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      1 /*
      2  * Copyright 2016 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 GrSingleOwner_DEFINED
      9 #define GrSingleOwner_DEFINED
     10 
     11 #include "SkTypes.h"
     12 
     13 #ifdef SK_DEBUG
     14 #include "SkMutex.h"
     15 #include "SkThreadID.h"
     16 
     17 // This is a debug tool to verify an object is only being used from one thread at a time.
     18 class GrSingleOwner {
     19 public:
     20      GrSingleOwner() : fOwner(kIllegalThreadID), fReentranceCount(0) {}
     21 
     22      struct AutoEnforce {
     23          AutoEnforce(GrSingleOwner* so) : fSO(so) { fSO->enter(); }
     24          ~AutoEnforce() { fSO->exit(); }
     25 
     26          GrSingleOwner* fSO;
     27      };
     28 
     29 private:
     30      void enter() {
     31          SkAutoMutexAcquire lock(fMutex);
     32          SkThreadID self = SkGetThreadID();
     33          SkASSERT(fOwner == self || fOwner == kIllegalThreadID);
     34          fReentranceCount++;
     35          fOwner = self;
     36      }
     37 
     38      void exit() {
     39          SkAutoMutexAcquire lock(fMutex);
     40          SkASSERT(fOwner == SkGetThreadID());
     41          fReentranceCount--;
     42          if (fReentranceCount == 0) {
     43              fOwner = kIllegalThreadID;
     44          }
     45      }
     46 
     47      SkMutex fMutex;
     48      SkThreadID fOwner;    // guarded by fMutex
     49      int fReentranceCount; // guarded by fMutex
     50 };
     51 #else
     52 class GrSingleOwner {}; // Provide a dummy implementation so we can pass pointers to constructors
     53 #endif
     54 
     55 #endif
     56