84 lines
2.8 KiB
C
84 lines
2.8 KiB
C
#ifndef _ZFTAPE_COMPRESS_H
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#define _ZFTAPE_COMPRESS_H
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/*
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* Copyright (c) 1994-1997 Claus-Justus Heine
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2, or (at
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your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
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USA.
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*
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* $Source: /homes/cvs/ftape-stacked/ftape/compressor/zftape-compress.h,v $
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* $Revision: 1.1 $
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* $Date: 1997/10/05 19:12:32 $
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*
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* This file contains macros and definitions for zftape's
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* builtin compression code.
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*
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*/
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#include "../zftape/zftape-buffers.h"
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#include "../zftape/zftape-vtbl.h"
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#include "../compressor/lzrw3.h"
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/* CMPR_WRK_MEM_SIZE gives the size of the compression wrk_mem */
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/* I got these out of lzrw3.c */
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#define U(X) ((__u32) X)
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#define SIZE_P_BYTE (U(sizeof(__u8 *)))
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#define ALIGNMENT_FUDGE (U(16))
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#define CMPR_WRK_MEM_SIZE (U(4096)*(SIZE_P_BYTE) + ALIGNMENT_FUDGE)
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/* the maximum number of bytes the size of the "compressed" data can
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* exceed the uncompressed data. As it is quite useless to compress
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* data twice it is sometimes the case that it is more efficient to
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* copy a block of data but to feed it to the "compression"
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* algorithm. In this case there are some flag bytes or the like
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* proceding the "compressed" data. THAT MUST NOT BE THE CASE for the
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* algorithm we use for this driver. Instead, the high bit 15 of
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* compressed_size:
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*
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* compressed_size = ftape_compress()
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*
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* must be set in such a case.
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*
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* Nevertheless, it might also be as for lzrw3 that there is an
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* "intermediate" overrun that exceeds the amount of the compressed
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* data that is actually produced. During the algorithm we need in the
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* worst case MAX_CMP_GROUP bytes more than the input-size.
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*/
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#define MAX_CMP_GROUP (2+16*2) /* from lzrw3.c */
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#define CMPR_OVERRUN MAX_CMP_GROUP /* during compression */
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/****************************************************/
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#define CMPR_BUFFER_SIZE (MAX_BLOCK_SIZE + CMPR_OVERRUN)
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/* the compression map stores the byte offset compressed blocks within
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* the current volume for catridges with format code 2,3 and 5
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* (and old versions of zftape) and the offset measured in kilobytes for
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* format code 4 and 6. This gives us a possible max. size of a
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* compressed volume of 1024*4GIG which should be enough.
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*/
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typedef __u32 CmprMap;
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/* globals
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*/
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/* exported functions
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*/
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#endif /* _ZFTAPE_COMPRESS_H */
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