class Opal::SourceMap::File

def absolute_mappings

each segment is made up of 1,4 or 5 variable length fields.
each segment is separated by a “,”
each group representing a line in the generated file is separated by a ”;”

The “mappings” data is broken down as follows: 
def absolute_mappings
  @absolute_mappings ||= begin
    mappings = []
    fragments_by_line.each do |raw_segments|
      generated_column = 0
      segments = []
      raw_segments.each do |(generated_code, fragment)|
        unless fragment.is_a?(Opal::Fragment) && fragment.skip_source_map?
          segments << segment_from_fragment(fragment, generated_column)
        end
        generated_column += generated_code.size
      end
      mappings << segments
    end
    mappings
  end
end