PSP::HTML::TokeParser - Alternative PSP::HTML::Parser interface

 require PSP::HTML::TokeParser;
 $p = PSP::HTML::TokeParser->new("index.html") || die "Can't open: $!";
 while (my $token = $p->get_token) {
     #...
 }

The PSP::HTML::TokeParser is an alternative interface to the PSP::HTML::Parser class. It basically turns the PSP::HTML::Parser inside out. You associate a file (or any IO::Handle object or string) with the parser at construction time and then repeatedly call CW$parser->get_token to obtain the tags and text found in the parsed document.

Calling the methods defined by the PSP::HTML::Parser base class will be confusing, so don't do that. Use the following methods instead: The object constructor argument is either a file name, a file handle object, or the complete document to be parsed. If the argument is a plain scalar, then it is taken as the name of a file to be opened and parsed. If the file can't be opened for reading, then the constructor will return an undefined value and $! will tell you why it failed. If the argument is a reference to a plain scalar, then this scalar is taken to be the literal document to parse. The value of this scalar should not be changed before all tokens have been extracted. Otherwise the argument is taken to be some object that the CWPSP::HTML::TokeParser can read() from when it needs more data. Typically it will be a filehandle of some kind. The stream will be read() until EOF, but not closed.

$p->get_token

This method will return the next token found in the HTML document, or CWundef at the end of the document. The token is returned as an array reference. The first element of the array will be a (mostly) single character string denoting the type of this token: S for start tag, E for end tag, T for text, C for comment, D for declaration, and PI for process instructions. The rest of the array is the same as the arguments passed to the corresponding PSP::HTML::Parser v2 compatible callbacks (see PSP::HTML::Parser). In summary, returned tokens look like this:

  ["S",  $tag, $attr, $attrseq, $text]
  ["E",  $tag, $text]
  ["T",  $text, $is_data]
  ["C",  $text]
  ["D",  $text]
  ["PI", $token0, $text]

where CW$attr is a hash reference, CW$attrseq is an array reference and the rest is plain scalars.

$p->unget_token($token,...)

If you find out you have read too many tokens you can push them back, so that they are returned the next time CW$p->get_token is called.

$p->get_tag( [$tag, ...] )

This method returns the next start or end tag (skipping any other tokens), or CWundef if there are no more tags in the document. If one or more arguments are given, then we skip tokens until one of the specified tag types is found. For example:

   $p->get_tag("font", "/font");

will find the next start or end tag for a font-element. The tag information is returned as an array reference in the same form as for CW$p->get_token above, but the type code (first element) is missing. A start tag will be returned like this:

  [$tag, $attr, $attrseq, $text]

The tagname of end tags are prefixed with /, i.e. end tag is returned like this:

  ["/$tag", $text]

$p->get_text( [$endtag] )

This method returns all text found at the current position. It will return a zero length string if the next token is not text. The optional CW$endtag argument specifies that any text occurring before the given tag is to be returned. Any entities will be converted to their corresponding character. The CW$p->{textify} attribute is a hash that defines how certain tags can be treated as text. If the name of a start tag matches a key in this hash then this tag is converted to text. The hash value is used to specify which tag attribute to obtain the text from. If this tag attribute is missing, then the upper case name of the tag enclosed in brackets is returned, e.g. [IMG]. The hash value can also be a subroutine reference. In this case the routine is called with the start tag token content as its argument and the return value is treated as the text. The default CW$p->{textify} value is:

  {img => "alt", applet => "alt"}

This means that <IMG> and <APPLET> tags are treated as text, and that the text to substitute can be found in the ALT attribute.

$p->get_trimmed_text( [$endtag] )

Same as CW$p->get_text above, but will collapse any sequences of white space to a single space character. Leading and trailing white space is removed.

This example extracts all links from a document. It will print one line for each link, containing the URL and the textual description between the <A>...</A> tags:

  use PSP::HTML::TokeParser;
  $p = PSP::HTML::TokeParser->new(shift||"index.html");

  while (my $token = $p->get_tag("a")) {
      my $url = $token->[1]{href} || "-";
      my $text = $p->get_trimmed_text("/a");
      print "$url\t$text\n";
  }

This example extract the <TITLE> from the document:

  use PSP::HTML::TokeParser;
  $p = PSP::HTML::TokeParser->new(shift||"index.html");
  if ($p->get_tag("title")) {
      my $title = $p->get_trimmed_text;
      print "Title: $title\n";
  }

PSP::HTML::Parser

Copyright 1998-2000 Gisle Aas.

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