Data::Stag::BaseGenerator(3p)

NAME
  Data::Stag::BaseGenerator     - base class for parsers and other event generators

SYNOPSIS
  # writing the parser
  package MyParser;
  use base qw(Data::Stag::BaseGenerator);

  sub parse_fh {
    my ($self, $fh) = shift;

    my $lnum = 0;
    $self->start_event('data');
    while (<$fh>) {
      ++$lnum;
      $self->line_no($lnum);
      # do stuff
      $self->start_event('foo');

      # ...
      $self->event(blah=>5);

      #
      if (/incorrect_line/) {
         $self->parse_err('line not in correct format');
      }

      # ...
      $self->end_event('foo');
    }
    $self->pop_stack_to_depth(0);
  }
  1;

  # using the parser
  my $p = MyParser->new;
  my $h = MyHandler->new; # see Data::Stag::BaseHandler
  my $eh = Data::Stag->makehandler;
  $p->handler($h);
  $p->errhandler($eh);
  $p->parse($file);

  # result tree
  print $h->stag->xml;

  # write parse errs on standard err
  printf \*STDERR $p->errhandler->stag->xml;

  # using the parser from the command line
  unix> stag-parse.pl -p MyParser -w xml -e err.xml > out.xml

  # using the parser from the command line via intermediate handler
  unix> stag-handle.pl -p MyParser -m MyHandler -w xml -e err.xml > out.xml

DESCRIPTION
This is the base class for all parsers and event generators

parsers/generators take some input (usually a filehandle, but a generator could be a socket listener, for example) and fire stag events

stag events are

start_event NODENAME
evbody DATA
end_event NODENAME {optional}
event NODENAME DATA

These events can be nested/hierarchical

If uncaught, these events are stacked into a stag tree, which can be written as xml or one of the other stag formats

specialised handlers can be written to catch the events your parser throws

For example, you may wish to write a pod parser that generates nested events like this:

  <pod>
   <section>
     <type>head1</type>
     <name>NAME</name>
     <text>Data::Stag - Structured Tags datastructures</text>
   </section>
   ...
  </pod>

(see the source for Data::Stag::PodParser for details)

You can write handlers that take the pod-xml and generate something - for example HTML

parsers may encounter unexpected things along the way - they may throw an exception, and fall over - or they may choose to fire an error event. by default, error event streams are diverted to STDERR. You can create your own error handlers

PUBLIC METHODS
new

       Title: new

        Args:
      Return: L<Data::Stag::BaseGenerator>
     Example:

CONSTRUCTOR

handler

       Title: handler
    Function: GET/SET ACCESSOR METHOD
        Args: handler L<Data::Stag::BaseHandler> optional
      Return: L<Data::Stag::BaseHandler>
     Example: $p->handler(MyHandler->new);

each parser has a handler - all events generated are passed onto the handler; the default handler simply sits there collecting events

errhandler

       Title: errhandler
    Function: GET/SET ACCESSOR METHOD
        Args: handler L<Data::Stag::BaseHandler> optional
      Return: L<Data::Stag::BaseHandler>
     Example: $p->errhandler(Data::Stag->makehandler);

each parser has an error handler - if the parser encounters things it does not expect, it can pass errors to the errorhandler

if no errorhandler is set, an XML event handler that writes to STDERR is used

cache_errors

       Title: cache_errors
        Args:
      Return:
     Example: $p->cache_errors

If this is called, all errors will be cached rather than written to STDERR

The error list can be accessed like this

  $p->parse($fn);
  @errs = $p->errhandler->stag->get_error;

  parse
  Example - $parser->parse($file1, $file2);
  Returns -
  Args    - filenames str-LIST

parses a file

  parse
  Example - $parser->parse_fh($fh)
  Returns -
  Args    - fh FILEHANDLE

parses an open filehandle

PROTECTED METHODS
These methods are only of interest if you are making your own parser/generator class

start_event NODENAME
evbody DATA
end_event NODENAME {optional}
event NODENAME DATA

SEE ALSO
Data::Stag Data::Stag::BaseHandler