329 lines
11 KiB
Java
329 lines
11 KiB
Java
/* Deflater.java - Compress a data stream
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Copyright (C) 1999, 2000, 2001, 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util.zip;
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import gnu.gcj.RawData;
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/**
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* This is the Deflater class. The deflater class compresses input
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* with the deflate algorithm described in RFC 1951. It has several
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* compression levels and three different strategies described below.
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*
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* This class is <i>not</i> thread safe. This is inherent in the API, due
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* to the split of deflate and setInput.
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*
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* @author Jochen Hoenicke
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* @author Tom Tromey
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*/
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public class Deflater
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{
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/**
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* The best and slowest compression level. This tries to find very
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* long and distant string repetitions.
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*/
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public static final int BEST_COMPRESSION = 9;
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/**
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* The worst but fastest compression level.
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*/
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public static final int BEST_SPEED = 1;
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/**
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* The default compression level.
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*/
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public static final int DEFAULT_COMPRESSION = -1;
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/**
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* This level won't compress at all but output uncompressed blocks.
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*/
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public static final int NO_COMPRESSION = 0;
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/**
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* The default strategy.
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*/
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public static final int DEFAULT_STRATEGY = 0;
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/**
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* This strategy will only allow longer string repetitions. It is
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* useful for random data with a small character set.
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*/
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public static final int FILTERED = 1;
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/**
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* This strategy will not look for string repetitions at all. It
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* only encodes with Huffman trees (which means, that more common
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* characters get a smaller encoding.
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*/
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public static final int HUFFMAN_ONLY = 2;
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/**
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* The compression method. This is the only method supported so far.
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* There is no need to use this constant at all.
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*/
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public static final int DEFLATED = 8;
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/** Compression level. */
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private int level;
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/** Compression strategy. */
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private int strategy;
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/** The zlib stream. */
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private RawData zstream;
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/** True if finished. */
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private boolean is_finished;
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/** `Flush' flag to pass to next call to deflate. */
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private int flush_flag;
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/**
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* Creates a new deflater with default compression level.
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*/
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public Deflater()
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{
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this(DEFAULT_COMPRESSION, false);
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}
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/**
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* Creates a new deflater with given compression level.
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* @param lvl the compression level, a value between NO_COMPRESSION
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* and BEST_COMPRESSION, or DEFAULT_COMPRESSION.
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* @exception IllegalArgumentException if lvl is out of range.
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*/
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public Deflater(int lvl)
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{
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this(lvl, false);
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}
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/**
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* Creates a new deflater with given compression level.
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* @param lvl the compression level, a value between NO_COMPRESSION
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* and BEST_COMPRESSION.
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* @param nowrap true, iff we should suppress the deflate header at the
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* beginning and the adler checksum at the end of the output. This is
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* useful for the GZIP format.
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* @exception IllegalArgumentException if lvl is out of range.
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*/
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public Deflater(int lvl, boolean noHeader)
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{
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this.strategy = DEFAULT_STRATEGY;
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init(lvl, noHeader);
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setLevel(lvl);
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}
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private native void init(int level, boolean noHeader);
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private native void update();
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/**
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* Resets the deflater. The deflater acts afterwards as if it was
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* just created with the same compression level and strategy as it
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* had before.
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*/
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public native void reset();
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/**
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* Frees all objects allocated by the compressor. There's no
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* reason to call this, since you can just rely on garbage
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* collection. Exists only for compatibility against Sun's JDK,
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* where the compressor allocates native memory.
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* If you call any method (even reset) afterwards the behaviour is
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* <i>undefined</i>.
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* @deprecated Just clear all references to deflater instead.
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*/
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public native void end();
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/**
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* Gets the current adler checksum of the data that was processed so
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* far.
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*/
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public native int getAdler();
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/**
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* Gets the number of input bytes processed so far.
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*/
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public native int getTotalIn();
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/**
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* Gets the number of output bytes so far.
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*/
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public native int getTotalOut();
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/**
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* Finalizes this object.
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*/
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protected void finalize()
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{
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end();
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}
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/**
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* Finishes the deflater with the current input block. It is an error
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* to give more input after this method was called. This method must
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* be called to force all bytes to be flushed.
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*/
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public native void finish();
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/**
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* Returns true iff the stream was finished and no more output bytes
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* are available.
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*/
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public synchronized boolean finished()
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{
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return is_finished;
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}
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/**
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* Returns true, if the input buffer is empty.
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* You should then call setInput(). <br>
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*
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* <em>NOTE</em>: This method can also return true when the stream
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* was finished.
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*/
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public native boolean needsInput();
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/**
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* Sets the data which should be compressed next. This should be only
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* called when needsInput indicates that more input is needed.
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* If you call setInput when needsInput() returns false, the
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* previous input that is still pending will be thrown away.
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* The given byte array should not be changed, before needsInput() returns
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* true again.
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* This call is equivalent to <code>setInput(input, 0, input.length)</code>.
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* @param input the buffer containing the input data.
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* @exception IllegalStateException if the buffer was finished() or ended().
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*/
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public void setInput(byte[] input)
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{
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setInput(input, 0, input.length);
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}
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/**
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* Sets the data which should be compressed next. This should be
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* only called when needsInput indicates that more input is needed.
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* The given byte array should not be changed, before needsInput() returns
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* true again.
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* @param input the buffer containing the input data.
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* @param off the start of the data.
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* @param len the length of the data.
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* @exception IllegalStateException if the buffer was finished() or ended()
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* or if previous input is still pending.
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*/
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public native void setInput(byte[] input, int off, int len);
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/**
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* Sets the compression level. There is no guarantee of the exact
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* position of the change, but if you call this when needsInput is
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* true the change of compression level will occur somewhere near
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* before the end of the so far given input.
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* @param lvl the new compression level.
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*/
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public synchronized void setLevel(int lvl)
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{
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if (lvl != -1 && (lvl < 0 || lvl > 9))
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throw new IllegalArgumentException();
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level = (lvl == -1) ? 6 : lvl;
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update();
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}
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/**
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* Sets the compression strategy. Strategy is one of
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* DEFAULT_STRATEGY, HUFFMAN_ONLY and FILTERED. For the exact
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* position where the strategy is changed, the same as for
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* setLevel() applies.
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* @param stgy the new compression strategy.
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*/
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public synchronized void setStrategy(int stgy)
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{
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if (stgy != DEFAULT_STRATEGY && stgy != FILTERED
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&& stgy != HUFFMAN_ONLY)
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throw new IllegalArgumentException();
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strategy = stgy;
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update();
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}
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/**
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* Deflates the current input block to the given array. It returns
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* the number of bytes compressed, or 0 if either
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* needsInput() or finished() returns true or length is zero.
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* @param output the buffer where to write the compressed data.
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*/
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public int deflate(byte[] output)
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{
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return deflate(output, 0, output.length);
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}
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/**
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* Deflates the current input block to the given array. It returns
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* the number of bytes compressed, or 0 if either
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* needsInput() or finished() returns true or length is zero.
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* @param output the buffer where to write the compressed data.
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* @param offset the offset into the output array.
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* @param length the maximum number of bytes that may be written.
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* @exception IllegalStateException if end() was called.
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* @exception IndexOutOfBoundsException if offset and/or length
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* don't match the array length.
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*/
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public native int deflate(byte[] output, int off, int len);
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/**
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* Sets the dictionary which should be used in the deflate process.
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* This call is equivalent to <code>setDictionary(dict, 0,
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* dict.length)</code>.
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* @param dict the dictionary.
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* @exception IllegalStateException if setInput () or deflate ()
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* were already called or another dictionary was already set.
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*/
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public void setDictionary(byte[] dict)
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{
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setDictionary(dict, 0, dict.length);
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}
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/**
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* Sets the dictionary which should be used in the deflate process.
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* The dictionary should be a byte array containing strings that are
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* likely to occur in the data which should be compressed. The
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* dictionary is not stored in the compressed output, only a
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* checksum. To decompress the output you need to supply the same
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* dictionary again.
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* @param dict the dictionary.
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* @param offset an offset into the dictionary.
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* @param length the length of the dictionary.
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* @exception IllegalStateException if setInput () or deflate () were
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* already called or another dictionary was already set.
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*/
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public native void setDictionary(byte[] buf, int off, int len);
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}
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