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/* * 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.OutputStream; import java.io.IOException; /** * This class implements a stream filter for writing compressed data in * the GZIP file format. * @author David Connelly * @since 1.1 * */ public class GZIPOutputStream extends DeflaterOutputStream { /** * CRC-32 of uncompressed data. */ protected CRC32 crc = new CRC32(); /* * GZIP header magic number. */ private static final int GZIP_MAGIC = 0x8b1f; /* * Trailer size in bytes. * */ private static final int TRAILER_SIZE = 8; /** * Creates a new output stream with the specified buffer size. * * <p>The new output stream instance is created as if by invoking * the 3-argument constructor GZIPOutputStream(out, size, false). * * @param out the output stream * @param size the output buffer size * @exception IOException If an I/O error has occurred. * @exception IllegalArgumentException if {@code size <= 0} */ public GZIPOutputStream(OutputStream out, int size) throws IOException { this(out, size, false); } /** * Creates a new output stream with the specified buffer size and * flush mode. * * @param out the output stream * @param size the output buffer size * @param syncFlush * if {@code true} invocation of the inherited * {@link DeflaterOutputStream#flush() flush()} method of * this instance flushes the compressor with flush mode * {@link Deflater#SYNC_FLUSH} before flushing the output * stream, otherwise only flushes the output stream * @exception IOException If an I/O error has occurred. * @exception IllegalArgumentException if {@code size <= 0} * * @since 1.7 */ public GZIPOutputStream(OutputStream out, int size, boolean syncFlush) throws IOException { super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size, syncFlush); usesDefaultDeflater = true; writeHeader(); crc.reset(); } /** * Creates a new output stream with a default buffer size. * * <p>The new output stream instance is created as if by invoking * the 2-argument constructor GZIPOutputStream(out, false). * * @param out the output stream * @exception IOException If an I/O error has occurred. */ public GZIPOutputStream(OutputStream out) throws IOException { this(out, 512, false); } /** * Creates a new output stream with a default buffer size and * the specified flush mode. * * @param out the output stream * @param syncFlush * if {@code true} invocation of the inherited * {@link DeflaterOutputStream#flush() flush()} method of * this instance flushes the compressor with flush mode * {@link Deflater#SYNC_FLUSH} before flushing the output * stream, otherwise only flushes the output stream * * @exception IOException If an I/O error has occurred. * * @since 1.7 */ public GZIPOutputStream(OutputStream out, boolean syncFlush) throws IOException { this(out, 512, syncFlush); } /** * Writes array of bytes to the compressed output stream. This method * will block until all the bytes are written. * @param buf the data to be written * @param off the start offset of the data * @param len the length of the data * @exception IOException If an I/O error has occurred. */ public synchronized void write(byte[] buf, int off, int len) throws IOException { super.write(buf, off, len); crc.update(buf, off, len); } /** * Finishes writing compressed data to the output stream without closing * the underlying stream. Use this method when applying multiple filters * in succession to the same output stream. * @exception IOException if an I/O error has occurred */ public void finish() throws IOException { if (!def.finished()) { def.finish(); while (!def.finished()) { int len = def.deflate(buf, 0, buf.length); if (def.finished() && len <= buf.length - TRAILER_SIZE) { // last deflater buffer. Fit trailer at the end writeTrailer(buf, len); len = len + TRAILER_SIZE; out.write(buf, 0, len); return; } if (len > 0) out.write(buf, 0, len); } // if we can't fit the trailer at the end of the last // deflater buffer, we write it separately byte[] trailer = new byte[TRAILER_SIZE]; writeTrailer(trailer, 0); out.write(trailer); } } /* * Writes GZIP member header. */ private void writeHeader() throws IOException { out.write(new byte[] { (byte) GZIP_MAGIC, // Magic number (short) (byte) (GZIP_MAGIC >> 8), // Magic number (short) Deflater.DEFLATED, // Compression method (CM) 0, // Flags (FLG) 0, // Modification time MTIME (int) 0, // Modification time MTIME (int) 0, // Modification time MTIME (int) 0, // Modification time MTIME (int) 0, // Extra flags (XFLG) 0 // Operating system (OS) }); } /* * Writes GZIP member trailer to a byte array, starting at a given * offset. */ private void writeTrailer(byte[] buf, int offset) throws IOException { writeInt((int) crc.getValue(), buf, offset); // CRC-32 of uncompr. data writeInt(def.getTotalIn(), buf, offset + 4); // Number of uncompr. bytes } /* * Writes integer in Intel byte order to a byte array, starting at a * given offset. */ private void writeInt(int i, byte[] buf, int offset) throws IOException { writeShort(i & 0xffff, buf, offset); writeShort((i >> 16) & 0xffff, buf, offset + 2); } /* * Writes short integer in Intel byte order to a byte array, starting * at a given offset */ private void writeShort(int s, byte[] buf, int offset) throws IOException { buf[offset] = (byte) (s & 0xff); buf[offset + 1] = (byte) ((s >> 8) & 0xff); } }