lock_impl.h revision 4154342345fc67972570f59528233826cd397f1e 
1// Copyright (c) 2011 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 BASE_SYNCHRONIZATION_LOCK_IMPL_H_
6#define BASE_SYNCHRONIZATION_LOCK_IMPL_H_
7#pragma once
8
9#include "build/build_config.h"
10
11#if defined(OS_WIN)
12#include <windows.h>
13#elif defined(OS_POSIX)
14#include <pthread.h>
15#endif
16
17#include "base/base_api.h"
18#include "base/basictypes.h"
19
20namespace base {
21namespace internal {
22
23// This class implements the underlying platform-specific spin-lock mechanism
24// used for the Lock class.  Most users should not use LockImpl directly, but
25// should instead use Lock.
26class BASE_API LockImpl {
27 public:
28#if defined(OS_WIN)
29  typedef CRITICAL_SECTION OSLockType;
30#elif defined(OS_POSIX)
31  typedef pthread_mutex_t OSLockType;
32#endif
33
34  LockImpl();
35  ~LockImpl();
36
37  // If the lock is not held, take it and return true.  If the lock is already
38  // held by something else, immediately return false.
39  bool Try();
40
41  // Take the lock, blocking until it is available if necessary.
42  void Lock();
43
44  // Release the lock.  This must only be called by the lock's holder: after
45  // a successful call to Try, or a call to Lock.
46  void Unlock();
47
48  // Return the native underlying lock.  Not supported for Windows builds.
49  // TODO(awalker): refactor lock and condition variables so that this is
50  // unnecessary.
51#if !defined(OS_WIN)
52  OSLockType* os_lock() { return &os_lock_; }
53#endif
54
55 private:
56  OSLockType os_lock_;
57
58  DISALLOW_COPY_AND_ASSIGN(LockImpl);
59};
60
61}  // namespace internal
62}  // namespace base
63
64#endif  // BASE_SYNCHRONIZATION_LOCK_IMPL_H_
65