gistfile1.rb

class Base64
	
	##
	def self.convert_to_char(n)
		if (0..25).cover?(n)
			return (65 + n).chr
		elsif (26..51).cover?(n)
			return (97 + n - 26).chr
		elsif (52..61).cover?(n)
			return (n - 52).to_s
		elsif n==62
			return '+'
		elsif n==63
			return '-'
		else
			raise 'Unknown index'
		end
	end

	##
	def self.convert_24_bits(s)
		first = (s[0].ord & 252) >> 2
		second = ((s[0].ord & 3) << 4) | (s[1].ord >> 4)
		third = ((s[1].ord & 15) << 2) | (s[2].ord >> 6)
		fourth = s[2].ord & 63
		[first, second, third, fourth].collect {|x| self.convert_to_char(x)}.join('')
	end

	##
	def self.encode(s)
		padding = 0

		
		if (s.length % 3 == 1)
			s += 0.chr + 0.chr
			padding = 2
		elsif (s.length % 3 == 2)
			s += 0.chr
			padding = 1
		end	

		output = ''
		(0..s.length-1).step(3) do |i|
			slice = s[i..(i+2)]
			output += self.convert_24_bits(slice)
		end	
		
		if padding == 1
			output[-1] = "="
		elsif padding == 2
			output[-1] = "="
			output[-2] = "="
		end
	
		return output
	end
end


test_string = "12345678"
encoded = Base64.encode(test_string)
decoded = Base64.decode(encoded)

if decoded == test_string
	puts "Pass"
else
	puts "Fail"
end