Java tutorial
/* * 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; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import org.apache.hadoop.conf.Configurable; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.io.compress.snappy.SnappyCompressor; import org.apache.hadoop.io.compress.snappy.SnappyDecompressor; import org.apache.hadoop.io.compress.snappy.SnappyDecompressor.SnappyDirectDecompressor; import org.apache.hadoop.fs.CommonConfigurationKeys; import org.apache.hadoop.util.NativeCodeLoader; /** * This class creates snappy compressors/decompressors. */ public class SnappyCodec implements Configurable, CompressionCodec, DirectDecompressionCodec { Configuration conf; /** * Set the configuration to be used by this object. * * @param conf the configuration object. */ @Override public void setConf(Configuration conf) { this.conf = conf; } /** * Return the configuration used by this object. * * @return the configuration object used by this objec. */ @Override public Configuration getConf() { return conf; } /** * Are the native snappy libraries loaded & initialized? */ public static void checkNativeCodeLoaded() { if (!NativeCodeLoader.buildSupportsSnappy()) { throw new RuntimeException("native snappy library not available: " + "this version of libhadoop was built without " + "snappy support."); } if (!NativeCodeLoader.isNativeCodeLoaded()) { throw new RuntimeException("Failed to load libhadoop."); } if (!SnappyCompressor.isNativeCodeLoaded()) { throw new RuntimeException( "native snappy library not available: " + "SnappyCompressor has not been loaded."); } if (!SnappyDecompressor.isNativeCodeLoaded()) { throw new RuntimeException( "native snappy library not available: " + "SnappyDecompressor has not been loaded."); } } public static boolean isNativeCodeLoaded() { return SnappyCompressor.isNativeCodeLoaded() && SnappyDecompressor.isNativeCodeLoaded(); } public static String getLibraryName() { return SnappyCompressor.getLibraryName(); } /** * Create a {@link CompressionOutputStream} that will write to the given * {@link OutputStream}. * * @param out the location for the final output stream * @return a stream the user can write uncompressed data to have it compressed * @throws IOException */ @Override public CompressionOutputStream createOutputStream(OutputStream out) throws IOException { return CompressionCodec.Util.createOutputStreamWithCodecPool(this, conf, out); } /** * Create a {@link CompressionOutputStream} that will write to the given * {@link OutputStream} with the given {@link Compressor}. * * @param out the location for the final output stream * @param compressor compressor to use * @return a stream the user can write uncompressed data to have it compressed * @throws IOException */ @Override public CompressionOutputStream createOutputStream(OutputStream out, Compressor compressor) throws IOException { checkNativeCodeLoaded(); int bufferSize = conf.getInt(CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_KEY, CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_DEFAULT); int compressionOverhead = (bufferSize / 6) + 32; return new BlockCompressorStream(out, compressor, bufferSize, compressionOverhead); } /** * Get the type of {@link Compressor} needed by this {@link CompressionCodec}. * * @return the type of compressor needed by this codec. */ @Override public Class<? extends Compressor> getCompressorType() { checkNativeCodeLoaded(); return SnappyCompressor.class; } /** * Create a new {@link Compressor} for use by this {@link CompressionCodec}. * * @return a new compressor for use by this codec */ @Override public Compressor createCompressor() { checkNativeCodeLoaded(); int bufferSize = conf.getInt(CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_KEY, CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_DEFAULT); return new SnappyCompressor(bufferSize); } /** * Create a {@link CompressionInputStream} that will read from the given * input stream. * * @param in the stream to read compressed bytes from * @return a stream to read uncompressed bytes from * @throws IOException */ @Override public CompressionInputStream createInputStream(InputStream in) throws IOException { return CompressionCodec.Util.createInputStreamWithCodecPool(this, conf, in); } /** * Create a {@link CompressionInputStream} that will read from the given * {@link InputStream} with the given {@link Decompressor}. * * @param in the stream to read compressed bytes from * @param decompressor decompressor to use * @return a stream to read uncompressed bytes from * @throws IOException */ @Override public CompressionInputStream createInputStream(InputStream in, Decompressor decompressor) throws IOException { checkNativeCodeLoaded(); return new BlockDecompressorStream(in, decompressor, conf.getInt(CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_KEY, CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_DEFAULT)); } /** * Get the type of {@link Decompressor} needed by this {@link CompressionCodec}. * * @return the type of decompressor needed by this codec. */ @Override public Class<? extends Decompressor> getDecompressorType() { checkNativeCodeLoaded(); return SnappyDecompressor.class; } /** * Create a new {@link Decompressor} for use by this {@link CompressionCodec}. * * @return a new decompressor for use by this codec */ @Override public Decompressor createDecompressor() { checkNativeCodeLoaded(); int bufferSize = conf.getInt(CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_KEY, CommonConfigurationKeys.IO_COMPRESSION_CODEC_SNAPPY_BUFFERSIZE_DEFAULT); return new SnappyDecompressor(bufferSize); } /** * {@inheritDoc} */ @Override public DirectDecompressor createDirectDecompressor() { return isNativeCodeLoaded() ? new SnappyDirectDecompressor() : null; } /** * Get the default filename extension for this kind of compression. * * @return <code>.snappy</code>. */ @Override public String getDefaultExtension() { return ".snappy"; } }