Alexander Terekhov wrote:

>  Michael Glassford wrote:
>  [...]
>  
> >Do you have a full-fledged implementation for such a beast? 
>  
>  
>  Trade secret.
>  
>  
> >I remember you posting sample code some time back, ...
>  
>  
>  class swap_based_mutex_for_windows { // noncopyable
>  
>    atomic<int>      m_lock_status; // 0: free, 1/-1: locked/contention
>    auto_reset_event m_retry_event; 
>  
>  public:
>  
>    // ctor/dtor [w/o lazy event init] 
>  
>    void lock() throw() {
>      if (m_lock_status.swap(1, msync::acq)) 
>        while (m_lock_status.swap(-1, msync::acq))
>          m_retry_event.wait();
>    } 
>  
>    bool trylock() throw() {
>      return !m_lock_status.swap(1, msync::acq) ? 
>        true : !m_lock_status.swap(-1, msync::acq);
>    }
>  
>    bool timedlock(absolute_timeout const & timeout) throw() {
>      if (m_lock_status.swap(1, msync::acq)) {
>        while (m_lock_status.swap(-1, msync::acq))
>          if (!m_retry_event.timedwait(timeout)) 
>            return false;
>      } 
>      return true;
>    }
>  
>    void unlock() throw() {
>      if (m_lock_status.swap(0, msync::rel) < 0) 
>        m_retry_event.set();
>    } 
>  
>  };

Looking at this again, it's not entirely clear to me what the return 
value of atomic<int> ::swap() is. Can you clarify?

Thanks,

Mike

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