Class: Origami::Filter::ASCII85

Inherits:
Object
  • Object
show all
Includes:
Origami::Filter
Defined in:
lib/origami/filters/ascii.rb

Overview

Class representing a filter used to encode and decode data written in base85 encoding.

Constant Summary collapse

EOD =

:nodoc:

"~>"

Constants included from Origami::Filter

A85, AHx, CCF, Fl, RL

Instance Method Summary collapse

Methods included from Origami::Filter

included, #initialize

Instance Method Details

#decode(string) ⇒ Object

Decodes the given data encoded in base85.

string

The data to decode.



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# File 'lib/origami/filters/ascii.rb', line 113

def decode(string)
  input = filter_input(string)

  i = 0
  result = ''.b

  while i < input.size

    outblock = ""
    value = 0
    addend = 0

    if input[i] == "z"
      codelen = 1
    else
      codelen = 5

      if input.length - i < codelen
        raise InvalidASCII85StringError.new("Invalid length", input_data: string, decoded_data: result) if input.length - i == 1

        addend = codelen - (input.length - i)
        input << "u" * addend
      end

      # Decode the 5 characters input block into a 32 bit integer.
      begin
        value = decode_block input[i, codelen]
      rescue InvalidASCII85StringError => error
        error.input_data = string
        error.decoded_data = result
        raise(error)
      end
    end

    outblock = [value].pack "L>"
    outblock = outblock[0, 4 - addend]

    result << outblock

    i += codelen
  end

  result
end

#encode(stream) ⇒ Object

Encodes given data into base85.

stream

The data to encode.



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# File 'lib/origami/filters/ascii.rb', line 77

def encode(stream)
  i = 0
  code = "".b
  input = stream.dup

  while i < input.size

    if input.length - i < 4
      addend = 4 - (input.length - i)
      input << "\0" * addend
    else
      addend = 0
    end

    # Encode the 4 bytes input value into a 5 character string.
    value = input[i, 4].unpack1("L>")
    outblock = encode_block(value)

    outblock = "z" if (outblock == "!!!!!") && (addend == 0)

    if addend != 0
      outblock = outblock[0, 4 - addend + 1]
    end

    code << outblock

    i += 4
  end

  code
end