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Re: Delta-composer && (undefined but required) stream behaviour

From: Erik Huelsmann <ehuels_at_gmail.com>
Date: 2005-12-12 23:01:06 CET

On 11 Dec 2005 21:59:49 -0600, kfogel@collab.net <kfogel@collab.net> wrote:
> Erik Huelsmann <ehuels@gmail.com> writes:
> > While writing new streams which I want to use to feed the delta
> > composer, I noticed the delta composer expects streams to support
> > reads after partial results have been returned. Ofcourse, a read like
> > that should return a zero-length block, but nowhere in the stream docs
> > is this requirement documented.
> >
> > Is it a bug in the window composer, or in the stream documentation?
>
> It sounds like at least a buglet in the window composer.

r17743.

> This documentation in svn_stream.h clearly says that a short read is
> okay the first time:
>
> * The read and write handlers accept length arguments via pointer.
> * On entry to the handler, the pointed-to value should be the amount
> * of data which can be read or the amount of data to write. When the
> * handler returns, the value is reset to the amount of data actually
> * read or written. Handlers are obliged to complete a read or write
> * to the maximum extent possible; thus, a short read with no
> * associated error implies the end of the input stream, and a short
> * write should never occur without an associated error.
>
> But yeah, we don't talk about what happens if you do another read on
> the same stream :-)
>
> > (I'm tempted to say it's a bug in the window composer, but that it's
> > desirable to have streams support the behaviour even if we fix the
> > window composer...)
>
> If we can change ("fix") the window composer to not do this, then why
> would we still think it's desirable for streams to support this
> behavior? Is there another use case?

No other use-case requirements that I know of....

> This is not a rhetorical question, by the way. If we can think of a
> reason why it's useful, I'm all for explicitly documenting that
> streams should allow reads after the first short read. But if there's
> no use case, I instinctively feel that streams should be strict by
> default.

Ok. I'll be creating a docstring patch to let stream documentation say so.

> Thoughts?,

Since the delta composer doesn't have the requirement anymore, I don't
think it's a problem to be strict.

> -Karl

bye,

Erik.
Received on Mon Dec 12 23:02:32 2005

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