XMLTV - Perl extension to read and write TV listings in XMLTV format

  use XMLTV;
  my $data = XMLTV::parsefile('tv.xml');
  my ($encoding, $credits, $ch, $progs) = @$data;
  my $langs = [ 'en', 'fr' ];
  print 'source of listings is: ', $credits->{'source-info-name'}, "\n"
      if defined $credits->{'source-info-name'};
  foreach (values %$ch) {
      my ($text, $lang) = @{XMLTV::best_name($langs, $_->{'display-name'})};
      print "channel $_->{id} has name $text\n";
      print "...in language $lang\n" if defined $lang;
  }
  foreach (@$progs) {
      print "programme on channel $_->{channel} at time $_->{start}\n";
      next if not defined $_->{desc};
      foreach (@{$_->{desc}}) {
          my ($text, $lang) = @$_;
          print "has description $text\n";
          print "...in language $lang\n" if defined $lang;
      }
  }

The value of CW$data will be something a bit like:

  [ 'UTF-8',
    { 'source-info-name' => 'Ananova', 'generator-info-name' => 'XMLTV' },
    { 'radio-4.bbc.co.uk' => { 'display-name' => [ [ 'en',  'BBC Radio 4' ],
                                                   [ 'en',  'Radio 4'     ],
                                                   [ undef, '4'           ] ],
                               'id' => 'radio-4.bbc.co.uk' },
      ... },
    [ { start => '200111121800', title => [ [ 'Simpsons', 'en' ] ],
        channel => 'radio-4.bbc.co.uk' },
      ... ] ]

This module provides an interface to read and write files in XMLTV format (a TV listings format defined by xmltv.dtd). In general element names in the XML correspond to hash keys in the Perl data structure. You can think of this module as a bit like XML::Simple, but specialized to the XMLTV file format.

The Perl data structure corresponding to an XMLTV file has four elements. The first gives the character encoding used for text data, typically UTF-8 or ISO-8859-1. (The encoding value could also be undef meaning 'unknown', when the library can't work out what it is.) The second element gives the attributes of the root <tv> element, which give information about the source of the TV listings. The third element is a list of channels, each list element being a hash corresponding to one <channel> element. The fourth element is similarly a list of programmes. More details about the data structure are given later. The easiest way to find out what it looks like is to load some small XMLTV files and use Data::Dumper to print out the resulting structure.

parse(document)

Takes an XMLTV document (a string) and returns the Perl data structure. It is assumed that the document is valid XMLTV; if not the routine may die() with an error (although the current implementation just warns and continues for most small errors). The first element of the listref returned, the encoding, may vary according to the encoding of the input document, the versions of perl and CWXML::Parser installed, the configuration of the XMLTV library and other factors including, but not limited to, the phase of the moon. With luck it should always be either the encoding of the input file or UTF-8. Attributes and elements in the XML file whose names begin with 'x-' are skipped silently. You can use these to include information which is not currently handled by the XMLTV format, or by this module.

parsefiles(filename...)

Like CWparse() but takes one or more filenames instead of a string document. The data returned is the merging of those file contents: the programmes will be concatenated in their original order, the channels just put together in arbitrary order (ordering of channels should not matter). It is necessary that each file have the same character encoding, if not, an exception is thrown. Ideally the credits information would also be the same between all the files, since there is no obvious way to merge it - but if the credits information differs from one file to the next, one file is picked arbitrarily to provide credits and a warning is printed. If two files give differing channel definitions for the same XMLTV channel id, then one is picked arbitrarily and a warning is printed. In the simple case, with just one file, you needn't worry about mismatching of encodings, credits or channels. The deprecated function CWparsefile() is a wrapper allowing just one filename.

parse_callback(document, encoding_callback, credits_callback, channel_callback, programme_callback)

An alternative interface. Whereas CWparse() reads the whole document and then returns a finished data structure, with this routine you specify a subroutine to be called as each <channel> element is read and another for each <programme> element. The first argument is the document to parse. The remaining arguments are code references, one for each part of the document. The callback for encoding will be called once with a string giving the encoding. In present releases of this module, it is also possible for the value to be undefined meaning 'unknown', but it's hoped that future releases will always be able to figure out the encoding used. The callback for credits will be called once with a hash reference. For channels and programmes, the appropriate function will be called zero or more times depending on how many channels / programmes are found in the file. The four subroutines will be called in order, that is, the encoding and credits will be done before the channel handler is called and all the channels will be dealt with before the first programme handler is called. If any of the code references is undef, nothing is called for that part of the file. For backwards compatibility, if the value for 'encoding callback' is not a code reference but a scalar reference, then the encoding found will be stored in that scalar. Similarly if the 'credits callback' is a scalar reference, the scalar it points to will be set to point to the hash of credits. This style of interface is deprecated: new code should just use four callbacks. For example:

    my $document = '<tv>...</tv>';

    my $encoding;
    sub encoding_cb( $ ) { $encoding = shift }

    my $credits;
    sub credits_cb( $ ) { $credits = shift }

    # The callback for each channel populates this hash.
    my %channels;
    sub channel_cb( $ ) {
        my $c = shift;
        $channels{$c->{id}} = $c;
    }

    # The callback for each programme.  We know that channels are
    # always read before programmes, so the %channels hash will be
    # fully populated.
    #
    sub programme_cb( $ ) {
        my $p = shift;
        print "got programme: $p->{title}->[0]->[0]\n";
        my $c = $channels{$p->{channel}};
        print 'channel name is: ', $c->{'display-name'}->[0]->[0], "\n";
    }

    # Let's go.
    XMLTV::parse_callback($document, \&encoding_cb, \&credits_cb,
                          \&channel_cb, \&programme_cb);

parsefiles_callback(encoding_callback, credits_callback, channel_callback, programme_callback, filenames...)

As CWparse_callback() but takes one or more filenames to open, merging their contents in the same manner as CWparsefiles(). Note that the reading is still gradual - you get the channels and programmes one at a time, as they are read. Note that the same <channel> may be present in more than one file, so the channel callback will get called more than once. It's your responsibility to weed out duplicate channel elements (since writing them out again requires that each have a unique id). For compatibility, there is an alias CWparsefile_callback() which is the same but takes only a single filename, before the callback arguments. This is deprecated.

write_data(data, options...)

Takes a data structure and writes it as XML to standard output. Any extra arguments are passed on to XML::Writer's constructor, for example

    my $f = new IO::File '>out.xml'; die if not $f;
    write_data($data, OUTPUT => $f);

The encoding used for the output is given by the first element of the data. Normally, there will be a warning for any Perl data which is not understood and cannot be written as XMLTV, such as strange keys in hashes. But as an exception, any hash key beginning with an underscore will be skipped over silently. You can store 'internal use only' data this way. If a programme or channel hash contains a key beginning with 'debug', this key and its value will be written out as a comment inside the <programme> or <channel> element. This lets you include small debugging messages in the XML output.

best_name(languages, pairs [, comparator])

The XMLTV format contains many places where human-readable text is given an optional 'lang' attribute, to allow mixed languages. This is represented in Perl as a pair [ text, lang ], although the second element may be missing or undef if the language is unknown. When several alernatives for an element (such as <title>) can be given, the representation is a list of [ text, lang ] pairs. Given such a list, what is the best text to use? It depends on the user's preferred language. This function takes a list of acceptable languages and a list of [string, language] pairs, and finds the best one to use. This means first finding the appropriate language and then picking the 'best' string in that language. The best is normally defined as the first one found in a usable language, since the XMLTV format puts the most canonical versions first. But you can pass in your own comparison function, for example if you want to choose the shortest piece of text that is in an acceptable language. The acceptable languages should be a reference to a list of language codes looking like 'ru', or like 'de_DE'. The text pairs should be a reference to a list of pairs [ string, language ]. (As a special case if this list is empty or undef, that means no text is present, and the result is undef.) The third argument if present should be a cmp-style function that compares two strings of text and returns 1 if the first argument is better, -1 if the second better, 0 if they're equally good. Returns: [s, l] pair, where s is the best of the strings to use and l is its language. This pair is 'live' - it is one of those from the list passed in. So you can use CWbest_name() to find the best pair from a list and then modify the content of that pair. (This routine depends on the CWLingua::Preferred module being installed; if that module is missing then the first available language is always chosen.) Example:

    my $langs = [ 'de', 'fr' ]; # German or French, please

    # Say we found the following under $p->{title} for a programme $p.
    my $pairs = [ [ 'La CitE des enfants perdus', 'fr' ],
                  [ 'The City of Lost Children', 'en_US' ] ];

    my $best = best_name($langs, $pairs);
    print "chose title $best->[0]\n";

list_channel_keys(), list_programme_keys()

Some users of this module may wish to enquire at runtime about which keys a programme or channel hash can contain. The data in the hash comes from the attributes and subelements of the corresponding element in the XML. The values of attributes are simply stored as strings, while subelements are processed with a handler which may return a complex data structure. These subroutines returns a hash mapping key to handler name and multiplicity. This lets you know what data types can be expected under each key. For keys which come from attributes rather than subelements, the handler is set to 'scalar', just as for subelements which give a simple string. See DATA STRUCTURE for details on what the different handler names mean. It is not possible to find out which keys are mandatory and which optional, only a list of all those which might possibly be present. An example use of these routines is the tv_grep(1) program, which creates its allowed command line arguments from the names of programme subelements.

catfiles(w_args, filename...)

Concatenate several listings files, writing the output to somewhere specified by CWw_args. Programmes are catenated together, channels are merged, for credits we just take the first and warn if the others differ. The first argument is a hash reference giving information to pass to CWXMLTV::Writer's constructor. But do not specify encoding, this will be taken from the input files. Currently CWcatfiles() will fail work if the input files have different encodings.

cat(data, ...)

Concatenate (and merge) listings data. Programmes are catenated together, channels are merged, for credits we just take the first and warn if the others differ (except that the 'date' of the result is the latest date of all the inputs). Whereas CWcatfiles() reads and writes files, this function takes already-parsed listings data and returns some more listings data. It is much more memory-hungry.

cat_noprogrammes

Like CWcat() but ignores the programme data and just returns encoding, credits and channels. This is in case for scalability reasons you want to handle programmes individually, but still merge the smaller data.

For completeness, we describe more precisely how channels and programmes are represented in Perl. Each element of the channels list is a hashref corresponding to one <channel> element, and likewise for programmes. The possible keys of a channel (programme) hash are the names of attributes or subelements of <channel> (<programme>).

The values for attributes are not processed in any way; an attribute CWfred="jim" in the XML will become a hash element with key CW'fred', value CW'jim'.

But for subelements, there is further processing needed to turn the XML content of a subelement into Perl data. What is done depends on what type of data is stored under that subelement. Also, if a certain element can appear several times then the hash key for that element points to a list of values rather than just one.

The conversion of a subelement's content to and from Perl data is done by a handler. The most common handler is with-lang, used for human-readable text content plus an optional 'lang' attribute. There are other handlers for other data structures in the file format. Often two subelements will share the same handler, since they hold the same type of data. The handlers defined are as follows; note that many of them will silently strip leading and trailing whitespace in element content. Look at the DTD itself for an explanation of the whole file format.

Unless specified otherwise, it is not allowed for an element expected to contain text to have empty content, nor for the text to contain newline characters.

credits

Turns a list of credits (for director, actor, writer, etc.) into a hash mapping 'role' to a list of names. The names in each role are kept in the same order.

scalar

Reads and writes a simple string as the content of the XML element.

length

Converts the content of a <length> element into a number of seconds (so <length units=minutes>5</minutes> would be returned as 300). On writing out again tries to convert a number of seconds to a time in minutes or hours if that would look better.

episode-num

The representation in Perl of XMLTV's odd episode numbers is as a pair of [ content, system ]. As specified by the DTD, if the system is not given in the file then 'onscreen' is assumed. Whitespace in the 'xmltv_ns' system is unimportant, so on reading it is normalized to a single space on either side of each dot.

video

The <video> section is converted to a hash. The <present> subelement corresponds to the key 'present' of this hash, 'yes' and 'no' are converted to Booleans. The same applies to <colour>. The content of the <aspect> subelement is stored under the key 'aspect'. These keys can be missing in the hash just as the subelements can be missing in the XML.

audio

This is similar to video. <present> is a Boolean value, while the content of <stereo> is stored unchanged.

previously-shown

The 'start' and 'channel' attributes are converted to keys in a hash.

presence

The content of the element is ignored: it signfies something by its very presence. So the conversion from XML to Perl is a constant true value whenever the element is found; the conversion from Perl to XML is to write out the element if true, don't write anything if false.

subtitles

The 'type' attribute and the 'language' subelement (both optional) become keys in a hash. But see language for what to pass as the value of that element.

rating

The rating is represented as a tuple of [ rating, system, icons ]. The last element is itself a listref of structures returned by the icon handler.

star-rating

In XML this is a string 'X/Y' plus a list of icons. In Perl represented as a pair [ rating, icons ] similar to rating.

icon

An icon in XMLTV files is like the <img> element in HTML. It is represented in Perl as a hashref with 'src' and optionally 'width' and 'height' keys.

with-lang

In XML something like title can be either <title>Foo</title> or <title lang=en>Foo</title>. In Perl these are stored as [ 'Foo' ] and [ 'Foo', 'en' ]. For the former [ 'Foo', undef ] would also be okay. This handler also has two modifiers which may be added to the name after '/'. /e means that empty text is allowed, and will be returned as the empty tuple [], to mean that the element is present but has no text. When writing with /e, undef will also be understood as present-but-empty. You cannot however specify a language if the text is empty. The modifier /m means that the text is allowed to span multiple lines. So for example with-lang/em is a handler for text with language, where the text may be empty and may contain newlines. Note that the with-lang-or-empty of earlier releases has been replaced by with-lang/e.

Now, which handlers are used for which subelements (keys) of channels and programmes? And what is the multiplicity (should you expect a single value or a list of values)?

The following tables map subelements of <channel> and of <programme> to the handlers used to read and write them. Many elements have their own handler with the same name, and most of the others use with-lang. The third column specifies the multiplicity of the element: * (any number) will give a list of values in Perl, + (one or more) will give a nonempty list, ? (maybe one) will give a scalar, and 1 (exactly one) will give a scalar which is not undef.

display-name, with-lang, +

icon, icon, *

url, scalar, *

title, with-lang, +

sub-title, with-lang, *

desc, with-lang/m, *

credits, credits, ?

date, scalar, ?

category, with-lang, *

language, with-lang, ?

orig-language, with-lang, ?

length, length, ?

icon, icon, *

url, scalar, *

country, with-lang, *

episode-num, episode-num, *

video, video, ?

audio, audio, ?

previously-shown, previously-shown, ?

premiere, with-lang/em, ?

last-chance, with-lang/em, ?

new, presence, ?

subtitles, subtitles, *

rating, rating, *

star-rating, star-rating, ?

At present, no parsing or validation on dates is done because dates may be partially specified in XMLTV. For example '2001' means that the year is known but not the month, day or time of day. Maybe in the future dates will be automatically converted to and from Date::Manip objects. For now they just use the scalar handler. Similar remarks apply to URLs.

When reading a file you have the choice of using CWparse() to gulp the whole file and return a data structure, or using CWparse_callback() to get the programmes one at a time, although channels and other data are still read all at once.

There is a similar choice when writing data: the CWwrite_data() routine prints a whole XMLTV document at once, but if you want to write an XMLTV document incrementally you can manually create an CWXMLTV::Writer object and call methods on it. Synopsis:

  use XMLTV;
  my $w = new XMLTV::Writer();
  $w->comment("Hello from XML::Writer's comment() method");
  $w->start({ 'generator-info-name' => 'Example code in pod' });
  my %ch = (id => 'test-channel', 'display-name' => [ [ 'Test', 'en' ] ]);
  $w->write_channel(\%ch);
  my %prog = (channel => 'test-channel', start => '200203161500',
              title => [ [ 'News', 'en' ] ]);
  $w->write_programme(\%prog);
  $w->end();

XMLTV::Writer inherits from XML::Writer, and provides the following extra or overridden methods:

new(), the constructor

Creates an XMLTV::Writer object and starts writing an XMLTV file, printing the DOCTYPE line. Arguments are passed on to XML::Writer's constructor, except that the 'encoding' key if present gives the XML character encoding. For example: my CW$w = new XMLTV::Writer(encoding => 'ISO-8859-1'); If encoding is not specified, XML::Writer's default is used (currently UTF-8).

start()

Write the start of the <tv> element. Parameter is a hashref which gives the attributes of this element.

write_channels()

Write several channels at once. Parameter is a reference to a hash mapping channel id to channel details. They will be written sorted by id, which is reasonable since the order of channels in an XMLTV file isn't significant.

write_channel()

Write a single channel. You can call this routine if you want, but most of the time CWwrite_channels() is a better interface.

write_programme()

Write details for a single programme as XML.

end()

Say you've finished writing programmes. This ends the <tv> element and the file.

Ed Avis, ed@membled.com

The file format is defined by the DTD xmltv.dtd, which is included in the xmltv package along with this module. It should be installed in your system's standard place for SGML and XML DTDs.

The xmltv package has a web page at <http://membled.com/work/apps/xmltv/> which carries information about the file format and the various tools and apps which are distributed with this module.