ppapi/utility/threading/lock.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef PPAPI_UTILITY_THREADING_LOCK_H_
   6 #define PPAPI_UTILITY_THREADING_LOCK_H_
   7
   8 #ifdef WIN32
   9 #include <windows.h>
  10 #else
  11 #include <pthread.h>
  12 #endif
  13
  14 namespace pp {
  15
  16 /// A simple wrapper around a platform-specific lock. See also AutoLock.
  17 class Lock {
  18  public:
  19   /// Creates a lock in the "not held" state.
  20   Lock();
  21
  22   /// Destroys the lock.
  23   ~Lock();
  24
  25   /// Acquires the lock, blocking if it's already held by a different thread.
  26   /// The lock must not already be held on the current thread (i.e. recursive
  27   /// locks are not supported).
  28   ///
  29   /// Most callers should consider using an AutoLock instead to automatically
  30   /// acquire and release the lock.
  31   void Acquire();
  32
  33   /// Releases the lock. This must be paired with a call to Acquire().
  34   void Release();
  35
  36  private:
  37 #if defined(WIN32)
  38   typedef CRITICAL_SECTION OSLockType;
  39 #else
  40   typedef pthread_mutex_t OSLockType;
  41 #endif
  42
  43   OSLockType os_lock_;
  44
  45   // Copy and assign not supported.
  46   Lock(const Lock&);
  47   Lock& operator=(const Lock&);
  48 };
  49
  50 /// A helper class that scopes holding a lock.
  51 ///
  52 /// @code
  53 ///   class MyClass {
  54 ///    public:
  55 ///     void DoSomething() {
  56 ///       pp::AutoLock lock(lock_);
  57 ///       ...do something with the lock held...
  58 ///     }
  59 ///
  60 ///    private:
  61 ///     pp::Lock lock_;
  62 ///   };
  63 /// @endcode
  64 class AutoLock {
  65  public:
  66   explicit AutoLock(Lock& lock) : lock_(lock) {
  67     lock_.Acquire();
  68   }
  69
  70   ~AutoLock() {
  71     lock_.Release();
  72   }
  73
  74  private:
  75   Lock& lock_;
  76
  77   // Copy and assign not supported.
  78   AutoLock(const AutoLock&);
  79   AutoLock& operator=(const AutoLock&);
  80 };
  81
  82 }  // namespace pp
  83
  84 #endif  // PPAPI_UTILITY_THREADING_LOCK_H_