Re: [boost] [iostreams] Major interace changes planned -- commentsrequested

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-03-03 08:04:07

Jonathan Turkanis wrote:

[...]

> II. The Solution (the easy part) ---------------------------
>
> I believe it will suffice to:
>
> - provide the functions put() and write() (both filter member
> functions and the free functions with the same names) with a way to
> indicate that fewer than the requested number of characters have been
> written to the underlying data sink even though no error has occurred.
>
> - Provide the functions get() and read() (both filter member
> functions and the free functions with the same names) with a way to
> indicate that fewer than the requested number of characters have been
> read from the underlying data source, even though no error has
> occurred and EOF has not been reached.

[...]

I haven't looked at the library in detail (but I have developed something 
similar).

In my opinion, get and put are non-essential functions, syntactic sugar for 
read and write. put(c) is just write(&c, 1); get() is read(&tmp, 1); return 
tmp. I wouldn't worry much about the "proper" interface of put and get, and 
I wouldn't require filters to implement them. A get() returning -1 for EOF 
and -2 for "no input available" should be good enough for 
character-at-a-time filters, which are mostly of the form "return xform( 
get() );".

In fact, a character-by-character filter is never the proper way to do 
things; the canonical form of the above should be

int r = read(buffer, size);

if( r > 0 )
    std::transform(buffer, buffer+r, buffer, xform);

return r;

so I'm not sure whether get/put should ever be used at all.

But as I said, I haven't looked at the library in detail, so I may be 
missing something.