[boost] Re: Functions as Filters (was Program Reuse...)

From: Bruno Martínez Aguerre (br1_at_[hidden])
Date: 2005-01-17 07:34:58

Coroutines or threads are overkill for this problem, IMHO.  What you need  
is laziness, as in haskell.  FC++ probably can handle decompress with less  
overhead than threads.

Bruno Martinez

On Thu, 13 Jan 2005 16:12:44 -0700, Jonathan Turkanis  
<technews_at_[hidden]> wrote:

> If we want to preserve the simplcity of the example without requiring  
> that an
> enitre stream of data be processed at once, we could switch to  
> thread-aware
> concepts. E.g.,
>
>    template<typename AsyncSource, typename AsynSink>
>    void decompress(AsyncSource& in, AsynSink& out)
>    {
>      char c;
>      while((c = boost::io::blocking_get(in)) != EOF)  {
>        if(c == 0xFF) {
>          int len = boost::io::blocking_get(in);
>          if(!in || !boost::io::blocking_get(in)) // Return an error.
>          while(len--) boost::io::blocking_put(out, c);
>        }
>        else {
>          boost::io::blocking_put(out, c);
>        }
>      }
>    }
>
> (I've been planning to introduce such concepts eventually, but  
> definitely not in
> the initial release.)
>
> With some sacrifice of efficiency, we could even use your example  
> unchanged, and
> stipulate that the provided istream and ostream wait on some  
> synchronization
> object until input is available or EOF is reached (for the istream) or  
> until the
> output buffers have free space (for the ostream).
>
> In short, I 'm not sure the co_filter idea can be implemented without  
> some cost
> in efficiency or simplicity.