You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
107 lines
3.8 KiB
107 lines
3.8 KiB
// ChunkIterator.java
|
|
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
|
|
// first published 14.01.2008 on http://yacy.net
|
|
//
|
|
// $LastChangedDate$
|
|
// $LastChangedRevision$
|
|
// $LastChangedBy$
|
|
//
|
|
// LICENSE
|
|
//
|
|
// This program is free software; you can redistribute it and/or modify
|
|
// it under the terms of the GNU General Public License as published by
|
|
// the Free Software Foundation; either version 2 of the License, or
|
|
// (at your option) any later version.
|
|
//
|
|
// This program 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 for more details.
|
|
//
|
|
// You should have received a copy of the GNU General Public License
|
|
// along with this program; if not, write to the Free Software
|
|
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
|
|
package net.yacy.kelondro.table;
|
|
|
|
import java.io.BufferedInputStream;
|
|
import java.io.DataInputStream;
|
|
import java.io.EOFException;
|
|
import java.io.File;
|
|
import java.io.FileInputStream;
|
|
import java.io.FileNotFoundException;
|
|
import java.io.IOException;
|
|
import java.util.Iterator;
|
|
|
|
import net.yacy.cora.util.ConcurrentLog;
|
|
import net.yacy.cora.util.LookAheadIterator;
|
|
|
|
public class ChunkIterator extends LookAheadIterator<byte[]> implements Iterator<byte[]> {
|
|
|
|
private final int chunksize;
|
|
|
|
/**
|
|
* create a ChunkIterator
|
|
* a ChunkIterator uses a BufferedInputStream to iterate through the file
|
|
* and is therefore a fast option to get all elements in the file as a sequence
|
|
* ATTENTION: before calling this class ensure that all file buffers are flushed
|
|
* ATTENTION: if the iterator is not read to the end or interrupted, close() must be called to release the InputStream
|
|
* @param file: the file
|
|
* @param recordsize: the size of the elements in the file
|
|
* @param chunksize: the size of the chunks that are returned by next(). remaining bytes until the lenght of recordsize are skipped
|
|
* @throws FileNotFoundException
|
|
*/
|
|
|
|
|
|
private final DataInputStream stream;
|
|
private final int recordsize;
|
|
|
|
public ChunkIterator(final File file, final int recordsize, final int chunksize) throws FileNotFoundException {
|
|
if (!file.exists()) throw new FileNotFoundException(file.getAbsolutePath());
|
|
assert (file.exists());
|
|
assert file.length() % recordsize == 0;
|
|
this.recordsize = recordsize;
|
|
this.chunksize = chunksize;
|
|
this.stream = new DataInputStream(new BufferedInputStream(new FileInputStream(file), 64 * 1024));
|
|
}
|
|
|
|
/**
|
|
* Special close methode to release the used InputStream
|
|
* stream is automatically closed on last next(),
|
|
* close() needs only be called if iterator not read to the end ( hasNext() or next() has not returned null)
|
|
*/
|
|
public void close() throws IOException {
|
|
this.stream.close();
|
|
}
|
|
|
|
@Override
|
|
public byte[] next0() {
|
|
final byte[] chunk = new byte[chunksize];
|
|
int r, s;
|
|
try {
|
|
// read the chunk
|
|
this.stream.readFully(chunk);
|
|
// skip remaining bytes
|
|
r = chunksize;
|
|
while (r < recordsize) {
|
|
s = (int) this.stream.skip(recordsize - r);
|
|
assert s > 0;
|
|
if (s <= 0) return null;
|
|
r += s;
|
|
}
|
|
return chunk;
|
|
} catch (final EOFException e) {
|
|
// no real exception, this is the normal termination
|
|
try {
|
|
this.stream.close(); // close the underlaying inputstream
|
|
} catch (IOException ex) {
|
|
ConcurrentLog.logException(ex);
|
|
}
|
|
return null;
|
|
} catch (final IOException e) {
|
|
ConcurrentLog.logException(e);
|
|
return null;
|
|
}
|
|
}
|
|
}
|