Line data    Source code

       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             : #include "../private/SkLeanWindows.h"
       9             : #include "../private/SkSemaphore.h"
      10             : 
      11             : #if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)
      12             :     #include <mach/mach.h>
      13             :     struct SkBaseSemaphore::OSSemaphore {
      14             :         semaphore_t fSemaphore;
      15             : 
      16             :         OSSemaphore()  {
      17             :             semaphore_create(mach_task_self(), &fSemaphore, SYNC_POLICY_LIFO, 0/*initial count*/);
      18             :         }
      19             :         ~OSSemaphore() { semaphore_destroy(mach_task_self(), fSemaphore); }
      20             : 
      21             :         void signal(int n) { while (n --> 0) { semaphore_signal(fSemaphore); } }
      22             :         void wait() { semaphore_wait(fSemaphore); }
      23             :     };
      24             : #elif defined(SK_BUILD_FOR_WIN32)
      25             :     struct SkBaseSemaphore::OSSemaphore {
      26             :         HANDLE fSemaphore;
      27             : 
      28             :         OSSemaphore()  {
      29             :             fSemaphore = CreateSemaphore(nullptr    /*security attributes, optional*/,
      30             :                                          0       /*initial count*/,
      31             :                                          MAXLONG /*max count*/,
      32             :                                          nullptr    /*name, optional*/);
      33             :         }
      34             :         ~OSSemaphore() { CloseHandle(fSemaphore); }
      35             : 
      36             :         void signal(int n) {
      37             :             ReleaseSemaphore(fSemaphore, n, nullptr/*returns previous count, optional*/);
      38             :         }
      39             :         void wait() { WaitForSingleObject(fSemaphore, INFINITE/*timeout in ms*/); }
      40             :     };
      41             : #else
      42             :     // It's important we test for Mach before this.  This code will compile but not work there.
      43             :     #include <errno.h>
      44             :     #include <semaphore.h>
      45             :     struct SkBaseSemaphore::OSSemaphore {
      46             :         sem_t fSemaphore;
      47             : 
      48           0 :         OSSemaphore()  { sem_init(&fSemaphore, 0/*cross process?*/, 0/*initial count*/); }
      49           0 :         ~OSSemaphore() { sem_destroy(&fSemaphore); }
      50             : 
      51           0 :         void signal(int n) { while (n --> 0) { sem_post(&fSemaphore); } }
      52           0 :         void wait() {
      53             :             // Try until we're not interrupted.
      54           0 :             while(sem_wait(&fSemaphore) == -1 && errno == EINTR);
      55           0 :         }
      56             :     };
      57             : #endif
      58             : 
      59             : ///////////////////////////////////////////////////////////////////////////////
      60             : 
      61           0 : void SkBaseSemaphore::osSignal(int n) {
      62           0 :     fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
      63           0 :     fOSSemaphore->signal(n);
      64           0 : }
      65             : 
      66           0 : void SkBaseSemaphore::osWait() {
      67           0 :     fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
      68           0 :     fOSSemaphore->wait();
      69           0 : }
      70             : 
      71         250 : void SkBaseSemaphore::cleanup() {
      72         250 :     delete fOSSemaphore;
      73         250 : }
      74             : 
      75           0 : bool SkBaseSemaphore::try_wait() {
      76           0 :     int count = fCount.load(std::memory_order_relaxed);
      77           0 :     if (count > 0) {
      78           0 :         return fCount.compare_exchange_weak(count, count-1, std::memory_order_acquire);
      79             :     }
      80           0 :     return false;
      81             : }