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91 lines
3.2 KiB
91 lines
3.2 KiB
16 years ago
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// FlatWordPartitionScheme.java
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// ------------------------------
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// part of YaCy
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// (C) 2009 by Michael Peter Christen; mc@yacy.net
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// first published on http://yacy.net
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// Frankfurt, Germany, 28.01.2009
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//
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// $LastChangedDate: 2009-01-23 16:32:27 +0100 (Fr, 23 Jan 2009) $
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// $LastChangedRevision: 5514 $
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// $LastChangedBy: orbiter $
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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 de.anomic.yacy.dht;
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import de.anomic.kelondro.order.Base64Order;
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import de.anomic.yacy.yacySeed;
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public class FlatWordPartitionScheme implements PartitionScheme {
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public static final FlatWordPartitionScheme std = new FlatWordPartitionScheme();
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public FlatWordPartitionScheme() {
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// nothing to initialize
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}
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public int verticalPartitions() {
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return 1;
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}
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public long dhtPosition(String wordHash, String urlHash) {
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// the urlHash has no relevance here
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// normalized to Long.MAX_VALUE
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long c = Base64Order.enhancedCoder.cardinal(wordHash.getBytes());
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assert c != Long.MAX_VALUE;
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if (c == Long.MAX_VALUE) return Long.MAX_VALUE - 1;
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return c;
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}
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public final long dhtDistance(final String word, final String urlHash, final yacySeed peer) {
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return dhtDistance(word, urlHash, peer.hash);
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}
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private final long dhtDistance(final String from, final String urlHash, final String to) {
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// the dht distance is a positive value between 0 and 1
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// if the distance is small, the word more probably belongs to the peer
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assert to != null;
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assert from != null;
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final long toPos = dhtPosition(to, null);
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final long fromPos = dhtPosition(from, urlHash);
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return dhtDistance(fromPos, toPos);
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}
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public long dhtPosition(String wordHash, int verticalPosition) {
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return dhtPosition(wordHash, null);
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}
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public long[] dhtPositions(String wordHash) {
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long[] l = new long[1];
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l[1] = dhtPosition(wordHash, null);
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return l;
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}
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public int verticalPosition(String urlHash) {
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return 0; // this is not a method stub, this is actually true for all FlatWordPartitionScheme
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}
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public final static long dhtDistance(final long fromPos, final long toPos) {
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final long d = toPos - fromPos;
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return (d >= 0) ? d : (d + Long.MAX_VALUE) + 1;
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}
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public static String positionToHash(final long l) {
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// transform the position of a peer position into a close peer hash
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return new String(Base64Order.enhancedCoder.uncardinal(l)) + "AA";
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}
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}
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