Re: [Boost-users] [iostreams] Prepending and appending output data in a filter

From: eg (egoots_at_[hidden])
Date: 2008-04-29 19:52:46

Edward Diener wrote:
> I have a filter, derived from multichar_output_filter, in which I am 
> both prepending data and appending data. In other words the data being 
> written to the sink will be greater than the data being passed into the 
>        filter's 'template<typename Sink> std::streamsize write(Sink& 
> dest, const char* s, std::streamsize n)' member function, which my 
> filter is implementing.
> 
> Is this an allowable use of filters ?

yes.

> 
> Do I still return the 'n' streamsize data being passed in or do I return 
> the actual length of the data being written ?
> 

 From one of the tutorial examples:

     template<typename Sink>
     std::streamsize write(Sink& dest, const char* s, std::streamsize n)
     {
         // Consume up to n filtered characters from the buffer s,
         // writing filtered characters to dest. Return the number
         // of characters consumed.
     }

> Can I use the
> 
> 'template<typename T> std::streamsize write( T& t, const typename 
> char_type_of<T>::type* s, std::streamsize n );'
> 
> function to write the data, 

yes