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XML::XPath::XMLParser - The default XML parsing class that produces a node tree
my $parser = XML::XPath::XMLParser->new(
filename => $self->get_filename,
xml => $self->get_xml,
ioref => $self->get_ioref,
parser => $self->get_parser,
);
my $root_node = $parser->parse;
This module generates a node tree for use as the context node for XPath processing. It aims to be a quick parser, nothing fancy, and yet has to store more information than most parsers. To achieve this I've used array refs everywhere - no hashes. I don't have any performance figures for the speedups achieved, so I make no appologies for anyone not used to using arrays instead of hashes. I think they make good sense here where we know the attributes of each type of node.
All nodes have the same first 2 entries in the array: node_parent
and node_pos. The type of the node is determined using the ref() function.
The node_parent always contains an entry for the parent of the current
node - except for the root node which has undef in there. And node_pos is the
position of this node in the array that it is in (think:
$node == $node->[node_parent]->[node_children]->[$node->[node_pos]] )
Nodes are structured as follows:
The root node is just an element node with no parent.
[
undef, # node_parent - check for undef to identify root node
undef, # node_pos
undef, # node_prefix
[ ... ], # node_children (see below)
]
[
$parent, # node_parent
<position in current array>, # node_pos
'xxx', # node_prefix - namespace prefix on this element
[ ... ], # node_children
'yyy', # node_name - element tag name
[ ... ], # node_attribs - attributes on this element
[ ... ], # node_namespaces - namespaces currently in scope
]
[
$parent, # node_parent - the element node
<position in current array>, # node_pos
'xxx', # node_prefix - namespace prefix on this element
'href', # node_key - attribute name
'ftp://ftp.com/', # node_value - value in the node
]
Each element has an associated set of namespace nodes that are currently in scope. Each namespace node stores a prefix and the expanded name (retrieved from the xmlns:prefix=``...'' attribute).
[
$parent,
<pos>,
'a', # node_prefix - the namespace as it was written as a prefix
'http://my.namespace.com', # node_expanded - the expanded name.
]
[
$parent,
<pos>,
'This is some text' # node_text - the text in the node
]
[
$parent,
<pos>,
'This is a comment' # node_comment
]
[
$parent,
<pos>,
'target', # node_target
'data', # node_data
]
If you feel the need to use this module outside of XML::XPath (for example you might use this module directly so that you can cache parsed trees), you can follow the following API:
The new method takes either no parameters, or any of the following parameters:
filename
xml
parser
ioref
This uses the familiar hash syntax, so an example might be:
use XML::XPath::XMLParser;
my $parser = XML::XPath::XMLParser->new(filename => 'example.xml');
The parameters represent a filename, a string containing XML, an XML::Parser instance and an open filehandle ref respectively. You can also set or get all of these properties using the get_ and set_ functions that have the same name as the property: e.g. get_filename, set_ioref, etc.
The parse method generally takes no parameters, however you are free to pass either an open filehandle reference or an XML string if you so require. The return value is a tree that XML::XPath can use. The parse method will die if there is an error in your XML, so be sure to use perl's exception handling mechanism (eval{};) if you want to avoid this.
The parsefile method is identical to parse() except it expects a single
parameter that is a string naming a file to open and parse. Again it
returns a tree and also dies if there are XML errors.
This file is distributed as part of the XML::XPath module, and is copyright 2000 Fastnet Software Ltd. Please see the documentation for the module as a whole for licencing information.