| 1 | /* lzw.h -- define the lzw functions.
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| 2 |
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| 3 | Copyright (C) 1992-1993 Jean-loup Gailly.
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| 4 |
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| 5 | This program is free software; you can redistribute it and/or modify
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| 6 | it under the terms of the GNU General Public License as published by
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| 7 | the Free Software Foundation; either version 2, or (at your option)
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| 8 | any later version.
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| 9 |
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| 10 | This program is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU General Public License
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| 16 | along with this program; if not, write to the Free Software Foundation,
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| 17 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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| 18 |
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| 19 | #if !defined(OF) && defined(lint)
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| 20 | # include "gzip.h"
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| 21 | #endif
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| 22 |
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| 23 | #ifndef BITS
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| 24 | # define BITS 16
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| 25 | #endif
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| 26 | #define INIT_BITS 9 /* Initial number of bits per code */
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| 27 |
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| 28 | #define LZW_MAGIC "\037\235" /* Magic header for lzw files, 1F 9D */
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| 29 |
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| 30 | #define BIT_MASK 0x1f /* Mask for 'number of compression bits' */
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| 31 | /* Mask 0x20 is reserved to mean a fourth header byte, and 0x40 is free.
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| 32 | * It's a pity that old uncompress does not check bit 0x20. That makes
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| 33 | * extension of the format actually undesirable because old compress
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| 34 | * would just crash on the new format instead of giving a meaningful
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| 35 | * error message. It does check the number of bits, but it's more
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| 36 | * helpful to say "unsupported format, get a new version" than
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| 37 | * "can only handle 16 bits".
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| 38 | */
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| 39 |
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| 40 | #define BLOCK_MODE 0x80
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| 41 | /* Block compression: if table is full and compression rate is dropping,
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| 42 | * clear the dictionary.
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| 43 | */
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| 44 |
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| 45 | #define LZW_RESERVED 0x60 /* reserved bits */
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| 46 |
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| 47 | #define CLEAR 256 /* flush the dictionary */
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| 48 | #define FIRST (CLEAR+1) /* first free entry */
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| 49 |
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| 50 | extern int maxbits; /* max bits per code for LZW */
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| 51 | extern int block_mode; /* block compress mode -C compatible with 2.0 */
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| 52 |
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| 53 | extern int lzw OF((int in, int out));
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| 54 | extern int unlzw OF((int in, int out));
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