mirror of
https://github.com/yacy/yacy_search_server.git
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121 lines
4.1 KiB
Java
121 lines
4.1 KiB
Java
// bitfield.java
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// -------------------------------------
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// (C) by Michael Peter Christen; mc@yacy.net
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// first published on http://www.anomic.de
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// Frankfurt, Germany, 2004
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package net.yacy.utils;
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import net.yacy.cora.document.encoding.ASCII;
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public class Bitfield {
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private byte[] bb;
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public Bitfield() {
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this(0);
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}
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public Bitfield(final int bytelength) {
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this.bb= new byte[bytelength];
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for (int i = 0 ; i < bytelength; i++) bb[i] = ' ';
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}
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public Bitfield(final byte[] field) {
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bb = field;
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}
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private static byte setAtom(final byte a, final int pos) {
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if ((pos > 5) || (pos < 0)) throw new RuntimeException("atom position out of bounds: " + pos);
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byte b = (byte) (((a - 32) | (1<<pos)) + 32);
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return b;
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}
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private static byte unsetAtom(final byte a, final int pos) {
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if ((pos > 5) || (pos < 0)) throw new RuntimeException("atom position out of bounds: " + pos);
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byte b = (byte) (((a - 32) & (0xff ^ (1<<pos))) + 32);
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return b;
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}
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public void set(final int pos, final boolean value) {
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final int slot = pos / 5;
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if (pos < 0) throw new RuntimeException("position out of bounds: " + pos);
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if (slot > bb.length) {
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// extend capacity
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byte[] nb = new byte[slot + 1];
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System.arraycopy(bb, 0, nb, 0, bb.length);
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for (int i = bb.length; i < nb.length; i++) nb[i] = 0;
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bb = nb;
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}
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bb[slot] = (value) ? setAtom(bb[slot], pos % 5) : unsetAtom(bb[slot], pos % 5);
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}
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public boolean get(final int pos) {
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final int slot = pos / 5;
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if (pos < 0) throw new RuntimeException("position out of bounds: " + pos);
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if (slot > bb.length) return false;
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boolean b = ((bb[slot] - 32) & (1 << (pos % 5))) > 0;
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return b;
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}
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public int length() {
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return bb.length * 5;
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}
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public byte[] getBytes() {
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return bb;
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}
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@Override
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public String toString() {
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//throw new UnsupportedOperationException("testing");
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StringBuilder sb = new StringBuilder(length());
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for (int i = length() - 1; i >= 0; i--) sb.append((get(i)) ? '1' : '0');
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return ASCII.String(bb) + " " + sb.toString();
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}
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public static void main(final String[] args) {
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//final bitfield f = new bitfield(ASCII.getBytes(Seed.FLAGSZERO));
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final Bitfield f = new Bitfield(4);
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for (int i = 0; i < 20; i++) {
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f.set(i, false);
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if (f.get(i)) System.out.println("i = " + i);
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f.set(i, true);
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if (!f.get(i)) System.out.println("!i = " + i);
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System.out.println(i + ":" + f.toString());
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}
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final Bitfield test = new Bitfield(4);
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final int l = test.length();
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System.out.println("available: " + l);
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System.out.println("before: " + test.toString());
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for (int i = 0; i < l/2; i++) {
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test.set(i, true);
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System.out.println(i + ":" + test.toString());
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}
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for (int i = l/2 - 1; i >= 0; i--) {
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test.set(i, false);
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System.out.println(i + ":" + test.toString());
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}
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System.out.println("after: " + test.toString());
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}
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}
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