From: Roland Schwarz (roland.schwarz_at_[hidden])
Date: 2004-12-23 02:25:35
Amerio wrote:
> Hello,
>
> I'm lacking a boost semaphore, so I tried to roll my own.
> Being carefull with threads, I present here my version, hoping you
> gurus will spot any flaw.
>
> class sem
> {
> sem(unsigned count): m_count(count) {}
>
> void post()
> {
> boost::mutex::scoped_lock lock(m_mutex);
> ++m_count;
> m_cond_.notify_one();
> }
>
> void wait()
> {
> boost::mutex::scoped_lock lock(m_mutex);
> while ( m_count==0 ) m_cond.wait( lock );
> --m_count;
> }
>
> private:
> unsigned m_count;
> boost::mutex m_mutex;
> boost::condition m_cond;
> };
>
> Objective : I need a semaphore to sync many readers to a single input
> queue.
> If you know another implementation or solution to this specific
> problem, your help is welcome.
Looks almost correct. But as you likely will have multiple waiters, I
suggest
using m_cond_.notify_all() instead. You might also consider to obtain a book
on pthreads (if you do not already own), where you will find that the
semaphore
is just a special case of (condvar, mutex, predicate) triple.
I also recommend to look at the "condvar" example of boost.thread, which
shows a simple queue implementation (albeit for single reader/writer).
Roland