lz4 format

sequence = token(1) + literalslen(i) + literals(token >> 4 + i) + [match copy: offset(2) + length(token >> 4 << 4)]

match copy:
	position = current postition - offset (0 is invalid)
	length = 4 + length

last 5 bytes = literals
last match starts 12 bytes before end of stream
last sequence is incomplete and stops after the literals