| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | */ |
| 75 | typedef __u32 CmprMap; |
| 76 | |
| 77 | /* globals |
| 78 | */ |
| 79 | |
| 80 | /* exported functions |
| 81 | */ |
| 82 | |
| 83 | #endif /* _ZFTAPE_COMPRESS_H */ |