }
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// Overwrite out with all the messages we've received since the last call. Threadsafe.
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void poll(SkTArray<Message>* out);
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private:
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SkTArray<Message> fMessages;
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SkMutex fMessagesMutex;
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uint32_t fUniqueID;
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friend class SkMessageBus;
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void receive(const Message& m); // SkMessageBus is a friend only to call this.
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};
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private:
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SkMessageBus();
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static SkMessageBus* Get();
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SkTDArray<Inbox*> fInboxes;
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SkMutex fInboxesMutex;
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};
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// This must go in a single .cpp file, not some .h, or we risk creating more than one global
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// SkMessageBus per type when using shared libraries. NOTE: at most one per file will compile.
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#define DECLARE_SKMESSAGEBUS_MESSAGE(Message) \
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template <> \
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SkMessageBus<Message>* SkMessageBus<Message>::Get() { \
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static SkOnce once; \
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static SkMessageBus<Message>* bus; \
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once([] { bus = new SkMessageBus<Message>(); }); \
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return bus; \
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}
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// ----------------------- Implementation of SkMessageBus::Inbox -----------------------
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template<typename Message>
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SkMessageBus<Message>::Inbox::Inbox(uint32_t uniqueID) : fUniqueID(uniqueID) {
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// Register ourselves with the corresponding message bus.
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SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
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SkAutoMutexAcquire lock(bus->fInboxesMutex);
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bus->fInboxes.push_back(this);
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}
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template<typename Message>
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SkMessageBus<Message>::Inbox::~Inbox() {
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// Remove ourselves from the corresponding message bus.
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SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
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SkAutoMutexAcquire lock(bus->fInboxesMutex);
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// This is a cheaper fInboxes.remove(fInboxes.find(this)) when order doesn't matter.
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for (int i = 0; i < bus->fInboxes.count(); i++) {
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if (this == bus->fInboxes[i]) {
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bus->fInboxes.removeShuffle(i);
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break;
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}
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}
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}
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template<typename Message>
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void SkMessageBus<Message>::Inbox::receive(const Message& m) {
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SkAutoMutexAcquire lock(fMessagesMutex);
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fMessages.push_back(m);
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}
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template<typename Message>
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void SkMessageBus<Message>::Inbox::poll(SkTArray<Message>* messages) {
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SkASSERT(messages);
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messages->reset();
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SkAutoMutexAcquire lock(fMessagesMutex);
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fMessages.swap(*messages);
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}
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// ----------------------- Implementation of SkMessageBus -----------------------
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template <typename Message>
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SkMessageBus<Message>::SkMessageBus() {}
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template <typename Message>
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/*static*/ void SkMessageBus<Message>::Post(const Message& m) {
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SkMessageBus<Message>* bus = SkMessageBus<Message>::Get();
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SkAutoMutexAcquire lock(bus->fInboxesMutex);
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for (int i = 0; i < bus->fInboxes.count(); i++) {
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if (SkShouldPostMessageToBus(m, bus->fInboxes[i]->fUniqueID)) {
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bus->fInboxes[i]->receive(m);
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}
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}
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}
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#endif // SkMessageBus_DEFINED
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