Re: Reading data from a file descriptor

["Jan Synáček" <jan.synacek@gmail.com>]

On Tue, Nov 17, 2015 at 1:59 PM, Chris Vine <chris@cvine.freeserve.co.uk> wrote:
> On Tue, 17 Nov 2015 10:53:19 +0100
> <tomas@tuxteam.de> wrote:
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>> On Mon, Nov 16, 2015 at 11:54:33AM +0100, Amirouche Boubekki wrote:
>> > On 2015-11-13 21:41, Jan Synáček wrote:
>>
>> [...]
>>
>> > >I have an open fd to a unix socket and I want to read data from
>> > >it. I know that the data is going to be only strings, but I don't
>> > >know the length in advance.
>> >
>> > Do you know a delimiter? maybe it's the null char?
>> >
>> > TCP is stream oriented, it's not structured at this layer into
>> > messages or segments. You need some knowledge about the byte stream
>> > to be able to split it into different meaningful piece for the
>> > upper layer.
>>
>> I think I "got" Jan's request, because I've been in a similar
>> situation before: delimiter is not (yet) part of it. What he's
>> looking for is an interface à la read(2), meaning "gimme as much
>> as there is in the queue, up to N bytes, and tell me how much
>> you gave me". Of course, putting stuff in a byte vector would
>> be preferable; the only functions I've seen[1] which "do" that
>> interface are read-string!/partial and write-string/partial
>> operate on strings, not byte arrays, alas.
>
> guile's R6RS implementation has get-bytevector-some, which will do that
> for you, with unix-read-like behaviour.
>
> You cannot use this for UTF-8 text by trying to convert the bytevector
> with utf8->string, because you could have received a partially formed
> utf-8 character.  So for text, you should use line orientated reading,
> such as with ice-9 read-line or R6RS get-line.
>
> Chris

This seems to be exactly what I'm looking for, thank you!

-- 
Jan Synáček