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      1 // Copyright (c) 2006-2008 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_LOCK_IMPL_H_
      6 #define BASE_LOCK_IMPL_H_
      7 
      8 #include "build/build_config.h"
      9 
     10 #if defined(OS_WIN)
     11 #include <windows.h>
     12 #elif defined(OS_POSIX)
     13 #include <pthread.h>
     14 #endif
     15 
     16 #include "base/basictypes.h"
     17 #include "base/platform_thread.h"
     18 
     19 // This class implements the underlying platform-specific spin-lock mechanism
     20 // used for the Lock class.  Most users should not use LockImpl directly, but
     21 // should instead use Lock.
     22 class LockImpl {
     23  public:
     24 #if defined(OS_WIN)
     25   typedef CRITICAL_SECTION OSLockType;
     26 #elif defined(OS_POSIX)
     27   typedef pthread_mutex_t OSLockType;
     28 #endif
     29 
     30   LockImpl();
     31   ~LockImpl();
     32 
     33   // If the lock is not held, take it and return true.  If the lock is already
     34   // held by something else, immediately return false.
     35   bool Try();
     36 
     37   // Take the lock, blocking until it is available if necessary.
     38   void Lock();
     39 
     40   // Release the lock.  This must only be called by the lock's holder: after
     41   // a successful call to Try, or a call to Lock.
     42   void Unlock();
     43 
     44   // Debug-only method that will DCHECK() if the lock is not acquired by the
     45   // current thread.  In non-debug builds, no check is performed.
     46   // Because linux and mac condition variables modify the underlyning lock
     47   // through the os_lock() method, runtime assertions can not be done on those
     48   // builds.
     49 #if defined(NDEBUG) || !defined(OS_WIN)
     50   void AssertAcquired() const {}
     51 #else
     52   void AssertAcquired() const;
     53 #endif
     54 
     55   // Return the native underlying lock.  Not supported for Windows builds.
     56   // TODO(awalker): refactor lock and condition variables so that this is
     57   // unnecessary.
     58 #if !defined(OS_WIN)
     59   OSLockType* os_lock() { return &os_lock_; }
     60 #endif
     61 
     62  private:
     63   OSLockType os_lock_;
     64 
     65 #if !defined(NDEBUG) && defined(OS_WIN)
     66   // All private data is implicitly protected by lock_.
     67   // Be VERY careful to only access members under that lock.
     68   PlatformThreadId owning_thread_id_;
     69   int32 recursion_count_shadow_;
     70   bool recursion_used_;      // Allow debugging to continued after a DCHECK().
     71 #endif  // NDEBUG
     72 
     73   DISALLOW_COPY_AND_ASSIGN(LockImpl);
     74 };
     75 
     76 
     77 #endif  // BASE_LOCK_IMPL_H_
     78