Copyright 2007 TeX Users Group.
You may freely use, modify and/or distribute this file.

Basic LZW encoding algorithm

Clear Table
Set Length <= 9
Clear Code
Clear String (string buffer)
Clear Test (test string buffer)
Clear Byte (byte buffer)
Write Clear 
For each byte in input stream {
	read value into Byte
	concatenate String + Byte => Test
	If content of Test in table {
		append Byte to String
		set Code to value for that String
	}
	else {
		write Code for String (*)
		add new table entry for Test (**)
		make String be single character Byte
	}
}
write Code for String
write EOI code

(*) Whenever the LZW code value would exceed the current code length, 
    the code length is increased by one. 

(**) When table becomes full (> 4095):
	write Code for String
	Clear Table
	Set Length <= 9
	Clear Code
	Clear String (string buffer)
	Clear Test (test string buffer)
	Clear Byte (byte buffer)
	Write Clear 

Initial table: 
	0 - 255 are single bytes of corresponding value
	256	Clear
	257	EOI
	
First available Code is 258.

Maximum Code value is 4095.

Codes are never shorter than 9 bits or longer than 12.