-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Sunday 23 March 2008 18:47 pm, Phil Endecott wrote:
The point is that all of the values share a mutex. Our Lockable<> classes could be used here if you wanted one mutex per value, but that could be wasteful and perhaps wrong. How can we adapt Lockable<> to work in this sort of situation? I'm wondering about something like this:
Lockable< array<int,100 > values;
for (int i=0; i<100; ++i) { start_updater(LockableRef<int>(values,values[i]); }
i.e. LockableRef contains a reference to the mutex and one element of its "parent" Lockable<>, and presents the same interface as a data-full Lockable<>.
I think what you would want to do is just create one scoped lock, perhaps outside of the loop (a lock_acquirer in the lockable lib syntax) and use that to access the values in the array. It could just pass an ordinary reference to the start_updater function, as long as start_updater doesn't keep any persistent copies of the reference around. You do give me an idea though, I could make poet::monitor_ptr (pointer-like monitor) constructible from poet::monitor (value-like monitor) which would I think be similar to what you're getting at with LockableRef. It would actually be very easy, since I implemented poet::monitor using monitor_ptr (out of laziness). Incidentally, I find the example usage of lock acquirers in the thread_lockable examples a bit verbose and dangerous. That is stuff like: mbox::writelock_acquirer<mutexlockable_int> int_lock(*pLockableInt); int& i = access_acquiree(int_lock); i = 5; Why not just support operator* (and operator-> for calling class methods) on the lock_acquirer class? Then you could do something like: mbox::writelock_acquirer<mutexlockable_int> int_lock(*pLockableInt); *int_lock = 5; Its less verbose, and by using the lock_acquirer directly it reduces the possibility of a dangling reference outliving the lock_acquirer it was obtained from. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFH57+S5vihyNWuA4URAro/AKDJKYhHEjUCcPFW+tgv35Ak5NT87ACePs+F sfW6gMAdgxWAoivYda2YL+M= =ssSm -----END PGP SIGNATURE-----