Time::OlsonTZ::Download(3pm)

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->source_data_files;
    $files = $download->zic_input_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"". The letter advances with each release in a year.

    Historical vesrions make the version numbers a bit more complicated. Prior to late 1996 the century portion of the year number was omitted, giving version numbers such as ""96g"". Prior to 1994 the first release of each year omitted the letter ""a"", giving version numbers such as "93" (with the second release of the year being ""93b"").

    From 1993 to to late 2012 the database was split into `code' and `data' parts that could each be released without releasing a new version of the other part. Each part had its own version number, sometimes advancing independently of each other, and sometimes skipping sequence letters in order to catch up with the other part. Where the two parts of some version of the database have different version numbers, the version number of the database as a whole is whichever part's version number is higher. If this would give two database versions the same number, due to multiple releases of one part happening while the other part has a higher version number, a digit "2" or "3" is appended after the letter to distinguish the second and third such versions.

    This module does not currently support downloading database versions earlier than version 93. One can expect to successfully download most versions from then on, but a handful are missing from the public archive. The public archive is complete from version 2006f onwards. Details of historical version availability may change in future.

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

  Basic information

$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.

  Zone metadata

$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->source_data_files
    Returns a reference to an array containing the pathnames of all the source data files. These express the database's data (i.e., a description of known civil timezones) in a textual format, and are intended for human editing. They are located in the local temporary directory used by this download.

    There is normally approximately one source data file per continent, though this arrangement could change in the future. The textual format is machine parseable, the same format intended for input to "zic", but when interpreted this way the files do not necessarily correspond to the the official content of the database. There may be transformations that the database code would normally apply between the source data files and the actual input to "zic".

    If you intend to parse the source, taking the place of "zic", then you should prefer to use the "zic_input_files" method, which provides the input that "zic" would actually see.

$download->zic_input_files
    Returns a reference to an array containing the pathnames of all the data files that would normally be fed to "zic". These express the database's data (i.e., a description of known civil timezones) in the format expected by "zic", and are suitable for machine parsing. They are located in the local temporary directory used by this download. This method will build the files if they didn't already exist.

    The "zic" input files are not necessarily source files intended for human editing. In older versions of the database they are such source files, but from database version "2017c" onwards there is a single "zic" input file, which is generated from the source files and omits the niceties of the source files. From database version "2018d" onwards there is some transformation between the source files and the "zic" input, such that they do not necessarily express the same data when parsed by "zic". These arrangements could change again in the future.

    The textual format of "zic" input is not standardised, and is peculiar to the Olson database. Parsing it directly is in principle a dubious proposition, but in practice it is very stable.

    If you want the human-editable source form of the data, use the "source_data_files" method instead.

$download->data_files
    Returns a reference to an array containing the pathnames of all the source data files, provided that the database code would feed the same data to "zic". This method is deprecated: you should use either "source_data_files" or "zic_input_files" depending on which aspect of the data files you are interested in. In older versions of the database the same files were both human-editable and used as "zic" input, so this single method served both roles. From database version "2018d" onwards there is some transformation between the source files and the "zic" input, so the two roles of the files need to be distinguished.

$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.

This class also depends on the availability of some tools beyond baseline Unix. Specifically, it requires GNU "gpgv", GNU "tar", "lzip", "sha512sum", and GNU "make".

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, 2017, 2018 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.