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.commons.compress.compressors.pack200; import java.io.File; import java.io.FilterInputStream; import java.io.IOException; import java.io.InputStream; import java.util.Map; import java.util.jar.JarOutputStream; import java.util.jar.Pack200; import org.apache.commons.compress.compressors.CompressorInputStream; /** * An input stream that decompresses from the Pack200 format to be read * as any other stream. * * <p>The {@link CompressorInputStream#getCount getCount} and {@link * CompressorInputStream#getBytesRead getBytesRead} methods always * return 0.</p> * * @NotThreadSafe * @since 1.3 */ public class Pack200CompressorInputStream extends CompressorInputStream { private final InputStream originalInput; private final StreamBridge streamBridge; /** * Decompresses the given stream, caching the decompressed data in * memory. * * <p>When reading from a file the File-arg constructor may * provide better performance.</p> * * @param in the InputStream from which this object should be created * @throws IOException if reading fails */ public Pack200CompressorInputStream(final InputStream in) throws IOException { this(in, Pack200Strategy.IN_MEMORY); } /** * Decompresses the given stream using the given strategy to cache * the results. * * <p>When reading from a file the File-arg constructor may * provide better performance.</p> * * @param in the InputStream from which this object should be created * @param mode the strategy to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final InputStream in, final Pack200Strategy mode) throws IOException { this(in, null, mode, null); } /** * Decompresses the given stream, caching the decompressed data in * memory and using the given properties. * * <p>When reading from a file the File-arg constructor may * provide better performance.</p> * * @param in the InputStream from which this object should be created * @param props Pack200 properties to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final InputStream in, final Map<String, String> props) throws IOException { this(in, Pack200Strategy.IN_MEMORY, props); } /** * Decompresses the given stream using the given strategy to cache * the results and the given properties. * * <p>When reading from a file the File-arg constructor may * provide better performance.</p> * * @param in the InputStream from which this object should be created * @param mode the strategy to use * @param props Pack200 properties to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final InputStream in, final Pack200Strategy mode, final Map<String, String> props) throws IOException { this(in, null, mode, props); } /** * Decompresses the given file, caching the decompressed data in * memory. * * @param f the file to decompress * @throws IOException if reading fails */ public Pack200CompressorInputStream(final File f) throws IOException { this(f, Pack200Strategy.IN_MEMORY); } /** * Decompresses the given file using the given strategy to cache * the results. * * @param f the file to decompress * @param mode the strategy to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final File f, final Pack200Strategy mode) throws IOException { this(null, f, mode, null); } /** * Decompresses the given file, caching the decompressed data in * memory and using the given properties. * * @param f the file to decompress * @param props Pack200 properties to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final File f, final Map<String, String> props) throws IOException { this(f, Pack200Strategy.IN_MEMORY, props); } /** * Decompresses the given file using the given strategy to cache * the results and the given properties. * * @param f the file to decompress * @param mode the strategy to use * @param props Pack200 properties to use * @throws IOException if reading fails */ public Pack200CompressorInputStream(final File f, final Pack200Strategy mode, final Map<String, String> props) throws IOException { this(null, f, mode, props); } private Pack200CompressorInputStream(final InputStream in, final File f, final Pack200Strategy mode, final Map<String, String> props) throws IOException { originalInput = in; streamBridge = mode.newStreamBridge(); try (final JarOutputStream jarOut = new JarOutputStream(streamBridge)) { final Pack200.Unpacker u = Pack200.newUnpacker(); if (props != null) { u.properties().putAll(props); } if (f == null) { u.unpack(new FilterInputStream(in) { @Override public void close() { // unpack would close this stream but we // want to give the user code more control } }, jarOut); } else { u.unpack(f, jarOut); } } } @Override public int read() throws IOException { return streamBridge.getInput().read(); } @Override public int read(final byte[] b) throws IOException { return streamBridge.getInput().read(b); } @Override public int read(final byte[] b, final int off, final int count) throws IOException { return streamBridge.getInput().read(b, off, count); } @Override public int available() throws IOException { return streamBridge.getInput().available(); } @Override public boolean markSupported() { try { return streamBridge.getInput().markSupported(); } catch (final IOException ex) { return false; } } @Override public void mark(final int limit) { try { streamBridge.getInput().mark(limit); } catch (final IOException ex) { throw new RuntimeException(ex); //NOSONAR } } @Override public void reset() throws IOException { streamBridge.getInput().reset(); } @Override public long skip(final long count) throws IOException { return streamBridge.getInput().skip(count); } @Override public void close() throws IOException { try { streamBridge.stop(); } finally { if (originalInput != null) { originalInput.close(); } } } private static final byte[] CAFE_DOOD = new byte[] { (byte) 0xCA, (byte) 0xFE, (byte) 0xD0, (byte) 0x0D }; private static final int SIG_LENGTH = CAFE_DOOD.length; /** * Checks if the signature matches what is expected for a pack200 * file (0xCAFED00D). * * @param signature * the bytes to check * @param length * the number of bytes to check * @return true, if this stream is a pack200 compressed stream, * false otherwise */ public static boolean matches(final byte[] signature, final int length) { if (length < SIG_LENGTH) { return false; } for (int i = 0; i < SIG_LENGTH; i++) { if (signature[i] != CAFE_DOOD[i]) { return false; } } return true; } }