org.apache.solr.common.util.ZLibCompressor Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.solr.common.util;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.zip.Deflater;
import java.util.zip.Inflater;
public class ZLibCompressor implements Compressor {
private static final byte[] ZLIB_MAGIC = new byte[] {0x78, 0x1};
private static final int COMPRESSED_SIZE_MAGIC_NUMBER = 2018370979;
/**
* {@inheritDoc}
*
* Uses the hex magic number for zlib compression '78 01' to check if the bytes are compressed
*/
@Override
public boolean isCompressedBytes(byte[] data) {
if (data == null || data.length < 2) return false;
return ZLIB_MAGIC[0] == data[0] && ZLIB_MAGIC[1] == data[1];
}
@Override
public byte[] decompressBytes(byte[] data) throws Exception {
if (data == null) return null;
Inflater inflater = new Inflater();
try {
inflater.setInput(data, 0, data.length);
// Attempt to get the decompressed size from trailing bytes, this will be present if
// compressed by Solr
ByteBuffer bb = ByteBuffer.wrap(data, data.length - 8, 8);
int decompressedSize = bb.getInt();
int xoredSize = bb.getInt();
if ((decompressedSize ^ COMPRESSED_SIZE_MAGIC_NUMBER) != xoredSize) {
// Take best guess of decompressed size since it wasn't included in trailing bytes, assume a
// 5:1 ratio
decompressedSize = 5 * data.length;
}
byte[] buf = new byte[decompressedSize];
int actualDecompressedSize = 0;
while (!inflater.finished()) {
if (actualDecompressedSize >= buf.length) {
buf = Arrays.copyOf(buf, (int) (buf.length * 1.5));
}
actualDecompressedSize += inflater.inflate(buf, actualDecompressedSize, decompressedSize);
}
if (buf.length != actualDecompressedSize) {
buf = Arrays.copyOf(buf, actualDecompressedSize);
}
return buf;
} finally {
inflater.end();
}
}
@Override
public byte[] compressBytes(byte[] data) {
// By default, the compression ratio is assumed to be 5:1 to set the initial capacity of the
// compression buffer.
return compressBytes(data, data.length / 5);
}
@Override
public byte[] compressBytes(byte[] data, int initialBufferCapacity) {
Deflater compressor = new Deflater(Deflater.BEST_SPEED);
try {
compressor.setInput(data);
compressor.finish();
byte[] buf = new byte[Math.max(initialBufferCapacity, 16)];
int compressedSize = 0;
while (!compressor.finished()) {
if (compressedSize >= buf.length) {
buf = Arrays.copyOf(buf, (int) (buf.length * 1.5));
}
compressedSize += compressor.deflate(buf, compressedSize, buf.length - compressedSize);
}
buf = Arrays.copyOf(buf, compressedSize + 8);
// Include the decompressed size and xored decompressed size in trailing bytes, this makes
// decompression
// efficient while also being compatible with alternative zlib implementations
ByteBuffer.wrap(buf, compressedSize, 8)
.putInt(data.length)
.putInt(data.length ^ COMPRESSED_SIZE_MAGIC_NUMBER);
return buf;
} finally {
compressor.end();
}
}
}