mirror of git://gcc.gnu.org/git/gcc.git
699 lines
20 KiB
Java
699 lines
20 KiB
Java
/* DeflaterEngine.java --
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Copyright (C) 2001, 2004, 2005 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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class DeflaterEngine implements DeflaterConstants
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{
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private static final int TOO_FAR = 4096;
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private int ins_h;
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/**
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* Hashtable, hashing three characters to an index for window, so
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* that window[index]..window[index+2] have this hash code.
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* Note that the array should really be unsigned short, so you need
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* to and the values with 0xffff.
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*/
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private short[] head;
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/**
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* prev[index & WMASK] points to the previous index that has the
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* same hash code as the string starting at index. This way
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* entries with the same hash code are in a linked list.
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* Note that the array should really be unsigned short, so you need
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* to and the values with 0xffff.
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*/
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private short[] prev;
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private int matchStart, matchLen;
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private boolean prevAvailable;
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private int blockStart;
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/**
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* strstart points to the current character in window.
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*/
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private int strstart;
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/**
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* lookahead is the number of characters starting at strstart in
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* window that are valid.
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* So window[strstart] until window[strstart+lookahead-1] are valid
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* characters.
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*/
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private int lookahead;
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/**
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* This array contains the part of the uncompressed stream that
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* is of relevance. The current character is indexed by strstart.
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*/
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private byte[] window;
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private int strategy, max_chain, max_lazy, niceLength, goodLength;
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/** The current compression function. */
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private int comprFunc;
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/** The input data for compression. */
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private byte[] inputBuf;
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/** The total bytes of input read. */
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private long totalIn;
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/** The offset into inputBuf, where input data starts. */
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private int inputOff;
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/** The end offset of the input data. */
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private int inputEnd;
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private DeflaterPending pending;
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private DeflaterHuffman huffman;
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/** The adler checksum */
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private Adler32 adler;
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/* DEFLATE ALGORITHM:
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*
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* The uncompressed stream is inserted into the window array. When
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* the window array is full the first half is thrown away and the
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* second half is copied to the beginning.
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*
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* The head array is a hash table. Three characters build a hash value
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* and they the value points to the corresponding index in window of
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* the last string with this hash. The prev array implements a
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* linked list of matches with the same hash: prev[index & WMASK] points
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* to the previous index with the same hash.
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*
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*
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*/
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DeflaterEngine(DeflaterPending pending) {
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this.pending = pending;
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huffman = new DeflaterHuffman(pending);
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adler = new Adler32();
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window = new byte[2*WSIZE];
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head = new short[HASH_SIZE];
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prev = new short[WSIZE];
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/* We start at index 1, to avoid a implementation deficiency, that
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* we cannot build a repeat pattern at index 0.
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*/
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blockStart = strstart = 1;
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}
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public void reset()
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{
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huffman.reset();
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adler.reset();
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blockStart = strstart = 1;
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lookahead = 0;
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totalIn = 0;
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prevAvailable = false;
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matchLen = MIN_MATCH - 1;
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for (int i = 0; i < HASH_SIZE; i++)
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head[i] = 0;
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for (int i = 0; i < WSIZE; i++)
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prev[i] = 0;
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}
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public final void resetAdler()
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{
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adler.reset();
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}
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public final int getAdler()
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{
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int chksum = (int) adler.getValue();
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return chksum;
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}
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public final long getTotalIn()
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{
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return totalIn;
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}
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public final void setStrategy(int strat)
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{
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strategy = strat;
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}
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public void setLevel(int lvl)
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{
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goodLength = DeflaterConstants.GOOD_LENGTH[lvl];
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max_lazy = DeflaterConstants.MAX_LAZY[lvl];
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niceLength = DeflaterConstants.NICE_LENGTH[lvl];
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max_chain = DeflaterConstants.MAX_CHAIN[lvl];
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if (DeflaterConstants.COMPR_FUNC[lvl] != comprFunc)
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{
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if (DeflaterConstants.DEBUGGING)
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System.err.println("Change from "+comprFunc +" to "
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+ DeflaterConstants.COMPR_FUNC[lvl]);
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switch (comprFunc)
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{
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case DEFLATE_STORED:
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if (strstart > blockStart)
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{
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huffman.flushStoredBlock(window, blockStart,
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strstart - blockStart, false);
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blockStart = strstart;
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}
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updateHash();
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break;
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case DEFLATE_FAST:
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if (strstart > blockStart)
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{
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huffman.flushBlock(window, blockStart, strstart - blockStart,
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false);
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blockStart = strstart;
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}
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break;
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case DEFLATE_SLOW:
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if (prevAvailable)
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huffman.tallyLit(window[strstart-1] & 0xff);
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if (strstart > blockStart)
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{
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huffman.flushBlock(window, blockStart, strstart - blockStart,
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false);
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blockStart = strstart;
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}
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prevAvailable = false;
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matchLen = MIN_MATCH - 1;
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break;
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}
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comprFunc = COMPR_FUNC[lvl];
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}
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}
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private void updateHash() {
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if (DEBUGGING)
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System.err.println("updateHash: "+strstart);
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ins_h = (window[strstart] << HASH_SHIFT) ^ window[strstart + 1];
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}
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/**
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* Inserts the current string in the head hash and returns the previous
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* value for this hash.
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*/
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private int insertString() {
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short match;
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int hash = ((ins_h << HASH_SHIFT) ^ window[strstart + (MIN_MATCH -1)])
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& HASH_MASK;
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if (DEBUGGING)
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{
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if (hash != (((window[strstart] << (2*HASH_SHIFT))
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^ (window[strstart + 1] << HASH_SHIFT)
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^ (window[strstart + 2])) & HASH_MASK))
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throw new InternalError("hash inconsistent: "+hash+"/"
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+window[strstart]+","
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+window[strstart+1]+","
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+window[strstart+2]+","+HASH_SHIFT);
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}
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prev[strstart & WMASK] = match = head[hash];
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head[hash] = (short) strstart;
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ins_h = hash;
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return match & 0xffff;
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}
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private void slideWindow()
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{
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System.arraycopy(window, WSIZE, window, 0, WSIZE);
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matchStart -= WSIZE;
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strstart -= WSIZE;
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blockStart -= WSIZE;
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/* Slide the hash table (could be avoided with 32 bit values
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* at the expense of memory usage).
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*/
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for (int i = 0; i < HASH_SIZE; i++)
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{
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int m = head[i] & 0xffff;
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head[i] = m >= WSIZE ? (short) (m - WSIZE) : 0;
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}
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/* Slide the prev table.
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*/
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for (int i = 0; i < WSIZE; i++)
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{
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int m = prev[i] & 0xffff;
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prev[i] = m >= WSIZE ? (short) (m - WSIZE) : 0;
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}
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}
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/**
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* Fill the window when the lookahead becomes insufficient.
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* Updates strstart and lookahead.
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*
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* OUT assertions: strstart + lookahead <= 2*WSIZE
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* lookahead >= MIN_LOOKAHEAD or inputOff == inputEnd
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*/
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private void fillWindow()
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{
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/* If the window is almost full and there is insufficient lookahead,
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* move the upper half to the lower one to make room in the upper half.
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*/
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if (strstart >= WSIZE + MAX_DIST)
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slideWindow();
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/* If there is not enough lookahead, but still some input left,
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* read in the input
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*/
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while (lookahead < DeflaterConstants.MIN_LOOKAHEAD && inputOff < inputEnd)
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{
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int more = 2*WSIZE - lookahead - strstart;
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if (more > inputEnd - inputOff)
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more = inputEnd - inputOff;
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System.arraycopy(inputBuf, inputOff,
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window, strstart + lookahead, more);
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adler.update(inputBuf, inputOff, more);
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inputOff += more;
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totalIn += more;
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lookahead += more;
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}
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if (lookahead >= MIN_MATCH)
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updateHash();
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}
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/**
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* Find the best (longest) string in the window matching the
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* string starting at strstart.
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*
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* Preconditions:
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* strstart + MAX_MATCH <= window.length.
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*
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*
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* @param curMatch
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*/
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private boolean findLongestMatch(int curMatch) {
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int chainLength = this.max_chain;
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int niceLength = this.niceLength;
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short[] prev = this.prev;
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int scan = this.strstart;
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int match;
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int best_end = this.strstart + matchLen;
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int best_len = Math.max(matchLen, MIN_MATCH - 1);
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int limit = Math.max(strstart - MAX_DIST, 0);
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int strend = scan + MAX_MATCH - 1;
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byte scan_end1 = window[best_end - 1];
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byte scan_end = window[best_end];
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/* Do not waste too much time if we already have a good match: */
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if (best_len >= this.goodLength)
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chainLength >>= 2;
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/* Do not look for matches beyond the end of the input. This is necessary
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* to make deflate deterministic.
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*/
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if (niceLength > lookahead)
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niceLength = lookahead;
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if (DeflaterConstants.DEBUGGING
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&& strstart > 2*WSIZE - MIN_LOOKAHEAD)
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throw new InternalError("need lookahead");
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do {
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if (DeflaterConstants.DEBUGGING && curMatch >= strstart)
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throw new InternalError("future match");
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if (window[curMatch + best_len] != scan_end
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|| window[curMatch + best_len - 1] != scan_end1
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|| window[curMatch] != window[scan]
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|| window[curMatch+1] != window[scan + 1])
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continue;
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match = curMatch + 2;
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scan += 2;
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/* We check for insufficient lookahead only every 8th comparison;
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* the 256th check will be made at strstart+258.
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*/
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while (window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& window[++scan] == window[++match]
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&& scan < strend)
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;
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if (scan > best_end) {
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// if (DeflaterConstants.DEBUGGING && ins_h == 0)
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// System.err.println("Found match: "+curMatch+"-"+(scan-strstart));
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matchStart = curMatch;
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best_end = scan;
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best_len = scan - strstart;
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if (best_len >= niceLength)
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break;
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scan_end1 = window[best_end-1];
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scan_end = window[best_end];
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}
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scan = strstart;
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} while ((curMatch = (prev[curMatch & WMASK] & 0xffff)) > limit
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&& --chainLength != 0);
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matchLen = Math.min(best_len, lookahead);
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return matchLen >= MIN_MATCH;
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}
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void setDictionary(byte[] buffer, int offset, int length) {
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if (DeflaterConstants.DEBUGGING && strstart != 1)
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throw new IllegalStateException("strstart not 1");
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adler.update(buffer, offset, length);
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if (length < MIN_MATCH)
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return;
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if (length > MAX_DIST) {
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offset += length - MAX_DIST;
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length = MAX_DIST;
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}
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System.arraycopy(buffer, offset, window, strstart, length);
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updateHash();
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length--;
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while (--length > 0)
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{
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insertString();
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strstart++;
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}
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strstart += 2;
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blockStart = strstart;
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}
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private boolean deflateStored(boolean flush, boolean finish)
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{
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if (!flush && lookahead == 0)
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return false;
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strstart += lookahead;
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lookahead = 0;
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int storedLen = strstart - blockStart;
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if ((storedLen >= DeflaterConstants.MAX_BLOCK_SIZE)
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/* Block is full */
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|| (blockStart < WSIZE && storedLen >= MAX_DIST)
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/* Block may move out of window */
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|| flush)
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{
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boolean lastBlock = finish;
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if (storedLen > DeflaterConstants.MAX_BLOCK_SIZE)
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{
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storedLen = DeflaterConstants.MAX_BLOCK_SIZE;
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lastBlock = false;
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}
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if (DeflaterConstants.DEBUGGING)
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System.err.println("storedBlock["+storedLen+","+lastBlock+"]");
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huffman.flushStoredBlock(window, blockStart, storedLen, lastBlock);
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blockStart += storedLen;
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return !lastBlock;
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}
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return true;
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}
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private boolean deflateFast(boolean flush, boolean finish)
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{
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if (lookahead < MIN_LOOKAHEAD && !flush)
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return false;
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while (lookahead >= MIN_LOOKAHEAD || flush)
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{
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if (lookahead == 0)
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{
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/* We are flushing everything */
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huffman.flushBlock(window, blockStart, strstart - blockStart,
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finish);
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blockStart = strstart;
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return false;
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}
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if (strstart > 2 * WSIZE - MIN_LOOKAHEAD)
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{
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/* slide window, as findLongestMatch need this.
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* This should only happen when flushing and the window
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* is almost full.
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*/
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slideWindow();
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}
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int hashHead;
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if (lookahead >= MIN_MATCH
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&& (hashHead = insertString()) != 0
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&& strategy != Deflater.HUFFMAN_ONLY
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&& strstart - hashHead <= MAX_DIST
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&& findLongestMatch(hashHead))
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{
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/* longestMatch sets matchStart and matchLen */
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if (DeflaterConstants.DEBUGGING)
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{
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for (int i = 0 ; i < matchLen; i++)
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{
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if (window[strstart+i] != window[matchStart + i])
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throw new InternalError();
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}
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}
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boolean full = huffman.tallyDist(strstart - matchStart, matchLen);
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lookahead -= matchLen;
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if (matchLen <= max_lazy && lookahead >= MIN_MATCH)
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{
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while (--matchLen > 0)
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{
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strstart++;
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insertString();
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}
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strstart++;
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}
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else
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{
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strstart += matchLen;
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if (lookahead >= MIN_MATCH - 1)
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updateHash();
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}
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matchLen = MIN_MATCH - 1;
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if (!full)
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continue;
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}
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else
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{
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/* No match found */
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huffman.tallyLit(window[strstart] & 0xff);
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strstart++;
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lookahead--;
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}
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if (huffman.isFull())
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{
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boolean lastBlock = finish && lookahead == 0;
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huffman.flushBlock(window, blockStart, strstart - blockStart,
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lastBlock);
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blockStart = strstart;
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return !lastBlock;
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}
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}
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return true;
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}
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private boolean deflateSlow(boolean flush, boolean finish)
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{
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if (lookahead < MIN_LOOKAHEAD && !flush)
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return false;
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while (lookahead >= MIN_LOOKAHEAD || flush)
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{
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if (lookahead == 0)
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{
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if (prevAvailable)
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huffman.tallyLit(window[strstart-1] & 0xff);
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prevAvailable = false;
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/* We are flushing everything */
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if (DeflaterConstants.DEBUGGING && !flush)
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throw new InternalError("Not flushing, but no lookahead");
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huffman.flushBlock(window, blockStart, strstart - blockStart,
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finish);
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blockStart = strstart;
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return false;
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}
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if (strstart >= 2 * WSIZE - MIN_LOOKAHEAD)
|
|
{
|
|
/* slide window, as findLongestMatch need this.
|
|
* This should only happen when flushing and the window
|
|
* is almost full.
|
|
*/
|
|
slideWindow();
|
|
}
|
|
|
|
int prevMatch = matchStart;
|
|
int prevLen = matchLen;
|
|
if (lookahead >= MIN_MATCH)
|
|
{
|
|
int hashHead = insertString();
|
|
if (strategy != Deflater.HUFFMAN_ONLY
|
|
&& hashHead != 0 && strstart - hashHead <= MAX_DIST
|
|
&& findLongestMatch(hashHead))
|
|
{
|
|
/* longestMatch sets matchStart and matchLen */
|
|
|
|
/* Discard match if too small and too far away */
|
|
if (matchLen <= 5
|
|
&& (strategy == Deflater.FILTERED
|
|
|| (matchLen == MIN_MATCH
|
|
&& strstart - matchStart > TOO_FAR))) {
|
|
matchLen = MIN_MATCH - 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* previous match was better */
|
|
if (prevLen >= MIN_MATCH && matchLen <= prevLen)
|
|
{
|
|
if (DeflaterConstants.DEBUGGING)
|
|
{
|
|
for (int i = 0 ; i < matchLen; i++)
|
|
{
|
|
if (window[strstart-1+i] != window[prevMatch + i])
|
|
throw new InternalError();
|
|
}
|
|
}
|
|
huffman.tallyDist(strstart - 1 - prevMatch, prevLen);
|
|
prevLen -= 2;
|
|
do
|
|
{
|
|
strstart++;
|
|
lookahead--;
|
|
if (lookahead >= MIN_MATCH)
|
|
insertString();
|
|
}
|
|
while (--prevLen > 0);
|
|
strstart ++;
|
|
lookahead--;
|
|
prevAvailable = false;
|
|
matchLen = MIN_MATCH - 1;
|
|
}
|
|
else
|
|
{
|
|
if (prevAvailable)
|
|
huffman.tallyLit(window[strstart-1] & 0xff);
|
|
prevAvailable = true;
|
|
strstart++;
|
|
lookahead--;
|
|
}
|
|
|
|
if (huffman.isFull())
|
|
{
|
|
int len = strstart - blockStart;
|
|
if (prevAvailable)
|
|
len--;
|
|
boolean lastBlock = (finish && lookahead == 0 && !prevAvailable);
|
|
huffman.flushBlock(window, blockStart, len, lastBlock);
|
|
blockStart += len;
|
|
return !lastBlock;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
public boolean deflate(boolean flush, boolean finish)
|
|
{
|
|
boolean progress;
|
|
do
|
|
{
|
|
fillWindow();
|
|
boolean canFlush = flush && inputOff == inputEnd;
|
|
if (DeflaterConstants.DEBUGGING)
|
|
System.err.println("window: ["+blockStart+","+strstart+","
|
|
+lookahead+"], "+comprFunc+","+canFlush);
|
|
switch (comprFunc)
|
|
{
|
|
case DEFLATE_STORED:
|
|
progress = deflateStored(canFlush, finish);
|
|
break;
|
|
case DEFLATE_FAST:
|
|
progress = deflateFast(canFlush, finish);
|
|
break;
|
|
case DEFLATE_SLOW:
|
|
progress = deflateSlow(canFlush, finish);
|
|
break;
|
|
default:
|
|
throw new InternalError();
|
|
}
|
|
}
|
|
while (pending.isFlushed() /* repeat while we have no pending output */
|
|
&& progress); /* and progress was made */
|
|
|
|
return progress;
|
|
}
|
|
|
|
public void setInput(byte[] buf, int off, int len)
|
|
{
|
|
if (inputOff < inputEnd)
|
|
throw new IllegalStateException
|
|
("Old input was not completely processed");
|
|
|
|
int end = off + len;
|
|
|
|
/* We want to throw an ArrayIndexOutOfBoundsException early. The
|
|
* check is very tricky: it also handles integer wrap around.
|
|
*/
|
|
if (0 > off || off > end || end > buf.length)
|
|
throw new ArrayIndexOutOfBoundsException();
|
|
|
|
inputBuf = buf;
|
|
inputOff = off;
|
|
inputEnd = end;
|
|
}
|
|
|
|
public final boolean needsInput()
|
|
{
|
|
return inputEnd == inputOff;
|
|
}
|
|
}
|