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3b40b98256
*) minor changes git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7567 6c8d7289-2bf4-0310-a012-ef5d649a1542
90 lines
3.1 KiB
Java
90 lines
3.1 KiB
Java
// ChunkIterator.java
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// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 14.01.2008 on http://yacy.net
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//
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// $LastChangedDate$
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// $LastChangedRevision$
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// $LastChangedBy$
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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.table;
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import java.io.BufferedInputStream;
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import java.io.DataInputStream;
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import java.io.EOFException;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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import java.util.Iterator;
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import net.yacy.kelondro.logging.Log;
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import net.yacy.kelondro.util.LookAheadIterator;
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public class ChunkIterator extends LookAheadIterator<byte[]> implements Iterator<byte[]> {
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private final int chunksize;
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/**
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* create a ChunkIterator
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* a ChunkIterator uses a BufferedInputStream to iterate through the file
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* and is therefore a fast option to get all elements in the file as a sequence
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* ATTENTION: before calling this class ensure that all file buffers are flushed
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* @param file: the file
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* @param recordsize: the size of the elements in the file
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* @param chunksize: the size of the chunks that are returned by next(). remaining bytes until the lenght of recordsize are skipped
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* @throws FileNotFoundException
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*/
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private final DataInputStream stream;
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private final int recordsize;
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public ChunkIterator(final File file, final int recordsize, final int chunksize) throws FileNotFoundException {
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assert (file.exists());
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assert file.length() % recordsize == 0;
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this.recordsize = recordsize;
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this.chunksize = chunksize;
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this.stream = new DataInputStream(new BufferedInputStream(new FileInputStream(file), 64 * 1024));
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}
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public byte[] next0() {
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final byte[] chunk = new byte[chunksize];
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int r, s;
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try {
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// read the chunk
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this.stream.readFully(chunk);
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// skip remaining bytes
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r = chunksize;
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while (r < recordsize) {
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s = (int) this.stream.skip(recordsize - r);
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assert s > 0;
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if (s <= 0) return null;
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r += s;
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}
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return chunk;
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} catch (final EOFException e) {
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// no real exception, this is the normal termination
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return null;
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} catch (final IOException e) {
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Log.logException(e);
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return null;
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}
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}
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}
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