Re: Reading binary data via a socket...

Le 22/11/2013 15:15, emacstheviking a
écrit :

Hi,

In a nutshell: how do I read binary data from a socket with
socket, get_byte et al ?

I have written a Redis client (against 2.8) which is fully
functional and ready to release but I have been writing test
cases for as many of the commands as I can without going mad
on it and when I use the DUMP command it barfs. Here is the
session:

| ?-
[gpredis].

compiling
/home/sean/tmp/gnu-prolog-redis-client/gpredis.pl
for byte code...

/home/sean/tmp/gnu-prolog-redis-client/gpredis.pl
compiled, 192 lines read - 16073 bytes written, 17 ms

(4 ms) yes

| ?-
redis(set(gnu_prolog, 'Is awesome!')).

STATUS: OK

yes

| ?-
redis(get(gnu_prolog)).

STRING: Is
awesome!

true ?

yes

| ?-
redis(dump(gnu_prolog)).

uncaught
exception:
error(representation_error(character),get_code/2)

| ?-

The problem is that I am opening the socket like this:

redis_connect(Conn)
:-

redis_connect(Conn,
localhost, 6379).

redis_connect(redis(SI,
SO, S), Host, Port) :-

socket('AF_INET',
S),

socket_connect(S,
'AF_INET'(Host, Port), SI, SO),

set_stream_type(S,
binary). %% added to see if I could fix it but no
dice so far!

and then I use get_code/2 everywhere. That seemed
like a good idea initially because redis deals with strings
but they are binary safe and this obviously isn't, I can cope
with that if I can figure out how to do it with
set_stream_type/. open/3,open/4 allow the mode to be set but
how do I coerce a socket into binary mode with GNU Prolog?

You have to set the stream(s) in binary mode (not the socket).

set_stream_type(SI, binary),

set_stream_type(SO, binary),

Then use get_byte(SI, X) or put_byte(SI, X).

Daniel

Somewhere in there I need to force it into binary mode but
it being Friday and all I can't seem to figure it out...I am
really keen to release this project to GitHub but I refuse
until I am happy with it!

My client handles all redis commands by
de-constructing the term passed into the redis() predicate,
output to the console but the redis_do() predicate passes back
the results. Once I have this issue solved it will be a matter
of days to complete and release it so any assistance would be
appreciated. I will probably crack it tonight myself but I am
at work and thought I would look into it at lunchtime! This is
my first "useful" bit of Prolog (well, useful to me so far!)
and I am keen to complete it *and* understand it.

:)

Thanks,

Sean.

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