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/*
This file is part of Advanced Strategic Command; http://www.asc-hq.de
Copyright (C) 1994-1999 Martin Bickel and Marc Schellenberger
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
*/
/*--- lzwunc.c ---------------------------- Listing 9-10 -------
* Decompress an LZW-compressed file
*
* Entry point: int LZWDecode(FILE *infile, FILE *outfile)
*
* Will decompress infile into outfile. Both
* files should already be open in binary mode.
* They will be closed by LZWDecode().
*
* LZWDecode() returns:
* 0: success
* 1: invalid signature byte
* 2: bad malloc
* 3: read error
* 4: write error
*
*
* Switches: DRIVER - compiles a test driver
* CODES - displays input codes
*-------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "lzw.h"
static int LZWIn ( FILE *infile )
{
if ( fread ( &incode, sizeof( CodeType ), 1, infile ) != 1 )
return ( 4 );
return ( 0 );
}
/* the active decompression routine */
static IndexType freecode;
static unsigned LZWLoadBuffer ( unsigned count, CodeType code )
{
if ( code >= freecode )
{
printf( "LZWLoad: code %u out of range!", code );
return ( 0 );
}
while ( code >= PRESET_CODE_MAX )
{
DecodeBuffer[ count++ ] = rdictionary[ code ].c;
if ( count == DecodeBufferSize )
{
DecodeBuffer =
realloc ( DecodeBuffer, DecodeBufferSize + 1000 );
if ( ! DecodeBuffer )
{
/* out of memory */
DecodeBufferSize = 0;
return ( 0 );
}
else
DecodeBufferSize += 1000;
}
code = rdictionary[ code ].parent;
}
DecodeBuffer[ count++ ] = code;
return ( count );
}
int LZWDecode ( FILE *infile, FILE *outfile )
{
char buffer[ 10 ];
int retval = 0;
unsigned int inchar;
unsigned count;
CodeType oldcode;
/* check the signature */
fgets ( buffer, strlen ( SIGNATURE ) + 2, infile );
if ( strcmp ( buffer, SIGNATURE ))
{
retval = 1;
goto done;
}
/* prime the pump */
if (!DecodeBufferSize)
{
DecodeBufferSize = 1000;
DecodeBuffer = malloc ( DecodeBufferSize );
if ( DecodeBuffer == NULL )
throw toutofmem ( DecodeBufferSize );
}
rdictionary = malloc( DICTIONARY_SIZE * sizeof( struct Rdictionary ) );
if ( rdictionary == NULL )
throw toutofmem ( DICTIONARY_SIZE * sizeof( struct Rdictionary ) );
priming:
freecode = STARTING_CODE;
if ( retval = LZWIn ( infile ))
goto done;
if ( incode == END_OF_INPUT )
goto done;
/* the first character always is itself */
oldcode = incode;
inchar = incode;
fputc( incode, outfile );
while ( ! ( retval = LZWIn ( infile )))
{
if ( incode == END_OF_INPUT )
break;
if ( incode == NEW_DICTIONARY )
goto priming;
if ( incode >= freecode )
{
/* We have a code that's not in our rdictionary! */
/* This can happen only one way--see text */
count = LZWLoadBuffer ( 1, oldcode );
/* Make last char same as first. Can use either */
/* inchar or the DecodeBuffer[count-1] */
DecodeBuffer[ 0 ] = inchar;
}
else
count = LZWLoadBuffer ( 0, incode );
if ( count == 0 )
return ( 2 ); /* had a memory problem */
inchar = DecodeBuffer[ count - 1 ];
while ( count )
{
fputc ( DecodeBuffer[--count], outfile);
}
/* now, update the rdictionary */
if ( freecode < MAX_CODE )
{
rdictionary[ freecode ].parent = oldcode;
rdictionary[ freecode ].c = inchar;
freecode += 1;
}
oldcode = incode;
}
done:
fclose ( infile );
fclose ( outfile );
return ( retval );
}
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