gzip: add tests for today's bug fix
[gzip.git] / lzw.h
blob69c479c49423f39737639499a1caea0f319407e5
1 /* lzw.h -- define the lzw functions.
3 Copyright (C) 1992-1993 Jean-loup Gailly.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
8 any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19 #if !defined(OF) && defined(lint)
20 # include "gzip.h"
21 #endif
23 #ifndef BITS
24 # define BITS 16
25 #endif
26 #define INIT_BITS 9 /* Initial number of bits per code */
28 #define LZW_MAGIC "\037\235" /* Magic header for lzw files, 1F 9D */
30 #define BIT_MASK 0x1f /* Mask for 'number of compression bits' */
31 /* Mask 0x20 is reserved to mean a fourth header byte, and 0x40 is free.
32 * It's a pity that old uncompress does not check bit 0x20. That makes
33 * extension of the format actually undesirable because old compress
34 * would just crash on the new format instead of giving a meaningful
35 * error message. It does check the number of bits, but it's more
36 * helpful to say "unsupported format, get a new version" than
37 * "can only handle 16 bits".
40 #define BLOCK_MODE 0x80
41 /* Block compression: if table is full and compression rate is dropping,
42 * clear the dictionary.
45 #define LZW_RESERVED 0x60 /* reserved bits */
47 #define CLEAR 256 /* flush the dictionary */
48 #define FIRST (CLEAR+1) /* first free entry */
50 extern int maxbits; /* max bits per code for LZW */
51 extern int block_mode; /* block compress mode -C compatible with 2.0 */
53 extern int lzw OF((int in, int out));
54 extern int unlzw OF((int in, int out));