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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* $URL$
* $Id$
*
*/
/***************************************************************************
** decomp.c
**
** Routines that deal with AGI version 3 specific features.
** The original LZW code is from DJJ, October 1989, p.86.
** It has been modified to handle AGI compression.
**
** (c) 1997 Lance Ewing
***************************************************************************/
#include "common/stdafx.h"
#include "agi/agi.h"
#include "agi/lzw.h"
namespace Agi {
#define MAXBITS 12
#define TABLE_SIZE 18041 /* strange number */
#define START_BITS 9
static int32 BITS, MAX_VALUE, MAX_CODE;
static uint32 *prefixCode;
static uint8 *appendCharacter;
static uint8 *decodeStack;
static int32 inputBitCount = 0; /* Number of bits in input bit buffer */
static uint32 inputBitBuffer = 0L;
static void initLZW() {
decodeStack = (uint8 *)calloc(1, 8192);
prefixCode = (uint32 *)malloc(TABLE_SIZE * sizeof(uint32));
appendCharacter = (uint8 *)malloc(TABLE_SIZE * sizeof(uint8));
inputBitCount = 0; /* Number of bits in input bit buffer */
inputBitBuffer = 0L;
}
static void closeLZW() {
free(decodeStack);
free(prefixCode);
free(appendCharacter);
}
/***************************************************************************
** setBits
**
** Purpose: To adjust the number of bits used to store codes to the value
** passed in.
***************************************************************************/
int setBits(int32 value) {
if (value == MAXBITS)
return true;
BITS = value;
MAX_VALUE = (1 << BITS) - 1;
MAX_CODE = MAX_VALUE - 1;
return false;
}
/***************************************************************************
** decode_string
**
** Purpose: To return the string that the code taken from the input buffer
** represents. The string is returned as a stack, i.e. the characters are
** in reverse order.
***************************************************************************/
static uint8 *decodeString(uint8 *buffer, uint32 code) {
uint32 i;
for (i = 0; code > 255;) {
*buffer++ = appendCharacter[code];
code = prefixCode[code];
if (i++ >= 4000) {
error("lzw: error in code expansion.");
}
}
*buffer = code;
return buffer;
}
/***************************************************************************
** input_code
**
** Purpose: To return the next code from the input buffer.
***************************************************************************/
static uint32 inputCode(uint8 **input) {
uint32 r;
while (inputBitCount <= 24) {
inputBitBuffer |= (uint32) * (*input)++ << inputBitCount;
inputBitCount += 8;
}
r = (inputBitBuffer & 0x7FFF) % (1 << BITS);
inputBitBuffer >>= BITS;
inputBitCount -= BITS;
return r;
}
/***************************************************************************
** expand
**
** Purpose: To uncompress the data contained in the input buffer and store
** the result in the output buffer. The fileLength parameter says how
** many bytes to uncompress. The compression itself is a form of LZW that
** adjusts the number of bits that it represents its codes in as it fills
** up the available codes. Two codes have special meaning:
**
** code 256 = start over
** code 257 = end of data
***************************************************************************/
void lzwExpand(uint8 *in, uint8 *out, int32 len) {
int32 c, lzwnext, lzwnew, lzwold;
uint8 *s, *end;
initLZW();
setBits(START_BITS); /* Starts at 9-bits */
lzwnext = 257; /* Next available code to define */
end = (unsigned char *)((long)out + (long)len);
lzwold = inputCode(&in); /* Read in the first code */
c = lzwold;
lzwnew = inputCode(&in);
while ((out < end) && (lzwnew != 0x101)) {
if (lzwnew == 0x100) {
/* Code to "start over" */
lzwnext = 258;
setBits(START_BITS);
lzwold = inputCode(&in);
c = lzwold;
*out++ = (char)c;
lzwnew = inputCode(&in);
} else {
if (lzwnew >= lzwnext) {
/* Handles special LZW scenario */
*decodeStack = c;
s = decodeString(decodeStack + 1, lzwold);
} else
s = decodeString(decodeStack, lzwnew);
/* Reverse order of decoded string and
* store in out buffer
*/
c = *s;
while (s >= decodeStack)
*out++ = *s--;
if (lzwnext > MAX_CODE)
setBits(BITS + 1);
prefixCode[lzwnext] = lzwold;
appendCharacter[lzwnext] = c;
lzwnext++;
lzwold = lzwnew;
lzwnew = inputCode(&in);
}
}
closeLZW();
}
} // End of namespace Agi
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