1 | /* |
2 | * Copyright 2013 Google Inc. |
3 | * |
4 | * Use of this source code is governed by a BSD-style license that can be |
5 | * found in the LICENSE file. |
6 | */ |
7 | |
8 | #ifndef SkMessageBus_DEFINED |
9 | #define SkMessageBus_DEFINED |
10 | |
11 | #include "include/core/SkTypes.h" |
12 | #include "include/private/SkMutex.h" |
13 | #include "include/private/SkNoncopyable.h" |
14 | #include "include/private/SkOnce.h" |
15 | #include "include/private/SkTArray.h" |
16 | #include "include/private/SkTDArray.h" |
17 | |
18 | /** |
19 | * The following method must have a specialization for type 'Message': |
20 | * |
21 | * bool SkShouldPostMessageToBus(const Message&, uint32_t msgBusUniqueID) |
22 | * |
23 | * We may want to consider providing a default template implementation, to avoid this requirement by |
24 | * sending to all inboxes when the specialization for type 'Message' is not present. |
25 | */ |
26 | template <typename Message> |
27 | class SkMessageBus : SkNoncopyable { |
28 | public: |
29 | // Post a message to be received by Inboxes for this Message type. Checks |
30 | // SkShouldPostMessageToBus() for each inbox. Threadsafe. |
31 | static void Post(const Message& m); |
32 | |
33 | class Inbox { |
34 | public: |
35 | Inbox(uint32_t uniqueID = SK_InvalidUniqueID); |
36 | ~Inbox(); |
37 | |
38 | uint32_t uniqueID() const { return fUniqueID; } |
39 | |
40 | // Overwrite out with all the messages we've received since the last call. Threadsafe. |
41 | void poll(SkTArray<Message>* out); |
42 | |
43 | private: |
44 | SkTArray<Message> fMessages; |
45 | SkMutex fMessagesMutex; |
46 | uint32_t fUniqueID; |
47 | |
48 | friend class SkMessageBus; |
49 | void receive(const Message& m); // SkMessageBus is a friend only to call this. |
50 | }; |
51 | |
52 | private: |
53 | SkMessageBus(); |
54 | static SkMessageBus* Get(); |
55 | |
56 | SkTDArray<Inbox*> fInboxes; |
57 | SkMutex fInboxesMutex; |
58 | }; |
59 | |
60 | // This must go in a single .cpp file, not some .h, or we risk creating more than one global |
61 | // SkMessageBus per type when using shared libraries. NOTE: at most one per file will compile. |
62 | #define DECLARE_SKMESSAGEBUS_MESSAGE(Message) \ |
63 | template <> \ |
64 | SkMessageBus<Message>* SkMessageBus<Message>::Get() { \ |
65 | static SkOnce once; \ |
66 | static SkMessageBus<Message>* bus; \ |
67 | once([] { bus = new SkMessageBus<Message>(); }); \ |
68 | return bus; \ |
69 | } |
70 | |
71 | // ----------------------- Implementation of SkMessageBus::Inbox ----------------------- |
72 | |
73 | template<typename Message> |
74 | SkMessageBus<Message>::Inbox::Inbox(uint32_t uniqueID) : fUniqueID(uniqueID) { |
75 | // Register ourselves with the corresponding message bus. |
76 | SkMessageBus<Message>* bus = SkMessageBus<Message>::Get(); |
77 | SkAutoMutexExclusive lock(bus->fInboxesMutex); |
78 | bus->fInboxes.push_back(this); |
79 | } |
80 | |
81 | template<typename Message> |
82 | SkMessageBus<Message>::Inbox::~Inbox() { |
83 | // Remove ourselves from the corresponding message bus. |
84 | SkMessageBus<Message>* bus = SkMessageBus<Message>::Get(); |
85 | SkAutoMutexExclusive lock(bus->fInboxesMutex); |
86 | // This is a cheaper fInboxes.remove(fInboxes.find(this)) when order doesn't matter. |
87 | for (int i = 0; i < bus->fInboxes.count(); i++) { |
88 | if (this == bus->fInboxes[i]) { |
89 | bus->fInboxes.removeShuffle(i); |
90 | break; |
91 | } |
92 | } |
93 | } |
94 | |
95 | template<typename Message> |
96 | void SkMessageBus<Message>::Inbox::receive(const Message& m) { |
97 | SkAutoMutexExclusive lock(fMessagesMutex); |
98 | fMessages.push_back(m); |
99 | } |
100 | |
101 | template<typename Message> |
102 | void SkMessageBus<Message>::Inbox::poll(SkTArray<Message>* messages) { |
103 | SkASSERT(messages); |
104 | messages->reset(); |
105 | SkAutoMutexExclusive lock(fMessagesMutex); |
106 | fMessages.swap(*messages); |
107 | } |
108 | |
109 | // ----------------------- Implementation of SkMessageBus ----------------------- |
110 | |
111 | template <typename Message> |
112 | SkMessageBus<Message>::SkMessageBus() {} |
113 | |
114 | template <typename Message> |
115 | /*static*/ void SkMessageBus<Message>::Post(const Message& m) { |
116 | SkMessageBus<Message>* bus = SkMessageBus<Message>::Get(); |
117 | SkAutoMutexExclusive lock(bus->fInboxesMutex); |
118 | for (int i = 0; i < bus->fInboxes.count(); i++) { |
119 | if (SkShouldPostMessageToBus(m, bus->fInboxes[i]->fUniqueID)) { |
120 | bus->fInboxes[i]->receive(m); |
121 | } |
122 | } |
123 | } |
124 | |
125 | #endif // SkMessageBus_DEFINED |
126 | |