Contents

# frozen_string_literal: true

module Base32
  class Chunk
    attr_reader :alphabet

    def initialize(bytes, alphabet = Base32::Alphabet::CHARS)
      @bytes    = bytes
      @alphabet = Base32::Alphabet.new alphabet
    end

    def self.call(str, size, alphabet)
      result = []
      bytes = str.bytes
      while bytes.any?
        result << Chunk.new(bytes.take(size), alphabet)
        bytes = bytes.drop(size)
      end
      result
    end

    def decode
      bytes = @bytes.take_while { |c| c != 61 } # strip padding
      n = (bytes.length * 5.0 / 8.0).floor
      p = bytes.length < 8 ? 5 - (n * 8) % 5 : 0

      c = bytes.inject(0) do |m, o|
        i = alphabet.to_s.index(o.chr)
        raise ArgumentError, "invalid character '#{o.chr}'" if i.nil?

        (m << 5) + i
      end >> p

      (0..n - 1).to_a.reverse.collect { |i| ((c >> i * 8) & 0xff).chr }
    end

    def encode
      n = (@bytes.length * 8.0 / 5.0).ceil
      p = n < 8 ? 5 - (@bytes.length * 8) % 5 : 0
      c = @bytes.inject(0) { |m, o| (m << 8) + o } << p

      [
        (0..n - 1).to_a.reverse.collect do |i|
          alphabet.to_s[(c >> i * 5) & 0x1f].chr
        end,
        ('=' * (8 - n)),
      ]
    end
  end
end

Version data entries

2 entries across 2 versions & 1 rubygems

Version	Path
base32.rb-0.4.2	lib/base32/chunk.rb
base32.rb-0.4.1	lib/base32/chunk.rb