/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
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; version 2 of the License.
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
*/
/*
* Created on Jun 29, 2012
*/
package com.bigdata.rdf.internal.encoder;
import java.io.DataInputStream;
import java.io.IOException;
import java.util.NoSuchElementException;
import org.apache.log4j.Logger;
import com.bigdata.bop.IBindingSet;
import com.bigdata.io.DataInputBuffer;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Stream decoder for solution sets (chunk oriented).
*
* @see SolutionSetStreamEncoder
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public class SolutionSetStreamDecoder implements
ICloseableIterator<IBindingSet[]> {
private static final Logger log = Logger
.getLogger(SolutionSetStreamDecoder.class);
/** The name of the solution set (optional). */
private final String name;
private final long solutionSetCount;
private final DataInputStream in;
private final IVSolutionSetDecoder decoder;
private boolean open = false;
/** The next chunk of solutions to be visited. */
private IBindingSet[] bsets = null;
/** The #of solution sets which have been decoded so far. */
private long nsolutions = 0;
/**
*
* @param name
* The name of the solution set.
* @param in
* The solutions are read from this stream.
* @param solutionSetCount
* The #of solutions to be read from the stream.
* @throws IOException
*/
public SolutionSetStreamDecoder(final String name,
final DataInputStream in, final long solutionSetCount) {
if (in == null)
throw new IllegalArgumentException();
if (solutionSetCount < 0)
throw new IllegalArgumentException();
this.name = name;
this.solutionSetCount = solutionSetCount;
this.in = in;
this.open = true;
this.decoder = new IVSolutionSetDecoder();
}
@Override
public void close() {
if (open) {
open = false;
try {
in.close();
} catch (IOException e) {
// Unexpected exception.
log.error(e, e);
}
}
}
@Override
public boolean hasNext() {
if (open && bsets == null) {
/*
* Read ahead and extract a chunk of solutions.
*/
try {
if ((bsets = decodeNextChunk()) == null) {
// Nothing more to be read.
close();
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
return open && bsets != null;
}
/**
* Read ahead and decode the next chunk of solutions.
*
* @return The decoded solutions.
*/
private IBindingSet[] decodeNextChunk() throws IOException {
if (nsolutions == solutionSetCount) {
// Nothing more to be read.
if (log.isDebugEnabled())
log.debug("Read solutionSet: name=" + name
+ ", solutionSetSize=" + nsolutions);
return null;
}
// The version# for this chunk.
// final int version =
in.readInt(); // version
// #of solutions in this chunk.
final int chunkSize = in.readInt();
// #of bytes in this chunk.
final int byteLength = in.readInt();
// Read in all the bytes in the next chunk.
final byte[] a = new byte[byteLength];
// read data
in.readFully(a);
// Wrap byte[] as stream.
final DataInputBuffer buf = new DataInputBuffer(a);
// Allocate array for the decoded solutions.
final IBindingSet[] t = new IBindingSet[chunkSize];
// Decode the solutions into the array.
for (int i = 0; i < chunkSize; i++) {
t[i] = decoder.decodeSolution(buf, true/* resolveCachedValues */);
if (log.isTraceEnabled())
log.trace("Read: name=" + name + ", solution=" + t[i]);
}
// Update the #of solution sets which have been decoded.
nsolutions += chunkSize;
if (log.isTraceEnabled())
log.trace("Read chunk: name=" + name + ", chunkSize=" + chunkSize
+ ", bytesRead="
+ (SolutionSetStreamEncoder.CHUNK_HEADER_SIZE + byteLength)
+ ", solutionSetSize=" + nsolutions);
// Return the decoded solutions.
return t;
}
@Override
public IBindingSet[] next() {
if (!hasNext())
throw new NoSuchElementException();
final IBindingSet[] t = bsets;
bsets = null;
return t;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}