BinarySem.h

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#ifndef BINARYSEM_H
#define BINARYSEM_H

#include "common.h"
#include "Exceptions.h"
#include "PtMutex.h"
#include "PtCondition.h"

BOREALIS_NAMESPACE_BEGIN;

class BinarySem
{
public:
  BinarySem(bool initiallyPosted = false)
    throw (std::exception);

  virtual ~BinarySem();

        // Ensures that the sem is posted. One threads presently invoking the
        // 'awaitPostThenClear()' method will unblock, and the sem will be cleared.
        // Returns 'true' iff the sem was already posted at the time this method
        // was called.
  bool post()
    throw (std::exception);

  // If the sem is posted, this clears the sem and returns immediately.
  // Otherwise, this waits until the sem is posted, and THEN clears it
  // and returns.
  void awaitPostThenClear()
    throw (std::exception);

  // If the sem is posted, this clears the sem and returns immediately.
  // Otherwise, this waits until the sem is posted, and returns. This
  // does *not* clear the sem.
  void awaitPost()
    throw (std::exception);

  // Simple, non-blocking method to test if the sem is currently posted.
  bool isPosted() const
    throw (std::exception);

private:
  mutable PtMutex _mtx;
  mutable PtCondition _cond;
  bool _isPosted;
};

BOREALIS_NAMESPACE_END;

#endif

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