org.apache.hadoop.io.compress.snappy.SnappyCompressor Maven / Gradle / Ivy
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* 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.hadoop.io.compress.snappy;
import java.io.IOException;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.compress.Compressor;
import org.apache.hadoop.util.NativeCodeLoader;
/**
* A {@link Compressor} based on the snappy compression algorithm.
* http://code.google.com/p/snappy/
*/
public class SnappyCompressor implements Compressor {
private static final Log LOG =
LogFactory.getLog(SnappyCompressor.class.getName());
private static final int DEFAULT_DIRECT_BUFFER_SIZE = 64 * 1024;
// HACK - Use this as a global lock in the JNI layer
@SuppressWarnings({"unchecked", "unused"})
private static Class clazz = SnappyCompressor.class;
private int directBufferSize;
private Buffer compressedDirectBuf = null;
private int uncompressedDirectBufLen;
private Buffer uncompressedDirectBuf = null;
private byte[] userBuf = null;
private int userBufOff = 0, userBufLen = 0;
private boolean finish, finished;
private long bytesRead = 0L;
private long bytesWritten = 0L;
private static boolean nativeSnappyLoaded = false;
static {
if (NativeCodeLoader.isNativeCodeLoaded() &&
NativeCodeLoader.buildSupportsSnappy()) {
try {
initIDs();
nativeSnappyLoaded = true;
} catch (Throwable t) {
LOG.error("failed to load SnappyCompressor", t);
}
}
}
public static boolean isNativeCodeLoaded() {
return nativeSnappyLoaded;
}
/**
* Creates a new compressor.
*
* @param directBufferSize size of the direct buffer to be used.
*/
public SnappyCompressor(int directBufferSize) {
this.directBufferSize = directBufferSize;
uncompressedDirectBuf = ByteBuffer.allocateDirect(directBufferSize);
compressedDirectBuf = ByteBuffer.allocateDirect(directBufferSize);
compressedDirectBuf.position(directBufferSize);
}
/**
* Creates a new compressor with the default buffer size.
*/
public SnappyCompressor() {
this(DEFAULT_DIRECT_BUFFER_SIZE);
}
/**
* Sets input data for compression.
* This should be called whenever #needsInput() returns
* true indicating that more input data is required.
*
* @param b Input data
* @param off Start offset
* @param len Length
*/
@Override
public synchronized void setInput(byte[] b, int off, int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
finished = false;
if (len > uncompressedDirectBuf.remaining()) {
// save data; now !needsInput
this.userBuf = b;
this.userBufOff = off;
this.userBufLen = len;
} else {
((ByteBuffer) uncompressedDirectBuf).put(b, off, len);
uncompressedDirectBufLen = uncompressedDirectBuf.position();
}
bytesRead += len;
}
/**
* If a write would exceed the capacity of the direct buffers, it is set
* aside to be loaded by this function while the compressed data are
* consumed.
*/
synchronized void setInputFromSavedData() {
if (0 >= userBufLen) {
return;
}
finished = false;
uncompressedDirectBufLen = Math.min(userBufLen, directBufferSize);
((ByteBuffer) uncompressedDirectBuf).put(userBuf, userBufOff,
uncompressedDirectBufLen);
// Note how much data is being fed to snappy
userBufOff += uncompressedDirectBufLen;
userBufLen -= uncompressedDirectBufLen;
}
/**
* Does nothing.
*/
@Override
public synchronized void setDictionary(byte[] b, int off, int len) {
// do nothing
}
/**
* Returns true if the input data buffer is empty and
* #setInput() should be called to provide more input.
*
* @return true if the input data buffer is empty and
* #setInput() should be called in order to provide more input.
*/
@Override
public synchronized boolean needsInput() {
return !(compressedDirectBuf.remaining() > 0
|| uncompressedDirectBuf.remaining() == 0 || userBufLen > 0);
}
/**
* When called, indicates that compression should end
* with the current contents of the input buffer.
*/
@Override
public synchronized void finish() {
finish = true;
}
/**
* Returns true if the end of the compressed
* data output stream has been reached.
*
* @return true if the end of the compressed
* data output stream has been reached.
*/
@Override
public synchronized boolean finished() {
// Check if all uncompressed data has been consumed
return (finish && finished && compressedDirectBuf.remaining() == 0);
}
/**
* Fills specified buffer with compressed data. Returns actual number
* of bytes of compressed data. A return value of 0 indicates that
* needsInput() should be called in order to determine if more input
* data is required.
*
* @param b Buffer for the compressed data
* @param off Start offset of the data
* @param len Size of the buffer
* @return The actual number of bytes of compressed data.
*/
@Override
public synchronized int compress(byte[] b, int off, int len)
throws IOException {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
// Check if there is compressed data
int n = compressedDirectBuf.remaining();
if (n > 0) {
n = Math.min(n, len);
((ByteBuffer) compressedDirectBuf).get(b, off, n);
bytesWritten += n;
return n;
}
// Re-initialize the snappy's output direct-buffer
compressedDirectBuf.clear();
compressedDirectBuf.limit(0);
if (0 == uncompressedDirectBuf.position()) {
// No compressed data, so we should have !needsInput or !finished
setInputFromSavedData();
if (0 == uncompressedDirectBuf.position()) {
// Called without data; write nothing
finished = true;
return 0;
}
}
// Compress data
n = compressBytesDirect();
compressedDirectBuf.limit(n);
uncompressedDirectBuf.clear(); // snappy consumes all buffer input
// Set 'finished' if snapy has consumed all user-data
if (0 == userBufLen) {
finished = true;
}
// Get atmost 'len' bytes
n = Math.min(n, len);
bytesWritten += n;
((ByteBuffer) compressedDirectBuf).get(b, off, n);
return n;
}
/**
* Resets compressor so that a new set of input data can be processed.
*/
@Override
public synchronized void reset() {
finish = false;
finished = false;
uncompressedDirectBuf.clear();
uncompressedDirectBufLen = 0;
compressedDirectBuf.clear();
compressedDirectBuf.limit(0);
userBufOff = userBufLen = 0;
bytesRead = bytesWritten = 0L;
}
/**
* Prepare the compressor to be used in a new stream with settings defined in
* the given Configuration
*
* @param conf Configuration from which new setting are fetched
*/
@Override
public synchronized void reinit(Configuration conf) {
reset();
}
/**
* Return number of bytes given to this compressor since last reset.
*/
@Override
public synchronized long getBytesRead() {
return bytesRead;
}
/**
* Return number of bytes consumed by callers of compress since last reset.
*/
@Override
public synchronized long getBytesWritten() {
return bytesWritten;
}
/**
* Closes the compressor and discards any unprocessed input.
*/
@Override
public synchronized void end() {
}
private native static void initIDs();
private native int compressBytesDirect();
}