michael@0: // Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #ifndef BASE_LOCK_H_
michael@0: #define BASE_LOCK_H_
michael@0: 
michael@0: #include "base/lock_impl.h"
michael@0: 
michael@0: // A convenient wrapper for an OS specific critical section.
michael@0: 
michael@0: class Lock {
michael@0:  public:
michael@0:   Lock() : lock_() {}
michael@0:   ~Lock() {}
michael@0:   void Acquire() { lock_.Lock(); }
michael@0:   void Release() { lock_.Unlock(); }
michael@0:   // If the lock is not held, take it and return true. If the lock is already
michael@0:   // held by another thread, immediately return false.
michael@0:   bool Try() { return lock_.Try(); }
michael@0: 
michael@0:   // In debug builds this method checks that the lock has been acquired by the
michael@0:   // calling thread.  If the lock has not been acquired, then the method
michael@0:   // will DCHECK().  In non-debug builds, the LockImpl's implementation of
michael@0:   // AssertAcquired() is an empty inline method.
michael@0:   void AssertAcquired() const { return lock_.AssertAcquired(); }
michael@0: 
michael@0:   // Return the underlying lock implementation.
michael@0:   // TODO(awalker): refactor lock and condition variables so that this is
michael@0:   // unnecessary.
michael@0:   LockImpl* lock_impl() { return &lock_; }
michael@0: 
michael@0:  private:
michael@0:   LockImpl lock_;  // Platform specific underlying lock implementation.
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(Lock);
michael@0: };
michael@0: 
michael@0: // A helper class that acquires the given Lock while the AutoLock is in scope.
michael@0: class AutoLock {
michael@0:  public:
michael@0:   explicit AutoLock(Lock& lock) : lock_(lock) {
michael@0:     lock_.Acquire();
michael@0:   }
michael@0: 
michael@0:   ~AutoLock() {
michael@0:     lock_.AssertAcquired();
michael@0:     lock_.Release();
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   Lock& lock_;
michael@0:   DISALLOW_COPY_AND_ASSIGN(AutoLock);
michael@0: };
michael@0: 
michael@0: // AutoUnlock is a helper that will Release() the |lock| argument in the
michael@0: // constructor, and re-Acquire() it in the destructor.
michael@0: class AutoUnlock {
michael@0:  public:
michael@0:   explicit AutoUnlock(Lock& lock) : lock_(lock) {
michael@0:     // We require our caller to have the lock.
michael@0:     lock_.AssertAcquired();
michael@0:     lock_.Release();
michael@0:   }
michael@0: 
michael@0:   ~AutoUnlock() {
michael@0:     lock_.Acquire();
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   Lock& lock_;
michael@0:   DISALLOW_COPY_AND_ASSIGN(AutoUnlock);
michael@0: };
michael@0: 
michael@0: #endif  // BASE_LOCK_H_