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// Gap.java
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 30.12.2008 on http:// yacy.net
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// 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.blob;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
/**
* this is an extension of a set of {seek, size} pairs
* it is used to denote the position and space of free records
* The class provides methods to dump such a set to a file and read it again
*/
public class Gap extends TreeMap<Long, Integer> {
private static final long serialVersionUID = 1L;
public Gap() {
super();
}
/**
* initialize a kelondroBLOBGap with the content of a dump
* @param file
* @throws IOException
* @throws IOException
*/
public Gap(final File file) throws IOException {
super();
// read the index dump and fill the index
DataInputStream is;
FileInputStream fis = null;
try {
fis = new FileInputStream(file);
is = new DataInputStream(new BufferedInputStream(fis, (Integer.SIZE + Long.SIZE) * 1024)); // equals 16*1024*recordsize
} catch (final OutOfMemoryError e) {
if(fis != null) {
/* Reuse if possible the already created FileInputStream */
is = new DataInputStream(fis);
} else {
is = new DataInputStream(new FileInputStream(file));
}
}
try {
long p;
int l;
while (true) {
try {
p = is.readLong();
l = is.readInt();
this.put(Long.valueOf(p), Integer.valueOf(l));
} catch (final IOException e) {
break;
}
}
} finally {
if(is != null) {
is.close();
}
}
is = null;
}
/**
* dump the set to a file
* @param file
* @return
* @throws IOException
*/
public int dump(File file) throws IOException {
File tmp = new File(file.getParentFile(), file.getName() + ".prt");
Iterator<Map.Entry<Long, Integer>> i = this.entrySet().iterator();
DataOutputStream os;
int c = 0;
try (/* Resource automatically closed by this try-with-resources statement */
final FileOutputStream fileStream = new FileOutputStream(tmp);
) {
try {
os = new DataOutputStream(new BufferedOutputStream(fileStream, (Integer.SIZE + Long.SIZE) * 1024)); // = 16*1024*recordsize
} catch (final OutOfMemoryError e) {
os = new DataOutputStream(fileStream);
}
try {
Map.Entry<Long, Integer> e;
while (i.hasNext()) {
e = i.next();
os.writeLong(e.getKey().longValue());
os.writeInt(e.getValue().intValue());
c++;
}
os.flush();
} finally {
os.close();
}
}
tmp.renameTo(file);
assert file.exists() : file.toString();
assert !tmp.exists() : tmp.toString();
return c;
}
}
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