Re: Mailbox locking

[Russ Allbery <rra@debian.org>]

Brendan O'Dea <bod@debian.org> writes:

> A better option if you need to use fcntl locking is to write an XS
> module.

I'm amazed that something like this doesn't already exist, but poking
around a little I didn't find it under any obvious name.  The code is
basically just several bits like:

int
fcntl_write_lock(fd, whence, start, len)
     int fd;
     short whence;
     long start;
     long len;
PROTOTYPE: $$$$
CODE:
{
    struct flock flock;

    flock.l_type = F_WRLCK;
    flock.l_whence = whence;
    flock.l_start = start;
    flock.l_len = len;
    RETVAL = (fcntl(fd, F_SETLK, &flock) == 0);
}
OUTPUT:
    RETVAL

as an example of one operation; a better interface could be devised that
would handle Perl file objects instead of file descriptors, and it would
be good to have a short-hand way of locking the entire file, but you get
the general idea.  I expect that writing the whole module would only take
an XS programmer four or five hours, including docs and packaging.

-- 
Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>