Re: [boost] Re: Boost.Threads draft library submission

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2001-03-22 11:22:27

On Thu, 22 Mar 2001 williamkempf_at_[hidden] wrote:
willia> I've been thinking about this, but haven't coded anything up yet. Let 
willia> me ramble on about an implementation.
willia> 
willia> namespace boost {
willia>   struct lock_tag { }
willia>   struct trylock_tag { }
willia>   struct timedlock_tag { }
willia> 
willia>   template <typename L>
willia>   struct lock_traits
willia>   {
willia>     typedef ... lock_category;
willia>   };
willia> };

One thing to keep in mind... the typical purpose of such categories is for
dispatching to different algorithms. However, off the top of my head I
can't imagine why someone would want to do this... isn't it the case that
if you need a trylock or timedlock, just a normal lock won't do?

willia> I can't see any other information that would go into a lock_traits 
willia> type.  Is there some useful type information that I'm not thinking of 
willia> that should go in here?
willia> 
willia> Also, one of the suggestions was to use a lock_category type that 
willia> allows further decoupling of the lock types from the mutex types.  
willia> Usage was like this:
willia> 
willia> boost::lock_category<boost::mutex>::trylock lock(mx);
willia> 
willia> The problem with this is that there's not a one-to-one correspondance 
willia> of lock types to mutex types here.  For instance, the 
willia> boost::fast_mutex doesn't have a trylock type.  I can think of a few 
willia> ways to deal with this but was interested in hearing other's thoughts 
willia> on this and wondering if there's existing practice for this sort of 
willia> thing.

One way to handle this is to allow some types to be void. Another
approach is to break the traits up.

boost::trylock<boost::mutex>::type
boost::lock<boost::mutex>::type

Cheers,
Jeremy

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 Jeremy Siek                        www: http://www.lsc.nd.edu/~jsiek/
 Ph.D. Candidate                  email: jsiek_at_[hidden]
 Univ. of Notre Dame         work phone: [phone]
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