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package de.lmu.ifi.dbs.elki.datasource.bundle;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2012
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.WritableByteChannel;
import de.lmu.ifi.dbs.elki.data.type.SimpleTypeInformation;
import de.lmu.ifi.dbs.elki.data.type.TypeInformationSerializer;
import de.lmu.ifi.dbs.elki.logging.Logging;
import de.lmu.ifi.dbs.elki.persistent.ByteBufferSerializer;
import de.lmu.ifi.dbs.elki.utilities.exceptions.AbortException;
/**
* Write an object bundle stream to a file channel.
*
* Bundle streams that add new columns are not supported.
*
* @author Erich Schubert
*
* @apiviz.uses BundleStreamSource
* @apiviz.uses WritableByteChannel
*/
public class BundleWriter {
/**
* Class logger for the bundle writer.
*/
private static final Logging LOG = Logging.getLogger(BundleWriter.class);
/**
* Initial buffer size.
*/
private static final int INITIAL_BUFFER = 4096;
/**
* Random magic number.
*/
public static final int MAGIC = 0xa8123b12;
/**
* Write a bundle stream to a file output channel.
*
* @param source Data source
* @param output Output channel
* @throws IOException on IO errors
*/
public void writeBundleStream(BundleStreamSource source, WritableByteChannel output) throws IOException {
ByteBuffer buffer = ByteBuffer.allocateDirect(INITIAL_BUFFER);
ByteBufferSerializer<Object>[] serializers = null;
loop: while (true) {
BundleStreamSource.Event ev = source.nextEvent();
switch(ev) {
case NEXT_OBJECT:
if (serializers == null) {
serializers = writeHeader(source, buffer, output);
}
for (int i = 0; i < serializers.length; i++) {
int size = serializers[i].getByteSize(source.data(i));
buffer = ensureBuffer(size, buffer, output);
serializers[i].toByteBuffer(buffer, source.data(i));
}
break; // switch
case META_CHANGED:
if (serializers != null) {
throw new AbortException("Meta changes are not supported, once the block header has been written.");
}
break; // switch
case END_OF_STREAM:
break loop;
default:
LOG.warning("Unknown bundle stream event. API inconsistent? " + ev);
break; // switch
}
}
if (buffer.position() > 0) {
flushBuffer(buffer, output);
}
}
/**
* Flush the current write buffer to disk.
*
* @param buffer Buffer to write
* @param output Output channel
* @throws IOException on IO errors
*/
private void flushBuffer(ByteBuffer buffer, WritableByteChannel output) throws IOException {
buffer.flip();
output.write(buffer);
buffer.flip();
buffer.limit(buffer.capacity());
}
/**
* Ensure the buffer is large enough.
*
* @param size Required size to add
* @param buffer Existing buffer
* @param output Output channel
* @return Buffer, eventually resized
* @throws IOException on IO errors
*/
private ByteBuffer ensureBuffer(int size, ByteBuffer buffer, WritableByteChannel output) throws IOException {
if (buffer.remaining() >= size) {
return buffer;
}
flushBuffer(buffer, output);
if (buffer.remaining() >= size) {
return buffer;
}
// Aggressively grow the buffer
return ByteBuffer.allocateDirect(Math.max(buffer.capacity() << 1, buffer.capacity() + size));
}
/**
* Write the header for the given stream to the stream.
*
* @param source Bundle stream
* @param buffer Buffer to use for writing
* @param output Output channel
* @return Array of serializers
* @throws IOException on IO errors
*/
@SuppressWarnings("unchecked")
private ByteBufferSerializer<Object>[] writeHeader(BundleStreamSource source, ByteBuffer buffer, WritableByteChannel output) throws IOException {
final BundleMeta meta = source.getMeta();
final int nummeta = meta.size();
@SuppressWarnings("rawtypes")
final ByteBufferSerializer[] serializers = new ByteBufferSerializer[nummeta];
// Write our magic ID first.
assert (buffer.position() == 0) : "Buffer is supposed to be at 0.";
buffer.putInt(MAGIC);
// Write the number of metas next
buffer.putInt(nummeta);
for (int i = 0; i < nummeta; i++) {
SimpleTypeInformation<?> type = meta.get(i);
ByteBufferSerializer<Object> ser = (ByteBufferSerializer<Object>) type.getSerializer();
if (ser == null) {
throw new AbortException("Cannot serialize - no serializer found for type: " + type.toString());
}
TypeInformationSerializer.STATIC.toByteBuffer(buffer, type);
serializers[i] = ser;
}
return serializers;
}
}
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