// Compressor.java
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 17.10.2008 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.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import java.util.zip.Deflater;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
import net.yacy.cora.order.ByteOrder;
import net.yacy.cora.order.CloneableIterator;
import net.yacy.cora.util.ByteArray;
import net.yacy.cora.util.ConcurrentLog;
import net.yacy.cora.util.SpaceExceededException;
import net.yacy.kelondro.util.MemoryControl;
public class Compressor implements BLOB, Iterable<byte[]> {
private static byte[] gzipMagic = {(byte) 'z', (byte) '|'}; // magic for gzip-encoded content
private static byte[] plainMagic = {(byte) 'p', (byte) '|'}; // magic for plain content (no encoding)
private final BLOB backend;
/** entries which are not yet compressed, format is RAW (without magic) */
private TreeMap<byte[], byte[]> buffer;
/** Total size (in bytes) of uncompressed entries in buffer */
private volatile long bufferlength;
/** Maximum {@link #bufferlength} value before compressing and flushing to the backend */
private final long maxbufferlength;
/** Maximum time (in milliseconds) to acquire a synchronization lock on get() and insert() */
private volatile long lockTimeout;
/** Synchronization lock */
private final ReentrantLock lock;
/** The compression level */
private volatile int compressionLevel;
/**
* @param backend the backend storage
* @param buffersize the maximum total size (in bytes) of uncompressed in-memory entries before compressing and flushing to the backend
* @param lockTimeout maximum time to acquire a synchronization lock on get() and insert() operations
* @param compressionLevel the compression level : supported values ranging from 0 - no compression, to 9 - best compression
*/
public Compressor(final BLOB backend, final long buffersize, final long lockTimeout, final int compressionLevel) {
this.backend = backend;
this.maxbufferlength = buffersize;
this.lockTimeout = lockTimeout;
this.lock = new ReentrantLock();
/* Ensure a value within the range supported by the Deflater class */
this.compressionLevel = Math.max(Deflater.NO_COMPRESSION, Math.min(Deflater.BEST_COMPRESSION, compressionLevel));
initBuffer();
}
@Override
public long mem() {
return this.backend.mem();
}
@Override
public void optimize() {
this.backend.optimize();
}
@Override
public String name() {
return this.backend.name();
}
@Override
public void clear() throws IOException {
this.lock.lock();
try {
initBuffer();
this.backend.clear();
} finally {
this.lock.unlock();
}
}
private void initBuffer() {
this.buffer = new TreeMap<byte[], byte[]>(this.backend.ordering());
this.bufferlength = 0;
}
@Override
public ByteOrder ordering() {
return this.backend.ordering();
}
@Override
public void close(final boolean writeIDX) {
this.lock.lock();
try {
// no more thread is running, flush all queues
flushAll();
this.backend.close(writeIDX);
} finally {
this.lock.unlock();
}
}
private static byte[] compress(final byte[] b, final int compressionLevel) {
final int l = b.length;
if (l < 100) return markWithPlainMagic(b);
final byte[] bb = compressAddMagic(b, compressionLevel);
if (bb.length >= l) return markWithPlainMagic(b);
return bb;
}
private static byte[] compressAddMagic(final byte[] b, final int compressionLevel) {
// compress a byte array and add a leading magic for the compression
try {
//System.out.print("/(" + cdr + ")"); // DEBUG
final ByteArrayOutputStream baos = new ByteArrayOutputStream(b.length / 5);
baos.write(gzipMagic);
final OutputStream os = new GZIPOutputStream(baos, 65536){{def.setLevel(compressionLevel);}};
os.write(b);
os.close();
baos.close();
return baos.toByteArray();
} catch (final IOException e) {
ConcurrentLog.severe("Compressor", "", e);
return null;
}
}
private static byte[] markWithPlainMagic(final byte[] b) {
//System.out.print("+"); // DEBUG
final byte[] r = new byte[b.length + 2];
r[0] = plainMagic[0];
r[1] = plainMagic[1];
System.arraycopy(b, 0, r, 2, b.length);
return r;
}
private static byte[] decompress(final byte[] b) {
// use a magic in the head of the bytes to identify compression type
if (b == null) return null;
if (ByteArray.startsWith(b, gzipMagic)) {
//System.out.print("\\"); // DEBUG
final ByteArrayInputStream bais = new ByteArrayInputStream(b);
// eat up the magic
bais.read();
bais.read();
// decompress what is remaining
InputStream gis;
try {
gis = new GZIPInputStream(bais);
final ByteArrayOutputStream baos = new ByteArrayOutputStream(b.length);
final byte[] buf = new byte[1024 * 4];
int n;
while ((n = gis.read(buf)) > 0) baos.write(buf, 0, n);
gis.close();
bais.close();
baos.close();
return baos.toByteArray();
} catch (final IOException e) {
ConcurrentLog.logException(e);
return null;
}
} else if (ByteArray.startsWith(b, plainMagic)) {
//System.out.print("-"); // DEBUG
final byte[] r = new byte[b.length - 2];
System.arraycopy(b, 2, r, 0, b.length - 2);
return r;
} else {
// we consider that the entry is also plain, but without leading magic
return b;
}
}
@Override
public byte[] get(final byte[] key) throws IOException, SpaceExceededException {
// depending on the source of the result, we additionally do entry compression
// because if a document was read once, we think that it will not be retrieved another time again soon
byte[] b = null;
boolean locked = false;
try {
locked = this.lock.tryLock(this.lockTimeout, TimeUnit.MILLISECONDS);
} catch (InterruptedException ignored) {
/* When interrupted, simply return null */
ConcurrentLog.fine("Compressor", "Interrupted while acquiring a synchronzation lock on get()");
}
if(locked) {
try {
b = this.buffer.remove(key);
if (b != null) {
this.bufferlength = this.bufferlength - b.length;
this.backend.insert(key, compress(b, this.compressionLevel));
return b;
}
} finally {
this.lock.unlock();
}
// return from the backend
b = this.backend.get(key);
if (b == null) return null;
if (!MemoryControl.request(b.length * 2, true)) {
throw new SpaceExceededException(b.length * 2, "decompress needs 2 * " + b.length + " bytes");
}
return decompress(b);
}
ConcurrentLog.fine("Compressor", "Could not acquire a synchronization lock for retrieval within " + this.lockTimeout + " milliseconds");
return b;
}
@Override
public byte[] get(final Object key) {
if (!(key instanceof byte[])) return null;
try {
return get((byte[]) key);
} catch (final IOException e) {
ConcurrentLog.logException(e);
} catch (final SpaceExceededException e) {
ConcurrentLog.logException(e);
}
return null;
}
@Override
public boolean containsKey(final byte[] key) {
this.lock.lock();
try {
return this.buffer.containsKey(key) || this.backend.containsKey(key);
} finally {
this.lock.unlock();
}
}
@Override
public int keylength() {
return this.backend.keylength();
}
@Override
public long length() {
this.lock.lock();
try {
return this.backend.length() + this.bufferlength;
} catch (final IOException e) {
ConcurrentLog.logException(e);
return 0;
} finally {
this.lock.unlock();
}
}
@Override
public long length(final byte[] key) throws IOException {
this.lock.lock();
try {
byte[] b = this.buffer.get(key);
if (b != null) return b.length;
try {
b = this.backend.get(key);
if (b == null) return 0;
b = decompress(b);
return (b == null) ? 0 : b.length;
} catch (final SpaceExceededException e) {
throw new IOException(e.getMessage());
}
} finally {
this.lock.unlock();
}
}
private int removeFromQueues(final byte[] key) {
final byte[] b = this.buffer.remove(key);
if (b != null) return b.length;
return 0;
}
@Override
public void insert(final byte[] key, final byte[] b) throws IOException {
boolean locked = false;
try {
locked = this.lock.tryLock(this.lockTimeout, TimeUnit.MILLISECONDS);
} catch (InterruptedException ignored) {
/* When interrupted, simply nothing is inserted */
ConcurrentLog.fine("Compressor", "Interrupted while acquiring a synchronzation lock on insert()");
}
if(locked) {
try {
// first ensure that the files do not exist anywhere
delete(key);
// check if the buffer is full or could be full after this write
if (this.bufferlength + b.length * 2 > this.maxbufferlength) {
// in case that we compress, just compress as much as is necessary to get enough room
while (this.bufferlength + b.length * 2 > this.maxbufferlength) {
if (this.buffer.isEmpty()) break;
flushOne();
}
// in case that this was not enough, just flush all
if (this.bufferlength + b.length * 2 > this.maxbufferlength) flushAll();
}
// files are written uncompressed to the uncompressed-queue
// they are either written uncompressed to the database
// or compressed later
this.buffer.put(key, b);
this.bufferlength += b.length;
} finally {
this.lock.unlock();
}
if (MemoryControl.shortStatus()) {
flushAll();
}
} else {
ConcurrentLog.fine("Compressor", "Could not acquire a synchronization lock for insertion within " + this.lockTimeout + " milliseconds");
}
}
@Override
public void delete(final byte[] key) throws IOException {
this.lock.lock();
try {
this.backend.delete(key);
final long rx = removeFromQueues(key);
if (rx > 0) this.bufferlength -= rx;
} finally {
this.lock.unlock();
}
}
@Override
public int size() {
this.lock.lock();
try {
return this.backend.size() + this.buffer.size();
} finally {
this.lock.unlock();
}
}
@Override
public boolean isEmpty() {
this.lock.lock();
try {
if (!this.backend.isEmpty()) return false;
if (!this.buffer.isEmpty()) return false;
return true;
} finally {
this.lock.unlock();
}
}
@Override
public CloneableIterator<byte[]> keys(final boolean up, final boolean rotating) throws IOException {
this.lock.lock();
try {
flushAll();
return this.backend.keys(up, rotating);
} finally {
this.lock.unlock();
}
}
@Override
public CloneableIterator<byte[]> keys(final boolean up, final byte[] firstKey) throws IOException {
this.lock.lock();
try {
flushAll();
return this.backend.keys(up, firstKey);
} finally {
this.lock.unlock();
}
}
@Override
public Iterator<byte[]> iterator() {
flushAll();
try {
return this.backend.keys(true, false);
} catch (final IOException e) {
return null;
}
}
private boolean flushOne() {
if (this.buffer.isEmpty()) return false;
// depending on process case, write it to the file or compress it to the other queue
final Map.Entry<byte[], byte[]> entry = this.buffer.entrySet().iterator().next();
this.buffer.remove(entry.getKey());
try {
this.backend.insert(entry.getKey(), compress(entry.getValue(), this.compressionLevel));
this.bufferlength -= entry.getValue().length;
return true;
} catch (final IOException e) {
this.buffer.put(entry.getKey(), entry.getValue());
return false;
}
}
public void flushAll() {
this.lock.lock();
try {
while (!this.buffer.isEmpty()) {
if (!flushOne()) {
break;
}
}
} finally {
this.lock.unlock();
}
}
@Override
public int replace(final byte[] key, final Rewriter rewriter) throws IOException, SpaceExceededException {
final byte[] b = get(key);
if (b == null) return 0;
final byte[] c = rewriter.rewrite(b);
final int reduction = c.length - b.length;
assert reduction >= 0;
if (reduction == 0) return 0;
insert(key, c);
return reduction;
}
@Override
public int reduce(final byte[] key, final Reducer reducer) throws IOException, SpaceExceededException {
final byte[] b = get(key);
if (b == null) return 0;
final byte[] c = reducer.rewrite(b);
final int reduction = c.length - b.length;
assert reduction >= 0;
if (reduction == 0) return 0;
insert(key, c);
return reduction;
}
/**
* Set the new content compression level.
* @param compressionLevel the new compression level. Supported values between 0 (no compression) and 9 (best compression).
*/
public void setCompressionLevel(final int compressionLevel) {
/* Ensure a value within the range supported by the Deflater class */
this.compressionLevel = Math.max(Deflater.NO_COMPRESSION, Math.min(Deflater.BEST_COMPRESSION, compressionLevel));
}
/**
* Set the new synchronization lock timeout.
* @param lockTimeout the new synchronization lock timeout (in milliseconds).
*/
public void setLockTimeout(final long lockTimeout) {
this.lockTimeout = lockTimeout;
}
}