Initial Windows agent repository
This commit is contained in:
commit
a0db0c2e5b
10589 changed files with 3844063 additions and 0 deletions
664
OGP64/usr/share/doc/perl-XML-Parser/README.md
Normal file
664
OGP64/usr/share/doc/perl-XML-Parser/README.md
Normal file
|
|
@ -0,0 +1,664 @@
|
|||
[](https://github.com/cpan-authors/XML-Parser/actions/workflows/testsuite.yml) [](https://codecov.io/gh/cpan-authors/XML-Parser)
|
||||
|
||||
# NAME
|
||||
|
||||
XML::Parser - A perl module for parsing XML documents
|
||||
|
||||
# SYNOPSIS
|
||||
|
||||
use XML::Parser;
|
||||
|
||||
$p1 = XML::Parser->new(Style => 'Debug');
|
||||
$p1->parsefile('REC-xml-19980210.xml');
|
||||
$p1->parse('<foo id="me">Hello World</foo>');
|
||||
|
||||
# Alternative
|
||||
$p2 = XML::Parser->new(Handlers => {Start => \&handle_start,
|
||||
End => \&handle_end,
|
||||
Char => \&handle_char});
|
||||
$p2->parse($socket);
|
||||
|
||||
# Another alternative
|
||||
$p3 = XML::Parser->new(ErrorContext => 2);
|
||||
|
||||
$p3->setHandlers(Char => \&text,
|
||||
Default => \&other);
|
||||
|
||||
open(my $fh, 'xmlgenerator |');
|
||||
$p3->parse($fh, ProtocolEncoding => 'ISO-8859-1');
|
||||
close($fh);
|
||||
|
||||
$p3->parsefile('junk.xml', ErrorContext => 3);
|
||||
|
||||
# DESCRIPTION
|
||||
|
||||
This module provides ways to parse XML documents. It is built on top of
|
||||
[XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat), which is a lower level interface to James Clark's
|
||||
expat library. Each call to one of the parsing methods creates a new
|
||||
instance of XML::Parser::Expat which is then used to parse the document.
|
||||
Expat options may be provided when the XML::Parser object is created.
|
||||
These options are then passed on to the Expat object on each parse call.
|
||||
They can also be given as extra arguments to the parse methods, in which
|
||||
case they override options given at XML::Parser creation time.
|
||||
|
||||
The behavior of the parser is controlled either by `["STYLES"](#styles)` and/or
|
||||
`["HANDLERS"](#handlers)` options, or by ["setHandlers"](#sethandlers) method. These all provide
|
||||
mechanisms for XML::Parser to set the handlers needed by XML::Parser::Expat.
|
||||
If neither `Style` nor `Handlers` are specified, then parsing just
|
||||
checks the document for being well-formed.
|
||||
|
||||
When underlying handlers get called, they receive as their first parameter
|
||||
the _Expat_ object, not the Parser object.
|
||||
|
||||
# METHODS
|
||||
|
||||
- new
|
||||
|
||||
This is a class method, the constructor for XML::Parser. Options are passed
|
||||
as keyword value pairs. Recognized options are:
|
||||
|
||||
- Style
|
||||
|
||||
This option provides an easy way to create a given style of parser. The
|
||||
built in styles are: ["Debug"](#debug), ["Subs"](#subs), ["Tree"](#tree), ["Objects"](#objects),
|
||||
and ["Stream"](#stream). These are all defined in separate packages under
|
||||
`XML::Parser::Style::*`, and you can find further documentation for
|
||||
each style both below, and in those packages.
|
||||
|
||||
Custom styles can be provided by giving a full package name containing
|
||||
at least one '::'. This package should then have subs defined for each
|
||||
handler it wishes to have installed. See ["STYLES"](#styles) below
|
||||
for a discussion of each built in style.
|
||||
|
||||
- Handlers
|
||||
|
||||
When provided, this option should be an anonymous hash containing as
|
||||
keys the type of handler and as values a sub reference to handle that
|
||||
type of event. All the handlers get passed as their 1st parameter the
|
||||
instance of expat that is parsing the document. Further details on
|
||||
handlers can be found in ["HANDLERS"](#handlers). Any handler set here
|
||||
overrides the corresponding handler set with the Style option.
|
||||
|
||||
- Pkg
|
||||
|
||||
Some styles will refer to subs defined in this package. If not provided,
|
||||
it defaults to the package which called the constructor.
|
||||
|
||||
- ErrorContext
|
||||
|
||||
This is an Expat option. When this option is defined, errors are reported
|
||||
in context. The value should be the number of lines to show on either side
|
||||
of the line in which the error occurred.
|
||||
|
||||
- ProtocolEncoding
|
||||
|
||||
This is an Expat option. This sets the protocol encoding name. It defaults
|
||||
to none. The built-in encodings are: `UTF-8`, `ISO-8859-1`, `UTF-16`, and
|
||||
`US-ASCII`. Other encodings may be used if they have encoding maps in one
|
||||
of the directories in the @Encoding\_Path list. Check ["ENCODINGS"](#encodings) for
|
||||
more information on encoding maps. Setting the protocol encoding overrides
|
||||
any encoding in the XML declaration.
|
||||
|
||||
- Namespaces
|
||||
|
||||
This is an Expat option. If this is set to a true value, then namespace
|
||||
processing is done during the parse. See ["Namespaces" in XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat#Namespaces)
|
||||
for further discussion of namespace processing.
|
||||
|
||||
- NoExpand
|
||||
|
||||
This is an Expat option. Normally, the parser will try to expand references
|
||||
to entities defined in the internal subset. If this option is set to a true
|
||||
value, and a default handler is also set, then the default handler will be
|
||||
called when an entity reference is seen in text. This has no effect if a
|
||||
default handler has not been registered, and it has no effect on the expansion
|
||||
of entity references inside attribute values.
|
||||
|
||||
- Stream\_Delimiter
|
||||
|
||||
This is an Expat option. It takes a string value. When this string is found
|
||||
alone on a line while parsing from a stream, then the parse is ended as if it
|
||||
saw an end of file. The intended use is with a stream of xml documents in a
|
||||
MIME multipart format. The string should not contain a trailing newline.
|
||||
|
||||
- ParseParamEnt
|
||||
|
||||
This is an Expat option. Unless standalone is set to "yes" in the XML
|
||||
declaration, setting this to a true value allows the external DTD to be read,
|
||||
and parameter entities to be parsed and expanded.
|
||||
|
||||
**Implicit vs explicit parameter entity parsing:** When `ParseParamEnt` is
|
||||
not set, parameter entity references (e.g. `%foo;`) in the internal DTD
|
||||
subset are passed through to the **Default** handler as literal text. This is
|
||||
the mode that XML::Twig and other DTD round-tripping tools rely on.
|
||||
|
||||
When `ParseParamEnt` is set to a true value, or when a declaration handler
|
||||
(**Entity**, **Element**, or **Attlist**) is registered, parameter entity parsing
|
||||
is activated. In this mode, PE references are resolved by expat (via the
|
||||
**ExternEnt** handler) and subsequent declarations are routed to their
|
||||
dedicated declaration handlers instead of the Default handler.
|
||||
|
||||
- NoLWP
|
||||
|
||||
This option has no effect if the ExternEnt or ExternEntFin handlers are
|
||||
directly set. Otherwise, if true, it forces the use of a file based external
|
||||
entity handler.
|
||||
|
||||
- BillionLaughsAttackProtectionMaximumAmplification
|
||||
|
||||
Sets the maximum amplification factor for the Billion Laughs attack
|
||||
protection. See ["SECURITY"](#security) below for details.
|
||||
|
||||
This is an Expat option.
|
||||
Requires libexpat >= 2.4.0 built with `XML_DTD` or `XML_GE`.
|
||||
|
||||
- BillionLaughsAttackProtectionActivationThreshold
|
||||
|
||||
Sets the activation threshold (in bytes) for the Billion Laughs attack
|
||||
protection. See ["SECURITY"](#security) below for details.
|
||||
|
||||
This is an Expat option.
|
||||
Requires libexpat >= 2.4.0 built with `XML_DTD` or `XML_GE`.
|
||||
|
||||
- AllocTrackerMaximumAmplification
|
||||
|
||||
Sets the maximum amplification factor for the allocation tracker.
|
||||
See ["SECURITY"](#security) below for details.
|
||||
|
||||
This is an Expat option.
|
||||
Requires libexpat >= 2.7.2 built with `XML_DTD` or `XML_GE`.
|
||||
|
||||
- AllocTrackerActivationThreshold
|
||||
|
||||
Sets the activation threshold (in bytes) for the allocation tracker.
|
||||
See ["SECURITY"](#security) below for details.
|
||||
|
||||
This is an Expat option.
|
||||
Requires libexpat >= 2.7.2 built with `XML_DTD` or `XML_GE`.
|
||||
|
||||
- ReparseDeferralEnabled
|
||||
|
||||
Enables or disables reparse deferral, a security mechanism that prevents
|
||||
certain token-boundary attacks. See ["SECURITY"](#security) below for details.
|
||||
|
||||
This is an Expat option.
|
||||
Requires libexpat >= 2.6.0.
|
||||
|
||||
- Non\_Expat\_Options
|
||||
|
||||
If provided, this should be an anonymous hash whose keys are options that
|
||||
shouldn't be passed to Expat. This should only be of concern to those
|
||||
subclassing XML::Parser.
|
||||
|
||||
- setHandlers(TYPE, HANDLER \[, TYPE, HANDLER \[...\]\])
|
||||
|
||||
This method registers handlers for various parser events. It overrides any
|
||||
previous handlers registered through the Style or Handler options or through
|
||||
earlier calls to setHandlers. By providing a false or undefined value as
|
||||
the handler, the existing handler can be unset.
|
||||
|
||||
This method returns a list of type, handler pairs corresponding to the
|
||||
input. The handlers returned are the ones that were in effect prior to
|
||||
the call.
|
||||
|
||||
See a description of the handler types in ["HANDLERS"](#handlers).
|
||||
|
||||
- parse(SOURCE \[, OPT => OPT\_VALUE \[...\]\])
|
||||
|
||||
The SOURCE parameter should either be a string containing the whole XML
|
||||
document, or it should be an open IO::Handle. Constructor options to
|
||||
XML::Parser::Expat given as keyword-value pairs may follow the SOURCE
|
||||
parameter. These override, for this call, any options or attributes passed
|
||||
through from the XML::Parser instance.
|
||||
|
||||
A die call is thrown if a parse error occurs. Otherwise it will return 1
|
||||
or whatever is returned from the **Final** handler, if one is installed.
|
||||
In other words, what parse may return depends on the style.
|
||||
|
||||
See ["ERROR HANDLING"](#error-handling) below for how to catch and handle parse errors.
|
||||
|
||||
- parsestring
|
||||
|
||||
This is just an alias for parse for backwards compatibility.
|
||||
|
||||
- parsefile(FILE \[, OPT => OPT\_VALUE \[...\]\])
|
||||
|
||||
Open FILE for reading, then call parse with the open handle. The file
|
||||
is closed no matter how parse returns. A die call is thrown if the file
|
||||
cannot be opened or if a parse error occurs. Returns what parse returns.
|
||||
|
||||
- parse\_start(\[ OPT => OPT\_VALUE \[...\]\])
|
||||
|
||||
Create and return a new instance of XML::Parser::ExpatNB. Constructor
|
||||
options may be provided. If an init handler has been provided, it is
|
||||
called before returning the ExpatNB object. Documents are parsed by
|
||||
making incremental calls to the parse\_more method of this object, which
|
||||
takes a string. A single call to the parse\_done method of this object,
|
||||
which takes no arguments, indicates that the document is finished.
|
||||
|
||||
If there is a final handler installed, it is executed by the parse\_done
|
||||
method before returning and the parse\_done method returns whatever is
|
||||
returned by the final handler.
|
||||
|
||||
# HANDLERS
|
||||
|
||||
Expat is an event based parser. As the parser recognizes parts of the
|
||||
document (say the start or end tag for an XML element), then any handlers
|
||||
registered for that type of an event are called with suitable parameters.
|
||||
All handlers receive an instance of XML::Parser::Expat as their first
|
||||
argument. See ["METHODS" in XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat#METHODS) for a discussion of the
|
||||
methods that can be called on this object.
|
||||
|
||||
## Init (Expat)
|
||||
|
||||
This is called just before the parsing of the document starts.
|
||||
|
||||
## Final (Expat)
|
||||
|
||||
This is called just after parsing has finished, but only if no errors
|
||||
occurred during the parse. Parse returns what this returns.
|
||||
|
||||
## Start (Expat, Element \[, Attr, Val \[,...\]\])
|
||||
|
||||
This event is generated when an XML start tag is recognized. Element is the
|
||||
name of the XML element type that is opened with the start tag. The Attr &
|
||||
Val pairs are generated for each attribute in the start tag.
|
||||
|
||||
## End (Expat, Element)
|
||||
|
||||
This event is generated when an XML end tag is recognized. Note that
|
||||
an XML empty tag (<foo/>) generates both a start and an end event.
|
||||
|
||||
## Char (Expat, String)
|
||||
|
||||
This event is generated when non-markup is recognized. The non-markup
|
||||
sequence of characters is in String. A single non-markup sequence of
|
||||
characters may generate multiple calls to this handler. Whatever the
|
||||
encoding of the string in the original document, this is given to the
|
||||
handler in UTF-8.
|
||||
|
||||
**Important:** Because the underlying expat library parses in fixed-size
|
||||
chunks, character data that spans a buffer boundary will arrive as two or
|
||||
more consecutive Char events. This typically occurs with files larger than
|
||||
about 32 KiB and is not a bug. To obtain the complete text of an element,
|
||||
accumulate the strings delivered between Start and End events:
|
||||
|
||||
my $current_text;
|
||||
sub start_handler { $current_text = ''; }
|
||||
sub char_handler { $current_text .= $_[1]; }
|
||||
sub end_handler { print "complete text: $current_text\n"; }
|
||||
|
||||
The Stream style (`XML::Parser::Style::Stream`) already performs this
|
||||
accumulation automatically.
|
||||
|
||||
## Proc (Expat, Target, Data)
|
||||
|
||||
This event is generated when a processing instruction is recognized.
|
||||
|
||||
## Comment (Expat, Data)
|
||||
|
||||
This event is generated when a comment is recognized.
|
||||
|
||||
## CdataStart (Expat)
|
||||
|
||||
This is called at the start of a CDATA section.
|
||||
|
||||
## CdataEnd (Expat)
|
||||
|
||||
This is called at the end of a CDATA section.
|
||||
|
||||
## Default (Expat, String)
|
||||
|
||||
This is called for any characters that don't have a registered handler.
|
||||
This includes both characters that are part of markup for which no
|
||||
events are generated (markup declarations) and characters that
|
||||
could generate events, but for which no handler has been registered.
|
||||
|
||||
Whatever the encoding in the original document, the string is returned to
|
||||
the handler in UTF-8.
|
||||
|
||||
## Unparsed (Expat, Entity, Base, Sysid, Pubid, Notation)
|
||||
|
||||
This is called for a declaration of an unparsed entity. Entity is the name
|
||||
of the entity. Base is the base to be used for resolving a relative URI.
|
||||
Sysid is the system id. Pubid is the public id. Notation is the notation
|
||||
name. Base and Pubid may be undefined.
|
||||
|
||||
## Notation (Expat, Notation, Base, Sysid, Pubid)
|
||||
|
||||
This is called for a declaration of notation. Notation is the notation name.
|
||||
Base is the base to be used for resolving a relative URI. Sysid is the system
|
||||
id. Pubid is the public id. Base, Sysid, and Pubid may all be undefined.
|
||||
|
||||
## ExternEnt (Expat, Base, Sysid, Pubid)
|
||||
|
||||
This is called when an external entity is referenced. Base is the base to be
|
||||
used for resolving a relative URI. Sysid is the system id. Pubid is the public
|
||||
id. Base, and Pubid may be undefined.
|
||||
|
||||
This handler should either return a string, which represents the contents of
|
||||
the external entity, or return an open filehandle that can be read to obtain
|
||||
the contents of the external entity, or return undef, which indicates the
|
||||
external entity couldn't be found and will generate a parse error.
|
||||
|
||||
If an open filehandle is returned, it must be returned as either a glob
|
||||
(\*FOO) or as a reference to a glob (e.g. an instance of IO::Handle).
|
||||
|
||||
A default handler is installed for this event. The default handler is
|
||||
XML::Parser::lwp\_ext\_ent\_handler unless the NoLWP option was provided with
|
||||
a true value, otherwise XML::Parser::file\_ext\_ent\_handler is the default
|
||||
handler for external entities. Even without the NoLWP option, if the
|
||||
URI or LWP modules are missing, the file based handler ends up being used
|
||||
after giving a warning on the first external entity reference.
|
||||
|
||||
The LWP external entity handler will use proxies defined in the environment
|
||||
(http\_proxy, ftp\_proxy, etc.).
|
||||
|
||||
Please note that the LWP external entity handler reads the entire
|
||||
entity into a string and returns it, where as the file handler opens a
|
||||
filehandle.
|
||||
|
||||
Also note that the file external entity handler will likely choke on
|
||||
absolute URIs or file names that don't fit the conventions of the local
|
||||
operating system.
|
||||
|
||||
The expat base method can be used to set a basename for
|
||||
relative pathnames. If no basename is given, or if the basename is itself
|
||||
a relative name, then it is relative to the current working directory.
|
||||
|
||||
## ExternEntFin (Expat)
|
||||
|
||||
This is called after parsing an external entity. It's not called unless
|
||||
an ExternEnt handler is also set. There is a default handler installed
|
||||
that pairs with the default ExternEnt handler.
|
||||
|
||||
If you're going to install your own ExternEnt handler, then you should
|
||||
set (or unset) this handler too.
|
||||
|
||||
## Entity (Expat, Name, Val, Sysid, Pubid, Ndata, IsParam)
|
||||
|
||||
This is called when an entity is declared. For internal entities, the Val
|
||||
parameter will contain the value and the remaining three parameters will be
|
||||
undefined. For external entities, the Val parameter will be undefined, the
|
||||
Sysid parameter will have the system id, the Pubid parameter will have the
|
||||
public id if it was provided (it will be undefined otherwise), the Ndata
|
||||
parameter will contain the notation for unparsed entities. If this is a
|
||||
parameter entity declaration, then the IsParam parameter is true.
|
||||
|
||||
Note that this handler and the Unparsed handler above overlap. If both are
|
||||
set, then this handler will not be called for unparsed entities.
|
||||
|
||||
## Element (Expat, Name, Model)
|
||||
|
||||
The element handler is called when an element declaration is found. Name
|
||||
is the element name, and Model is the content model as an XML::Parser::Content
|
||||
object. See ["XML::Parser::ContentModel Methods" in XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat#XML::Parser::ContentModel-Methods)
|
||||
for methods available for this class.
|
||||
|
||||
## Attlist (Expat, Elname, Attname, Type, Default, Fixed)
|
||||
|
||||
This handler is called for each attribute in an ATTLIST declaration.
|
||||
So an ATTLIST declaration that has multiple attributes will generate multiple
|
||||
calls to this handler. The Elname parameter is the name of the element with
|
||||
which the attribute is being associated. The Attname parameter is the name
|
||||
of the attribute. Type is the attribute type, given as a string. Default is
|
||||
the default value, which will either be "#REQUIRED", "#IMPLIED" or a quoted
|
||||
string (i.e. the returned string will begin and end with a quote character).
|
||||
If Fixed is true, then this is a fixed attribute.
|
||||
|
||||
## Doctype (Expat, Name, Sysid, Pubid, Internal)
|
||||
|
||||
This handler is called for DOCTYPE declarations. Name is the document type
|
||||
name. Sysid is the system id of the document type, if it was provided,
|
||||
otherwise it's undefined. Pubid is the public id of the document type,
|
||||
which will be undefined if no public id was given. Internal will be
|
||||
true or false, indicating whether or not the doctype declaration contains
|
||||
an internal subset.
|
||||
|
||||
## \* DoctypeFin (Expat)
|
||||
|
||||
This handler is called after parsing of the DOCTYPE declaration has finished,
|
||||
including any internal or external DTD declarations.
|
||||
|
||||
## XMLDecl (Expat, Version, Encoding, Standalone)
|
||||
|
||||
This handler is called for xml declarations. Version is a string containing
|
||||
the version. Encoding is either undefined or contains an encoding string.
|
||||
Standalone will be either true, false, or undefined if the standalone attribute
|
||||
is yes, no, or not made respectively.
|
||||
|
||||
# STYLES
|
||||
|
||||
## Debug
|
||||
|
||||
This just prints out the document in outline form. Nothing special is
|
||||
returned by parse.
|
||||
|
||||
## Subs
|
||||
|
||||
Each time an element starts, a sub by that name in the package specified
|
||||
by the Pkg option is called with the same parameters that the Start
|
||||
handler gets called with.
|
||||
|
||||
Each time an element ends, a sub with that name appended with an underscore
|
||||
("\_"), is called with the same parameters that the End handler gets called
|
||||
with.
|
||||
|
||||
Nothing special is returned by parse.
|
||||
|
||||
## Tree
|
||||
|
||||
Parse will return a parse tree for the document. Each node in the tree
|
||||
takes the form of a tag, content pair. Text nodes are represented with
|
||||
a pseudo-tag of "0" and the string that is their content. For elements,
|
||||
the content is an array reference. The first item in the array is a
|
||||
(possibly empty) hash reference containing attributes. The remainder of
|
||||
the array is a sequence of tag-content pairs representing the content
|
||||
of the element.
|
||||
|
||||
So for example the result of parsing:
|
||||
|
||||
<foo><head id="a">Hello <em>there</em></head><bar>Howdy<ref/></bar>do</foo>
|
||||
|
||||
would be:
|
||||
|
||||
Tag Content
|
||||
==================================================================
|
||||
[foo, [{}, head, [{id => "a"}, 0, "Hello ", em, [{}, 0, "there"]],
|
||||
bar, [ {}, 0, "Howdy", ref, [{}]],
|
||||
0, "do"
|
||||
]
|
||||
]
|
||||
|
||||
The root document "foo", has 3 children: a "head" element, a "bar"
|
||||
element and the text "do". After the empty attribute hash, these are
|
||||
represented in it's contents by 3 tag-content pairs.
|
||||
|
||||
## Objects
|
||||
|
||||
This is similar to the Tree style, except that a hash object is created for
|
||||
each element. The corresponding object will be in the class whose name
|
||||
is created by appending "::" and the element name to the package set with
|
||||
the Pkg option. Non-markup text will be in the ::Characters class. The
|
||||
contents of the corresponding object will be in an anonymous array that
|
||||
is the value of the Kids property for that object.
|
||||
|
||||
## Stream
|
||||
|
||||
This style also uses the Pkg package. If none of the subs that this
|
||||
style looks for is there, then the effect of parsing with this style is
|
||||
to print a canonical copy of the document without comments or declarations.
|
||||
All the subs receive as their 1st parameter the Expat instance for the
|
||||
document they're parsing.
|
||||
|
||||
It looks for the following routines:
|
||||
|
||||
- StartDocument
|
||||
|
||||
Called at the start of the parse .
|
||||
|
||||
- StartTag
|
||||
|
||||
Called for every start tag with a second parameter of the element type. The $\_
|
||||
variable will contain a copy of the tag and the %\_ variable will contain
|
||||
attribute values supplied for that element.
|
||||
|
||||
- EndTag
|
||||
|
||||
Called for every end tag with a second parameter of the element type. The $\_
|
||||
variable will contain a copy of the end tag.
|
||||
|
||||
- Text
|
||||
|
||||
Called just before start or end tags with accumulated non-markup text in
|
||||
the $\_ variable.
|
||||
|
||||
- PI
|
||||
|
||||
Called for processing instructions. The $\_ variable will contain a copy of
|
||||
the PI and the target and data are sent as 2nd and 3rd parameters
|
||||
respectively.
|
||||
|
||||
- EndDocument
|
||||
|
||||
Called at conclusion of the parse.
|
||||
|
||||
# ENCODINGS
|
||||
|
||||
XML documents may be encoded in character sets other than Unicode as
|
||||
long as they may be mapped into the Unicode character set. Expat has
|
||||
further restrictions on encodings. Read the xmlparse.h header file in
|
||||
the expat distribution to see details on these restrictions.
|
||||
|
||||
Expat has built-in encodings for: `UTF-8`, `ISO-8859-1`, `UTF-16`, and
|
||||
`US-ASCII`. Encodings are set either through the XML declaration
|
||||
encoding attribute or through the ProtocolEncoding option to XML::Parser
|
||||
or XML::Parser::Expat.
|
||||
|
||||
For encodings other than the built-ins, expat calls the function
|
||||
load\_encoding in the Expat package with the encoding name. This function
|
||||
looks for a file in the path list @XML::Parser::Expat::Encoding\_Path, that
|
||||
matches the lower-cased name with a '.enc' extension. The first one it
|
||||
finds, it loads.
|
||||
|
||||
If you wish to build your own encoding maps, check out the XML::Encoding
|
||||
module from CPAN.
|
||||
|
||||
# ERROR HANDLING
|
||||
|
||||
XML::Parser throws an exception (dies) when it encounters a parse error.
|
||||
This includes malformed XML, encoding errors, and other problems detected
|
||||
by the underlying expat library.
|
||||
|
||||
The `parse`, `parsefile`, and `parse_done` methods may all throw
|
||||
exceptions. To handle parse errors gracefully in your application, wrap
|
||||
the parse call in an `eval` block:
|
||||
|
||||
my $parser = XML::Parser->new(Style => 'Tree');
|
||||
|
||||
my $tree = eval { $parser->parsefile('data.xml') };
|
||||
if ($@) {
|
||||
# Handle the parse error
|
||||
warn "Parse failed: $@";
|
||||
}
|
||||
|
||||
The error message (in `$@`) will include the line number, column number,
|
||||
and byte position where the error was detected. For additional context
|
||||
around the error location, set the **ErrorContext** option when constructing
|
||||
the parser:
|
||||
|
||||
my $parser = XML::Parser->new(
|
||||
Style => 'Tree',
|
||||
ErrorContext => 2,
|
||||
);
|
||||
|
||||
This will include 2 lines of context on either side of the error in the
|
||||
error message.
|
||||
|
||||
# SECURITY
|
||||
|
||||
XML::Parser relies on the expat C library for parsing. Modern versions of
|
||||
expat include several security mechanisms that can be tuned through
|
||||
constructor options passed to `new()`. These options are forwarded directly
|
||||
to [XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat) and take effect for every subsequent `parse`,
|
||||
`parsefile`, or `parse_start` call on the parser instance.
|
||||
|
||||
All of these options will `croak` at runtime if the underlying libexpat does
|
||||
not support them.
|
||||
|
||||
## Billion Laughs Attack Protection
|
||||
|
||||
The Billion Laughs attack (also known as an XML bomb) uses deeply nested
|
||||
entity definitions to cause exponential expansion, consuming memory and CPU.
|
||||
Expat >= 2.4.0 (built with `XML_DTD` or `XML_GE`) includes built-in
|
||||
protection controlled by two parameters:
|
||||
|
||||
- **BillionLaughsAttackProtectionMaximumAmplification**
|
||||
|
||||
The maximum ratio between the size of the expanded output and the size of
|
||||
the input. For example, a value of `100.0` means the parser will abort if
|
||||
entity expansion would produce output more than 100 times the size of the
|
||||
input.
|
||||
|
||||
- **BillionLaughsAttackProtectionActivationThreshold**
|
||||
|
||||
The number of bytes of expanded output before the amplification limit takes
|
||||
effect. This prevents false positives on small documents that happen to
|
||||
have a high amplification ratio.
|
||||
|
||||
## Allocation Tracker
|
||||
|
||||
Expat >= 2.7.2 (built with `XML_DTD` or `XML_GE`) adds a second layer
|
||||
of amplification tracking through the allocation tracker, which measures
|
||||
memory allocation rather than output size:
|
||||
|
||||
- **AllocTrackerMaximumAmplification**
|
||||
|
||||
The maximum ratio of allocated memory to input size.
|
||||
|
||||
- **AllocTrackerActivationThreshold**
|
||||
|
||||
The number of bytes of allocation before the limit takes effect.
|
||||
|
||||
## Reparse Deferral
|
||||
|
||||
Expat >= 2.6.0 includes reparse deferral, which prevents attacks that
|
||||
exploit token boundaries. Rather than reparsing incomplete tokens
|
||||
immediately, the parser defers until more input arrives.
|
||||
|
||||
- **ReparseDeferralEnabled**
|
||||
|
||||
A boolean. Set to a true value to enable reparse deferral, or `0` to
|
||||
disable it.
|
||||
|
||||
For full details on each option, see ["new" in XML::Parser::Expat](https://metacpan.org/pod/XML%3A%3AParser%3A%3AExpat#new).
|
||||
|
||||
# Example: tighten Billion Laughs limits
|
||||
my $parser = XML::Parser->new(
|
||||
Style => 'Tree',
|
||||
BillionLaughsAttackProtectionMaximumAmplification => 50,
|
||||
BillionLaughsAttackProtectionActivationThreshold => 1024,
|
||||
);
|
||||
|
||||
# LICENSE
|
||||
|
||||
This library is free software; you can redistribute it and/or modify it
|
||||
under the same terms as Perl itself.
|
||||
|
||||
See [https://dev.perl.org/licenses/](https://dev.perl.org/licenses/) for more information.
|
||||
|
||||
# AUTHORS
|
||||
|
||||
Larry Wall <`larry@wall.org`> wrote version 1.0.
|
||||
|
||||
Clark Cooper <`coopercc@netheaven.com`> picked up support, changed the API
|
||||
for this version (2.x), provided documentation,
|
||||
and added some standard package features.
|
||||
|
||||
Matt Sergeant <`matt@sergeant.org`> was maintaining XML::Parser from 2003 to 2007.
|
||||
|
||||
Alexandr Ciornii <`alexchorny@gmail.com`> was maintaining XML::Parser from 2007 to 2013.
|
||||
|
||||
Todd Rinaldo <`toddr@cpan.org`> has been maintaining XML::Parser since 2013.
|
||||
|
||||
The project started making use of Claude Code <`https://claude.ai/code`> in January 2026.
|
||||
Loading…
Add table
Add a link
Reference in a new issue