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Lock.h

// **********************************************************************
//
// Copyright (c) 2003-2005 ZeroC, Inc. All rights reserved.
//
// This copy of Ice is licensed to you under the terms described in the
// ICE_LICENSE file included in this distribution.
//
// **********************************************************************

#ifndef ICE_UTIL_LOCK_H
#define ICE_UTIL_LOCK_H

#include <IceUtil/Config.h>
#include <IceUtil/ThreadException.h>

namespace IceUtil
{

//
// Forward declarations.
//
class Cond;


// LockT and TryLockT are the preferred construct to lock/tryLock/unlock
// simple and recursive mutexes. You typically allocate them on the
// stack to hold a lock on a mutex.
// LockT and TryLockT are not recursive: you cannot acquire several times 
// in a row a lock with the same Lock or TryLock object.
// 
// We must name this LockT instead of Lock, because otherwise some
// compilers (such as Sun C++ 5.4) have problems with constructs
// such as:
//
// class Foo
// {
//     // ...
//     typedef Lock<Mutex> Lock;
// }
//
template <typename T>
class LockT
{
public:
    
    LockT(const T& mutex) :
      _mutex(mutex)
    {
      _mutex.lock();
      _acquired = true;
    }

    ~LockT()
    {
      if (_acquired)
      {
          _mutex.unlock();
      }
    }
    
    void acquire() const
    {
      if (_acquired)
      {
          throw ThreadLockedException(__FILE__, __LINE__);
      }
      _mutex.lock();
      _acquired = true;
    }


    bool tryAcquire() const
    {
      if (_acquired)
      {
          throw ThreadLockedException(__FILE__, __LINE__);
      }
      _acquired = _mutex.tryLock();
      return _acquired;
    }

    void release() const
    {
      if (!_acquired)
      {
          throw ThreadLockedException(__FILE__, __LINE__);
      }
      _mutex.unlock();
      _acquired = false;
    }

    bool acquired() const
    {
      return _acquired;
    }
   
protected:
    
    // TryLockT's contructor
    LockT(const T& mutex, bool) :
      _mutex(mutex)
    {
      _acquired = _mutex.tryLock();
    }

private:
    
    // Not implemented; prevents accidental use.
    //
    LockT(const LockT&);
    LockT& operator=(const LockT&);

    const T& _mutex;
    mutable bool _acquired;

    friend class Cond;
};

//
// Must be name TryLockT, not TryLock. See the comment for LockT for
// an explanation.
//
template <typename T>
class TryLockT : public LockT<T>
{
public:

    TryLockT(const T& mutex) :
      LockT<T>(mutex, true)
    {}
};

} // End namespace IceUtil

#endif

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