Re: Glib::IO->add_watch and reading the filehandle

["muppet" <scott asofyet org>]

Matthew Braid wrote:
> Every so often it would stop working (ie, the helper process would
> claim it sent a message, but the main process wouldn't act on it), and
> after a lot of debugging it turned out that if an incoming message was
> longer than 1024 characters the remaining part after the first 1024
> characters wouldn't be handled until the _next_ message was sent - in
> other words, if I sysread 1024 characters off a 1025
> character-available stream, the Glib::IO watch doesn't still see the
> file handle as readable, and so doesn't trigger the callback until
> more data is pushed onto it. Unfortunately I can't use a while
> (sysread(...)) in the callback cos then it hangs waiting for data.

The trick in C code is to mark the file as non-blocking, and read chunks until
read returns 0 bytes.  I can't take the time to experiment right now, but i'm
reasonably certain that this works in perl, as well.

Unless you're using datagram sockets, there is no guarantee that an entire
message showed up at once, so you always have to be able to handle partial
reads.


-- 
muppet <scott at asofyet dot org>