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