/**
* Copyright (C) 1995-2010 levigo holding gmbh.
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*/
package com.levigo.jbig2.decoder.arithmetic;
import java.io.IOException;
import javax.imageio.stream.ImageInputStream;
/**
* This class represents the arithmetic decoder, described in ISO/IEC 14492:2001 in E.3
*
* @author <a href="mailto:m.krzikalla@levigo.de">Matthus Krzikalla</a>
*
*/
public class ArithmeticDecoder {
private static final int QE[][] = {
{
0x5601, 1, 1, 1
}, {
0x3401, 2, 6, 0
}, {
0x1801, 3, 9, 0
}, {
0x0AC1, 4, 12, 0
}, {
0x0521, 5, 29, 0
}, {
0x0221, 38, 33, 0
}, {
0x5601, 7, 6, 1
}, {
0x5401, 8, 14, 0
}, {
0x4801, 9, 14, 0
}, {
0x3801, 10, 14, 0
}, {
0x3001, 11, 17, 0
}, {
0x2401, 12, 18, 0
}, {
0x1C01, 13, 20, 0
}, {
0x1601, 29, 21, 0
}, {
0x5601, 15, 14, 1
}, {
0x5401, 16, 14, 0
}, {
0x5101, 17, 15, 0
}, {
0x4801, 18, 16, 0
}, {
0x3801, 19, 17, 0
}, {
0x3401, 20, 18, 0
}, {
0x3001, 21, 19, 0
}, {
0x2801, 22, 19, 0
}, {
0x2401, 23, 20, 0
}, {
0x2201, 24, 21, 0
}, {
0x1C01, 25, 22, 0
}, {
0x1801, 26, 23, 0
}, {
0x1601, 27, 24, 0
}, {
0x1401, 28, 25, 0
}, {
0x1201, 29, 26, 0
}, {
0x1101, 30, 27, 0
}, {
0x0AC1, 31, 28, 0
}, {
0x09C1, 32, 29, 0
}, {
0x08A1, 33, 30, 0
}, {
0x0521, 34, 31, 0
}, {
0x0441, 35, 32, 0
}, {
0x02A1, 36, 33, 0
}, {
0x0221, 37, 34, 0
}, {
0x0141, 38, 35, 0
}, {
0x0111, 39, 36, 0
}, {
0x0085, 40, 37, 0
}, {
0x0049, 41, 38, 0
}, {
0x0025, 42, 39, 0
}, {
0x0015, 43, 40, 0
}, {
0x0009, 44, 41, 0
}, {
0x0005, 45, 42, 0
}, {
0x0001, 45, 43, 0
}, {
0x5601, 46, 46, 0
}
};
private int a;
private long c;
private int ct;
private int b;
private long streamPos0;
private final ImageInputStream iis;
public ArithmeticDecoder(ImageInputStream iis) throws IOException {
this.iis = iis;
init();
}
private void init() throws IOException {
this.streamPos0 = iis.getStreamPosition();
b = this.iis.read();
c = b << 16;
byteIn();
c <<= 7;
ct -= 7;
a = 0x8000;
}
public int decode(CX cx) throws IOException {
int d;
final int qeValue = QE[cx.cx()][0];
final int icx = cx.cx();
a -= qeValue;
if ((c >> 16) < qeValue) {
d = lpsExchange(cx, icx, qeValue);
renormalize();
} else {
c -= (qeValue << 16);
if ((a & 0x8000) == 0) {
d = mpsExchange(cx, icx);
renormalize();
} else {
return cx.mps();
}
}
return d;
}
private void byteIn() throws IOException {
if (iis.getStreamPosition() > streamPos0) {
iis.seek(iis.getStreamPosition() - 1);
}
b = iis.read();
if (b == 0xFF) {
final int b1 = iis.read();
if (b1 > 0x8f) {
c += 0xff00;
ct = 8;
iis.seek(iis.getStreamPosition() - 2);
} else {
c += b1 << 9;
ct = 7;
}
} else {
b = iis.read();
c += b << 8;
ct = 8;
}
c &= 0xffffffffL;
}
private void renormalize() throws IOException {
do {
if (ct == 0) {
byteIn();
}
a <<= 1;
c <<= 1;
ct--;
} while ((a & 0x8000) == 0);
c &= 0xffffffffL;
}
private int mpsExchange(CX cx, int icx) {
final int mps = cx.mps();
if (a < QE[icx][0]) {
if (QE[icx][3] == 1) {
cx.toggleMps();
}
cx.setCx(QE[icx][2]);
return 1 - mps;
} else {
cx.setCx(QE[icx][1]);
return mps;
}
}
private int lpsExchange(CX cx, int icx, int qeValue) {
final int mps = cx.mps();
if (a < qeValue) {
cx.setCx(QE[icx][1]);
a = qeValue;
return mps;
} else {
if (QE[icx][3] == 1) {
cx.toggleMps();
}
cx.setCx(QE[icx][2]);
a = qeValue;
return 1 - mps;
}
}
int getA() {
return a;
}
long getC() {
return c;
}
}
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