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      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 
     21     void acquire() {
     22         fSemaphore.wait();
     23         SkDEBUGCODE(fOwner = SkGetThreadID();)
     24     }
     25 
     26     void release() {
     27         this->assertHeld();
     28         SkDEBUGCODE(fOwner = kIllegalThreadID;)
     29         fSemaphore.signal();
     30     }
     31 
     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;
     44     ~SkMutex() { fSemaphore.cleanup(); }
     45 };
     46 
     47 class SkAutoMutexAcquire {
     48 public:
     49     template <typename T>
     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>
     58     SkAutoMutexAcquire(T& mutex) : SkAutoMutexAcquire(&mutex) {}
     59 
     60     ~SkAutoMutexAcquire() { this->release(); }
     61 
     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>
     80     SkAutoExclusive(T& mutex) : fMutex(&mutex) {
     81         mutex.acquire();
     82 
     83         fRelease = [](void* mutex) { ((T*)mutex)->release(); };
     84     }
     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