// HeapModifier.java
// (C) 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 05.01.2009 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.blob;
import java.io.File;
import java.io.IOException;
import java.util.SortedMap;
import net.yacy.cora.document.UTF8;
import net.yacy.cora.order.ByteOrder;
import net.yacy.cora.util.SpaceExceededException;
import net.yacy.kelondro.io.CachedFileWriter;
import net.yacy.kelondro.logging.Log;
import net.yacy.kelondro.util.FileUtils;
import net.yacy.kelondro.util.MemoryControl;
public class HeapModifier extends HeapReader implements BLOB {
/*
* This class adds a remove operation to a BLOBHeapReader. That means that a BLOBModifier can
* - read elements from a BLOB
* - remove elements from a BLOB
* but cannot write new entries to the BLOB
*/
/**
* create a heap file: a arbitrary number of BLOBs, indexed by an access key
* The heap file will be indexed upon initialization.
* @param heapFile
* @param keylength
* @param ordering
* @throws IOException
*/
public HeapModifier(final File heapFile, final int keylength, final ByteOrder ordering) throws IOException {
super(heapFile, keylength, ordering);
}
/**
* clears the content of the database
* @throws IOException
*/
@Override
public synchronized void clear() throws IOException {
this.index.clear();
this.free.clear();
this.file.close();
this.file = null;
FileUtils.deletedelete(this.heapFile);
super.deleteFingerprint();
this.file = new CachedFileWriter(this.heapFile);
}
/**
* close the BLOB table
*/
@Override
public synchronized void close(boolean writeIDX) {
shrinkWithGapsAtEnd();
super.close(writeIDX);
}
@Override
public synchronized void close() {
close(true);
}
@Override
public void finalize() {
this.close();
}
/**
* remove a BLOB
* @param key the primary key
* @throws IOException
*/
@Override
public void delete(byte[] key) throws IOException {
key = normalizeKey(key);
// pre-check before synchronization
long seek = this.index.get(key);
if (seek < 0) return;
synchronized (this) {
// check again if the index contains the key
seek = this.index.get(key);
if (seek < 0) return;
// check consistency of the index
//assert (checkKey(key, seek)) : "key compare failed; key = " + UTF8.String(key) + ", seek = " + seek;
// access the file and read the container
this.file.seek(seek);
int size = this.file.readInt();
//assert seek + size + 4 <= this.file.length() : heapFile.getName() + ": too long size " + size + " in record at " + seek;
long filelength = this.file.length(); // put in separate variable for debugging
if (seek + size + 4 > filelength) {
Log.logSevere("BLOBHeap", this.heapFile.getName() + ": too long size " + size + " in record at " + seek);
throw new IOException(this.heapFile.getName() + ": too long size " + size + " in record at " + seek);
}
super.deleteFingerprint();
// add entry to free array
this.free.put(seek, size);
// fill zeros to the content
int l = size; byte[] fill = new byte[size];
while (l-- > 0) fill[l] = 0;
this.file.write(fill, 0, size);
// remove entry from index
this.index.remove(key);
// recursively merge gaps
tryMergeNextGaps(seek, size);
tryMergePreviousGap(seek);
}
}
private void tryMergePreviousGap(final long thisSeek) throws IOException {
// this is called after a record has been removed. That may cause that a new
// empty record was surrounded by gaps. We merge with a previous gap, if this
// is also empty, but don't do that recursively
// If this is successful, it removes the given marker for thisSeed and
// because of this, this method MUST be called AFTER tryMergeNextGaps was called.
// first find the gap entry for the closest gap in front of the give gap
SortedMap<Long, Integer> head = this.free.headMap(thisSeek);
if (head.isEmpty()) return;
long previousSeek = head.lastKey().longValue();
int previousSize = head.get(previousSeek).intValue();
// check if this is directly in front
if (previousSeek + previousSize + 4 == thisSeek) {
// right in front! merge the gaps
Integer thisSize = this.free.get(thisSeek);
assert thisSize != null;
mergeGaps(previousSeek, previousSize, thisSeek, thisSize.intValue());
}
}
private void tryMergeNextGaps(final long thisSeek, final int thisSize) throws IOException {
// try to merge two gaps if one gap has been processed already and the position of the next record is known
// if the next record is also a gap, merge these gaps and go on recursively
// first check if next gap position is outside of file size
long nextSeek = thisSeek + thisSize + 4;
if (nextSeek >= this.file.length()) return; // end of recursion
// move to next position and read record size
Integer nextSize = this.free.get(nextSeek);
if (nextSize == null) return; // finished, this is not a gap
// check if the record is a gap-record
assert nextSize.intValue() > 0;
if (nextSize.intValue() == 0) {
// a strange gap record: we can extend the thisGap with four bytes
// the nextRecord is a gap record; we remove that from the free list because it will be joined with the current gap
mergeGaps(thisSeek, thisSize, nextSeek, 0);
// recursively go on
tryMergeNextGaps(thisSeek, thisSize + 4);
} else {
// check if this is a true gap!
this.file.seek(nextSeek + 4);
byte[] o = new byte[1];
this.file.readFully(o, 0, 1);
int t = o[0];
assert t == 0;
if (t == 0) {
// the nextRecord is a gap record; we remove that from the free list because it will be joined with the current gap
mergeGaps(thisSeek, thisSize, nextSeek, nextSize.intValue());
// recursively go on
tryMergeNextGaps(thisSeek, thisSize + 4 + nextSize.intValue());
}
}
}
private void mergeGaps(final long seek0, final int size0, final long seek1, final int size1) throws IOException {
//System.out.println("*** DEBUG-BLOBHeap " + heapFile.getName() + ": merging gap from pos " + seek0 + ", len " + size0 + " with next record of size " + size1 + " (+ 4)");
Integer g = this.free.remove(seek1); // g is only used for debugging
assert g != null;
assert g.intValue() == size1;
// overwrite the size bytes of next records with zeros
this.file.seek(seek1);
this.file.writeInt(0);
// the new size of the current gap: old size + len + 4
int newSize = size0 + 4 + size1;
this.file.seek(seek0);
this.file.writeInt(newSize);
// register new gap in the free array; overwrite old gap entry
g = this.free.put(seek0, newSize);
assert g != null;
assert g.intValue() == size0;
}
protected void shrinkWithGapsAtEnd() {
// find gaps at the end of the file and shrink the file by these gaps
if (this.free == null) return;
try {
while (!this.free.isEmpty()) {
Long seek = this.free.lastKey();
int size = this.free.get(seek).intValue();
if (seek.longValue() + size + 4 != this.file.length()) return;
// shrink the file
this.file.setLength(seek.longValue());
this.free.remove(seek);
}
} catch (IOException e) {
Log.logException(e);
}
}
@Override
public void insert(byte[] key, byte[] b) throws IOException {
throw new UnsupportedOperationException("put is not supported in BLOBHeapModifier");
}
@Override
public int replace(byte[] key, final Rewriter rewriter) throws IOException {
throw new UnsupportedOperationException();
}
@Override
public int reduce(byte[] key, final Reducer reducer) throws IOException, SpaceExceededException {
key = normalizeKey(key);
assert key.length == this.keylength;
// pre-check before synchronization
long pos = this.index.get(key);
if (pos < 0) return 0;
synchronized (this) {
long m = this.mem();
// check again if the index contains the key
pos = this.index.get(key);
if (pos < 0) return 0;
// check consistency of the index
//assert checkKey(key, pos) : "key compare failed; key = " + UTF8.String(key) + ", seek = " + pos;
// access the file and read the container
this.file.seek(pos);
final int len = this.file.readInt() - this.keylength;
if (MemoryControl.available() < len) {
if (!MemoryControl.request(len, true)) return 0; // not enough memory available for this blob
}
super.deleteFingerprint();
// read the key
final byte[] keyf = new byte[this.keylength];
this.file.readFully(keyf, 0, keyf.length);
assert this.ordering == null || this.ordering.equal(key, keyf) : "key = " + UTF8.String(key) + ", keyf = " + UTF8.String(keyf);
// read the blob
byte[] blob = new byte[len];
this.file.readFully(blob, 0, blob.length);
// rewrite the entry
blob = reducer.rewrite(blob);
int reduction = len - blob.length;
if (reduction == 0) {
// even if the reduction is zero then it is still be possible that the record has been changed
this.file.seek(pos + 4 + key.length);
this.file.write(blob);
return 0;
}
// the new entry must be smaller than the old entry and must at least be 4 bytes smaller
// because that is the space needed to write a new empty entry record at the end of the gap
if (blob.length > len - 4) throw new IOException("replace of BLOB for key " + UTF8.String(key) + " failed (too large): new size = " + blob.length + ", old size = " + (len - 4));
// replace old content
this.file.seek(pos);
this.file.writeInt(blob.length + key.length);
this.file.write(key);
this.file.write(blob);
// define the new empty entry
final int newfreereclen = reduction - 4;
assert newfreereclen >= 0;
this.file.writeInt(newfreereclen);
// fill zeros to the content
int l = newfreereclen; byte[] fill = new byte[newfreereclen];
while (l-- > 0) fill[l] = 0;
this.file.write(fill, 0, newfreereclen);
// add a new free entry
this.free.put(pos + 4 + blob.length + key.length, newfreereclen);
assert mem() <= m : "m = " + m + ", mem() = " + mem();
return reduction;
}
}
}