[iolib-devel] Bug when using READ-LINE on non-blocking fds

[Matthew Mondor]

On Sun, 08 Feb 2009 01:59:56 +0530
Chaitanya Gupta <mail at chaitanyagupta.com> wrote:

> On that note, does iolib provide any function to read a chunk of data 
> without blocking i.e. something like READ-CHAR-NO-HANG for sequences? 
> (or, something akin to what read(2) provides when O_NONBLOCK is set).

It is possible to use RECEIVE-FROM which would signal
IOLIB.SYSCALLS:EWOULDBLOCK if the socket is non-blocking and no
remaining data is ready to read, or IOLIB.SYSCALLS:EINTR on reception
of a signal, but I'm not sure if this could work with buffering, or if
it would conflict with stream operations (i.e. in C you wouldn't use
stdio fread()/fgets() and read() concurrently).

I've used RECEIVE-FROM without issues when creating sockets with 0
bytes receive and send buffers and using custom buffers.
An example may be found at
http://cvs.pulsar-zone.net/cgi-bin/cvsweb.cgi/mmondor/mmsoftware/cl/lib/rw-queue.lisp?rev=1.5;content-type=text%2Fplain
(Note that READ-LINE-FROM-QUEUE and WRITE-STRING-TO-QUEUE are
SBCL-specific as they use SB-EXT to convert between UTF-8 strings and
8-bit bytes representations).

-- 
Matt