NAME¶
Time::OlsonTZ::Download - Olson timezone database from source
SYNOPSIS¶
use Time::OlsonTZ::Download;
$version = Time::OlsonTZ::Download->latest_version;
$download = Time::OlsonTZ::Download->new;
$version = $download->version;
$version = $download->code_version;
$version = $download->data_version;
$dir = $download->dir;
$dir = $download->unpacked_dir;
$names = $download->canonical_names;
$names = $download->link_names;
$names = $download->all_names;
$links = $download->raw_links;
$links = $download->threaded_links;
$countries = $download->country_selection;
$files = $download->data_files;
$zic = $download->zic_exe;
$dir = $download->zoneinfo_dir;
DESCRIPTION¶
An object of this class represents a local copy of the source of the Olson
timezone database, possibly used to build binary tzfiles. The source copy
always begins by being downloaded from the canonical repository of the Olson
database. This class provides methods to help with extracting useful
information from the source.
CLASS METHODS¶
- Time::OlsonTZ::Download->latest_version
- Returns the version number of the latest available version of the Olson
timezone database. This requires consulting the repository, but is much
cheaper than actually downloading the database.
CONSTRUCTORS¶
- Time::OlsonTZ::Download->new([VERSION])
- Downloads a copy of the source of the Olson database, and returns an
object representing that copy.
VERSION, if supplied, is a version number specifying which version
of the database is to be downloaded. If not supplied, the latest available
version will be downloaded. Version numbers for the Olson database
currently consist of a year number and a lowercase letter, such as
""2010k"". Availability of versions other than the
latest is limited: until 2011 there was no official archive, so this
module is at the mercy of historical mirror administrators' whims.
- Time::OlsonTZ::Download->new_from_local_source(ATTR => VALUE)
- Acquires Olson database source locally, without downloading, and returns
an object representing a copy of it ready to use like a download. This can
be used to work with locally-modified versions of the database. The
following attributes may be given:
- source_dir
- Local directory containing Olson source files. Must be supplied. The
entire directory will be copied into a temporary location to be worked
on.
- version
- Olson version number to attribute to the source files. Must be
supplied.
- code_version
- data_version
- Olson version number to attribute to the code and data parts of the source
files. Both default to the main version number.
METHODS¶
- $download->version
- Returns the version number of the database of which a copy is represented
by this object.
The database consists of code and data parts which are updated
semi-independently. The latest version of the database as a whole consists
of the latest version of the code and the latest version of the data. If
both parts are updated at once then they will both get the same version
number, and that will be the version number of the database as a whole.
However, in general they may be updated at different times, and a single
version of the database may be made up of code and data parts that have
different version numbers. The version number of the database as a whole
will then be the version number of the most recently updated part.
- $download->code_version
- Returns the version number of the code part of the database of which a
copy is represented by this object.
- $download->data_version
- Returns the version number of the data part of the database of which a
copy is represented by this object.
- $download->dir
- Returns the pathname of the directory in which the files of this download
are located. With this method, there is no guarantee of particular files
being available in the directory; see other directory-related methods
below that establish particular directory contents.
The directory does not move during the lifetime of the download object: this
method will always return the same pathname. The directory and all of its
contents, including subdirectories, will be automatically deleted when
this object is destroyed. This will be when the main program terminates,
if it is not otherwise destroyed. Any files that it is desired to keep
must be copied to a permanent location.
- $download->unpacked_dir
- Returns the pathname of the directory in which the downloaded source files
have been unpacked. This is the local temporary directory used by this
download. This method will unpack the files there if they have not already
been unpacked.
- $download->canonical_names
- Returns the set of timezone names that this version of the database
defines as canonical. These are the timezone names that are directly
associated with a set of observance data. The return value is a reference
to a hash, in which the keys are the canonical timezone names and the
values are all "undef".
- $download->link_names
- Returns the set of timezone names that this version of the database
defines as links. These are the timezone names that are aliases for other
names. The return value is a reference to a hash, in which the keys are
the link timezone names and the values are all "undef".
- $download->all_names
- Returns the set of timezone names that this version of the database
defines. These are the "canonical_names" and the
"link_names". The return value is a reference to a hash, in
which the keys are the timezone names and the values are all
"undef".
- $download->raw_links
- Returns details of the timezone name links in this version of the
database. Each link defines one timezone name as an alias for some other
timezone name. The return value is a reference to a hash, in which the
keys are the aliases and each value is the preferred timezone name to
which that alias directly refers. It is possible for an alias to point to
another alias, or to point to a non-existent name. For a more processed
view of links, see "threaded_links".
- $download->threaded_links
- Returns details of the timezone name links in this version of the
database. Each link defines one timezone name as an alias for some other
timezone name. The return value is a reference to a hash, in which the
keys are the aliases and each value is the canonical name of the timezone
to which that alias refers. All such canonical names can be found in the
"canonical_names" hash.
- $download->country_selection
- Returns information about how timezones relate to countries, intended to
aid humans in selecting a geographical timezone. This information is
derived from the "zone.tab" and "iso3166.tab" files in
the database source.
The return value is a reference to a hash, keyed by (ISO 3166 alpha-2
uppercase) country code. The value for each country is a hash containing
these values:
- alpha2_code
- The ISO 3166 alpha-2 uppercase country code.
- olson_name
- An English name for the country, possibly in a modified form, optimised to
help humans find the right entry in alphabetical lists. This is not
necessarily identical to the country's standard short or long name. (For
other forms of the name, consult a database of countries, keying by the
country code.)
- regions
- Information about the regions of the country that use distinct timezones.
This is a hash, keyed by English description of the region. The
description is empty if there is only one region. The value for each
region is a hash containing these values:
- olson_description
- Brief English description of the region, used to distinguish between the
regions of a single country. Empty string if the country has only one
region for timezone purposes. (This is the same string used as the key in
the regions hash.)
- timezone_name
- Name of the Olson timezone used in this region. This is not necessarily a
canonical name (it may be a link). Typically, where there are aliases or
identical canonical zones, a name is chosen that refers to a location in
the country of interest. It is not guaranteed that the named timezone
exists in the database (though it always should).
- location_coords
- Geographical coordinates of some point within the location referred to in
the timezone name. This is a latitude and longitude, in ISO 6709
format.
This data structure is intended to help a human select the appropriate timezone
based on political geography, specifically working from a selection of
country. It is of essentially no use for any other purpose. It is not strictly
guaranteed that every geographical timezone in the database is listed
somewhere in this structure, so it is of limited use in providing information
about an already-selected timezone. It does not include non-geographic
timezones at all. It also does not claim to be a comprehensive list of
countries, and does not make any claims regarding the political status of any
entity listed: the "country" classification is loose, and used only
for identification purposes.
Compiling zone data¶
- $download->data_files
- Returns a reference to an array containing the pathnames of all the source
data files in the database. These are located in the local temporary
directory used by this download.
There is approximately one source data file per continent. Each data file,
in a human-editable textual format, describes the known civil timezones
used on the file's continent. The textual format is not standardised, and
is peculiar to the Olson database, so parsing it directly is in principle
a dubious proposition, but in practice it is very stable.
- $download->zic_exe
- Returns the pathname of the "zic" executable that has been built
from the downloaded source. This is located in the local temporary
directory used by this download. This method will build "zic" if
it has not already been built.
- $download->zoneinfo_dir([OPTIONS])
- Returns the pathname of the directory containing binary tzfiles (in
tzfile(5) format) that have been generated from the downloaded
source. This is located in the local temporary directory used by this
download, and the files within it have names that match the timezone names
(as returned by "all_names"). This method will generate the
tzfiles if they have not already been generated.
The optional parameter OPTIONS controls which kind of tzfiles are
desired. If supplied, it must be a reference to a hash, in which these
keys are permitted:
- leaps
- Truth value, controls whether the tzfiles incorporate information about
known leap seconds offsets that account for the known leap seconds. If
false (which is the default), the tzfiles have no knowledge of leap
seconds, and are intended to be used on a system where "time_t"
is some flavour of UT (as is conventional on Unix and is the POSIX
standard). If true, the tzfiles know about leap seconds that have occurred
between 1972 and the date of the database, and are intended to be used on
a system where "time_t" is (from 1972 onwards) a linear count of
TAI seconds (which is a non-standard arrangement).
BUGS¶
Most of what this class does will only work on Unix platforms. This is largely
because the Olson database source is heavily Unix-oriented.
It also won't be much good if you're not connected to the Internet.
This class is liable to break if the format of the Olson database source ever
changes substantially. If that happens, an update of this class will be
required. It should at least recognise that it can't perform, rather than do
the wrong thing.
SEE ALSO¶
DateTime::TimeZone::Tzfile, Time::OlsonTZ::Data,
tzfile(5)
AUTHOR¶
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT¶
Copyright (C) 2010, 2011, 2012 Andrew Main (Zefram) <zefram@fysh.org>
LICENSE¶
This module is free software; you can redistribute it and/or modify it under the
same terms as Perl itself.