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/drivers/char/ftape/compressor/zftape-compress.h

https://bitbucket.org/evzijst/gittest
C Header | 83 lines | 14 code | 11 blank | 58 comment | 0 complexity | 2a1f69a318d025a65870fcc39d13641f MD5 | raw file
 1#ifndef _ZFTAPE_COMPRESS_H
 2#define _ZFTAPE_COMPRESS_H
 3/*
 4 *      Copyright (c) 1994-1997 Claus-Justus Heine
 5
 6 This program is free software; you can redistribute it and/or
 7 modify it under the terms of the GNU General Public License as
 8 published by the Free Software Foundation; either version 2, or (at
 9 your option) any later version.
10 
11 This program is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 General Public License for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with this program; see the file COPYING.  If not, write to
18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
19 USA.
20
21 *
22 * $Source: /homes/cvs/ftape-stacked/ftape/compressor/zftape-compress.h,v $
23 * $Revision: 1.1 $
24 * $Date: 1997/10/05 19:12:32 $
25 *
26 * This file contains macros and definitions for zftape's
27 * builtin compression code.
28 *
29 */
30
31#include "../zftape/zftape-buffers.h"
32#include "../zftape/zftape-vtbl.h"
33#include "../compressor/lzrw3.h"
34
35/* CMPR_WRK_MEM_SIZE gives the size of the compression wrk_mem */
36/* I got these out of lzrw3.c */
37#define U(X)            ((__u32) X)
38#define SIZE_P_BYTE     (U(sizeof(__u8 *)))
39#define ALIGNMENT_FUDGE (U(16))
40
41#define CMPR_WRK_MEM_SIZE (U(4096)*(SIZE_P_BYTE) + ALIGNMENT_FUDGE)
42
43/* the maximum number of bytes the size of the "compressed" data can
44 * exceed the uncompressed data. As it is quite useless to compress
45 * data twice it is sometimes the case that it is more efficient to
46 * copy a block of data but to feed it to the "compression"
47 * algorithm. In this case there are some flag bytes or the like
48 * proceding the "compressed" data.  THAT MUST NOT BE THE CASE for the
49 * algorithm we use for this driver. Instead, the high bit 15 of
50 * compressed_size:
51 *
52 * compressed_size = ftape_compress()
53 *
54 * must be set in such a case.
55 *
56 * Nevertheless, it might also be as for lzrw3 that there is an
57 * "intermediate" overrun that exceeds the amount of the compressed
58 * data that is actually produced. During the algorithm we need in the
59 * worst case MAX_CMP_GROUP bytes more than the input-size.
60 */
61#define MAX_CMP_GROUP (2+16*2) /* from lzrw3.c */
62
63#define CMPR_OVERRUN      MAX_CMP_GROUP /* during compression */
64
65/****************************************************/
66
67#define     CMPR_BUFFER_SIZE (MAX_BLOCK_SIZE + CMPR_OVERRUN)
68
69/* the compression map stores the byte offset compressed blocks within
70 * the current volume for catridges with format code 2,3 and 5
71 * (and old versions of zftape) and the offset measured in kilobytes for
72 * format code 4 and 6. This gives us a possible max. size of a 
73 * compressed volume of 1024*4GIG which should be enough.
74 */
75typedef __u32 CmprMap;
76
77/* globals 
78 */
79
80/* exported functions
81 */
82
83#endif /* _ZFTAPE_COMPRESS_H */