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/*
* @(#)Compressor.java 1.9 06/10/30
*
* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
/**
* @date 2/17/98
* @author Jacek R. Ambroziak
* @group Sun Microsystems Laboratories
*/
package com.sun.java.help.search;
import java.io.*;
class Compressor
{
private static final int NBits = 32;
private static final int BeginK = 5;
private BitBuffer _buffer = new BitBuffer();
public void write(DataOutput out) throws IOException {
_buffer.write(out);
}
public int byteCount() {
return _buffer.byteCount();
}
public void clear() {
_buffer.clear();
}
public void concatenate(Compressor other) {
_buffer.concatenate(other._buffer);
}
public void encode(IntegerArray pos, int k)
{
int power = 1 << k, n1 = 0;
for (int i = 0; i < pos.cardinality(); i++)
{
int n2 = pos.at(i) >>> k;
int rem = pos.at(i) % power;
if (n2 != n1)
{
int min = n1, a = n1;
int lev = 0, power2 = 1;
if (n2 > n1)
for (int max = n1; max < n2; a >>>= 1, power2 <<= 1, lev++)
if ((a & 1) != 0)
min -= power2;
else
max += power2;
else
for ( ; min > n2; a >>>= 1, power2 <<= 1, lev++)
if ((a & 1) != 0)
min -= power2;
// lev 0s, 1, lev bits of (n2 - min) plus following value
// no 'V' symbol needed here
if (lev*2 + 1 + k <= NBits)
_buffer.append((1<<lev | (n2 - min)) << k | rem, lev*2+1+k);
else
{
if (lev*2 + 1 <= NBits)
_buffer.append(1 << lev | (n2 - min), lev*2 + 1);
else
{
_buffer.append(0, lev);
_buffer.append(1 << lev | (n2 - min), lev + 1);
}
_buffer.append(rem, k);
}
n1 = n2;
}
else
_buffer.append(rem | power, k + 1); // 'V' + value
}
_buffer.append(2 | n1 & 1, 3); // marking end
_buffer.close();
}
public void encode(IntegerArray pos, IntegerArray len, int k, int k2)
{
int power = 1 << k, n1 = 0;
for (int i = 0; i < pos.cardinality(); i++)
{
int n2 = pos.at(i) >>> k;
int rem = pos.at(i) % power;
if (n2 != n1)
{
int min = n1, a = n1;
int lev = 0, power2 = 1;
if (n2 > n1)
for (int max = n1; max < n2; a >>>= 1, power2 <<= 1, lev++)
if ((a & 1) != 0)
min -= power2;
else
max += power2;
else
for ( ; min > n2; a >>>= 1, power2 <<= 1, lev++)
if ((a & 1) != 0)
min -= power2;
// lev 0s, 1, lev bits of (n2 - min) plus following value
if (lev*2 + 1 + k <= NBits)
_buffer.append((1<<lev | (n2 - min)) << k | rem, lev*2+1+k);
else
{
if (lev*2 + 1 <= NBits)
_buffer.append(1 << lev | (n2 - min), lev*2 + 1);
else
{
_buffer.append(0, lev);
_buffer.append(1 << lev | (n2 - min), lev + 1);
}
_buffer.append(rem, k);
}
_buffer.append(len.at(i), k2);
n1 = n2;
}
else
_buffer.append((rem|power)<<k2 | len.at(i), k+k2+1); // 'V' + v1,v2
}
_buffer.append(2 | n1 & 1, 3); // marking end
_buffer.close();
}
// k: starting value for minimization
public int minimize(IntegerArray array, int startK)
{
BitBuffer saved = new BitBuffer();
int minK = startK;
_buffer.clear();
encode(array, startK);
int min = _buffer.bitCount(); // init w/ first value
saved.setFrom(_buffer);
_buffer.clear();
encode(array, startK + 1);
if (_buffer.bitCount() < min)
{
int k = startK + 1;
do {
saved.setFrom(_buffer);
min = _buffer.bitCount();
minK = k;
_buffer.clear();
encode(array, ++k);
}
while (_buffer.bitCount() < min);
}
else // try smaller values through 1
for (int k = startK - 1; k > 0; k--)
{
_buffer.clear();
encode(array, k);
if (_buffer.bitCount() < min)
{
saved.setFrom(_buffer);
min = _buffer.bitCount();
minK = k;
}
else
break;
}
_buffer.setFrom(saved);
return minK;
}
public int compressAscending(IntegerArray array)
{
IntegerArray differences = new IntegerArray(array.cardinality());
array.toDifferences(differences);
return minimize(differences, BeginK);
}
}
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