A no-allocation naive lempel-ziv-welch codec^H^H^H^H^H entropy coder.

FAQ:

Q: Why should I use your program when there are others out there that have
   better compression performance, are faster, are more portable, or even just
   easier to understand?
A: Ouch. :(

How to use:

Define two functions with prototype

   // These functions are used to do the action I/O.
   int emit_code(void *p, unsigned code);
   int emit_char(void *p, unsigned char ch);


Then to encode:

    extern int emit_code(void *p, unsigned code);
    extern void *emit_char_data;
    unsigned char ch;
    struct lzw_state enc;
    lzw_state_init(&enc);
    while(get_input_char(&ch))
        // emit_code_data is passed as the arg 'p' to emit_code
        if(lzw_encode(&enc, emit_code, emit_code_data, ch))
            handle_error();
    lzw_encode_finish(&enc, emit_code, emit_code_data);

Or to decode:

    extern int emit_char(void *p, unsigned char ch);
    extern void *emit_char_data;
    unsigned int code;
    struct lzw_state dec;
    lzw_state_init(&dec);
    while(get_input_code(&code))
        // emit_char_data is passed as the arg 'p' to emit_char
        if(lzw_decode(&dec, emit_char, emit_char_data, code))
				handle_error();

Other tips & tricks:

When building, there are two macros that can be overridden to control behavior:

1. You can override the DICTSIZE macro to be any value strictly larger than
   255. This affects the maximum sizeo of the string dictionary, which may have
   an effect on the level of compression possible.

2. You can override the SYMCOUNT macro to more closely correspond with the
   number of symbols in the alphabet you are compressing. This may help make
   some space in the dictionary for small values of DICTSIZE, or may simply
   be more reflective of the alphabet you are compressing.

Don't be afraid to peek inside the lzw_state struct, as the next_code field
may be useful to pass to your I/O system to help determine the number of bits
to use when emitting or reading the symbol codes.

If the dictionary grows past DICTSIZE, it is reset by being truncated to
SYMCOUNT.