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.bzip2; import java.io.IOException; import java.nio.Buffer; import java.nio.ByteBuffer; import org.apache.hadoop.io.compress.Decompressor; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * A {@link Decompressor} based on the popular * bzip2 compression algorithm. * http://www.bzip2.org/ * */ public class Bzip2Decompressor implements Decompressor { private static final int DEFAULT_DIRECT_BUFFER_SIZE = 64 * 1024; private static final Log LOG = LogFactory.getLog(Bzip2Decompressor.class); private long stream; private boolean conserveMemory; private int directBufferSize; private Buffer compressedDirectBuf = null; private int compressedDirectBufOff, compressedDirectBufLen; private Buffer uncompressedDirectBuf = null; private byte[] userBuf = null; private int userBufOff = 0, userBufLen = 0; private boolean finished; /** * Creates a new decompressor. */ public Bzip2Decompressor(boolean conserveMemory, int directBufferSize) { this.conserveMemory = conserveMemory; this.directBufferSize = directBufferSize; compressedDirectBuf = ByteBuffer.allocateDirect(directBufferSize); uncompressedDirectBuf = ByteBuffer.allocateDirect(directBufferSize); uncompressedDirectBuf.position(directBufferSize); stream = init(conserveMemory ? 1 : 0); } public Bzip2Decompressor() { this(false, DEFAULT_DIRECT_BUFFER_SIZE); } @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(); } this.userBuf = b; this.userBufOff = off; this.userBufLen = len; setInputFromSavedData(); // Reinitialize bzip2's output direct buffer. uncompressedDirectBuf.limit(directBufferSize); uncompressedDirectBuf.position(directBufferSize); } synchronized void setInputFromSavedData() { compressedDirectBufOff = 0; compressedDirectBufLen = userBufLen; if (compressedDirectBufLen > directBufferSize) { compressedDirectBufLen = directBufferSize; } // Reinitialize bzip2's input direct buffer. compressedDirectBuf.rewind(); ((ByteBuffer) compressedDirectBuf).put(userBuf, userBufOff, compressedDirectBufLen); // Note how much data is being fed to bzip2. userBufOff += compressedDirectBufLen; userBufLen -= compressedDirectBufLen; } @Override public synchronized void setDictionary(byte[] b, int off, int len) { throw new UnsupportedOperationException(); } @Override public synchronized boolean needsInput() { // Consume remaining compressed data? if (uncompressedDirectBuf.remaining() > 0) { return false; } // Check if bzip2 has consumed all input. if (compressedDirectBufLen <= 0) { // Check if we have consumed all user-input. if (userBufLen <= 0) { return true; } else { setInputFromSavedData(); } } return false; } @Override public synchronized boolean needsDictionary() { return false; } @Override public synchronized boolean finished() { // Check if bzip2 says it has finished and // all compressed data has been consumed. return (finished && uncompressedDirectBuf.remaining() == 0); } @Override public synchronized int decompress(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 uncompressed data. int n = uncompressedDirectBuf.remaining(); if (n > 0) { n = Math.min(n, len); ((ByteBuffer) uncompressedDirectBuf).get(b, off, n); return n; } // Re-initialize bzip2's output direct buffer. uncompressedDirectBuf.rewind(); uncompressedDirectBuf.limit(directBufferSize); // Decompress the data. n = finished ? 0 : inflateBytesDirect(); uncompressedDirectBuf.limit(n); // Get at most 'len' bytes. n = Math.min(n, len); ((ByteBuffer) uncompressedDirectBuf).get(b, off, n); return n; } /** * Returns the total number of uncompressed bytes output so far. * * @return the total (non-negative) number of uncompressed bytes output so far */ public synchronized long getBytesWritten() { checkStream(); return getBytesWritten(stream); } /** * Returns the total number of compressed bytes input so far.</p> * * @return the total (non-negative) number of compressed bytes input so far */ public synchronized long getBytesRead() { checkStream(); return getBytesRead(stream); } /** * Returns the number of bytes remaining in the input buffers; normally * called when finished() is true to determine amount of post-gzip-stream * data.</p> * * @return the total (non-negative) number of unprocessed bytes in input */ @Override public synchronized int getRemaining() { checkStream(); return userBufLen + getRemaining(stream); // userBuf + compressedDirectBuf } /** * Resets everything including the input buffers (user and direct).</p> */ @Override public synchronized void reset() { checkStream(); end(stream); stream = init(conserveMemory ? 1 : 0); finished = false; compressedDirectBufOff = compressedDirectBufLen = 0; uncompressedDirectBuf.limit(directBufferSize); uncompressedDirectBuf.position(directBufferSize); userBufOff = userBufLen = 0; } @Override public synchronized void end() { if (stream != 0) { end(stream); stream = 0; } } static void initSymbols(String libname) { initIDs(libname); } private void checkStream() { if (stream == 0) throw new NullPointerException(); } private native static void initIDs(String libname); private native static long init(int conserveMemory); private native int inflateBytesDirect(); private native static long getBytesRead(long strm); private native static long getBytesWritten(long strm); private native static int getRemaining(long strm); private native static void end(long strm); }