class HexaPDF::Font::Encoding::DifferenceEncoding

See: PDF2.0 s9.6.5.1
The difference encoding uses a base encoding that can be overlayed with additional mappings.

def code(name)

the name, or from the base encoding.
Returns the code for the given glyph name, either from this object, if a code references 
def code(name)
  code_to_name.key(name) || base_encoding.code(name)
end

def initialize(base_encoding)

Initializes the Differences object with the given base encoding object. 
def initialize(base_encoding)
  super()
  @base_encoding = base_encoding
end

def name(code)

from the base encoding.
Returns the name for the given code, either from this object, if it contains the code, or 
def name(code)
  code_to_name[code] || base_encoding.name(code)
end