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//
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//
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// notice, this list of conditions and the following disclaimer.
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// in the documentation and/or other materials provided with the
// distribution.
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#ifndef BASE_LOCK_IMPL_H__
#define BASE_LOCK_IMPL_H__

#include "base/basictypes.h"

#if defined(WIN32)
#include <Windows.h>
#elif defined(__APPLE__)
#include <libkern/OSAtomic.h>
#endif

// This class implements the underlying platform-specific spin-lock mechanism
// used for the Lock class.  Most users should not use LockImpl directly, but
// should instead use Lock.
class LockImpl {
 public:
  LockImpl();
  ~LockImpl();

  // If the lock is not held, take it and return true.  If the lock is already
  // held by something else, immediately return false.
  bool Try();

  // Take the lock, blocking until it is available if necessary.
  void Lock();

  // Release the lock.  This must only be called by the lock's holder: after
  // a successful call to Try, or a call to Lock.
  void Unlock();

 private:
#if defined(WIN32)
  CRITICAL_SECTION critical_section_;
#elif defined(__APPLE__)
  OSSpinLock spin_lock_;
#endif

  DISALLOW_EVIL_CONSTRUCTORS(LockImpl);
};

class AutoLockImpl {
 public:
  AutoLockImpl(LockImpl* lock_impl)
      : lock_impl_(lock_impl) {
    lock_impl_->Lock();
  }

  ~AutoLockImpl() {
    lock_impl_->Unlock();
  }

 private:
  DISALLOW_EVIL_CONSTRUCTORS(AutoLockImpl);

  LockImpl* lock_impl_;
};

#endif  // BASE_LOCK_IMPL_H__