[boost] Re: [Boost.Thread] mutex Win32 implementation changes

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2004-05-15 13:33:59

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();
  } 

};

regards,
alexander.