Rough implementation of Base64 done to understand it a bit better

gistfile1.rb

# This doesnt handle padding or non ascii, but its a rough implementation based on the wikipedia description

module RobBase64
  def self.encodebyte(byte)
    case byte
    when 0..25 then (byte+65).chr
    when 26..51 then (byte-26+97).chr
    when 52..61 then (byte-4).chr
    when 62 then "+"
    when 63 then "/"
    else puts "Not found #{byte}"
    end
    
  end

  def self.decodebyte(byte)
    case byte
    when "A".."Z" then byte.ord-65
    when "a".."z" then byte.ord-71
    when "0".."9" then byte.ord+4
    when "+" then 62 
    when "/" then 63
    end
  end

  def self.bits(str)
    str.bytes.map { |c|
      ("%08d" % c.to_s(2)).split('')
    }.flatten
  end

  def self.encode(str)
    puts "Encoding #{str}" 
    self.bits(str).each_slice(6).map { |i|
      self.encodebyte(i.join('').to_i(2))
    }.join('')
  end

  def self.decode(str)
    puts "Decoding #{str}"
    str.each_char.map {|i|
      "%06d" % self.decodebyte(i).to_s(2)
    }.join('').split('').each_slice(8).map{ |i|
      i.join('').to_i(2).chr
    }.join('')
  end

end


encoded = RobBase64.encode("How now brown cow.")
decoded = RobBase64.decode(encoded)

puts encoded
puts decoded