1 /*
2  * Copyright 2015 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 SkMutex_DEFINED
9 #define SkMutex_DEFINED
10 
11 #include "../private/SkSemaphore.h"
12 #include "../private/SkThreadID.h"
13 #include "SkTypes.h"
14 
15 #define SK_DECLARE_STATIC_MUTEX(name) static SkBaseMutex name;
16 
17 class SkBaseMutex {
18 public:
19     constexpr SkBaseMutex() = default;
20 
acquire()21     void acquire() {
22         fSemaphore.wait();
23         SkDEBUGCODE(fOwner = SkGetThreadID();)
24     }
25 
release()26     void release() {
27         this->assertHeld();
28         SkDEBUGCODE(fOwner = kIllegalThreadID;)
29         fSemaphore.signal();
30     }
31 
assertHeld()32     void assertHeld() {
33         SkASSERT(fOwner == SkGetThreadID());
34     }
35 
36 protected:
37     SkBaseSemaphore fSemaphore{1};
38     SkDEBUGCODE(SkThreadID fOwner{kIllegalThreadID};)
39 };
40 
41 class SkMutex : public SkBaseMutex {
42 public:
43     using SkBaseMutex::SkBaseMutex;
~SkMutex()44     ~SkMutex() { fSemaphore.cleanup(); }
45 };
46 
47 class SkAutoMutexAcquire {
48 public:
49     template <typename T>
SkAutoMutexAcquire(T * mutex)50     SkAutoMutexAcquire(T* mutex) : fMutex(mutex) {
51         if (mutex) {
52             mutex->acquire();
53         }
54         fRelease = [](void* mutex) { ((T*)mutex)->release(); };
55     }
56 
57     template <typename T>
SkAutoMutexAcquire(T & mutex)58     SkAutoMutexAcquire(T& mutex) : SkAutoMutexAcquire(&mutex) {}
59 
~SkAutoMutexAcquire()60     ~SkAutoMutexAcquire() { this->release(); }
61 
release()62     void release() {
63         if (fMutex) {
64             fRelease(fMutex);
65         }
66         fMutex = nullptr;
67     }
68 
69 private:
70     void*  fMutex;
71     void (*fRelease)(void*);
72 };
73 #define SkAutoMutexAcquire(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexAcquire)
74 
75 // SkAutoExclusive is a lighter weight version of SkAutoMutexAcquire.
76 // It assumes that there is a valid mutex, obviating the null check.
77 class SkAutoExclusive {
78 public:
79     template <typename T>
SkAutoExclusive(T & mutex)80     SkAutoExclusive(T& mutex) : fMutex(&mutex) {
81         mutex.acquire();
82 
83         fRelease = [](void* mutex) { ((T*)mutex)->release(); };
84     }
~SkAutoExclusive()85     ~SkAutoExclusive() { fRelease(fMutex); }
86 
87 private:
88     void* fMutex;
89     void (*fRelease)(void*);
90 };
91 #define SkAutoExclusive(...) SK_REQUIRE_LOCAL_VAR(SkAutoExclusive)
92 
93 #endif//SkMutex_DEFINED
94