Re: [boost] [iostream] Device::read return inconsistency

Subject: Re: [boost] [iostream] Device::read return inconsistency
From: eg (egoots_at_[hidden])
Date: 2009-05-08 13:23:24

Richard Smith wrote:
> 
> The example in the documentation for the Source concept in 
> Boost.Iostreams says:
> 
>     std::streamsize read(char* s, std::streamsize n)
>     {
>         // Read up to n characters from the input
>         // sequence into the buffer s, returning
>         // the number of characters read, or -1
>         // to indicate end-of-sequence.
>     }
> 
> (The same text appears in 'valid expressions / semantics' table, which 
> is probably more definitive.)
> 
> What does a return of less than n actually mean?

I think the tutorial example for the multi-char shell comments filter 
gives an example of one such case (c  == WOULD_BLOCK).

see:
http://www.boost.org/doc/libs/1_39_0/libs/iostreams/doc/tutorial/multichar_filters.html#shell_comments_multichar_input_filter

The meaning of WOULD_BLOCK is mentioned in the section where they create 
this same filter as a  regular input filter.

http://www.boost.org/doc/libs/1_39_0/libs/iostreams/doc/tutorial/shell_comments_filters.html#shell_comments_input_filter