Java tutorial
/* * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.util.zip; import java.io.FilterInputStream; import java.io.InputStream; import java.io.IOException; import java.io.EOFException; /** * This class implements a stream filter for uncompressing data in the * "deflate" compression format. It is also used as the basis for other * decompression filters, such as GZIPInputStream. * * @see Inflater * @author David Connelly * @since 1.1 */ public class InflaterInputStream extends FilterInputStream { /** * Decompressor for this stream. */ protected Inflater inf; /** * Input buffer for decompression. */ protected byte[] buf; /** * Length of input buffer. */ protected int len; private boolean closed = false; // this flag is set to true after EOF has reached private boolean reachEOF = false; /** * Check to make sure that this stream has not been closed */ private void ensureOpen() throws IOException { if (closed) { throw new IOException("Stream closed"); } } /** * Creates a new input stream with the specified decompressor and * buffer size. * @param in the input stream * @param inf the decompressor ("inflater") * @param size the input buffer size * @exception IllegalArgumentException if {@code size <= 0} */ public InflaterInputStream(InputStream in, Inflater inf, int size) { super(in); if (in == null || inf == null) { throw new NullPointerException(); } else if (size <= 0) { throw new IllegalArgumentException("buffer size <= 0"); } this.inf = inf; buf = new byte[size]; } /** * Creates a new input stream with the specified decompressor and a * default buffer size. * @param in the input stream * @param inf the decompressor ("inflater") */ public InflaterInputStream(InputStream in, Inflater inf) { this(in, inf, 512); } boolean usesDefaultInflater = false; /** * Creates a new input stream with a default decompressor and buffer size. * @param in the input stream */ public InflaterInputStream(InputStream in) { this(in, new Inflater()); usesDefaultInflater = true; } private byte[] singleByteBuf = new byte[1]; /** * Reads a byte of uncompressed data. This method will block until * enough input is available for decompression. * @return the byte read, or -1 if end of compressed input is reached * @exception IOException if an I/O error has occurred */ public int read() throws IOException { ensureOpen(); return read(singleByteBuf, 0, 1) == -1 ? -1 : Byte.toUnsignedInt(singleByteBuf[0]); } /** * Reads uncompressed data into an array of bytes. If <code>len</code> is not * zero, the method will block until some input can be decompressed; otherwise, * no bytes are read and <code>0</code> is returned. * @param b the buffer into which the data is read * @param off the start offset in the destination array <code>b</code> * @param len the maximum number of bytes read * @return the actual number of bytes read, or -1 if the end of the * compressed input is reached or a preset dictionary is needed * @exception NullPointerException If <code>b</code> is <code>null</code>. * @exception IndexOutOfBoundsException If <code>off</code> is negative, * <code>len</code> is negative, or <code>len</code> is greater than * <code>b.length - off</code> * @exception ZipException if a ZIP format error has occurred * @exception IOException if an I/O error has occurred */ public int read(byte[] b, int off, int len) throws IOException { ensureOpen(); if (b == null) { throw new NullPointerException(); } else if (off < 0 || len < 0 || len > b.length - off) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return 0; } try { int n; while ((n = inf.inflate(b, off, len)) == 0) { if (inf.finished() || inf.needsDictionary()) { reachEOF = true; return -1; } if (inf.needsInput()) { fill(); } } return n; } catch (DataFormatException e) { String s = e.getMessage(); throw new ZipException(s != null ? s : "Invalid ZLIB data format"); } } /** * Returns 0 after EOF has been reached, otherwise always return 1. * <p> * Programs should not count on this method to return the actual number * of bytes that could be read without blocking. * * @return 1 before EOF and 0 after EOF. * @exception IOException if an I/O error occurs. * */ public int available() throws IOException { ensureOpen(); if (reachEOF) { return 0; } else if (inf.finished()) { // the end of the compressed data stream has been reached reachEOF = true; return 0; } else { return 1; } } private byte[] b = new byte[512]; /** * Skips specified number of bytes of uncompressed data. * @param n the number of bytes to skip * @return the actual number of bytes skipped. * @exception IOException if an I/O error has occurred * @exception IllegalArgumentException if {@code n < 0} */ public long skip(long n) throws IOException { if (n < 0) { throw new IllegalArgumentException("negative skip length"); } ensureOpen(); int max = (int) Math.min(n, Integer.MAX_VALUE); int total = 0; while (total < max) { int len = max - total; if (len > b.length) { len = b.length; } len = read(b, 0, len); if (len == -1) { reachEOF = true; break; } total += len; } return total; } /** * Closes this input stream and releases any system resources associated * with the stream. * @exception IOException if an I/O error has occurred */ public void close() throws IOException { if (!closed) { if (usesDefaultInflater) inf.end(); in.close(); closed = true; } } /** * Fills input buffer with more data to decompress. * @exception IOException if an I/O error has occurred */ protected void fill() throws IOException { ensureOpen(); len = in.read(buf, 0, buf.length); if (len == -1) { throw new EOFException("Unexpected end of ZLIB input stream"); } inf.setInput(buf, 0, len); } /** * Tests if this input stream supports the <code>mark</code> and * <code>reset</code> methods. The <code>markSupported</code> * method of <code>InflaterInputStream</code> returns * <code>false</code>. * * @return a <code>boolean</code> indicating if this stream type supports * the <code>mark</code> and <code>reset</code> methods. * @see java.io.InputStream#mark(int) * @see java.io.InputStream#reset() */ public boolean markSupported() { return false; } /** * Marks the current position in this input stream. * * <p> The <code>mark</code> method of <code>InflaterInputStream</code> * does nothing. * * @param readlimit the maximum limit of bytes that can be read before * the mark position becomes invalid. * @see java.io.InputStream#reset() */ public synchronized void mark(int readlimit) { } /** * Repositions this stream to the position at the time the * <code>mark</code> method was last called on this input stream. * * <p> The method <code>reset</code> for class * <code>InflaterInputStream</code> does nothing except throw an * <code>IOException</code>. * * @exception IOException if this method is invoked. * @see java.io.InputStream#mark(int) * @see java.io.IOException */ public synchronized void reset() throws IOException { throw new IOException("mark/reset not supported"); } }