<wmmeta name="Title" value="Data Sources for the &lt;contents&gt; and &lt;media&gt; Tags" />
<wmmeta name="Section" value="02-tags_attrs" />
<wmmeta name="Score" value="60" />
<wmmeta name="Abstract">
the protocols supported by &lt;contents&gt; and &lt;media&gt;
</wmmeta>

Contents or URLs can be searched for using the "&lt;contents&gt;" [contents]
or "&lt;media&gt;" [media] tags, which allow you to search a data source
(directory, delimiter-separated-values file, database etc.) for a pattern.

Currently two data source protocols are defined, file: [1] and svfile: [2] .
More will probably follow, especially if other people contribute them, hint
hint ;)

	[1]: #file
	[2]: #svfile

file: [1] is the default protocol, if none is specified.

Attributes Supported By Datasource Tags
=======================================

	__src__:	All datasources require this attribute, which
	specifies a protocol and path, in a URL-style syntax:

		**protocol**:**path**

	__name__:	This attribute is used to specify the pattern of data,
	under this path, which will be converted into content items. The part
	of the data's location which matches this name pattern will become the
	name of the item. Typically, glob patterns, such as ''*.txt'' or
	''.../*.html'' are used.

	__prefix__:	The items' names can be further modified by specifying
	a __prefix__ and/or __suffix__; these strings are prepended or
	appended to the raw name to make the name the content is given.

	__suffix__:	See above.

	__namesubst__:	a Perl-formatted s// substitution, which is used
	to convert source filenames to content names.

	__nametr__:	a Perl tr// translation, which is used to convert
	source filenames to content names.

	__listname__:	a name of a content item.  This content item will be
	created, and will contain the names of all content items picked up by
	the "&lt;contents&gt;" [contents] or "&lt;media&gt;" [media] search.

In addition, the attributes supported by the "content tag" [content] can
be specified as attributes to "&lt;contents&gt;" [contents], including
__format__, __up__, __map__, etc.

The content blocks picked up from a "&lt;contents&gt;" [contents] search can
also contain meta-data, such as headlines, visibilty dates, workflow approval
statuses, etc. by including metadata [meta].

	[contents]: $(contents)
	[meta]: $(wmmeta)


<a name=file>

The file: Protocol
==================

</a>

The file: protocol loads content from a directory; each file is made into one
content chunk.  The __src__ attribute indicates the source directory, the
__name__ attribute indicates the "glob pattern" [globs] that will pick up the
content items in question.  The filename of the file will be used as the
content chunk's name.

        &lt;contents src="stories" name="*.txt" /&gt;

Note that the files in question are not actually opened until their content
chunks are referenced using &wmdollar;{name} or get_content(''name'').

Normally only the top level of files inside the __src__ directory are added to
the content set. However, if the __name__ pattern starts with **.../**,
the directory will be searched recursively:

        &lt;contents src="stories" name=".../*.txt" /&gt;

The resulting content items will contain the full path from that directory
down, i.e. the file **stories/dir1/foo/bar.txt** exists, the example
above would define a content item called
**&wmdollar;{dir1/foo/bar.txt}**.

<a name=svfile>

The svfile: Protocol
====================

</a>

The svfile: protocol loads content from a delimiter-separated-file; the
__src__ attribute is the name of the file, the __name__ is the "glob
pattern" [globs] used to catch the relevant content items.  The __namefield__
attribute specifies the field number (counting from 1) which the __name__
pattern is matched against, and the __valuefield__ specifies the number of
the field from which the content chunk is read.  The __delimiter__
attribute specifies the delimiter used to separate values in the file.

        &lt;contents src="svfile:stories.csv" name="*"
                namefield=1 valuefield=2 delimiter="," /&gt;

Adding New Protocols
====================

New data sources for &lt;contents&gt; and &lt;media&gt; tags are added by
writing an implementation of the __DataSourceBase.pm__ module, in the
__HTML::WebMake::DataSources__ package space (the
__lib/HTML/WebMake/DataSources__ directory of the distribution).

Every data source needs a __protocol__, an alphanumeric lowercase identifier
to use at the start of the __src__ attribute to indicate that a data source is
of that type.

Each implementation of this module should implement these methods:

	##new ($parent)##:	instantiate the object, as usual.

	##add ()##:	add all the items in that data source as content
	chunks.  (See below!)

	##get_location_url ($location)##:	get the location (in URL
	format) of a content chunk loaded by ##add()##.

	##get_location_contents ($location)##:	get the contents of the
	location. The location, again, is the string provided by ##add()##.

	##get_location_mod_time ($location)##:	get the current modification
	date of a location for dependency checking.  The location, again, is
	in the format of the string provided by ##add()##.

Notes:

	- If you want ##add()## to read the content immediately, call
	  ##$self->{parent}->add_text ($name, $text, $self->{src},
	  $modtime)##.

	- ##add()## can defer opening and reading content chunks straight away.
	  If it calls ##$self->{parent}->add_location ($name, $location,
	  $lastmod)##, providing a location string which starts with the data
	  source's protocol identifier, the content will not be loaded until
	  it is needed, at which point ##get_location_contents()## is called.

	- This location string should contain all the information needed to
	  access that content chunk later, even if ##add()## was not been
	  called.  Consider it as similar to a URL.  This is required so that
	  ##get_location_mod_time()## (see below) can work.

	- All implementations of ##add()## should call ##$fixed =
	  $self->{parent}->fixname ($name);## to modify the name of each
	  content chunk appropriately, followed by
	  ##$self->{parent}->add_file_to_list ($fixed);## to add the content
	  chunk's name to the __filelist__ content item.

	- Data sources that support the &lt;media&gt; tag need to implement
	  ##get_location_url##, otherwise an error message will be output.

	- Data sources that support the &lt;contents&gt; tag, and defer
	  reading the content until it's required, need to implement
	  ##get_location_contents##, which is used to provide content from a
	  location set using ##$self->{parent}->add_location()##.

	- Data sources that support the &lt;contents&gt; tag need to implement
	  ##get_location_mod_time##. This is used to support dependency
	  checking, and should return the modification time (in UNIX
	  ##time()## format) of that location.  Note that since this is used
	  to compare the modification time of a content chunk from the
	  previous time webmake was run, and the current modification time,
	  this is called before the **real** data source is opened.


	[globs]: $(globs)
	[contents]: $(contents)
	[media]: $(media)
