class Base32::Chunk

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 = Base32.table.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 {|i| Base32.table[(c >> i * 5) & 0x1f].chr},
   ("=" * (8-n))]
end

def initialize(bytes)
  @bytes = bytes
end