class Huffman

def self.encode(str)
	bitstring = str.each_byte.map {|chr| ENCODE_TABLE[chr]}.join
	bitstring << "1" * ((8 - bitstring.size) % 8)
	[bitstring].pack("B*")
end

def self.decode(buffer)
	emit = String.new.b
	state = 0 # start state

	mask = (1 << BITS_AT_ONCE) - 1
	buffer.each_byte do |c|
		shift = BITS_AT_ONCE
		while shift >= 0
			branch = (c >> shift) & mask
			
			# MACHINE[state] = [final, [transitions]]
			#  [final] unfinished bits so far are prefix of the EOS code.
			# Each transition is [emit, next]
			#  [emit] character to be emitted on this transition, empty string, or EOS.
			#  [next] next state number.
			value, state = MACHINE[state][branch]
			
			raise CompressionError, "Huffman decode error (EOS found)" if value == EOS
			
			emit << value.chr if value
			shift -= BITS_AT_ONCE
		end
	end
	# Check whether partial input is correctly filled
	unless state <= MAX_FINAL_STATE
		raise CompressionError, "Huffman decode error (EOS invalid)"
	end
	emit.force_encoding(Encoding::BINARY)
end

CODES = [
	[0x1ff8, 13],
	[0x7fffd8, 23],
	[0xfffffe2, 28],
	[0xfffffe3, 28],
	[0xfffffe4, 28],
	[0xfffffe5, 28],
	[0xfffffe6, 28],
	[0xfffffe7, 28],
	[0xfffffe8, 28],
	[0xffffea, 24],
	[0x3ffffffc, 30],
	[0xfffffe9, 28],
	[0xfffffea, 28],
	[0x3ffffffd, 30],
	[0xfffffeb, 28],
	[0xfffffec, 28],
	[0xfffffed, 28],
	[0xfffffee, 28],
	[0xfffffef, 28],
	[0xffffff0, 28],
	[0xffffff1, 28],
	[0xffffff2, 28],
	[0x3ffffffe, 30],
	[0xffffff3, 28],
	[0xffffff4, 28],
	[0xffffff5, 28],
	[0xffffff6, 28],
	[0xffffff7, 28],
	[0xffffff8, 28],
	[0xffffff9, 28],
	[0xffffffa, 28],
	[0xffffffb, 28],
	[0x14, 6],
	[0x3f8, 10],
	[0x3f9, 10],
	[0xffa, 12],
	[0x1ff9, 13],
	[0x15, 6],
	[0xf8, 8],
	[0x7fa, 11],
	[0x3fa, 10],
	[0x3fb, 10],
	[0xf9, 8],
	[0x7fb, 11],
	[0xfa, 8],
	[0x16, 6],
	[0x17, 6],
	[0x18, 6],
	[0x0, 5],
	[0x1, 5],
	[0x2, 5],
	[0x19, 6],
	[0x1a, 6],
	[0x1b, 6],
	[0x1c, 6],
	[0x1d, 6],
	[0x1e, 6],
	[0x1f, 6],
	[0x5c, 7],
	[0xfb, 8],
	[0x7ffc, 15],
	[0x20, 6],
	[0xffb, 12],
	[0x3fc, 10],
	[0x1ffa, 13],
	[0x21, 6],
	[0x5d, 7],
	[0x5e, 7],
	[0x5f, 7],
	[0x60, 7],
	[0x61, 7],
	[0x62, 7],
	[0x63, 7],
	[0x64, 7],
	[0x65, 7],
	[0x66, 7],
	[0x67, 7],
	[0x68, 7],
	[0x69, 7],
	[0x6a, 7],
	[0x6b, 7],
	[0x6c, 7],
	[0x6d, 7],
	[0x6e, 7],
	[0x6f, 7],
	[0x70, 7],
	[0x71, 7],
	[0x72, 7],
	[0xfc, 8],
	[0x73, 7],
	[0xfd, 8],
	[0x1ffb, 13],
	[0x7fff0, 19],
	[0x1ffc, 13],
	[0x3ffc, 14],
	[0x22, 6],
	[0x7ffd, 15],
	[0x3, 5],
	[0x23, 6],
	[0x4, 5],
	[0x24, 6],
	[0x5, 5],
	[0x25, 6],
	[0x26, 6],
	[0x27, 6],
	[0x6, 5],
	[0x74, 7],
	[0x75, 7],
	[0x28, 6],
	[0x29, 6],
	[0x2a, 6],
	[0x7, 5],
	[0x2b, 6],
	[0x76, 7],
	[0x2c, 6],
	[0x8, 5],
	[0x9, 5],
	[0x2d, 6],
	[0x77, 7],
	[0x78, 7],
	[0x79, 7],
	[0x7a, 7],
	[0x7b, 7],
	[0x7ffe, 15],
	[0x7fc, 11],
	[0x3ffd, 14],
	[0x1ffd, 13],
	[0xffffffc, 28],
	[0xfffe6, 20],
	[0x3fffd2, 22],
	[0xfffe7, 20],
	[0xfffe8, 20],
	[0x3fffd3, 22],
	[0x3fffd4, 22],
	[0x3fffd5, 22],
	[0x7fffd9, 23],
	[0x3fffd6, 22],
	[0x7fffda, 23],
	[0x7fffdb, 23],
	[0x7fffdc, 23],
	[0x7fffdd, 23],
	[0x7fffde, 23],
	[0xffffeb, 24],
	[0x7fffdf, 23],
	[0xffffec, 24],
	[0xffffed, 24],
	[0x3fffd7, 22],
	[0x7fffe0, 23],
	[0xffffee, 24],
	[0x7fffe1, 23],
	[0x7fffe2, 23],
	[0x7fffe3, 23],
	[0x7fffe4, 23],
	[0x1fffdc, 21],
	[0x3fffd8, 22],
	[0x7fffe5, 23],
	[0x3fffd9, 22],
	[0x7fffe6, 23],
	[0x7fffe7, 23],
	[0xffffef, 24],
	[0x3fffda, 22],
	[0x1fffdd, 21],
	[0xfffe9, 20],
	[0x3fffdb, 22],
	[0x3fffdc, 22],
	[0x7fffe8, 23],
	[0x7fffe9, 23],
	[0x1fffde, 21],
	[0x7fffea, 23],
	[0x3fffdd, 22],
	[0x3fffde, 22],
	[0xfffff0, 24],
	[0x1fffdf, 21],
	[0x3fffdf, 22],
	[0x7fffeb, 23],
	[0x7fffec, 23],
	[0x1fffe0, 21],
	[0x1fffe1, 21],
	[0x3fffe0, 22],
	[0x1fffe2, 21],
	[0x7fffed, 23],
	[0x3fffe1, 22],
	[0x7fffee, 23],
	[0x7fffef, 23],
	[0xfffea, 20],
	[0x3fffe2, 22],
	[0x3fffe3, 22],
	[0x3fffe4, 22],
	[0x7ffff0, 23],
	[0x3fffe5, 22],
	[0x3fffe6, 22],
	[0x7ffff1, 23],
	[0x3ffffe0, 26],
	[0x3ffffe1, 26],
	[0xfffeb, 20],
	[0x7fff1, 19],
	[0x3fffe7, 22],
	[0x7ffff2, 23],
	[0x3fffe8, 22],
	[0x1ffffec, 25],
	[0x3ffffe2, 26],
	[0x3ffffe3, 26],
	[0x3ffffe4, 26],
	[0x7ffffde, 27],
	[0x7ffffdf, 27],
	[0x3ffffe5, 26],
	[0xfffff1, 24],
	[0x1ffffed, 25],
	[0x7fff2, 19],
	[0x1fffe3, 21],
	[0x3ffffe6, 26],
	[0x7ffffe0, 27],
	[0x7ffffe1, 27],
	[0x3ffffe7, 26],
	[0x7ffffe2, 27],
	[0xfffff2, 24],
	[0x1fffe4, 21],
	[0x1fffe5, 21],
	[0x3ffffe8, 26],
	[0x3ffffe9, 26],
	[0xffffffd, 28],
	[0x7ffffe3, 27],
	[0x7ffffe4, 27],
	[0x7ffffe5, 27],
	[0xfffec, 20],
	[0xfffff3, 24],
	[0xfffed, 20],
	[0x1fffe6, 21],
	[0x3fffe9, 22],
	[0x1fffe7, 21],
	[0x1fffe8, 21],
	[0x7ffff3, 23],
	[0x3fffea, 22],
	[0x3fffeb, 22],
	[0x1ffffee, 25],
	[0x1ffffef, 25],
	[0xfffff4, 24],
	[0xfffff5, 24],
	[0x3ffffea, 26],
	[0x7ffff4, 23],
	[0x3ffffeb, 26],
	[0x7ffffe6, 27],
	[0x3ffffec, 26],
	[0x3ffffed, 26],
	[0x7ffffe7, 27],
	[0x7ffffe8, 27],
	[0x7ffffe9, 27],
	[0x7ffffea, 27],
	[0x7ffffeb, 27],
	[0xffffffe, 28],
	[0x7ffffec, 27],
	[0x7ffffed, 27],
	[0x7ffffee, 27],
	[0x7ffffef, 27],
	[0x7fffff0, 27],
	[0x3ffffee, 26],
	[0x3fffffff, 30],
].each(&:freeze).freeze