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Java Source | 1998-09-22 | 9.4 KB | 307 lines |
- /*
- * @(#)Deflater.java 1.19 98/08/20
- *
- * Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
- *
- * This software is the confidential and proprietary information of Sun
- * Microsystems, Inc. ("Confidential Information"). You shall not
- * disclose such Confidential Information and shall use it only in
- * accordance with the terms of the license agreement you entered into
- * with Sun.
- *
- * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
- * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
- * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
- * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
- * THIS SOFTWARE OR ITS DERIVATIVES.
- *
- * CopyrightVersion 1.1_beta
- *
- */
-
- package java.util.zip;
-
- /**
- * This class provides support for general purpose decompression using
- * the popular ZLIB compression library. The ZLIB compression library
- * was initially developed as part of the PNG graphics standard and is
- * not protected by patents. It is fully described in RFCs 1950, 1951,
- * and 1952, which can be found at
- * <a href="http://info.internet.isi.edu:80/in-notes/rfc/files/">
- * http://info.internet.isi.edu:80/in-notes/rfc/files/
- * </a> in the files rfc1950.txt (zlib format),
- * rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
- *
- * @see Inflater
- * @version 1.19, 08/20/98
- * @author David Connelly
- */
- public
- class Deflater {
- private int strm;
- private byte[] buf = new byte[0];
- private int off, len;
- private int level, strategy;
- private boolean setParams;
- private boolean finish, finished;
-
- /**
- * Compression method for the deflate algorithm (the only one currently
- * supported).
- */
- public static final int DEFLATED = 8;
-
- /**
- * Compression level for no compression.
- */
- public static final int NO_COMPRESSION = 0;
-
- /**
- * Compression level for fastest compression.
- */
- public static final int BEST_SPEED = 1;
-
- /**
- * Compression level for best compression.
- */
- public static final int BEST_COMPRESSION = 9;
-
- /**
- * Default compression level.
- */
- public static final int DEFAULT_COMPRESSION = -1;
-
- /**
- * Compression strategy best used for data consisting mostly of small
- * values with a somewhat random distribution. Forces more Huffman coding
- * and less string matching.
- */
- public static final int FILTERED = 1;
-
- /**
- * Compression strategy for Huffman coding only.
- */
- public static final int HUFFMAN_ONLY = 2;
-
- /**
- * Default compression strategy.
- */
- public static final int DEFAULT_STRATEGY = 0;
-
- /*
- * Loads the ZLIB library.
- */
- static {
- System.loadLibrary("zip");
- }
-
- /**
- * Creates a new compressor using the specified compression level.
- * If 'nowrap' is true then the ZLIB header and checksum fields will
- * not be used in order to support the compression format used in
- * both GZIP and PKZIP.
- * @param level the compression level (0-9)
- * @param nowrap if true then use GZIP compatible compression
- */
- public Deflater(int level, boolean nowrap) {
- this.level = level;
- this.strategy = DEFAULT_STRATEGY;
- init(nowrap);
- }
-
- /**
- * Creates a new compressor using the specified compression level.
- * Compressed data will be generated in ZLIB format.
- * @param level the compression level (0-9)
- */
- public Deflater(int level) {
- this(level, false);
- }
-
- /**
- * Creates a new compressor with the default compression level.
- * Compressed data will be generated in ZLIB format.
- */
- public Deflater() {
- this(DEFAULT_COMPRESSION, false);
- }
-
- /**
- * Sets input data for compression. This should be called whenever
- * needsInput() returns true indicating that more input data is required.
- * @param b the input data bytes
- * @param off the start offset of the data
- * @param len the length of the data
- * @see Deflater#needsInput
- */
- public synchronized void setInput(byte[] b, int off, int len) {
- if (b== null) {
- throw new NullPointerException();
- }
- if (off < 0 || len < 0 || off + len > b.length) {
- throw new ArrayIndexOutOfBoundsException();
- }
- this.buf = b;
- this.off = off;
- this.len = len;
- }
-
- /**
- * Sets input data for compression. This should be called whenever
- * needsInput() returns true indicating that more input data is required.
- * @param b the input data bytes
- * @see Deflater#needsInput
- */
- public void setInput(byte[] b) {
- setInput(b);
- }
-
- /**
- * Sets preset dictionary for compression. A preset dictionary is used
- * when the history buffer can be predetermined. When the data is later
- * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
- * in order to get the Adler-32 value of the dictionary required for
- * decompression.
- * @param b the dictionary data bytes
- * @param off the start offset of the data
- * @param len the length of the data
- * @see Inflater#inflate
- * @see Inflater#getAdler
- */
- public synchronized native void setDictionary(byte[] b, int off, int len);
-
- /**
- * Sets preset dictionary for compression. A preset dictionary is used
- * when the history buffer can be predetermined. When the data is later
- * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
- * in order to get the Adler-32 value of the dictionary required for
- * decompression.
- * @param b the dictionary data bytes
- * @see Inflater#inflate
- * @see Inflater#getAdler
- */
- public void setDictionary(byte[] b) {
- setDictionary(b, 0, b.length);
- }
-
- /**
- * Sets the compression strategy to the specified value.
- * @param strategy the new compression strategy
- * @exception IllegalArgumentException if the compression strategy is
- * invalid
- */
- public synchronized void setStrategy(int strategy) {
- switch (strategy) {
- case DEFAULT_STRATEGY:
- case FILTERED:
- case HUFFMAN_ONLY:
- break;
- default:
- throw new IllegalArgumentException();
- }
- if (this.strategy != strategy) {
- this.strategy = strategy;
- setParams = true;
- }
- }
-
- /**
- * Sets the current compression level to the specified value.
- * @param level the new compression level (0-9)
- * @exception IllegalArgumentException if the compression level is invalid
- */
- public synchronized void setLevel(int level) {
- if ((level < 0 || level > 9) && level != DEFAULT_COMPRESSION) {
- throw new IllegalArgumentException("invalid compression level");
- }
- if (this.level != level) {
- this.level = level;
- setParams = true;
- }
- }
-
- /**
- * Returns true if the input data buffer is empty and setInput()
- * should be called in order to provide more input.
- */
- public boolean needsInput() {
- return len <= 0;
- }
-
- /**
- * When called, indicates that compression should end with the current
- * contents of the input buffer.
- */
- public synchronized void finish() {
- finish = true;
- }
-
- /**
- * Returns true if the end of the compressed data output stream has
- * been reached.
- */
- public synchronized boolean finished() {
- return finished;
- }
-
- /**
- * Fills specified buffer with compressed data. Returns actual number
- * of bytes of compressed data. A return value of 0 indicates that
- * needsInput() should be called in order to determine if more input
- * data is required.
- * @param b the buffer for the compressed data
- * @param off the start offset of the data
- * @param len the maximum number of bytes of compressed data
- * @return the actual number of bytes of compressed data
- */
- public synchronized native int deflate(byte[] b, int off, int len);
-
- /**
- * Fills specified buffer with compressed data. Returns actual number
- * of bytes of compressed data. A return value of 0 indicates that
- * needsInput() should be called in order to determine if more input
- * data is required.
- * @param b the buffer for the compressed data
- * @return the actual number of bytes of compressed data
- */
- public int deflate(byte[] b) {
- return deflate(b, 0, b.length);
- }
-
- /**
- * Returns the ADLER-32 value of the uncompressed data.
- */
- public synchronized native int getAdler();
-
- /**
- * Returns the total number of bytes input so far.
- */
- public synchronized native int getTotalIn();
-
- /**
- * Returns the total number of bytes output so far.
- */
- public synchronized native int getTotalOut();
-
- /**
- * Resets deflater so that a new set of input data can be processed.
- * Keeps current compression level and strategy settings.
- */
- public synchronized native void reset();
-
- /**
- * Discards unprocessed input and frees internal data.
- */
- public synchronized native void end();
-
- /**
- * Frees the compressor when garbage is collected.
- */
- protected void finalize() {
- end();
- }
-
- private native void init(boolean nowrap);
- }
-