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