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4a5100789f
git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@6510 6c8d7289-2bf4-0310-a012-ef5d649a1542
69 lines
3.2 KiB
Java
69 lines
3.2 KiB
Java
// AbstractBufferedIndex.java
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// -----------------------------
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// (C) 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 16.3.2009 on http://yacy.net
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//
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// This is a part of YaCy, a peer-to-peer based web search engine
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//
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// $LastChangedDate: 2006-04-02 22:40:07 +0200 (So, 02 Apr 2006) $
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// $LastChangedRevision: 1986 $
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// $LastChangedBy: orbiter $
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//
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// LICENSE
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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.kelondro.rwi;
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import java.io.IOException;
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import java.util.Iterator;
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import java.util.TreeSet;
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import net.yacy.kelondro.order.Order;
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public abstract class AbstractBufferedIndex<ReferenceType extends Reference> extends AbstractIndex<ReferenceType> implements BufferedIndex<ReferenceType> {
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public AbstractBufferedIndex(final ReferenceFactory<ReferenceType> factory) {
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super(factory);
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}
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public synchronized TreeSet<ReferenceContainer<ReferenceType>> references(byte[] startHash, final boolean rot, int count, boolean ram) throws IOException {
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// creates a set of indexContainers
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// this does not use the cache
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final Order<ReferenceContainer<ReferenceType>> containerOrder = new ReferenceContainerOrder<ReferenceType>(factory, this.ordering().clone());
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if (startHash.length == 0) startHash = null;
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ReferenceContainer<ReferenceType> emptyContainer = ReferenceContainer.emptyContainer(factory, startHash, 0);
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containerOrder.rotate(emptyContainer);
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final TreeSet<ReferenceContainer<ReferenceType>> containers = new TreeSet<ReferenceContainer<ReferenceType>>(containerOrder);
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final Iterator<ReferenceContainer<ReferenceType>> i = references(startHash, rot, ram);
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if (ram) count = Math.min(size(), count);
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ReferenceContainer<ReferenceType> container;
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// this loop does not terminate using the i.hasNex() predicate when rot == true
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// because then the underlying iterator is a rotating iterator without termination
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// in this case a termination must be ensured with a counter
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// It must also be ensured that the counter is in/decreased every loop
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while ((count > 0) && (i.hasNext())) {
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container = i.next();
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if (container != null && !container.isEmpty()) {
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containers.add(container);
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}
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count--; // decrease counter even if the container was null or empty to ensure termination
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}
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return containers; // this may return less containers as demanded
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}
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}
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