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 125

def decode(string)
    input = (string.include?(EOD) ? string[0..string.index(EOD) - 1] : string).delete(" \f\t\r\n\0")

    i = 0
    result = "".b
    while i < input.size do

        outblock = ""

        if input[i] == "z"
            inblock = 0
            codelen = 1
        else
            inblock = 0
            codelen = 5

            if input.length - i < 5
                raise InvalidASCII85StringError.new("Invalid length", input_data: string, decoded_data: result) if input.length - i == 1

                addend = 5 - (input.length - i)
                input << "u" * addend
            else
                addend = 0
            end

            # Checking if this string is in base85
            5.times do |j|
                if input[i+j].ord > "u".ord or input[i+j].ord < "!".ord
                    raise InvalidASCII85StringError.new(
                            "Invalid character sequence: #{input[i,5].inspect}",
                            input_data: string,
                            decoded_data: result
                    )
                else
                    inblock += (input[i+j].ord - "!".ord) * 85 ** (4 - j)
                end
            end

            raise InvalidASCII85StringError.new(
                    "Invalid value (#{inblock}) for block #{input[i,5].inspect}",
                    input_data: string,
                    decoded_data: result
            ) if inblock >= 2**32
        end

        4.times do |p|
            c = inblock / 256 ** (3 - p)
            outblock << c.chr

            inblock -= c * 256 ** (3 - p)
        end

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

        result << outblock

        i = 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 80

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

    while i < input.size do

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

        inblock = (input[i].ord * 256**3 +
                   input[i+1].ord * 256**2 +
                   input[i+2].ord * 256 +
                   input[i+3].ord)
        outblock = ""

        5.times do |p|
            c = inblock / 85 ** (4 - p)
            outblock << ("!".ord + c).chr

            inblock -= c * 85 ** (4 - p)
        end

        outblock = "z" if outblock == "!!!!!" and addend == 0

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

        code << outblock

        i = i + 4
    end

    code
end