yaml.pm

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package YAML;
use strict; use warnings;
use YAML::Base;
use base 'YAML::Base';
use YAML::Node;         # XXX This is a temp fix for Module::Build
use 5.006001;
our $VERSION = '0.66';
our @EXPORT = qw'Dump Load';
our @EXPORT_OK = qw'freeze thaw DumpFile LoadFile Bless Blessed';

# XXX This VALUE nonsense needs to go.
use constant VALUE => "\x07YAML\x07VALUE\x07";

# YAML Object Properties
field dumper_class => 'YAML::Dumper';
field loader_class => 'YAML::Loader';
field dumper_object =>
    -init => '$self->init_action_object("dumper")';
field loader_object =>
    -init => '$self->init_action_object("loader")';

sub Dump {
    my $yaml = YAML->new;
    $yaml->dumper_class($YAML::DumperClass)
        if $YAML::DumperClass;
    return $yaml->dumper_object->dump(@_);
}

sub Load {
    my $yaml = YAML->new;
    $yaml->loader_class($YAML::LoaderClass)
        if $YAML::LoaderClass;
    return $yaml->loader_object->load(@_);
}

{
    no warnings 'once';
    # freeze/thaw is the API for Storable string serialization. Some
    # modules make use of serializing packages on if they use freeze/thaw.
    *freeze = \ &Dump;
    *thaw   = \ &Load;
}

sub DumpFile {
    my $OUT;
    my $filename = shift;
    if (ref $filename eq 'GLOB') {
        $OUT = $filename;
    }
    else {
        my $mode = '>';
        if ($filename =~ /^\s*(>{1,2})\s*(.*)$/) {
            ($mode, $filename) = ($1, $2);
        }
        open $OUT, $mode, $filename
          or YAML::Base->die('YAML_DUMP_ERR_FILE_OUTPUT', $filename, $!);
    }  
    local $/ = "\n"; # reset special to "sane"
    print $OUT Dump(@_);
}

sub LoadFile {
    my $IN;
    my $filename = shift;
    if (ref $filename eq 'GLOB') {
        $IN = $filename;
    }
    else {
        open $IN, $filename
          or YAML::Base->die('YAML_LOAD_ERR_FILE_INPUT', $filename, $!);
    }
    return Load(do { local $/; <$IN> });
}

sub init_action_object {
    my $self = shift;
    my $object_class = (shift) . '_class';
    my $module_name = $self->$object_class;
    eval "require $module_name";
    $self->die("Error in require $module_name - $@")
        if $@ and "$@" !~ /Can't locate/;
    my $object = $self->$object_class->new;
    $object->set_global_options;
    return $object;
}

my $global = {};
sub Bless {
    require YAML::Dumper::Base;
    YAML::Dumper::Base::bless($global, @_)
}
sub Blessed {
    require YAML::Dumper::Base;
    YAML::Dumper::Base::blessed($global, @_)
}
sub global_object { $global }

1;

__END__

=head1 NAME

YAML - YAML Ain't Markup Language (tm)

=head1 SYNOPSIS

    use YAML;
    
    # Load a YAML stream of 3 YAML documents into Perl data structures.
    my ($hashref, $arrayref, $string) = Load(<<'...');
    ---
    name: ingy
    age: old
    weight: heavy
    # I should comment that I also like pink, but don't tell anybody.
    favorite colors:
        - red
        - green
        - blue
    ---
    - Clark Evans
    - Oren Ben-Kiki
    - Ingy d枚t Net
    --- >
    You probably think YAML stands for "Yet Another Markup Language". It
    ain't! YAML is really a data serialization language. But if you want
    to think of it as a markup, that's OK with me. A lot of people try
    to use XML as a serialization format.
    
    "YAML" is catchy and fun to say. Try it. "YAML, YAML, YAML!!!"
    ...
    
    # Dump the Perl data structures back into YAML.
    print Dump($string, $arrayref, $hashref); 
    
    # YAML::Dump is used the same way you'd use Data::Dumper::Dumper
    use Data::Dumper;
    print Dumper($string, $arrayref, $hashref); 

=head1 DESCRIPTION

The YAML.pm module implements a YAML Loader and Dumper based on the YAML
1.0 specification. L<http://www.yaml.org/spec/>

YAML is a generic data serialization language that is optimized for
human readability. It can be used to express the data structures of most
modern programming languages. (Including Perl!!!)

For information on the YAML syntax, please refer to the YAML
specification.

=head1 WHY YAML IS COOL

=over 4

=item YAML is readable for people. 

It makes clear sense out of complex data structures. You should find
that YAML is an exceptional data dumping tool. Structure is shown
through indentation, YAML supports recursive data, and hash keys are
sorted by default. In addition, YAML supports several styles of scalar
formatting for different types of data.

=item YAML is editable.

YAML was designed from the ground up to be an excellent syntax for
configuration files. Almost all programs need configuration files, so
why invent a new syntax for each one? And why subject users to the
complexities of XML or native Perl code?

=item YAML is multilingual.

Yes, YAML supports Unicode. But I'm actually referring to programming
languages. YAML was designed to meet the serialization needs of Perl,
Python, Ruby, Tcl, PHP, Javascript and Java. It was also designed to be
interoperable between those languages. That means YAML serializations
produced by Perl can be processed by Python.

=item YAML is taint safe.

Using modules like Data::Dumper for serialization is fine as long as you
can be sure that nobody can tamper with your data files or
transmissions. That's because you need to use Perl's C<eval()> built-in
to deserialize the data. Somebody could add a snippet of Perl to erase
your files.

YAML's parser does not need to eval anything.

=item YAML is full featured.

YAML can accurately serialize all of the common Perl data structures and
deserialize them again without losing data relationships. Although it is
not 100% perfect (no serializer is or can be perfect), it fares as well
as the popular current modules: Data::Dumper, Storable, XML::Dumper and
Data::Denter.

YAML.pm also has the ability to handle code (subroutine) references and
typeglobs. (Still experimental) These features are not found in Perl's
other serialization modules.

=item YAML is extensible.

The YAML language has been designed to be flexible enough to solve it's
own problems. The markup itself has 3 basic construct which resemble
Perl's hash, array and scalar. By default, these map to their Perl
equivalents. But each YAML node also supports a tagging mechanism (type
system) which can cause that node to be interpreted in a completely
different manner. That's how YAML can support object serialization and
oddball structures like Perl's typeglob.

=back

=head1 YAML IMPLEMENTATIONS IN PERL

This module, YAML.pm, is really just the interface module for YAML
modules written in Perl. The basic interface for YAML consists of two
functions: C<Dump> and C<Load>. The real work is done by the modules
YAML::Dumper and YAML::Loader.

Different YAML module distributions can be created by subclassing
YAML.pm and YAML::Loader and YAML::Dumper. For example, YAML-Simple
consists of YAML::Simple YAML::Dumper::Simple and YAML::Loader::Simple.

Why would there be more than one implementation of YAML? Well, despite
YAML's offering of being a simple data format, YAML is actually very
deep and complex. Implementing the entirety of the YAML specification is
a daunting task.

For this reason I am currently working on 3 different YAML implementations.

=over

=item YAML

The main YAML distribution will keeping evolving to support the entire
YAML specification in pure Perl. This may not be the fastest or most
stable module though. Currently, YAML.pm has lots of known bugs. It is
mostly a great tool for dumping Perl data structures to a readable form.

=item YAML::Lite

The point of YAML::Lite is to strip YAML down to the 90% that people
use most and offer that in a small, fast, stable, pure Perl form.
YAML::Lite will simply die when it is asked to do something it can't.

=item YAML::Syck

C<libsyck> is the C based YAML processing library used by the Ruby
programming language (and also Python, PHP and Pugs). YAML::Syck is the
Perl binding to C<libsyck>. It should be very fast, but may have
problems of its own. It will also require C compilation.

NOTE: Audrey Tang has actually completed this module and it works great
      and is 10 times faster than YAML.pm.

=back

In the future, there will likely be even more YAML modules. Remember,
people other than Ingy are allowed to write YAML modules!

=head1 FUNCTIONAL USAGE

YAML is completely OO under the hood. Still it exports a few useful top
level functions so that it is dead simple to use. These functions just
do the OO stuff for you. If you want direct access to the OO API see the
documentation for YAML::Dumper and YAML::Loader.

=head2 Exported Functions

The following functions are exported by YAML.pm by default. The reason
they are exported is so that YAML works much like Data::Dumper. If you
don't want functions to be imported, just use YAML with an empty
import list:

    use YAML ();

=over 4

=item Dump(list-of-Perl-data-structures)

Turn Perl data into YAML. This function works very much like
Data::Dumper::Dumper(). It takes a list of Perl data strucures and
dumps them into a serialized form. It returns a string containing the
YAML stream. The structures can be references or plain scalars.

=item Load(string-containing-a-YAML-stream) 

Turn YAML into Perl data. This is the opposite of Dump. Just like
Storable's thaw() function or the eval() function in relation to
Data::Dumper. It parses a string containing a valid YAML stream into a
list of Perl data structures.

=back

=head2 Exportable Functions

These functions are not exported by default but you can request them in
an import list like this:

    use YAML qw'freeze thaw Bless';

=over 4

=item freeze() and thaw()

Aliases to Dump() and Load() for Storable fans. This will also allow
YAML.pm to be plugged directly into modules like POE.pm, that use the
freeze/thaw API for internal serialization.

=item DumpFile(filepath, list)

Writes the YAML stream to a file instead of just returning a string.

=item LoadFile(filepath)

Reads the YAML stream from a file instead of a string.

=item Bless(perl-node, [yaml-node | class-name])

Associate a normal Perl node, with a yaml node. A yaml node is an object
tied to the YAML::Node class. The second argument is either a yaml node
that you've already created or a class (package) name that supports a
yaml_dump() function. A yaml_dump() function should take a perl node and
return a yaml node. If no second argument is provided, Bless will create
a yaml node. This node is not returned, but can be retrieved with the
Blessed() function.

Here's an example of how to use Bless. Say you have a hash containing
three keys, but you only want to dump two of them. Furthermore the keys
must be dumped in a certain order. Here's how you do that:

    use YAML qw(Dump Bless);
    $hash = {apple => 'good', banana => 'bad', cauliflower => 'ugly'};
    print Dump $hash;
    Bless($hash)->keys(['banana', 'apple']);
    print Dump $hash;

produces:

    ---
    apple: good
    banana: bad
    cauliflower: ugly
    ---
    banana: bad
    apple: good

Bless returns the tied part of a yaml-node, so that you can call the
YAML::Node methods. This is the same thing that YAML::Node::ynode()
returns. So another way to do the above example is:

    use YAML qw(Dump Bless);
    use YAML::Node;
    $hash = {apple => 'good', banana => 'bad', cauliflower => 'ugly'};
    print Dump $hash;
    Bless($hash);
    $ynode = ynode(Blessed($hash));
    $ynode->keys(['banana', 'apple']);
    print Dump $hash;

Note that Blessing a Perl data structure does not change it anyway. The
extra information is stored separately and looked up by the Blessed
node's memory address.

=item Blessed(perl-node)

Returns the yaml node that a particular perl node is associated with
(see above). Returns undef if the node is not (YAML) Blessed.

=back

=head1 GLOBAL OPTIONS

YAML options are set using a group of global variables in the YAML
namespace. This is similar to how Data::Dumper works.

For example, to change the indentation width, do something like:

    local $YAML::Indent = 3;

The current options are:

=over 4

=item DumperClass

You can override which module/class YAML uses for Dumping data.

=item LoaderClass

You can override which module/class YAML uses for Loading data.

=item Indent