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A Minecraft Bedrock Edition server software implementation made in Java from scratch which supports all new features.
package cn.nukkit.nbt.stream;
import cn.nukkit.api.PowerNukkitOnly;
import cn.nukkit.api.Since;
import it.unimi.dsi.fastutil.ints.IntArrayList;
import it.unimi.dsi.fastutil.ints.IntList;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.concurrent.*;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
/**
* A multi-threaded version of {@link java.util.zip.GZIPOutputStream}.
*
* @author shevek
*/
public class PGZIPOutputStream extends FilterOutputStream {
private static final ExecutorService EXECUTOR = Executors.newCachedThreadPool();
public static ExecutorService getSharedThreadPool() {
return EXECUTOR;
}
// private static final Logger LOG = LoggerFactory.getLogger(PGZIPOutputStream.class);
private final static int GZIP_MAGIC = 0x8b1f;
// todo: remove after block guessing is implemented
// array list that contains the block sizes
private IntList blockSizes = new IntArrayList();
private int level = Deflater.BEST_SPEED;
private int strategy = Deflater.DEFAULT_STRATEGY;
protected Deflater newDeflater() {
Deflater def = new Deflater(level, true);
def.setStrategy(strategy);
return def;
}
public void setStrategy(int strategy) {
this.strategy = strategy;
}
public void setLevel(int level) {
this.level = level;
}
protected static DeflaterOutputStream newDeflaterOutputStream(OutputStream out, Deflater deflater) {
return new DeflaterOutputStream(out, deflater, 512, true);
}
// TODO: Share, daemonize.
private final ExecutorService executor;
private final int nthreads;
private final CRC32 crc = new CRC32();
private final BlockingQueue> emitQueue;
private PGZIPBlock block = new PGZIPBlock(this/* 0 */);
/**
* Used as a sentinel for 'closed'.
*/
private int bytesWritten = 0;
// Master thread only
public PGZIPOutputStream(OutputStream out, ExecutorService executor, int nthreads) throws IOException {
super(out);
this.executor = executor;
this.nthreads = nthreads;
this.emitQueue = new ArrayBlockingQueue>(nthreads);
writeHeader();
}
/**
* Creates a PGZIPOutputStream
* using {@link PGZIPOutputStream#getSharedThreadPool()}.
*
* @param out the eventual output stream for the compressed data.
* @throws java.io.IOException if it all goes wrong.
*/
public PGZIPOutputStream(OutputStream out, int nthreads) throws IOException {
this(out, PGZIPOutputStream.getSharedThreadPool(), nthreads);
}
/**
* Creates a PGZIPOutputStream
* using {@link PGZIPOutputStream#getSharedThreadPool()}
* and {@link Runtime#availableProcessors()}.
*
* @param out the eventual output stream for the compressed data.
* @throws java.io.IOException if it all goes wrong.
*/
public PGZIPOutputStream(OutputStream out) throws IOException {
this(out, Runtime.getRuntime().availableProcessors());
}
/*
* @see http://www.gzip.org/zlib/rfc-gzip.html#file-format
*/
private void writeHeader() throws IOException {
out.write(new byte[]{
(byte) GZIP_MAGIC, // ID1: Magic number (little-endian short)
(byte) (GZIP_MAGIC >> 8), // ID2: Magic number (little-endian short)
Deflater.DEFLATED, // CM: Compression method
0, // FLG: Flags (byte)
0, 0, 0, 0, // MTIME: Modification time (int)
0, // XFL: Extra flags
3 // OS: Operating system (3 = Linux)
});
}
// Master thread only
@Override
public void write(int b) throws IOException {
byte[] single = new byte[1];
single[0] = (byte) (b & 0xFF);
write(single);
}
// Master thread only
@Override
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
// Master thread only
@Override
public void write(byte[] b, int off, int len) throws IOException {
crc.update(b, off, len);
bytesWritten += len;
while (len > 0) {
// assert block.in_length < block.in.length
int capacity = block.in.length - block.in_length;
if (len >= capacity) {
System.arraycopy(b, off, block.in, block.in_length, capacity);
block.in_length += capacity; // == block.in.length
off += capacity;
len -= capacity;
submit();
} else {
System.arraycopy(b, off, block.in, block.in_length, len);
block.in_length += len;
// off += len;
// len = 0;
break;
}
}
}
// Master thread only
private void submit() throws IOException {
emitUntil(nthreads - 1);
emitQueue.add(executor.submit(block));
block = new PGZIPBlock(this/* block.index + 1 */);
}
// Emit If Available - submit always
// Emit At Least one - submit when executor is full
// Emit All Remaining - flush(), close()
// Master thread only
private void tryEmit() throws IOException, InterruptedException, ExecutionException {
for (; ; ) {
Future future = emitQueue.peek();
// LOG.info("Peeked future " + future);
if (future == null)
return;
if (!future.isDone())
return;
// It's an ordered queue. This MUST be the same element as above.
emitQueue.remove();
byte[] toWrite = future.get();
blockSizes.add(toWrite.length); // todo: remove after block guessing is implemented
out.write(toWrite);
}
}
// Master thread only
/**
* Emits any opportunistically available blocks. Furthermore, emits blocks until the number of executing tasks is less than taskCountAllowed.
*/
private void emitUntil(int taskCountAllowed) throws IOException {
try {
while (emitQueue.size() > taskCountAllowed) {
// LOG.info("Waiting for taskCount=" + emitQueue.size() + " -> " + taskCountAllowed);
Future future = emitQueue.remove(); // Valid because emitQueue.size() > 0
byte[] toWrite = future.get(); // Blocks until this task is done.
blockSizes.add(toWrite.length); // todo: remove after block guessing is implemented
out.write(toWrite);
}
// We may have achieved more opportunistically available blocks
// while waiting for a block above. Let's emit them here.
tryEmit();
} catch (ExecutionException e) {
throw new IOException(e);
} catch (InterruptedException e) {
throw new InterruptedIOException();
}
}
// Master thread only
@Override
public void flush() throws IOException {
// LOG.info("Flush: " + block);
if (block.in_length > 0)
submit();
emitUntil(0);
super.flush();
}
@PowerNukkitOnly
@Since("1.4.0.0-PN")
public void finish() throws IOException {
if (bytesWritten >= 0) {
flush();
newDeflaterOutputStream(out, newDeflater()).finish();
ByteBuffer buf = ByteBuffer.allocate(8);
buf.order(ByteOrder.LITTLE_ENDIAN);
// LOG.info("CRC is " + crc.getValue());
buf.putInt((int) crc.getValue());
buf.putInt(bytesWritten);
out.write(buf.array()); // allocate() guarantees a backing array.
// LOG.info("trailer is " + Arrays.toString(buf.array()));
}
}
// Master thread only
@Override
public void close() throws IOException {
// LOG.info("Closing: bytesWritten=" + bytesWritten);
if (bytesWritten >= 0) {
finish();
out.flush();
out.close();
bytesWritten = Integer.MIN_VALUE;
// } else {
// LOG.warn("Already closed.");
}
}
}