/* lzw.h -- define the lzw functions. * Copyright (C) 1992-1993 Jean-loup Gailly. * This is free software; you can redistribute it and/or modify it under the * terms of the GNU General Public License, see the file COPYING. */ #if !defined(OF) && defined(lint) # include "gzip.h" #endif #ifndef BITS # define BITS 16 #endif #define INIT_BITS 9 /* Initial number of bits per code */ #define LZW_MAGIC "\037\235" /* Magic header for lzw files, 1F 9D */ #define BIT_MASK 0x1f /* Mask for 'number of compression bits' */ /* Mask 0x20 is reserved to mean a fourth header byte, and 0x40 is free. * It's a pity that old uncompress does not check bit 0x20. That makes * extension of the format actually undesirable because old compress * would just crash on the new format instead of giving a meaningful * error message. It does check the number of bits, but it's more * helpful to say "unsupported format, get a new version" than * "can only handle 16 bits". */ #define BLOCK_MODE 0x80 /* Block compression: if table is full and compression rate is dropping, * clear the dictionary. */ #define LZW_RESERVED 0x60 /* reserved bits */ #define CLEAR 256 /* flush the dictionary */ #define FIRST (CLEAR+1) /* first free entry */ extern int maxbits; /* max bits per code for LZW */ extern int block_mode; /* block compress mode -C compatible with 2.0 */ extern int lzw OF((int in, int out)); extern int unlzw OF((int in, int out));