AtomicCounter.h

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/*
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   Copyright (c) 2009 Scientific Computing and Imaging Institute,
   University of Utah.

   
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/*
 *@file  AtomicCounter.h
 *@brief Thread-safe integer variable
 *
 *   @author Steve Parker
 *   Department of Computer Science
 *   University of Utah
 *   @date  June 1997
 *
 */

#ifndef Core_Thread_AtomicCounter_h
#define Core_Thread_AtomicCounter_h

#include <Core/Thread/Legacy/share.h>

namespace SCIRun {

class AtomicCounter_private;

/**************************************

@class
 AtomicCounter

 KEYWORDS
 Thread

@details
 Provides a simple atomic counter.  This will work just like an
 integer, but guarantees atomicty of the ++ and -- operators.
 Despite their convenience, you do not want to make a large number
 of these objects.  See also WorkQueue.

 Not that this implementation does not offer an operator=, but
 instead uses a "set" method.  This is to avoid the inadvertant
 use of a statement like: x=x+2, which would NOT be thread safe.

****************************************/
class SCISHARE AtomicCounter {
public:
  //////////
  /// Create an atomic counter with an unspecified initial value.
  /// <tt>name</tt> should be a static string which describes the
  /// primitive for debugging purposes.
  AtomicCounter(const char* name);

  //////////
  /// Create an atomic counter with an initial value.  name should
  /// be a static string which describes the primitive for debugging
  /// purposes.
  AtomicCounter(const char* name, int value);

  //////////
  /// Destroy the atomic counter.
  ~AtomicCounter();

  //////////
  /// Allows the atomic counter to be used in expressions like
  /// a normal integer.  Note that multiple calls to this function
  /// may return different values if other threads are manipulating
  /// the counter.
  operator int() const;

  //////////
  /// Increment the counter and return the new value.
  /// This does not return AtomicCounter& like a normal ++
  /// operator would, because it would destroy atomicity
  int operator++();
    
  //////////
  ///   Increment the counter and return the old value
  int operator++(int);

  //////////
  /// Decrement the counter and return the new value
  /// This does not return AtomicCounter& like a normal --
  /// operator would, because it would destroy atomicity
  int operator--();
    
  //////////
  /// Decrement the counter and return the old value
  int operator--(int);

  //////////
  /// Set the counter to a new value
  void set(int);

private:
  const char* name_;
  AtomicCounter_private* priv_;

  // Cannot copy them
  AtomicCounter(const AtomicCounter&);
  AtomicCounter& operator=(const AtomicCounter&);
};
} // End namespace SCIRun

#endif