Provided by: libhtml-parser-perl_3.71-1build1_amd64 
NAME
HTML::Parser - HTML parser class
SYNOPSIS
use HTML::Parser ();
# Create parser object
$p = HTML::Parser->new( api_version => 3,
start_h => [\&start, "tagname, attr"],
end_h => [\&end, "tagname"],
marked_sections => 1,
);
# Parse document text chunk by chunk
$p->parse($chunk1);
$p->parse($chunk2);
#...
$p->eof; # signal end of document
# Parse directly from file
$p->parse_file("foo.html");
# or
open(my $fh, "<:utf8", "foo.html") || die;
$p->parse_file($fh);
DESCRIPTION
Objects of the "HTML::Parser" class will recognize markup and separate it from plain text (alias data
content) in HTML documents. As different kinds of markup and text are recognized, the corresponding
event handlers are invoked.
"HTML::Parser" is not a generic SGML parser. We have tried to make it able to deal with the HTML that is
actually "out there", and it normally parses as closely as possible to the way the popular web browsers
do it instead of strictly following one of the many HTML specifications from W3C. Where there is
disagreement, there is often an option that you can enable to get the official behaviour.
The document to be parsed may be supplied in arbitrary chunks. This makes on-the-fly parsing as
documents are received from the network possible.
If event driven parsing does not feel right for your application, you might want to use
"HTML::PullParser". This is an "HTML::Parser" subclass that allows a more conventional program
structure.
METHODS
The following method is used to construct a new "HTML::Parser" object:
$p = HTML::Parser->new( %options_and_handlers )
This class method creates a new "HTML::Parser" object and returns it. Key/value argument pairs may
be provided to assign event handlers or initialize parser options. The handlers and parser options
can also be set or modified later by the method calls described below.
If a top level key is in the form "<event>_h" (e.g., "text_h") then it assigns a handler to that
event, otherwise it initializes a parser option. The event handler specification value must be an
array reference. Multiple handlers may also be assigned with the 'handlers => [%handlers]' option.
See examples below.
If new() is called without any arguments, it will create a parser that uses callback methods
compatible with version 2 of "HTML::Parser". See the section on "version 2 compatibility" below for
details.
The special constructor option 'api_version => 2' can be used to initialize version 2 callbacks while
still setting other options and handlers. The 'api_version => 3' option can be used if you don't
want to set any options and don't want to fall back to v2 compatible mode.
Examples:
$p = HTML::Parser->new(api_version => 3,
text_h => [ sub {...}, "dtext" ]);
This creates a new parser object with a text event handler subroutine that receives the original text
with general entities decoded.
$p = HTML::Parser->new(api_version => 3,
start_h => [ 'my_start', "self,tokens" ]);
This creates a new parser object with a start event handler method that receives the $p and the
tokens array.
$p = HTML::Parser->new(api_version => 3,
handlers => { text => [\@array, "event,text"],
comment => [\@array, "event,text"],
});
This creates a new parser object that stores the event type and the original text in @array for text
and comment events.
The following methods feed the HTML document to the "HTML::Parser" object:
$p->parse( $string )
Parse $string as the next chunk of the HTML document. Handlers invoked should not attempt to modify
the $string in-place until $p->parse returns.
If an invoked event handler aborts parsing by calling $p->eof, then $p->parse() will return a FALSE
value. Otherwise the return value is a reference to the parser object ($p).
$p->parse( $code_ref )
If a code reference is passed as the argument to be parsed, then the chunks to be parsed are obtained
by invoking this function repeatedly. Parsing continues until the function returns an empty (or
undefined) result. When this happens $p->eof is automatically signaled.
Parsing will also abort if one of the event handlers calls $p->eof.
The effect of this is the same as:
while (1) {
my $chunk = &$code_ref();
if (!defined($chunk) || !length($chunk)) {
$p->eof;
return $p;
}
$p->parse($chunk) || return undef;
}
But it is more efficient as this loop runs internally in XS code.
$p->parse_file( $file )
Parse text directly from a file. The $file argument can be a filename, an open file handle, or a
reference to an open file handle.
If $file contains a filename and the file can't be opened, then the method returns an undefined value
and $! tells why it failed. Otherwise the return value is a reference to the parser object.
If a file handle is passed as the $file argument, then the file will normally be read until EOF, but
not closed.
If an invoked event handler aborts parsing by calling $p->eof, then $p->parse_file() may not have
read the entire file.
On systems with multi-byte line terminators, the values passed for the offset and length argspecs may
be too low if parse_file() is called on a file handle that is not in binary mode.
If a filename is passed in, then parse_file() will open the file in binary mode.
$p->eof
Signals the end of the HTML document. Calling the $p->eof method outside a handler callback will
flush any remaining buffered text (which triggers the "text" event if there is any remaining text).
Calling $p->eof inside a handler will terminate parsing at that point and cause $p->parse to return a
FALSE value. This also terminates parsing by $p->parse_file().
After $p->eof has been called, the parse() and parse_file() methods can be invoked to feed new
documents with the parser object.
The return value from eof() is a reference to the parser object.
Most parser options are controlled by boolean attributes. Each boolean attribute is enabled by calling
the corresponding method with a TRUE argument and disabled with a FALSE argument. The attribute value is
left unchanged if no argument is given. The return value from each method is the old attribute value.
Methods that can be used to get and/or set parser options are:
$p->attr_encoded
$p->attr_encoded( $bool )
By default, the "attr" and @attr argspecs will have general entities for attribute values decoded.
Enabling this attribute leaves entities alone.
$p->backquote
$p->backquote( $bool )
By default, only ' and " are recognized as quote characters around attribute values. MSIE also
recognizes backquotes for some reason. Enabling this attribute provides compatibility with this
behaviour.
$p->boolean_attribute_value( $val )
This method sets the value reported for boolean attributes inside HTML start tags. By default, the
name of the attribute is also used as its value. This affects the values reported for "tokens" and
"attr" argspecs.
$p->case_sensitive
$p->case_sensitive( $bool )
By default, tagnames and attribute names are down-cased. Enabling this attribute leaves them as
found in the HTML source document.
$p->closing_plaintext
$p->closing_plaintext( $bool )
By default, "plaintext" element can never be closed. Everything up to the end of the document is
parsed in CDATA mode. This historical behaviour is what at least MSIE does. Enabling this attribute
makes closing "</plaintext>" tag effective and the parsing process will resume after seeing this tag.
This emulates early gecko-based browsers.
$p->empty_element_tags
$p->empty_element_tags( $bool )
By default, empty element tags are not recognized as such and the "/" before ">" is just treated like
a normal name character (unless "strict_names" is enabled). Enabling this attribute make
"HTML::Parser" recognize these tags.
Empty element tags look like start tags, but end with the character sequence "/>" instead of ">".
When recognized by "HTML::Parser" they cause an artificial end event in addition to the start event.
The "text" for the artificial end event will be empty and the "tokenpos" array will be undefined even
though the the token array will have one element containing the tag name.
$p->marked_sections
$p->marked_sections( $bool )
By default, section markings like <![CDATA[...]]> are treated like ordinary text. When this
attribute is enabled section markings are honoured.
There are currently no events associated with the marked section markup, but the text can be returned
as "skipped_text".
$p->strict_comment
$p->strict_comment( $bool )
By default, comments are terminated by the first occurrence of "-->". This is the behaviour of most
popular browsers (like Mozilla, Opera and MSIE), but it is not correct according to the official HTML
standard. Officially, you need an even number of "--" tokens before the closing ">" is recognized
and there may not be anything but whitespace between an even and an odd "--".
The official behaviour is enabled by enabling this attribute.
Enabling of 'strict_comment' also disables recognizing these forms as comments:
</ comment>
<! comment>
$p->strict_end
$p->strict_end( $bool )
By default, attributes and other junk are allowed to be present on end tags in a manner that emulates
MSIE's behaviour.
The official behaviour is enabled with this attribute. If enabled, only whitespace is allowed
between the tagname and the final ">".
$p->strict_names
$p->strict_names( $bool )
By default, almost anything is allowed in tag and attribute names. This is the behaviour of most
popular browsers and allows us to parse some broken tags with invalid attribute values like:
<IMG SRC=newprevlstGr.gif ALT=[PREV LIST] BORDER=0>
By default, "LIST]" is parsed as a boolean attribute, not as part of the ALT value as was clearly
intended. This is also what Mozilla sees.
The official behaviour is enabled by enabling this attribute. If enabled, it will cause the tag
above to be reported as text since "LIST]" is not a legal attribute name.
$p->unbroken_text
$p->unbroken_text( $bool )
By default, blocks of text are given to the text handler as soon as possible (but the parser takes
care always to break text at a boundary between whitespace and non-whitespace so single words and
entities can always be decoded safely). This might create breaks that make it hard to do
transformations on the text. When this attribute is enabled, blocks of text are always reported in
one piece. This will delay the text event until the following (non-text) event has been recognized
by the parser.
Note that the "offset" argspec will give you the offset of the first segment of text and "length" is
the combined length of the segments. Since there might be ignored tags in between, these numbers
can't be used to directly index in the original document file.
$p->utf8_mode
$p->utf8_mode( $bool )
Enable this option when parsing raw undecoded UTF-8. This tells the parser that the entities
expanded for strings reported by "attr", @attr and "dtext" should be expanded as decoded UTF-8 so
they end up compatible with the surrounding text.
If "utf8_mode" is enabled then it is an error to pass strings containing characters with code above
255 to the parse() method, and the parse() method will croak if you try.
Example: The Unicode character "\x{2665}" is "\xE2\x99\xA5" when UTF-8 encoded. The character can
also be represented by the entity "♥" or "♥". If we feed the parser:
$p->parse("\xE2\x99\xA5♥");
then "dtext" will be reported as "\xE2\x99\xA5\x{2665}" without "utf8_mode" enabled, but as
"\xE2\x99\xA5\xE2\x99\xA5" when enabled. The later string is what you want.
This option is only available with perl-5.8 or better.
$p->xml_mode
$p->xml_mode( $bool )
Enabling this attribute changes the parser to allow some XML constructs. This enables the behaviour
controlled by individually by the "case_sensitive", "empty_element_tags", "strict_names" and
"xml_pic" attributes and also suppresses special treatment of elements that are parsed as CDATA for
HTML.
$p->xml_pic
$p->xml_pic( $bool )
By default, processing instructions are terminated by ">". When this attribute is enabled, processing
instructions are terminated by "?>" instead.
As markup and text is recognized, handlers are invoked. The following method is used to set up handlers
for different events:
$p->handler( event => \&subroutine, $argspec )
$p->handler( event => $method_name, $argspec )
$p->handler( event => \@accum, $argspec )
$p->handler( event => "" );
$p->handler( event => undef );
$p->handler( event );
This method assigns a subroutine, method, or array to handle an event.
Event is one of "text", "start", "end", "declaration", "comment", "process", "start_document",
"end_document" or "default".
The "\&subroutine" is a reference to a subroutine which is called to handle the event.
The $method_name is the name of a method of $p which is called to handle the event.
The @accum is an array that will hold the event information as sub-arrays.
If the second argument is "", the event is ignored. If it is undef, the default handler is invoked
for the event.
The $argspec is a string that describes the information to be reported for the event. Any requested
information that does not apply to a specific event is passed as "undef". If argspec is omitted,
then it is left unchanged.
The return value from $p->handler is the old callback routine or a reference to the accumulator
array.
Any return values from handler callback routines/methods are always ignored. A handler callback can
request parsing to be aborted by invoking the $p->eof method. A handler callback is not allowed to
invoke the $p->parse() or $p->parse_file() method. An exception will be raised if it tries.
Examples:
$p->handler(start => "start", 'self, attr, attrseq, text' );
This causes the "start" method of object $p to be called for 'start' events. The callback signature
is $p->start(\%attr, \@attr_seq, $text).
$p->handler(start => \&start, 'attr, attrseq, text' );
This causes subroutine start() to be called for 'start' events. The callback signature is
start(\%attr, \@attr_seq, $text).
$p->handler(start => \@accum, '"S", attr, attrseq, text' );
This causes 'start' event information to be saved in @accum. The array elements will be ['S',
\%attr, \@attr_seq, $text].
$p->handler(start => "");
This causes 'start' events to be ignored. It also suppresses invocations of any default handler for
start events. It is in most cases equivalent to $p->handler(start => sub {}), but is more efficient.
It is different from the empty-sub-handler in that "skipped_text" is not reset by it.
$p->handler(start => undef);
This causes no handler to be associated with start events. If there is a default handler it will be
invoked.
Filters based on tags can be set up to limit the number of events reported. The main bottleneck during
parsing is often the huge number of callbacks made from the parser. Applying filters can improve
performance significantly.
The following methods control filters:
$p->ignore_elements( @tags )
Both the "start" event and the "end" event as well as any events that would be reported in between
are suppressed. The ignored elements can contain nested occurrences of itself. Example:
$p->ignore_elements(qw(script style));
The "script" and "style" tags will always nest properly since their content is parsed in CDATA mode.
For most other tags "ignore_elements" must be used with caution since HTML is often not well formed.
$p->ignore_tags( @tags )
Any "start" and "end" events involving any of the tags given are suppressed. To reset the filter
(i.e. don't suppress any "start" and "end" events), call "ignore_tags" without an argument.
$p->report_tags( @tags )
Any "start" and "end" events involving any of the tags not given are suppressed. To reset the filter
(i.e. report all "start" and "end" events), call "report_tags" without an argument.
Internally, the system has two filter lists, one for "report_tags" and one for "ignore_tags", and both
filters are applied. This effectively gives "ignore_tags" precedence over "report_tags".
Examples:
$p->ignore_tags(qw(style));
$p->report_tags(qw(script style));
results in only "script" events being reported.
Argspec
Argspec is a string containing a comma-separated list that describes the information reported by the
event. The following argspec identifier names can be used:
"attr"
Attr causes a reference to a hash of attribute name/value pairs to be passed.
Boolean attributes' values are either the value set by $p->boolean_attribute_value, or the attribute
name if no value has been set by $p->boolean_attribute_value.
This passes undef except for "start" events.
Unless "xml_mode" or "case_sensitive" is enabled, the attribute names are forced to lower case.
General entities are decoded in the attribute values and one layer of matching quotes enclosing the
attribute values is removed.
The Unicode character set is assumed for entity decoding.
@attr
Basically the same as "attr", but keys and values are passed as individual arguments and the original
sequence of the attributes is kept. The parameters passed will be the same as the @attr calculated
here:
@attr = map { $_ => $attr->{$_} } @$attrseq;
assuming $attr and $attrseq here are the hash and array passed as the result of "attr" and "attrseq"
argspecs.
This passes no values for events besides "start".
"attrseq"
Attrseq causes a reference to an array of attribute names to be passed. This can be useful if you
want to walk the "attr" hash in the original sequence.
This passes undef except for "start" events.
Unless "xml_mode" or "case_sensitive" is enabled, the attribute names are forced to lower case.
"column"
Column causes the column number of the start of the event to be passed. The first column on a line
is 0.
"dtext"
Dtext causes the decoded text to be passed. General entities are automatically decoded unless the
event was inside a CDATA section or was between literal start and end tags ("script", "style", "xmp",
"iframe", "title", "textarea" and "plaintext").
The Unicode character set is assumed for entity decoding. With Perl version 5.6 or earlier only the
Latin-1 range is supported, and entities for characters outside the range 0..255 are left unchanged.
This passes undef except for "text" events.
"event"
Event causes the event name to be passed.
The event name is one of "text", "start", "end", "declaration", "comment", "process",
"start_document" or "end_document".
"is_cdata"
Is_cdata causes a TRUE value to be passed if the event is inside a CDATA section or between literal
start and end tags ("script", "style", "xmp", "iframe", "title", "textarea" and "plaintext").
if the flag is FALSE for a text event, then you should normally either use "dtext" or decode the
entities yourself before the text is processed further.
"length"
Length causes the number of bytes of the source text of the event to be passed.
"line"
Line causes the line number of the start of the event to be passed. The first line in the document
is 1. Line counting doesn't start until at least one handler requests this value to be reported.
"offset"
Offset causes the byte position in the HTML document of the start of the event to be passed. The
first byte in the document has offset 0.
"offset_end"
Offset_end causes the byte position in the HTML document of the end of the event to be passed. This
is the same as "offset" + "length".
"self"
Self causes the current object to be passed to the handler. If the handler is a method, this must be
the first element in the argspec.
An alternative to passing self as an argspec is to register closures that capture $self by themselves
as handlers. Unfortunately this creates circular references which prevent the HTML::Parser object
from being garbage collected. Using the "self" argspec avoids this problem.
"skipped_text"
Skipped_text returns the concatenated text of all the events that have been skipped since the last
time an event was reported. Events might be skipped because no handler is registered for them or
because some filter applies. Skipped text also includes marked section markup, since there are no
events that can catch it.
If an ""-handler is registered for an event, then the text for this event is not included in
"skipped_text". Skipped text both before and after the ""-event is included in the next reported
"skipped_text".
"tag"
Same as "tagname", but prefixed with "/" if it belongs to an "end" event and "!" for a declaration.
The "tag" does not have any prefix for "start" events, and is in this case identical to "tagname".
"tagname"
This is the element name (or generic identifier in SGML jargon) for start and end tags. Since HTML
is case insensitive, this name is forced to lower case to ease string matching.
Since XML is case sensitive, the tagname case is not changed when "xml_mode" is enabled. The same
happens if the "case_sensitive" attribute is set.
The declaration type of declaration elements is also passed as a tagname, even if that is a bit
strange. In fact, in the current implementation tagname is identical to "token0" except that the
name may be forced to lower case.
"token0"
Token0 causes the original text of the first token string to be passed. This should always be the
same as $tokens->[0].
For "declaration" events, this is the declaration type.
For "start" and "end" events, this is the tag name.
For "process" and non-strict "comment" events, this is everything inside the tag.
This passes undef if there are no tokens in the event.
"tokenpos"
Tokenpos causes a reference to an array of token positions to be passed. For each string that
appears in "tokens", this array contains two numbers. The first number is the offset of the start of
the token in the original "text" and the second number is the length of the token.
Boolean attributes in a "start" event will have (0,0) for the attribute value offset and length.
This passes undef if there are no tokens in the event (e.g., "text") and for artificial "end" events
triggered by empty element tags.
If you are using these offsets and lengths to modify "text", you should either work from right to
left, or be very careful to calculate the changes to the offsets.
"tokens"
Tokens causes a reference to an array of token strings to be passed. The strings are exactly as they
were found in the original text, no decoding or case changes are applied.
For "declaration" events, the array contains each word, comment, and delimited string starting with
the declaration type.
For "comment" events, this contains each sub-comment. If $p->strict_comments is disabled, there will
be only one sub-comment.
For "start" events, this contains the original tag name followed by the attribute name/value pairs.
The values of boolean attributes will be either the value set by $p->boolean_attribute_value, or the
attribute name if no value has been set by $p->boolean_attribute_value.
For "end" events, this contains the original tag name (always one token).
For "process" events, this contains the process instructions (always one token).
This passes "undef" for "text" events.
"text"
Text causes the source text (including markup element delimiters) to be passed.
"undef"
Pass an undefined value. Useful as padding where the same handler routine is registered for multiple
events.
'...'
A literal string of 0 to 255 characters enclosed in single (') or double (") quotes is passed as
entered.
The whole argspec string can be wrapped up in '@{...}' to signal that the resulting event array should be
flattened. This only makes a difference if an array reference is used as the handler target. Consider
this example:
$p->handler(text => [], 'text');
$p->handler(text => [], '@{text}']);
With two text events; "foo", "bar"; then the first example will end up with [["foo"], ["bar"]] and the
second with ["foo", "bar"] in the handler target array.
Events
Handlers for the following events can be registered:
"comment"
This event is triggered when a markup comment is recognized.
Example:
<!-- This is a comment -- -- So is this -->
"declaration"
This event is triggered when a markup declaration is recognized.
For typical HTML documents, the only declaration you are likely to find is <!DOCTYPE ...>.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
DTDs inside <!DOCTYPE ...> will confuse HTML::Parser.
"default"
This event is triggered for events that do not have a specific handler. You can set up a handler for
this event to catch stuff you did not want to catch explicitly.
"end"
This event is triggered when an end tag is recognized.
Example:
</A>
"end_document"
This event is triggered when $p->eof is called and after any remaining text is flushed. There is no
document text associated with this event.
"process"
This event is triggered when a processing instructions markup is recognized.
The format and content of processing instructions are system and application dependent.
Examples:
<? HTML processing instructions >
<? XML processing instructions ?>
"start"
This event is triggered when a start tag is recognized.
Example:
<A HREF="http://www.perl.com/">
"start_document"
This event is triggered before any other events for a new document. A handler for it can be used to
initialize stuff. There is no document text associated with this event.
"text"
This event is triggered when plain text (characters) is recognized. The text may contain multiple
lines. A sequence of text may be broken between several text events unless $p->unbroken_text is
enabled.
The parser will make sure that it does not break a word or a sequence of whitespace between two text
events.
Unicode
"HTML::Parser" can parse Unicode strings when running under perl-5.8 or better. If Unicode is passed to
$p->parse() then chunks of Unicode will be reported to the handlers. The offset and length argspecs will
also report their position in terms of characters.
It is safe to parse raw undecoded UTF-8 if you either avoid decoding entities and make sure to not use
argspecs that do, or enable the "utf8_mode" for the parser. Parsing of undecoded UTF-8 might be useful
when parsing from a file where you need the reported offsets and lengths to match the byte offsets in the
file.
If a filename is passed to $p->parse_file() then the file will be read in binary mode. This will be fine
if the file contains only ASCII or Latin-1 characters. If the file contains UTF-8 encoded text then care
must be taken when decoding entities as described in the previous paragraph, but better is to open the
file with the UTF-8 layer so that it is decoded properly:
open(my $fh, "<:utf8", "index.html") || die "...: $!";
$p->parse_file($fh);
If the file contains text encoded in a charset besides ASCII, Latin-1 or UTF-8 then decoding will always
be needed.
VERSION 2 COMPATIBILITY
When an "HTML::Parser" object is constructed with no arguments, a set of handlers is automatically
provided that is compatible with the old HTML::Parser version 2 callback methods.
This is equivalent to the following method calls:
$p->handler(start => "start", "self, tagname, attr, attrseq, text");
$p->handler(end => "end", "self, tagname, text");
$p->handler(text => "text", "self, text, is_cdata");
$p->handler(process => "process", "self, token0, text");
$p->handler(comment =>
sub {
my($self, $tokens) = @_;
for (@$tokens) {$self->comment($_);}},
"self, tokens");
$p->handler(declaration =>
sub {
my $self = shift;
$self->declaration(substr($_[0], 2, -1));},
"self, text");
Setting up these handlers can also be requested with the "api_version => 2" constructor option.
SUBCLASSING
The "HTML::Parser" class is subclassable. Parser objects are plain hashes and "HTML::Parser" reserves
only hash keys that start with "_hparser". The parser state can be set up by invoking the init() method,
which takes the same arguments as new().
EXAMPLES
The first simple example shows how you might strip out comments from an HTML document. We achieve this
by setting up a comment handler that does nothing and a default handler that will print out anything
else:
use HTML::Parser;
HTML::Parser->new(default_h => [sub { print shift }, 'text'],
comment_h => [""],
)->parse_file(shift || die) || die $!;
An alternative implementation is:
use HTML::Parser;
HTML::Parser->new(end_document_h => [sub { print shift },
'skipped_text'],
comment_h => [""],
)->parse_file(shift || die) || die $!;
This will in most cases be much more efficient since only a single callback will be made.
The next example prints out the text that is inside the <title> element of an HTML document. Here we
start by setting up a start handler. When it sees the title start tag it enables a text handler that
prints any text found and an end handler that will terminate parsing as soon as the title end tag is
seen:
use HTML::Parser ();
sub start_handler
{
return if shift ne "title";
my $self = shift;
$self->handler(text => sub { print shift }, "dtext");
$self->handler(end => sub { shift->eof if shift eq "title"; },
"tagname,self");
}
my $p = HTML::Parser->new(api_version => 3);
$p->handler( start => \&start_handler, "tagname,self");
$p->parse_file(shift || die) || die $!;
print "\n";
On a Debian box, more examples can be found in the /usr/share/doc/libhtml-parser-perl/examples directory.
The program "hrefsub" shows how you can edit all links found in a document and "htextsub" how to edit the
text only; the program "hstrip" shows how you can strip out certain tags/elements and/or attributes; and
the program "htext" show how to obtain the plain text, but not any script/style content.
You can browse the eg/ directory online from the [Browse] link on the
http://search.cpan.org/~gaas/HTML-Parser/ page.
BUGS
The <style> and <script> sections do not end with the first "</", but need the complete corresponding end
tag. The standard behaviour is not really practical.
When the strict_comment option is enabled, we still recognize comments where there is something other
than whitespace between even and odd "--" markers.
Once $p->boolean_attribute_value has been set, there is no way to restore the default behaviour.
There is currently no way to get both quote characters into the same literal argspec.
Empty tags, e.g. "<>" and "</>", are not recognized. SGML allows them to repeat the previous start tag
or close the previous start tag respectively.
NET tags, e.g. "code/.../" are not recognized. This is SGML shorthand for "<code>...</code>".
Unclosed start or end tags, e.g. "<tt<b>...</b</tt>" are not recognized.
DIAGNOSTICS
The following messages may be produced by HTML::Parser. The notation in this listing is the same as used
in perldiag:
Not a reference to a hash
(F) The object blessed into or subclassed from HTML::Parser is not a hash as required by the
HTML::Parser methods.
Bad signature in parser state object at %p
(F) The _hparser_xs_state element does not refer to a valid state structure. Something must have
changed the internal value stored in this hash element, or the memory has been overwritten.
_hparser_xs_state element is not a reference
(F) The _hparser_xs_state element has been destroyed.
Can't find '_hparser_xs_state' element in HTML::Parser hash
(F) The _hparser_xs_state element is missing from the parser hash. It was either deleted, or not
created when the object was created.
API version %s not supported by HTML::Parser %s
(F) The constructor option 'api_version' with an argument greater than or equal to 4 is reserved for
future extensions.
Bad constructor option '%s'
(F) An unknown constructor option key was passed to the new() or init() methods.
Parse loop not allowed
(F) A handler invoked the parse() or parse_file() method. This is not permitted.
marked sections not supported
(F) The $p->marked_sections() method was invoked in a HTML::Parser module that was compiled without
support for marked sections.
Unknown boolean attribute (%d)
(F) Something is wrong with the internal logic that set up aliases for boolean attributes.
Only code or array references allowed as handler
(F) The second argument for $p->handler must be either a subroutine reference, then name of a
subroutine or method, or a reference to an array.
No handler for %s events
(F) The first argument to $p->handler must be a valid event name; i.e. one of "start", "end", "text",
"process", "declaration" or "comment".
Unrecognized identifier %s in argspec
(F) The identifier is not a known argspec name. Use one of the names mentioned in the argspec
section above.
Literal string is longer than 255 chars in argspec
(F) The current implementation limits the length of literals in an argspec to 255 characters. Make
the literal shorter.
Backslash reserved for literal string in argspec
(F) The backslash character "\" is not allowed in argspec literals. It is reserved to permit quoting
inside a literal in a later version.
Unterminated literal string in argspec
(F) The terminating quote character for a literal was not found.
Bad argspec (%s)
(F) Only identifier names, literals, spaces and commas are allowed in argspecs.
Missing comma separator in argspec
(F) Identifiers in an argspec must be separated with ",".
Parsing of undecoded UTF-8 will give garbage when decoding entities
(W) The first chunk parsed appears to contain undecoded UTF-8 and one or more argspecs that decode
entities are used for the callback handlers.
The result of decoding will be a mix of encoded and decoded characters for any entities that expand
to characters with code above 127. This is not a good thing.
The recommened solution is to apply Encode::decode_utf8() on the data before feeding it to the
$p->parse(). For $p->parse_file() pass a file that has been opened in ":utf8" mode.
The alternative solution is to enable the "utf8_mode" and not decode before passing strings to
$p->parse(). The parser can process raw undecoded UTF-8 sanely if the "utf8_mode" is enabled, or if
the "attr", "@attr" or "dtext" argspecs are avoided.
Parsing string decoded with wrong endianness
(W) The first character in the document is U+FFFE. This is not a legal Unicode character but a byte
swapped BOM. The result of parsing will likely be garbage.
Parsing of undecoded UTF-32
(W) The parser found the Unicode UTF-32 BOM signature at the start of the document. The result of
parsing will likely be garbage.
Parsing of undecoded UTF-16
(W) The parser found the Unicode UTF-16 BOM signature at the start of the document. The result of
parsing will likely be garbage.
SEE ALSO
HTML::Entities, HTML::PullParser, HTML::TokeParser, HTML::HeadParser, HTML::LinkExtor, HTML::Form
HTML::TreeBuilder (part of the HTML-Tree distribution)
<http://www.w3.org/TR/html4/>
More information about marked sections and processing instructions may be found at
<http://www.is-thought.co.uk/book/sgml-8.htm>.
COPYRIGHT
Copyright 1996-2008 Gisle Aas. All rights reserved.
Copyright 1999-2000 Michael A. Chase. All rights reserved.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
perl v5.18.1 2013-10-18 Parser(3pm)