Re: Threads docs updated in CVS

From: flameframe_at_[hidden]
Date: 2001-08-13 04:23:05

--- In boost_at_y..., "Alexander Terekhov" <terekhov_at_d...> wrote:
> 
> 
> > I have written some high level abstractions
> > like reader-writer lock using events without getting something 
like
> > CVs in source code.
> 
> could you please show your reader-writer lock using events ?
> 
> regards,
> alexander.

Just a cut-edit-and-paste from simple redaction of a class:

// Comments : 
// class Mutex - wraps Win32 mutex API
// class Event - wraps Win32 event API
// class Enter - wraps WaitForSingleObjectEx/WaitForMultipleObjectsEx 
API
//Usage:
//class A : RWLock
//{
//    void read_function() const
//    {
//        ReadEnter guard(this);
//        ....
//    }
//    void write_function() 
//    {
//        WriteEnter guard(this);
//        ....
//    }
//};
struct RWLock
{
           class ReadEnter;        class WriteEnter; 
    friend class ReadEnter; friend class WriteEnter;

    Mutex     lock;       
    Event     noReaders;

    int       numOfReaders;

    
    void oneReaderMore()
    {
        numOfReaders++; 
        noReaders = false; //Reset manual reset-event 
    }
    void oneReaderLess()
    {
        if( --numOfReaders == 0 ) // ( no more readers )
        {
            noReaders = true; //Set manual reset-event
        }
    }
    RWLock() 
    {
        numOfReaders = 0       ;
        noReaders    = true    ;
    }

    class ReadEnter 
    {
        RWLock* s;
        DWORD timeout;
    public:
        explicit ReadEnter( RWLock*s_
                          , DWORD timeout_=INFINITE)
            : s(s_),timeout(timeout_)
        {
            Enter e(s->lock,timeout);
            s->oneReaderMore(); 
        }
       ~ReadEnter()
        {
            Enter e(s->lock,timeout);
            s->oneReaderLess(); 
        }
    };
    class WriteEnter : public Enter
    {
    public:
        explicit WriteEnter( RWLock*s_
                           , DWORD timeout=INFINITE)
            : Enter(s->lock, s->noReaders
            , waitAll, timeout)
        {
        }
    };
};

Regards,
Vitalij.