class Kramdown::Parser::Base

Base class for parsers

This class serves as base class for parsers. It provides common methods that can/should be used by all parsers, especially by those using StringScanner(Kramdown) for parsing.

A parser object is used as a throw-away object, i.e. it is only used for storing the needed state information during parsing. Therefore one can't instantiate a parser object directly but only use the Base::parse method.

Implementing a parser

Implementing a new parser is rather easy: just derive a new class from this class and put it in the Kramdown::Parser module – the latter is needed so that the auto-detection of the new parser works correctly. Then you need to implement the #parse method which has to contain the parsing code.

Have a look at the Base::parse, Base::new and Base#parse methods for additional information!



The hash with the parsing options.


The root element of element tree that is created from the source string.


The original source string.


The array with the parser warnings.

Public Class Methods

parse(source, options = {}) click to toggle source

Parse the source string into an element tree, possibly using the parsing options, and return the root element of the element tree and an array with warning messages.

Initializes a new instance of the calling class and then calls the #parse method that must be implemented by each subclass.

# File lib/kramdown/parser/base.rb, line 66
def self.parse(source, options = {})
  parser = new(source, options)
  [parser.root, parser.warnings]

Public Instance Methods

adapt_source(source) click to toggle source

Modify the string source to be usable by the parser (unifies line ending characters to \n and makes sure source ends with a new line character).

# File lib/kramdown/parser/base.rb, line 90
def adapt_source(source)
  unless source.valid_encoding?
    raise "The source text contains invalid characters for the used encoding #{source.encoding}"
  source = source.encode('UTF-8')
  source.gsub!(/\r\n?/, "\n")
  source << "\n"
add_text(text, tree = @tree, type = @text_type) click to toggle source

This helper method adds the given text either to the last element in the tree if it is a type element or creates a new text element with the given type.

# File lib/kramdown/parser/base.rb, line 102
def add_text(text, tree = @tree, type = @text_type)
  last = tree.children.last
  if last && last.type == type
    last.value << text
  elsif !text.empty?
    location = (last && last.options[:location] || tree.options[:location])
    tree.children <<, text, nil, location: location)
extract_string(range, strscan) click to toggle source

Extract the part of the StringScanner strscan backed string specified by the range. This method works correctly under Ruby 1.8 and Ruby 1.9.

# File lib/kramdown/parser/base.rb, line 114
def extract_string(range, strscan)
  result = nil
    enc = strscan.string.encoding
    result = strscan.string[range].force_encoding(enc)
parse() click to toggle source

Parse the source string into an element tree.

The parsing code should parse the source provided in @source and build an element tree the root of which should be @root.

This is the only method that has to be implemented by sub-classes!

# File lib/kramdown/parser/base.rb, line 78
def parse
  raise NotImplementedError
warning(text) click to toggle source

Add the given warning text to the warning array.

# File lib/kramdown/parser/base.rb, line 83
def warning(text)
  @warnings << text
  # TODO: add position information