/******************************************************************************
Module:  SWMRG.h
Notices: Copyright (c) 2000 Jeffrey Richter
******************************************************************************/


#pragma once


///////////////////////////////////////////////////////////////////////////////


class CSWMRG {
public:
   CSWMRG();                 // Constructor
   ~CSWMRG();                // Destructor

   VOID WaitToRead();        // Call this to gain shared read access
   VOID WaitToWrite();       // Call this to gain exclusive write access
   VOID Done();              // Call this when done accessing the resource

private:
   CRITICAL_SECTION m_cs;    // Permits exclusive access to other members
   HANDLE m_hsemReaders;     // Readers wait on this if a writer has access
   HANDLE m_hsemWriters;     // Writers wait on this if a reader has access
   int    m_nWaitingReaders; // Number of readers waiting for access
   int    m_nWaitingWriters; // Number of writers waiting for access
   int    m_nActive;         // Number of threads currently with access
                             //   (0=no threads, >0=# of readers, -1=1 writer)
};


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