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/* * @(#)Inflater.java 1.47 06/04/07 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ 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 the specifications at * the <a href="package-summary.html#package_description">java.util.zip * package description</a>. * * <p>The following code fragment demonstrates a trivial compression * and decompression of a string using <tt>Deflater</tt> and * <tt>Inflater</tt>. * * <blockquote><pre> * try { * // Encode a String into bytes * String inputString = "blahblahblah\u20AC\u20AC"; * byte[] input = inputString.getBytes("UTF-8"); * * // Compress the bytes * byte[] output = new byte[100]; * Deflater compresser = new Deflater(); * compresser.setInput(input); * compresser.finish(); * int compressedDataLength = compresser.deflate(output); * * // Decompress the bytes * Inflater decompresser = new Inflater(); * decompresser.setInput(output, 0, compressedDataLength); * byte[] result = new byte[100]; * int resultLength = decompresser.inflate(result); * decompresser.end(); * * // Decode the bytes into a String * String outputString = new String(result, 0, resultLength, "UTF-8"); * } catch(java.io.UnsupportedEncodingException ex) { * // handle * } catch (java.util.zip.DataFormatException ex) { * // handle * } * </pre></blockquote> * * @see Deflater * @version 1.47, 04/07/06 * @author David Connelly * */ public class Inflater { private long strm; private byte[] buf = new byte[0]; private int off, len; private boolean finished; private boolean needDict; static { /* Zip library is loaded from System.initializeSystemClass */ initIDs(); } /** * Creates a new decompressor. If the parameter 'nowrap' is true then * the ZLIB header and checksum fields will not be used. This provides * compatibility with the compression format used by both GZIP and PKZIP. * <p> * Note: When using the 'nowrap' option it is also necessary to provide * an extra "dummy" byte as input. This is required by the ZLIB native * library in order to support certain optimizations. * * @param nowrap if true then support GZIP compatible compression */ public Inflater(boolean nowrap) { strm = init(nowrap); } /** * Creates a new decompressor. */ public Inflater() { this(false); } /** * Sets input data for decompression. 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 input data * @param len the length of the input data * @see Inflater#needsInput */ public synchronized void setInput(byte[] b, int off, int len) { if (b == null) { throw new NullPointerException(); } if (off < 0 || len < 0 || off > b.length - len) { throw new ArrayIndexOutOfBoundsException(); } this.buf = b; this.off = off; this.len = len; } /** * Sets input data for decompression. Should be called whenever * needsInput() returns true indicating that more input data is * required. * @param b the input data bytes * @see Inflater#needsInput */ public void setInput(byte[] b) { setInput(b, 0, b.length); } /** * Sets the preset dictionary to the given array of bytes. Should be * called when inflate() returns 0 and needsDictionary() returns true * indicating that a preset dictionary is required. The method getAdler() * can be used to get the Adler-32 value of the dictionary needed. * @param b the dictionary data bytes * @param off the start offset of the data * @param len the length of the data * @see Inflater#needsDictionary * @see Inflater#getAdler */ public synchronized void setDictionary(byte[] b, int off, int len) { if (strm == 0 || b == null) { throw new NullPointerException(); } if (off < 0 || len < 0 || off > b.length - len) { throw new ArrayIndexOutOfBoundsException(); } setDictionary(strm, b, off, len); needDict = false; } /** * Sets the preset dictionary to the given array of bytes. Should be * called when inflate() returns 0 and needsDictionary() returns true * indicating that a preset dictionary is required. The method getAdler() * can be used to get the Adler-32 value of the dictionary needed. * @param b the dictionary data bytes * @see Inflater#needsDictionary * @see Inflater#getAdler */ public void setDictionary(byte[] b) { setDictionary(b, 0, b.length); } /** * Returns the total number of bytes remaining in the input buffer. * This can be used to find out what bytes still remain in the input * buffer after decompression has finished. * @return the total number of bytes remaining in the input buffer */ public synchronized int getRemaining() { return len; } /** * Returns true if no data remains in the input buffer. This can * be used to determine if #setInput should be called in order * to provide more input. * @return true if no data remains in the input buffer */ public synchronized boolean needsInput() { return len <= 0; } /** * Returns true if a preset dictionary is needed for decompression. * @return true if a preset dictionary is needed for decompression * @see Inflater#setDictionary */ public synchronized boolean needsDictionary() { return needDict; } /** * Returns true if the end of the compressed data stream has been * reached. * @return true if the end of the compressed data stream has been * reached */ public synchronized boolean finished() { return finished; } /** * Uncompresses bytes into specified buffer. Returns actual number * of bytes uncompressed. A return value of 0 indicates that * needsInput() or needsDictionary() should be called in order to * determine if more input data or a preset dictionary is required. * In the latter case, getAdler() can be used to get the Adler-32 * value of the dictionary required. * @param b the buffer for the uncompressed data * @param off the start offset of the data * @param len the maximum number of uncompressed bytes * @return the actual number of uncompressed bytes * @exception DataFormatException if the compressed data format is invalid * @see Inflater#needsInput * @see Inflater#needsDictionary */ public synchronized int inflate(byte[] b, int off, int len) throws DataFormatException { if (b == null) { throw new NullPointerException(); } if (off < 0 || len < 0 || off > b.length - len) { throw new ArrayIndexOutOfBoundsException(); } return inflateBytes(b, off, len); } /** * Uncompresses bytes into specified buffer. Returns actual number * of bytes uncompressed. A return value of 0 indicates that * needsInput() or needsDictionary() should be called in order to * determine if more input data or a preset dictionary is required. * In the latter case, getAdler() can be used to get the Adler-32 * value of the dictionary required. * @param b the buffer for the uncompressed data * @return the actual number of uncompressed bytes * @exception DataFormatException if the compressed data format is invalid * @see Inflater#needsInput * @see Inflater#needsDictionary */ public int inflate(byte[] b) throws DataFormatException { return inflate(b, 0, b.length); } /** * Returns the ADLER-32 value of the uncompressed data. * @return the ADLER-32 value of the uncompressed data */ public synchronized int getAdler() { ensureOpen(); return getAdler(strm); } /** * Returns the total number of compressed bytes input so far. * * <p>Since the number of bytes may be greater than * Integer.MAX_VALUE, the {@link #getBytesRead()} method is now * the preferred means of obtaining this information.</p> * * @return the total number of compressed bytes input so far */ public int getTotalIn() { return (int) getBytesRead(); } /** * Returns the total number of compressed bytes input so far.</p> * * @return the total (non-negative) number of compressed bytes input so far * @since 1.5 */ public synchronized long getBytesRead() { ensureOpen(); return getBytesRead(strm); } /** * Returns the total number of uncompressed bytes output so far. * * <p>Since the number of bytes may be greater than * Integer.MAX_VALUE, the {@link #getBytesWritten()} method is now * the preferred means of obtaining this information.</p> * * @return the total number of uncompressed bytes output so far */ public int getTotalOut() { return (int) getBytesWritten(); } /** * Returns the total number of uncompressed bytes output so far.</p> * * @return the total (non-negative) number of uncompressed bytes output so far * @since 1.5 */ public synchronized long getBytesWritten() { ensureOpen(); return getBytesWritten(strm); } /** * Resets inflater so that a new set of input data can be processed. */ public synchronized void reset() { ensureOpen(); reset(strm); finished = false; needDict = false; off = len = 0; } /** * Closes the decompressor and discards any unprocessed input. * This method should be called when the decompressor is no longer * being used, but will also be called automatically by the finalize() * method. Once this method is called, the behavior of the Inflater * object is undefined. */ public synchronized void end() { if (strm != 0) { end(strm); strm = 0; buf = null; } } /** * Closes the decompressor when garbage is collected. */ protected void finalize() { end(); } private void ensureOpen () { if (strm == 0) throw new NullPointerException(); } private native static void initIDs(); private native static long init(boolean nowrap); private native static void setDictionary(long strm, byte[] b, int off, int len); private native int inflateBytes(byte[] b, int off, int len) throws DataFormatException; private native static int getAdler(long strm); private native static long getBytesRead(long strm); private native static long getBytesWritten(long strm); private native static void reset(long strm); private native static void end(long strm); }