projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 3013fe88 NW |
1 | /* lzw.h -- define the lzw functions. |
| 2 | * Copyright (C) 1992-1993 Jean-loup Gailly. | |
| 3 | * This is free software; you can redistribute it and/or modify it under the | |
| 4 | * terms of the GNU General Public License, see the file COPYING. | |
| 5 | */ | |
| 6 | ||
| 7 | #if !defined(OF) && defined(lint) | |
| 8 | # include "gzip.h" | |
| 9 | #endif | |
| 10 | ||
| 11 | #ifndef BITS | |
| 12 | # define BITS 16 | |
| 13 | #endif | |
| 14 | #define INIT_BITS 9 /* Initial number of bits per code */ | |
| 15 | ||
| 16 | #define LZW_MAGIC "\037\235" /* Magic header for lzw files, 1F 9D */ | |
| 17 | ||
| 18 | #define BIT_MASK 0x1f /* Mask for 'number of compression bits' */ | |
| 19 | /* Mask 0x20 is reserved to mean a fourth header byte, and 0x40 is free. | |
| 20 | * It's a pity that old uncompress does not check bit 0x20. That makes | |
| 21 | * extension of the format actually undesirable because old compress | |
| 22 | * would just crash on the new format instead of giving a meaningful | |
| 23 | * error message. It does check the number of bits, but it's more | |
| 24 | * helpful to say "unsupported format, get a new version" than | |
| 25 | * "can only handle 16 bits". | |
| 26 | */ | |
| 27 | ||
| 28 | #define BLOCK_MODE 0x80 | |
| 29 | /* Block compression: if table is full and compression rate is dropping, | |
| 30 | * clear the dictionary. | |
| 31 | */ | |
| 32 | ||
| 33 | #define LZW_RESERVED 0x60 /* reserved bits */ | |
| 34 | ||
| 35 | #define CLEAR 256 /* flush the dictionary */ | |
| 36 | #define FIRST (CLEAR+1) /* first free entry */ | |
| 37 | ||
| 38 | extern int maxbits; /* max bits per code for LZW */ | |
| 39 | extern int block_mode; /* block compress mode -C compatible with 2.0 */ | |
| 40 | ||
| 41 | extern int lzw OF((int in, int out)); | |
| 42 | extern int unlzw OF((int in, int out)); |