| /* Deflater.java - Compress a data stream |
| Copyright (C) 1999, 2000, 2001, 2004 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package java.util.zip; |
| |
| /** |
| * This is the Deflater class. The deflater class compresses input |
| * with the deflate algorithm described in RFC 1951. It has several |
| * compression levels and three different strategies described below. |
| * |
| * This class is <i>not</i> thread safe. This is inherent in the API, due |
| * to the split of deflate and setInput. |
| * |
| * @author Jochen Hoenicke |
| * @author Tom Tromey |
| */ |
| public class Deflater |
| { |
| /** |
| * The best and slowest compression level. This tries to find very |
| * long and distant string repetitions. |
| */ |
| public static final int BEST_COMPRESSION = 9; |
| /** |
| * The worst but fastest compression level. |
| */ |
| public static final int BEST_SPEED = 1; |
| /** |
| * The default compression level. |
| */ |
| public static final int DEFAULT_COMPRESSION = -1; |
| /** |
| * This level won't compress at all but output uncompressed blocks. |
| */ |
| public static final int NO_COMPRESSION = 0; |
| |
| /** |
| * The default strategy. |
| */ |
| public static final int DEFAULT_STRATEGY = 0; |
| /** |
| * This strategy will only allow longer string repetitions. It is |
| * useful for random data with a small character set. |
| */ |
| public static final int FILTERED = 1; |
| |
| /** |
| * This strategy will not look for string repetitions at all. It |
| * only encodes with Huffman trees (which means, that more common |
| * characters get a smaller encoding. |
| */ |
| public static final int HUFFMAN_ONLY = 2; |
| |
| /** |
| * The compression method. This is the only method supported so far. |
| * There is no need to use this constant at all. |
| */ |
| public static final int DEFLATED = 8; |
| |
| /* |
| * The Deflater can do the following state transitions: |
| * |
| * (1) -> INIT_STATE ----> INIT_FINISHING_STATE ---. |
| * / | (2) (5) | |
| * / v (5) | |
| * (3)| SETDICT_STATE ---> SETDICT_FINISHING_STATE |(3) |
| * \ | (3) | ,-------' |
| * | | | (3) / |
| * v v (5) v v |
| * (1) -> BUSY_STATE ----> FINISHING_STATE |
| * | (6) |
| * v |
| * FINISHED_STATE |
| * \_____________________________________/ |
| * | (7) |
| * v |
| * CLOSED_STATE |
| * |
| * (1) If we should produce a header we start in INIT_STATE, otherwise |
| * we start in BUSY_STATE. |
| * (2) A dictionary may be set only when we are in INIT_STATE, then |
| * we change the state as indicated. |
| * (3) Whether a dictionary is set or not, on the first call of deflate |
| * we change to BUSY_STATE. |
| * (4) -- intentionally left blank -- :) |
| * (5) FINISHING_STATE is entered, when flush() is called to indicate that |
| * there is no more INPUT. There are also states indicating, that |
| * the header wasn't written yet. |
| * (6) FINISHED_STATE is entered, when everything has been flushed to the |
| * internal pending output buffer. |
| * (7) At any time (7) |
| * |
| */ |
| |
| private static final int IS_SETDICT = 0x01; |
| private static final int IS_FLUSHING = 0x04; |
| private static final int IS_FINISHING = 0x08; |
| |
| private static final int INIT_STATE = 0x00; |
| private static final int SETDICT_STATE = 0x01; |
| private static final int INIT_FINISHING_STATE = 0x08; |
| private static final int SETDICT_FINISHING_STATE = 0x09; |
| private static final int BUSY_STATE = 0x10; |
| private static final int FLUSHING_STATE = 0x14; |
| private static final int FINISHING_STATE = 0x1c; |
| private static final int FINISHED_STATE = 0x1e; |
| private static final int CLOSED_STATE = 0x7f; |
| |
| /** Compression level. */ |
| private int level; |
| |
| /** should we include a header. */ |
| private boolean noHeader; |
| |
| /** The current state. */ |
| private int state; |
| |
| /** The total bytes of output written. */ |
| private int totalOut; |
| |
| /** The pending output. */ |
| private DeflaterPending pending; |
| |
| /** The deflater engine. */ |
| private DeflaterEngine engine; |
| |
| /** |
| * Creates a new deflater with default compression level. |
| */ |
| public Deflater() |
| { |
| this(DEFAULT_COMPRESSION, false); |
| } |
| |
| /** |
| * Creates a new deflater with given compression level. |
| * @param lvl the compression level, a value between NO_COMPRESSION |
| * and BEST_COMPRESSION, or DEFAULT_COMPRESSION. |
| * @exception IllegalArgumentException if lvl is out of range. |
| */ |
| public Deflater(int lvl) |
| { |
| this(lvl, false); |
| } |
| |
| /** |
| * Creates a new deflater with given compression level. |
| * @param lvl the compression level, a value between NO_COMPRESSION |
| * and BEST_COMPRESSION. |
| * @param nowrap true, iff we should suppress the deflate header at the |
| * beginning and the adler checksum at the end of the output. This is |
| * useful for the GZIP format. |
| * @exception IllegalArgumentException if lvl is out of range. |
| */ |
| public Deflater(int lvl, boolean nowrap) |
| { |
| if (lvl == DEFAULT_COMPRESSION) |
| lvl = 6; |
| else if (lvl < NO_COMPRESSION || lvl > BEST_COMPRESSION) |
| throw new IllegalArgumentException(); |
| |
| pending = new DeflaterPending(); |
| engine = new DeflaterEngine(pending); |
| this.noHeader = nowrap; |
| setStrategy(DEFAULT_STRATEGY); |
| setLevel(lvl); |
| reset(); |
| } |
| |
| /** |
| * Resets the deflater. The deflater acts afterwards as if it was |
| * just created with the same compression level and strategy as it |
| * had before. |
| */ |
| public void reset() |
| { |
| state = (noHeader ? BUSY_STATE : INIT_STATE); |
| totalOut = 0; |
| pending.reset(); |
| engine.reset(); |
| } |
| |
| /** |
| * Frees all objects allocated by the compressor. There's no |
| * reason to call this, since you can just rely on garbage |
| * collection. Exists only for compatibility against Sun's JDK, |
| * where the compressor allocates native memory. |
| * If you call any method (even reset) afterwards the behaviour is |
| * <i>undefined</i>. |
| */ |
| public void end() |
| { |
| engine = null; |
| pending = null; |
| state = CLOSED_STATE; |
| } |
| |
| /** |
| * Gets the current adler checksum of the data that was processed so |
| * far. |
| */ |
| public int getAdler() |
| { |
| return engine.getAdler(); |
| } |
| |
| /** |
| * Gets the number of input bytes processed so far. |
| */ |
| public int getTotalIn() |
| { |
| return engine.getTotalIn(); |
| } |
| |
| /** |
| * Gets the number of output bytes so far. |
| */ |
| public int getTotalOut() |
| { |
| return totalOut; |
| } |
| |
| /** |
| * Finalizes this object. |
| */ |
| protected void finalize() |
| { |
| /* Exists solely for compatibility. We don't have any native state. */ |
| } |
| |
| /** |
| * Flushes the current input block. Further calls to deflate() will |
| * produce enough output to inflate everything in the current input |
| * block. This is not part of Sun's JDK so I have made it package |
| * private. It is used by DeflaterOutputStream to implement |
| * flush(). |
| */ |
| void flush() { |
| state |= IS_FLUSHING; |
| } |
| |
| /** |
| * Finishes the deflater with the current input block. It is an error |
| * to give more input after this method was called. This method must |
| * be called to force all bytes to be flushed. |
| */ |
| public void finish() { |
| state |= IS_FLUSHING | IS_FINISHING; |
| } |
| |
| /** |
| * Returns true iff the stream was finished and no more output bytes |
| * are available. |
| */ |
| public boolean finished() |
| { |
| return state == FINISHED_STATE && pending.isFlushed(); |
| } |
| |
| /** |
| * Returns true, if the input buffer is empty. |
| * You should then call setInput(). <br> |
| * |
| * <em>NOTE</em>: This method can also return true when the stream |
| * was finished. |
| */ |
| public boolean needsInput() |
| { |
| return engine.needsInput(); |
| } |
| |
| /** |
| * Sets the data which should be compressed next. This should be only |
| * called when needsInput indicates that more input is needed. |
| * If you call setInput when needsInput() returns false, the |
| * previous input that is still pending will be thrown away. |
| * The given byte array should not be changed, before needsInput() returns |
| * true again. |
| * This call is equivalent to <code>setInput(input, 0, input.length)</code>. |
| * @param input the buffer containing the input data. |
| * @exception IllegalStateException if the buffer was finished() or ended(). |
| */ |
| public void setInput(byte[] input) |
| { |
| setInput(input, 0, input.length); |
| } |
| |
| /** |
| * Sets the data which should be compressed next. This should be |
| * only called when needsInput indicates that more input is needed. |
| * The given byte array should not be changed, before needsInput() returns |
| * true again. |
| * @param input the buffer containing the input data. |
| * @param off the start of the data. |
| * @param len the length of the data. |
| * @exception IllegalStateException if the buffer was finished() or ended() |
| * or if previous input is still pending. |
| */ |
| public void setInput(byte[] input, int off, int len) |
| { |
| if ((state & IS_FINISHING) != 0) |
| throw new IllegalStateException("finish()/end() already called"); |
| engine.setInput(input, off, len); |
| } |
| |
| /** |
| * Sets the compression level. There is no guarantee of the exact |
| * position of the change, but if you call this when needsInput is |
| * true the change of compression level will occur somewhere near |
| * before the end of the so far given input. |
| * @param lvl the new compression level. |
| */ |
| public void setLevel(int lvl) |
| { |
| if (lvl == DEFAULT_COMPRESSION) |
| lvl = 6; |
| else if (lvl < NO_COMPRESSION || lvl > BEST_COMPRESSION) |
| throw new IllegalArgumentException(); |
| |
| |
| if (level != lvl) |
| { |
| level = lvl; |
| engine.setLevel(lvl); |
| } |
| } |
| |
| /** |
| * Sets the compression strategy. Strategy is one of |
| * DEFAULT_STRATEGY, HUFFMAN_ONLY and FILTERED. For the exact |
| * position where the strategy is changed, the same as for |
| * setLevel() applies. |
| * @param stgy the new compression strategy. |
| */ |
| public void setStrategy(int stgy) |
| { |
| if (stgy != DEFAULT_STRATEGY && stgy != FILTERED |
| && stgy != HUFFMAN_ONLY) |
| throw new IllegalArgumentException(); |
| engine.setStrategy(stgy); |
| } |
| |
| /** |
| * Deflates the current input block to the given array. It returns |
| * the number of bytes compressed, or 0 if either |
| * needsInput() or finished() returns true or length is zero. |
| * @param output the buffer where to write the compressed data. |
| */ |
| public int deflate(byte[] output) |
| { |
| return deflate(output, 0, output.length); |
| } |
| |
| /** |
| * Deflates the current input block to the given array. It returns |
| * the number of bytes compressed, or 0 if either |
| * needsInput() or finished() returns true or length is zero. |
| * @param output the buffer where to write the compressed data. |
| * @param offset the offset into the output array. |
| * @param length the maximum number of bytes that may be written. |
| * @exception IllegalStateException if end() was called. |
| * @exception IndexOutOfBoundsException if offset and/or length |
| * don't match the array length. |
| */ |
| public int deflate(byte[] output, int offset, int length) |
| { |
| int origLength = length; |
| |
| if (state == CLOSED_STATE) |
| throw new IllegalStateException("Deflater closed"); |
| |
| if (state < BUSY_STATE) |
| { |
| /* output header */ |
| int header = (DEFLATED + |
| ((DeflaterConstants.MAX_WBITS - 8) << 4)) << 8; |
| int level_flags = (level - 1) >> 1; |
| if (level_flags < 0 || level_flags > 3) |
| level_flags = 3; |
| header |= level_flags << 6; |
| if ((state & IS_SETDICT) != 0) |
| /* Dictionary was set */ |
| header |= DeflaterConstants.PRESET_DICT; |
| header += 31 - (header % 31); |
| |
| pending.writeShortMSB(header); |
| if ((state & IS_SETDICT) != 0) |
| { |
| int chksum = engine.getAdler(); |
| engine.resetAdler(); |
| pending.writeShortMSB(chksum >> 16); |
| pending.writeShortMSB(chksum & 0xffff); |
| } |
| |
| state = BUSY_STATE | (state & (IS_FLUSHING | IS_FINISHING)); |
| } |
| |
| for (;;) |
| { |
| int count = pending.flush(output, offset, length); |
| offset += count; |
| totalOut += count; |
| length -= count; |
| if (length == 0 || state == FINISHED_STATE) |
| break; |
| |
| if (!engine.deflate((state & IS_FLUSHING) != 0, |
| (state & IS_FINISHING) != 0)) |
| { |
| if (state == BUSY_STATE) |
| /* We need more input now */ |
| return origLength - length; |
| else if (state == FLUSHING_STATE) |
| { |
| if (level != NO_COMPRESSION) |
| { |
| /* We have to supply some lookahead. 8 bit lookahead |
| * are needed by the zlib inflater, and we must fill |
| * the next byte, so that all bits are flushed. |
| */ |
| int neededbits = 8 + ((-pending.getBitCount()) & 7); |
| while (neededbits > 0) |
| { |
| /* write a static tree block consisting solely of |
| * an EOF: |
| */ |
| pending.writeBits(2, 10); |
| neededbits -= 10; |
| } |
| } |
| state = BUSY_STATE; |
| } |
| else if (state == FINISHING_STATE) |
| { |
| pending.alignToByte(); |
| /* We have completed the stream */ |
| if (!noHeader) |
| { |
| int adler = engine.getAdler(); |
| pending.writeShortMSB(adler >> 16); |
| pending.writeShortMSB(adler & 0xffff); |
| } |
| state = FINISHED_STATE; |
| } |
| } |
| } |
| |
| return origLength - length; |
| } |
| |
| /** |
| * Sets the dictionary which should be used in the deflate process. |
| * This call is equivalent to <code>setDictionary(dict, 0, |
| * dict.length)</code>. |
| * @param dict the dictionary. |
| * @exception IllegalStateException if setInput () or deflate () |
| * were already called or another dictionary was already set. |
| */ |
| public void setDictionary(byte[] dict) |
| { |
| setDictionary(dict, 0, dict.length); |
| } |
| |
| /** |
| * Sets the dictionary which should be used in the deflate process. |
| * The dictionary should be a byte array containing strings that are |
| * likely to occur in the data which should be compressed. The |
| * dictionary is not stored in the compressed output, only a |
| * checksum. To decompress the output you need to supply the same |
| * dictionary again. |
| * @param dict the dictionary. |
| * @param offset an offset into the dictionary. |
| * @param length the length of the dictionary. |
| * @exception IllegalStateException if setInput () or deflate () were |
| * already called or another dictionary was already set. |
| */ |
| public void setDictionary(byte[] dict, int offset, int length) |
| { |
| if (state != INIT_STATE) |
| throw new IllegalStateException(); |
| |
| state = SETDICT_STATE; |
| engine.setDictionary(dict, offset, length); |
| } |
| } |