yaml.pm

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

This is the number of space characters to use for each indentation level
when doing a Dump(). The default is 2.

By the way, YAML can use any number of characters for indentation at any
level. So if you are editing YAML by hand feel free to do it anyway that
looks pleasing to you; just be consistent for a given level.

=item SortKeys

Default is 1. (true)

Tells YAML.pm whether or not to sort hash keys when storing a document. 

YAML::Node objects can have their own sort order, which is usually what
you want. To override the YAML::Node order and sort the keys anyway, set
SortKeys to 2.

=item Stringify

Default is 0. (false)

Objects with string overloading should honor the overloading and dump the
stringification of themselves, rather than the actual object's guts.

=item UseHeader

Default is 1. (true)

This tells YAML.pm whether to use a separator string for a Dump
operation. This only applies to the first document in a stream.
Subsequent documents must have a YAML header by definition.

=item UseVersion

Default is 0. (false)

Tells YAML.pm whether to include the YAML version on the
separator/header.

    --- %YAML:1.0

=item AnchorPrefix

Default is ''.

Anchor names are normally numeric. YAML.pm simply starts with '1' and
increases by one for each new anchor. This option allows you to specify a
string to be prepended to each anchor number.

=item UseCode

Setting the UseCode option is a shortcut to set both the DumpCode and
LoadCode options at once. Setting UseCode to '1' tells YAML.pm to dump
Perl code references as Perl (using B::Deparse) and to load them back
into memory using eval(). The reason this has to be an option is that
using eval() to parse untrusted code is, well, untrustworthy.

=item DumpCode

Determines if and how YAML.pm should serialize Perl code references. By
default YAML.pm will dump code references as dummy placeholders (much
like Data::Dumper). If DumpCode is set to '1' or 'deparse', code
references will be dumped as actual Perl code.

DumpCode can also be set to a subroutine reference so that you can
write your own serializing routine. YAML.pm passes you the code ref. You
pass back the serialization (as a string) and a format indicator. The
format indicator is a simple string like: 'deparse' or 'bytecode'.

=item LoadCode

LoadCode is the opposite of DumpCode. It tells YAML if and how to
deserialize code references. When set to '1' or 'deparse' it will use
C<eval()>. Since this is potentially risky, only use this option if you
know where your YAML has been.

LoadCode can also be set to a subroutine reference so that you can write
your own deserializing routine. YAML.pm passes the serialization (as a
string) and a format indicator. You pass back the code reference.

=item UseBlock

YAML.pm uses heuristics to guess which scalar style is best for a given
node. Sometimes you'll want all multiline scalars to use the 'block'
style. If so, set this option to 1.

NOTE: YAML's block style is akin to Perl's here-document. 

=item UseFold

If you want to force YAML to use the 'folded' style for all multiline
scalars, then set $UseFold to 1.

NOTE: YAML's folded style is akin to the way HTML folds text,
      except smarter.

=item UseAliases

YAML has an alias mechanism such that any given structure in memory gets
serialized once. Any other references to that structure are serialized
only as alias markers. This is how YAML can serialize duplicate and
recursive structures.

Sometimes, when you KNOW that your data is nonrecursive in nature, you
may want to serialize such that every node is expressed in full. (ie as
a copy of the original). Setting $YAML::UseAliases to 0 will allow you
to do this. This also may result in faster processing because the lookup
overhead is by bypassed.

THIS OPTION CAN BE DANGEROUS. *If* your data is recursive, this option
*will* cause Dump() to run in an endless loop, chewing up your computers
memory. You have been warned.

=item CompressSeries

Default is 1.

Compresses the formatting of arrays of hashes:

    -
      foo: bar
    - 
      bar: foo

becomes:

    - foo: bar
    - bar: foo

Since this output is usually more desirable, this option is turned on by
default.

=back

=head1 YAML TERMINOLOGY

YAML is a full featured data serialization language, and thus has its
own terminology.

It is important to remember that although YAML is heavily influenced by
Perl and Python, it is a language in its own right, not merely just a
representation of Perl structures.

YAML has three constructs that are conspicuously similar to Perl's hash,
array, and scalar. They are called mapping, sequence, and string
respectively. By default, they do what you would expect. But each
instance may have an explicit or implicit tag (type) that makes it
behave differently. In this manner, YAML can be extended to represent
Perl's Glob or Python's tuple, or Ruby's Bigint.

=over 4

=item stream

A YAML stream is the full sequence of unicode characters that a YAML
parser would read or a YAML emitter would write. A stream may contain
one or more YAML documents separated by YAML headers.

    ---
    a: mapping
    foo: bar
    ---
    - a
    - sequence

=item document

A YAML document is an independent data structure representation within a
stream. It is a top level node. Each document in a YAML stream must
begin with a YAML header line. Actually the header is optional on the
first document.

    ---
    This: top level mapping
    is:
        - a
        - YAML
        - document

=item header

A YAML header is a line that begins a YAML document. It consists of
three dashes, possibly followed by more info. Another purpose of the
header line is that it serves as a place to put top level tag and anchor
information.

    --- !recursive-sequence &001
    - * 001
    - * 001

=item node

A YAML node is the representation of a particular data stucture. Nodes
may contain other nodes. (In Perl terms, nodes are like scalars.
Strings, arrayrefs and hashrefs. But this refers to the serialized
format, not the in-memory structure.)

=item tag

This is similar to a type. It indicates how a particular YAML node
serialization should be transferred into or out of memory. For instance
a Foo::Bar object would use the tag 'perl/Foo::Bar':

    - !perl/Foo::Bar
        foo: 42
        bar: stool

=item collection

A collection is the generic term for a YAML data grouping. YAML has two
types of collections: mappings and sequences. (Similar to hashes and arrays)

=item mapping

A mapping is a YAML collection defined by unordered key/value pairs with
unique keys. By default YAML mappings are loaded into Perl hashes.

    a mapping:
        foo: bar
        two: times two is 4

=item sequence

A sequence is a YAML collection defined by an ordered list of elements. By
default YAML sequences are loaded into Perl arrays.

    a sequence:
        - one bourbon
        - one scotch
        - one beer

=item scalar

A scalar is a YAML node that is a single value. By default YAML scalars
are loaded into Perl scalars.

    a scalar key: a scalar value

YAML has many styles for representing scalars. This is important because
varying data will have varying formatting requirements to retain the
optimum human readability.

=item plain scalar

A plain sclar is unquoted. All plain scalars are automatic candidates
for "implicit tagging". This means that their tag may be determined
automatically by examination. The typical uses for this are plain alpha
strings, integers, real numbers, dates, times and currency.

    - a plain string
    - -42
    - 3.1415
    - 12:34
    - 123 this is an error

=item single quoted scalar

This is similar to Perl's use of single quotes. It means no escaping
except for single quotes which are escaped by using two adjacent
single quotes.

    - 'When I say ''\n'' I mean "backslash en"'

=item double quoted scalar

This is similar to Perl's use of double quotes. Character escaping can
be used.

    - "This scalar\nhas two lines, and a bell -->\a"

=item folded scalar

This is a multiline scalar which begins on the next line. It is
indicated by a single right angle bracket. It is unescaped like the
single quoted scalar. Line folding is also performed.

    - > 
     This is a multiline scalar which begins on
     the next line. It is indicated by a single
     carat. It is unescaped like the single
     quoted scalar. Line folding is also
     performed.

=item block scalar

This final multiline form is akin to Perl's here-document except that
(as in all YAML data) scope is indicated by indentation. Therefore, no
ending marker is required. The data is verbatim. No line folding.

    - |
        QTY  DESC          PRICE  TOTAL
        ---  ----          -----  -----
          1  Foo Fighters  $19.95 $19.95
          2  Bar Belles    $29.95 $59.90

=item parser

A YAML processor has four stages: parse, load, dump, emit. 

A parser parses a YAML stream. YAML.pm's Load() function contains a
parser.

=item loader

The other half of the Load() function is a loader. This takes the
information from the parser and loads it into a Perl data structure.

=item dumper

The Dump() function consists of a dumper and an emitter. The dumper
walks through each Perl data structure and gives info to the emitter.

=item emitter

The emitter takes info from the dumper and turns it into a YAML stream. 

NOTE: 
In YAML.pm the parser/loader and the dumper/emitter code are currently
very closely tied together. In the future they may be broken into
separate stages.

=back

For more information please refer to the immensely helpful YAML
specification available at L<http://www.yaml.org/spec/>.

=head1 ysh - The YAML Shell

The YAML distribution ships with a script called 'ysh', the YAML shell.
ysh provides a simple, interactive way to play with YAML. If you type in
Perl code, it displays the result in YAML. If you type in YAML it turns
it into Perl code.

To run ysh, (assuming you installed it along with YAML.pm) simply type:

    ysh [options]

Please read the C<ysh> documentation for the full details. There are
lots of options.

=head1 BUGS & DEFICIENCIES

If you find a bug in YAML, please try to recreate it in the YAML Shell
with logging turned on ('ysh -L'). When you have successfully reproduced
the bug, please mail the LOG file to the author ([e-mail]).

WARNING: This is still *ALPHA* code. Well, most of this code has been
around for years...

BIGGER WARNING: YAML.pm has been slow in the making, but I am committed
to having top notch YAML tools in the Perl world. The YAML team is close
to finalizing the YAML 1.1 spec. This version of YAML.pm is based off of
a very old pre 1.0 spec. In actuality there isn't a ton of difference,
and this YAML.pm is still fairly useful. Things will get much better in
the future.

=head1 RESOURCES

L<http://lists.sourceforge.net/lists/listinfo/yaml-core> is the mailing
list. This is where the language is discussed and designed.

L<http://www.yaml.org> is the official YAML website.

L<http://www.yaml.org/spec/> is the YAML 1.0 specification.

L<http://yaml.kwiki.org> is the official YAML wiki.

=head1 SEE ALSO

See YAML::Syck. Fast!

=head1 AUTHOR

Ingy d枚t Net <[e-mail]>

is resonsible for YAML.pm.

The YAML serialization language is the result of years of collaboration
between Oren Ben-Kiki, Clark Evans and Ingy d枚t Net. Several others
have added help along the way.

=head1 COPYRIGHT

Copyright (c) 2005, 2006. Ingy d枚t Net. All rights reserved.

Copyright (c) 2001, 2002, 2005. Brian Ingerson. All rights reserved.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

See L<http://www.perl.com/perl/misc/Artistic.html>

=cut