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654 lines
18 KiB
C#
654 lines
18 KiB
C#
// DeflaterEngine.cs
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// Copyright (C) 2001 Mike Krueger
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//
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// This file was translated from java, it was part of the GNU Classpath
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// Copyright (C) 2001 Free Software Foundation, Inc.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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//
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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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//
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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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using System;
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using ICSharpCode.SharpZipLib.Checksums;
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namespace ICSharpCode.SharpZipLib.Zip.Compression
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{
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public enum DeflateStrategy
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{
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// The default strategy.
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Default = 0,
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// This strategy will only allow longer string repetitions. It is
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// useful for random data with a small character set.
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Filtered = 1,
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// This strategy will not look for string repetitions at all. It
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// only encodes with Huffman trees (which means, that more common
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// characters get a smaller encoding.
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HuffmanOnly = 2
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}
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public class DeflaterEngine : DeflaterConstants
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{
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static int TOO_FAR = 4096;
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int ins_h;
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// private byte[] buffer;
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short[] head;
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short[] prev;
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int matchStart, matchLen;
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bool prevAvailable;
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int blockStart;
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int strstart, lookahead;
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byte[] window;
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DeflateStrategy strategy;
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int max_chain, max_lazy, niceLength, goodLength;
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/// <summary>
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/// The current compression function.
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/// </summary>
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int comprFunc;
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/// <summary>
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/// The input data for compression.
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/// </summary>
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byte[] inputBuf;
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/// <summary>
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/// The total bytes of input read.
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/// </summary>
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int totalIn;
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/// <summary>
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/// The offset into inputBuf, where input data starts.
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/// </summary>
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int inputOff;
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/// <summary>
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/// The end offset of the input data.
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/// </summary>
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int inputEnd;
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DeflaterPending pending;
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DeflaterHuffman huffman;
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/// <summary>
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/// The adler checksum
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/// </summary>
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Adler32 adler;
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public DeflaterEngine(DeflaterPending pending)
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{
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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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}
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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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}
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public void ResetAdler()
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{
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adler.Reset();
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}
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public int Adler {
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get {
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return (int)adler.Value;
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}
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}
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public int TotalIn {
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get {
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return totalIn;
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}
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}
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public DeflateStrategy Strategy {
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get {
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return strategy;
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}
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set {
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strategy = value;
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}
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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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// if (DeflaterConstants.DEBUGGING) {
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// //Console.WriteLine("Change from "+comprFunc +" to "
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// + DeflaterConstants.COMPR_FUNC[lvl]);
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// }
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switch (comprFunc) {
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case DEFLATE_STORED:
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if (strstart > blockStart) {
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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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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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}
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if (strstart > blockStart) {
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huffman.FlushBlock(window, blockStart, strstart - blockStart, 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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void UpdateHash()
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{
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// if (DEBUGGING) {
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// //Console.WriteLine("updateHash: "+strstart);
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// }
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ins_h = (window[strstart] << HASH_SHIFT) ^ window[strstart + 1];
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}
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int InsertString()
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{
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short match;
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int hash = ((ins_h << HASH_SHIFT) ^ window[strstart + (MIN_MATCH -1)]) & HASH_MASK;
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// if (DEBUGGING) {
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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 Exception("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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// }
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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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void SlideWindow()
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{
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Array.Copy(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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int m = head[i] & 0xffff;
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head[i] = (short)(m >= WSIZE ? (m - WSIZE) : 0);
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}
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/* Slide the prev table. */
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for (int i = 0; i < WSIZE; i++) {
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int m = prev[i] & 0xffff;
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prev[i] = (short)(m >= WSIZE ? (m - WSIZE) : 0);
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}
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}
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public 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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}
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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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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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}
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System.Array.Copy(inputBuf, inputOff, 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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bool FindLongestMatch(int curMatch)
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{
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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 = strstart + 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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}
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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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}
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if (DeflaterConstants.DEBUGGING && strstart > 2 * WSIZE - MIN_LOOKAHEAD) {
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throw new InvalidOperationException("need lookahead");
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}
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do {
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if (DeflaterConstants.DEBUGGING && curMatch >= strstart) {
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throw new InvalidOperationException("future match");
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}
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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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}
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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] && scan < strend) ;
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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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}
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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 && --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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public void SetDictionary(byte[] buffer, int offset, int length)
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{
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if (DeflaterConstants.DEBUGGING && strstart != 1) {
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throw new InvalidOperationException("strstart not 1");
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}
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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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}
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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.Array.Copy(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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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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bool DeflateStored(bool flush, bool finish)
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{
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if (!flush && lookahead == 0) {
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return false;
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}
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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) || /* Block is full */
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(blockStart < WSIZE && storedLen >= MAX_DIST) || /* Block may move out of window */
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flush) {
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bool lastBlock = finish;
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if (storedLen > DeflaterConstants.MAX_BLOCK_SIZE) {
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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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// //Console.WriteLine("storedBlock["+storedLen+","+lastBlock+"]");
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// }
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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 bool DeflateFast(bool flush, bool finish)
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{
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if (lookahead < MIN_LOOKAHEAD && !flush) {
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return false;
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}
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while (lookahead >= MIN_LOOKAHEAD || flush) {
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if (lookahead == 0) {
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/* We are flushing everything */
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huffman.FlushBlock(window, blockStart, strstart - blockStart, 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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/* 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 != DeflateStrategy.HuffmanOnly &&
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strstart - hashHead <= MAX_DIST &&
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FindLongestMatch(hashHead)) {
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/* longestMatch sets matchStart and matchLen */
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// if (DeflaterConstants.DEBUGGING) {
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// for (int i = 0 ; i < matchLen; i++) {
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// if (window[strstart+i] != window[matchStart + i]) {
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// throw new Exception();
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// }
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// }
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// }
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// -jr- Hak hak hak this stops problems with fast/low compression and index out of range
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if (huffman.TallyDist(strstart - matchStart, matchLen)) {
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bool lastBlock = finish && lookahead == 0;
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huffman.FlushBlock(window, blockStart, strstart - blockStart, lastBlock);
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blockStart = strstart;
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}
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lookahead -= matchLen;
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if (matchLen <= max_lazy && lookahead >= MIN_MATCH) {
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while (--matchLen > 0) {
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++strstart;
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InsertString();
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}
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++strstart;
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} else {
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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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}
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matchLen = MIN_MATCH - 1;
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continue;
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} else {
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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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bool lastBlock = finish && lookahead == 0;
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huffman.FlushBlock(window, blockStart, strstart - blockStart, 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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bool DeflateSlow(bool flush, bool finish)
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{
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if (lookahead < MIN_LOOKAHEAD && !flush) {
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return false;
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}
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while (lookahead >= MIN_LOOKAHEAD || flush) {
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if (lookahead == 0) {
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if (prevAvailable) {
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huffman.TallyLit(window[strstart-1] & 0xff);
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}
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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 Exception("Not flushing, but no lookahead");
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}
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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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/* 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 prevMatch = matchStart;
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int prevLen = matchLen;
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if (lookahead >= MIN_MATCH) {
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int hashHead = InsertString();
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if (strategy != DeflateStrategy.HuffmanOnly && hashHead != 0 && strstart - hashHead <= MAX_DIST && FindLongestMatch(hashHead)) {
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/* longestMatch sets matchStart and matchLen */
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/* Discard match if too small and too far away */
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if (matchLen <= 5 && (strategy == DeflateStrategy.Filtered || (matchLen == MIN_MATCH && strstart - matchStart > TOO_FAR))) {
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matchLen = MIN_MATCH - 1;
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}
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}
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}
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/* 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 Exception();
|
|
// }
|
|
// }
|
|
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--;
|
|
}
|
|
bool lastBlock = (finish && lookahead == 0 && !prevAvailable);
|
|
huffman.FlushBlock(window, blockStart, len, lastBlock);
|
|
blockStart += len;
|
|
return !lastBlock;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
public bool Deflate(bool flush, bool finish)
|
|
{
|
|
bool progress;
|
|
do {
|
|
FillWindow();
|
|
bool canFlush = flush && inputOff == inputEnd;
|
|
// if (DeflaterConstants.DEBUGGING) {
|
|
// //Console.WriteLine("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 InvalidOperationException("unknown comprFunc");
|
|
}
|
|
} while (pending.IsFlushed && progress); /* repeat while we have no pending output and progress was made */
|
|
return progress;
|
|
}
|
|
|
|
public void SetInput(byte[] buf, int off, int len)
|
|
{
|
|
if (inputOff < inputEnd) {
|
|
throw new InvalidOperationException("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 ArgumentOutOfRangeException();
|
|
}
|
|
|
|
inputBuf = buf;
|
|
inputOff = off;
|
|
inputEnd = end;
|
|
}
|
|
|
|
public bool NeedsInput()
|
|
{
|
|
return inputEnd == inputOff;
|
|
}
|
|
}
|
|
}
|