Re: Looking for help to understand external filter driver code

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 19, 2016, 21:33 UTC
Message-ID: <xmqqr3ape2ju.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <7B44C694-7CB2-411D-9CC6-7334CCBAD20B@gmail.com>

Lars Schneider <larsxschneider@gmail.com> writes:

> Git writes --> 4 byte filename length
> Git writes --> filename string

Why limit to 32GB? Perhaps NUL termination is more appropriate here?

> Git writes --> 4 byte content length
> Git writes --> content string
> Git reads <-- 4 byte filtered content length
> Git reads <-- filtered content

Do you really need to force the sender to know the length in advance? Together with the sequential nature of the above exchange, i.e. the filter is forbidden from producing even a single byte of its output before reading everything Git feeds it, you are making it impossible to use filters that perform streaming conversion.

Of course, with the "sequential" thing, you do not have to worry about deadlocking hence no need for poll/select, but I am not sure that is a good thing.