The following code fragment demonstrates a trivial compression * and decompression of a string using Deflater and * Inflater. * *
* try {
* // Encode a String into bytes
* String inputString = "blahblahblah";
* 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);
* compresser.end();
*
* // 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
* }
* If the compression strategy is changed, the next invocation * of {@code deflate} methods will compress the input available * so far with the old strategy (and may be flushed); the new strategy * will take effect only after that invocation. * * @param strategy the new compression strategy * @exception IllegalArgumentException if the compression strategy is * invalid */ public void setStrategy(int strategy) { switch (strategy) { case DEFAULT_STRATEGY: case FILTERED: case HUFFMAN_ONLY: break; default: throw new IllegalArgumentException(); } synchronized (zsRef) { if (this.strategy != strategy) { this.strategy = strategy; setParams = true; } } } /** * Sets the compression level to the specified value. * *
If the compression level is changed, the next invocation * of {@code deflate} methods will compress the input available * so far with the old level (and may be flushed); the new level * will take effect only after that invocation. * * @param level the new compression level (0-9) * @exception IllegalArgumentException if the compression level is invalid */ public void setLevel(int level) { if ((level < 0 || level > 9) && level != DEFAULT_COMPRESSION) { throw new IllegalArgumentException("invalid compression level"); } synchronized (zsRef) { 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. * @return 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 void finish() { synchronized (zsRef) { finish = true; } } /** * Returns true if the end of the compressed data output stream has * been reached. * @return true if the end of the compressed data output stream has * been reached */ public boolean finished() { synchronized (zsRef) { return finished; } } /** * Compresses the input data and fills specified buffer with compressed * data. Returns actual number of bytes of compressed data. A return value * of 0 indicates that {@link #needsInput() needsInput} should be called * in order to determine if more input data is required. * *
This method uses {@link #NO_FLUSH} as its compression flush mode. * An invocation of this method of the form {@code deflater.deflate(b, off, len)} * yields the same result as the invocation of * {@code deflater.deflate(b, off, len, Deflater.NO_FLUSH)}. * * @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 written to the * output buffer */ public int deflate(byte[] b, int off, int len) { return deflate(b, off, len, NO_FLUSH); } /** * Compresses the input data and fills specified buffer with compressed * data. Returns actual number of bytes of compressed data. A return value * of 0 indicates that {@link #needsInput() needsInput} should be called * in order to determine if more input data is required. * *
This method uses {@link #NO_FLUSH} as its compression flush mode. * An invocation of this method of the form {@code deflater.deflate(b)} * yields the same result as the invocation of * {@code deflater.deflate(b, 0, b.length, Deflater.NO_FLUSH)}. * * @param b the buffer for the compressed data * @return the actual number of bytes of compressed data written to the * output buffer */ public int deflate(byte[] b) { return deflate(b, 0, b.length, NO_FLUSH); } /** * Compresses the input data and fills the specified buffer with compressed * data. Returns actual number of bytes of data compressed. * *
Compression flush mode is one of the following three modes: * *
In the case of {@link #FULL_FLUSH} or {@link #SYNC_FLUSH}, if * the return value is {@code len}, the space available in output * buffer {@code b}, this method should be invoked again with the same * {@code flush} parameter and more output space. * * @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 * @param flush the compression flush mode * @return the actual number of bytes of compressed data written to * the output buffer * * @throws IllegalArgumentException if the flush mode is invalid * @since 1.7 */ public int deflate(byte[] b, int off, int len, int flush) { if (b == null) { throw new NullPointerException(); } if (off < 0 || len < 0 || off > b.length - len) { throw new ArrayIndexOutOfBoundsException(); } synchronized (zsRef) { ensureOpen(); if (flush == NO_FLUSH || flush == SYNC_FLUSH || flush == FULL_FLUSH) { int thisLen = this.len; int n = deflateBytes(zsRef.address(), b, off, len, flush); bytesWritten += n; bytesRead += (thisLen - this.len); return n; } throw new IllegalArgumentException(); } } /** * Returns the ADLER-32 value of the uncompressed data. * @return the ADLER-32 value of the uncompressed data */ public int getAdler() { synchronized (zsRef) { ensureOpen(); return getAdler(zsRef.address()); } } /** * Returns the total number of uncompressed bytes input so far. * *
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.
* * @return the total number of uncompressed bytes input so far */ public int getTotalIn() { return (int) getBytesRead(); } /** * Returns the total number of uncompressed bytes input so far. * * @return the total (non-negative) number of uncompressed bytes input so far * @since 1.5 */ public long getBytesRead() { synchronized (zsRef) { ensureOpen(); return bytesRead; } } /** * Returns the total number of compressed bytes output so far. * *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.
* * @return the total number of compressed bytes output so far */ public int getTotalOut() { return (int) getBytesWritten(); } /** * Returns the total number of compressed bytes output so far. * * @return the total (non-negative) number of compressed bytes output so far * @since 1.5 */ public long getBytesWritten() { synchronized (zsRef) { ensureOpen(); return bytesWritten; } } /** * Resets deflater so that a new set of input data can be processed. * Keeps current compression level and strategy settings. */ public void reset() { synchronized (zsRef) { ensureOpen(); reset(zsRef.address()); finish = false; finished = false; off = len = 0; bytesRead = bytesWritten = 0; } } /** * Closes the compressor and discards any unprocessed input. * This method should be called when the compressor is no longer * being used, but will also be called automatically by the * finalize() method. Once this method is called, the behavior * of the Deflater object is undefined. */ public void end() { synchronized (zsRef) { long addr = zsRef.address(); zsRef.clear(); if (addr != 0) { end(addr); buf = null; } } } /** * Closes the compressor when garbage is collected. */ protected void finalize() { end(); } private void ensureOpen() { assert Thread.holdsLock(zsRef); if (zsRef.address() == 0) throw new NullPointerException("Deflater has been closed"); } private static native void initIDs(); private native static long init(int level, int strategy, boolean nowrap); private native static void setDictionary(long addr, byte[] b, int off, int len); private native int deflateBytes(long addr, byte[] b, int off, int len, int flush); private native static int getAdler(long addr); private native static void reset(long addr); private native static void end(long addr); }