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/* Copyright (c) 1996-2004, Adaptec Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - Neither the name of the Adaptec Corporation nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This is the LZSS module, which implements an LZ77 style compression
* algorithm. As iplemented here it uses a 12 bit index into the sliding
* window, and a 4 bit length, which is adjusted to reflect phrase lengths
* of between 2 and 17 bytes.
*/
#include "osd_util.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#if defined(_DPT_MSDOS) && !defined (NO_EXPAND_FILE)
#include "diskio.h"
#endif
#include "bufio.h"
#ifndef INDEX_BIT_COUNT
#define INDEX_BIT_COUNT 12 /* bits to use for indeces into text window */
#endif
#ifndef LENGTH_BIT_COUNT
#define LENGTH_BIT_COUNT 4 /* bits to use for length of an encoded phrase */
#endif
#define WINDOW_SIZE ( 1 << INDEX_BIT_COUNT )
#define BREAK_EVEN ( ( 1 + INDEX_BIT_COUNT + LENGTH_BIT_COUNT ) / 9 )
#define END_OF_STREAM 0 /* index used to flag end of encoded file */
#define MOD_WINDOW( a ) ( ( a ) & ( WINDOW_SIZE - 1 ) )
/*
* This is the expansion routine for the LZSS algorithm. All it has
* to do is read in flag bits, decide whether to read in a character or
* an index/length pair, and take the appropriate action.
*/
#if defined(_DPT_MSDOS) && !defined (NO_EXPAND_FILE)
int ExpandFile( IOBUF *input, DISK *output)
{
int i, result;
int current_position;
int c;
int match_length;
int match_position;
unsigned char *window;
window = new unsigned char[WINDOW_SIZE];
if(window == NULL) return 99;
current_position = 1;
for ( ; ; )
{
if ( InputBufBit( input ) )
{
c = (int) InputBufBits( input, 8 );
result = putdiskc( c, output );
if(result) return result;
window[ current_position ] = (unsigned char) c;
current_position = MOD_WINDOW( current_position + 1 );
}
else
{
match_position = (int) InputBufBits( input, INDEX_BIT_COUNT );
if ( match_position == END_OF_STREAM )
break;
match_length = (int) InputBufBits( input, LENGTH_BIT_COUNT );
match_length += BREAK_EVEN;
for ( i = 0 ; i <= match_length ; i++ )
{
c = window[ MOD_WINDOW( match_position + i ) ];
result = putdiskc( c, output );
if(result) return result;
window[ current_position ] = (unsigned char) c;
current_position = MOD_WINDOW( current_position + 1 );
}
}
}
delete[] window;
// return success
return 0;
}
#endif
void ExpandBuffer( IOBUF *input, IOBUF *output)
{
int i;
int current_position;
int c;
int match_length;
int match_position;
unsigned char *window;
window = new unsigned char[WINDOW_SIZE];
if(window == NULL) return;
current_position = 1;
for ( ; ; )
{
if ( InputBufBit( input ) )
{
c = (int) InputBufBits( input, 8 );
putbufc( c, output );
window[ current_position ] = (unsigned char) c;
current_position = MOD_WINDOW( current_position + 1 );
}
else
{
match_position = (int) InputBufBits( input, INDEX_BIT_COUNT );
if ( match_position == END_OF_STREAM )
break;
match_length = (int) InputBufBits( input, LENGTH_BIT_COUNT );
match_length += BREAK_EVEN;
for ( i = 0 ; i <= match_length ; i++ )
{
c = window[ MOD_WINDOW( match_position + i ) ];
putbufc( c, output );
window[ current_position ] = (unsigned char) c;
current_position = MOD_WINDOW( current_position + 1 );
}
}
}
delete[] window;
}
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