Re: [Caml-list] Localising timestamps

[Dario Teixeira <darioteixeira@yahoo.com>]

Hi,

> This might not meet your performance requirements, but it's
> certainly
> easy to program with Unix.process_open etc.
> 
> $ TZ=Europe/Paris date --date="2010-07-01 15:30 UTC" +"%F
> %T %Z"
> 2010-07-01 17:30:00 CEST
> 
> The built-in date parser is quite powerful.

Currently I'm using glibc's routines accessed via a small C stub, since
Ocaml's Unix library does not give direct access to the 'tzname' array [1].
I'm avoiding the concurrency issues related to setting the TZ environment
variable only because the web application is written using Ocsigen and
thus also Lwt, allowing me control when there is a switch to another thread.
Nevertheless, this mechanism of changing a global TZ variable to affect
the behaviour of a function is ugly and error-prone.  Hence why I'm
looking for a purely functional solution.

Ironically, glibc already includes all the code to make the zoneinfo
parsing, and it's a pity that it does not expose it to userspace in a
more flexible manner (and yes, I realise there is probably some POSIX
mandate that justifies this broken interface).  I'm beginning to
understand why the Debian folks switched to eglibc...

Anyway, apparently what is happening at the moment is that any applications
with similar requirements to mine just duplicate and adapt the relevant code
from glibc.  Postgresql is doing this, for example.  

Cheers,
Dario

[1] http://caml.inria.fr/mantis/view.php?id=5063