C:/rwlock/VladRWLock.h

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//
// http://discuss.microsoft.com/SCRIPTS/WA-MSD.EXE?A2=ind0009A&L=ATL&P=R6194&D=0&I=-3
// Posted by Pavel Lebedinsky <pll@INFRA2000.COM>
//
#ifndef __Simple_LOCK_H_Included__
#define __Simple_LOCK_H_Included__

#include "Windows.h"

class SimpleRWLock
{
    long m_nReaders;
    long m_nWriters;

public:
    SimpleRWLock()
    {
        m_nReaders = 0;
        m_nWriters = 0;
    }

        static const char *name() { return "VladRWLock"; }

        void enter_read(void)
    {
        for (;;)
        {
            InterlockedIncrement (&m_nReaders);
            if (m_nWriters == 0) break;
            InterlockedDecrement (&m_nReaders);
            Sleep(0);
        }
    }

        void enter_write(void)
    {
        for (;;)
        {
            if (InterlockedCompareExchange (&m_nWriters, 1, 0) == 0)
            {
                while (m_nReaders != 0) Sleep(0);
                break;
            }
            Sleep(0);
        }
    }

    void leave_read(void)
    {
        InterlockedDecrement (&m_nReaders);
    }

    void leave_write(void)
    {
        InterlockedDecrement (&m_nWriters);
    }
};
#endif // __Simple_LOCK_H_Included__

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