source-to-json.py

#!/usr/bin/env python2

# tz.js - Library for working with timezones in JavaScript

# Written in 2011 by L. David Baron <dbaron@dbaron.org>

# To the extent possible under law, the author(s) have dedicated all
# copyright and related and neighboring rights to this software to the
# public domain worldwide.  This software is distributed without any
# warranty.
#
# You should have received a copy of the CC0 Public Domain Dedication
# along with this software.  If not, see
# <http://creativecommons.org/publicdomain/zero/1.0/>.

# This script is intended to convert the source time zone data from the
# Olson time zone database (http://www.twinsun.com/tz/tz-link.htm), that
# is, the tzdata* data, into a JSON format suitable for inclusion in the
# tz.js JavaScript library.

# It is not yet anywhere near complete, but at some point in the future
# I would like to replace the current data (generated by
# compiled-to-json.py) with a more compact data format generated here.

from optparse import OptionParser
import os.path
import re
import tarfile

op = OptionParser()
(options, args) = op.parse_args()

if len(args) == 1:
    tzdatatar = args[0]
else:
    op.error("expected a single argument (the tzdata archive)")

tzversion = re.match('tzdata(.*)\.tar\.gz$', os.path.basename(tzdatatar))
if tzversion is None:
    raise StandardError("argument must be tzdata archive")
tzversion = tzversion.groups()[0]
print "/* Time zone data version " + tzversion + ". */"

def read_lines():
    tar = tarfile.open(name=tzdatatar, mode="r:*")
    members_of_tar = set([
        # We use only these members of the tar file and ignore the rest,
        # since they have information we don't want.
        "africa",
        "antarctica",
        "asia",
        "australasia",
        "europe",
        "northamerica",
        "southamerica"
    ])
    for tarinfo in tar:
        if not tarinfo.isfile() or not tarinfo.name in members_of_tar:
            continue
        # FIXME: Should set encoding on this |io| to iso-8859-1.
        io = tar.extractfile(tarinfo)
        for line in io:
            line = line.rstrip("\n")
            line = line.partition("#")[0]
            line = line.rstrip(" \t")
            if line is "":
                continue
            yield line
        io.close()
    tar.close()

zones = {}
rules = {}

def process_time(s):
    if s == '-':
        return 0
    negate = 1
    if s[0] == '-':
        negate = -1
        s = s[1:]
    # FIXME: Do a little more validation on these integers?
    words = [int(n) for n in s.split(":")]
    value = words[0] * 3600
    if len(words) > 1:
        value = value + words[1] * 60
        if len(words) > 2:
            value = value + words[2]
            if len(words) > 3:
                raise StandardError("unexpected time " + s)
    return value * negate

def handle_zone_line(words):
    (gmtoff, rules, fmt) = words[0:3]
    until = " ".join(words[3:])
    # FIXME: process the "until" instead -- it's in LOCAL time unless suffixed
    return { "o": process_time(gmtoff), "r": rules, "f": fmt, "u": until }

ws_re = re.compile("[ \t]+")
current_zone = None
for line in read_lines():
    # For documentation, see zic(8), which is included in the tzcode*
    # distribution.
    words = ws_re.split(line)
    if words[0] == '':
        # FIXME: Check appending consistency with UNTIL value
        if current_zone is None:
           raise StandardError("continuation line when not in Zone")
        current_zone.append(handle_zone_line(words[1:]))
    elif words[0] == 'Zone':
        # FIXME: Check appending consistency with UNTIL value
        current_zone = []
        current_zone.append(handle_zone_line(words[2:]))
        name = words[1]
        if name in zones:
            raise StandardError("duplicate zone " + name)
        zones[name] = current_zone
    elif words[0] == 'Rule':
        current_zone = None
        (name_, from_, to_, type_, in_, on_, at_, save_, letter_) = words[1:]
        rule = rules.setdefault(name_, [])
        rule.append(words[2:])
    elif words[0] == 'Link':
        current_zone = None
        # ignore
    else:
        raise StandardError("unexpected line " + " ".join(words))

print zones
print rules

# FIXME: TO BE WRITTEN
# For rule generation, see the stringzone (and stringrule) functions in
# zic.c in the tzcode distribution, noting the cases that stringzone
# generates the empty string.
# In the cases where rules aren't much use, or when they can't be
# generated at all, it may be better to use the dominant format
# generated by compiled-to-json.py, though.  See the outzone function in
# zic.c.