// DeflaterEngine.cs
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program 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
// of the License, or (at your option) any later version.
//
// This program 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 this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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.
using System;
using ICSharpCode.SharpZipLib.Checksums;
namespace ICSharpCode.SharpZipLib.Zip.Compression
{
public enum DeflateStrategy
{
// The default strategy.
Default = 0,
// This strategy will only allow longer string repetitions. It is
// useful for random data with a small character set.
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.
HuffmanOnly = 2
}
public class DeflaterEngine : DeflaterConstants
{
static int TOO_FAR = 4096;
int ins_h;
// private byte[] buffer;
short[] head;
short[] prev;
int matchStart, matchLen;
bool prevAvailable;
int blockStart;
int strstart, lookahead;
byte[] window;
DeflateStrategy strategy;
int max_chain, max_lazy, niceLength, goodLength;
/// <summary>
/// The current compression function.
/// </summary>
int comprFunc;
/// <summary>
/// The input data for compression.
/// </summary>
byte[] inputBuf;
/// <summary>
/// The total bytes of input read.
/// </summary>
int totalIn;
/// <summary>
/// The offset into inputBuf, where input data starts.
/// </summary>
int inputOff;
/// <summary>
/// The end offset of the input data.
/// </summary>
int inputEnd;
DeflaterPending pending;
DeflaterHuffman huffman;
/// <summary>
/// The adler checksum
/// </summary>
Adler32 adler;
public DeflaterEngine(DeflaterPending pending)
{
this.pending = pending;
huffman = new DeflaterHuffman(pending);
adler = new Adler32();
window = new byte[2 * WSIZE];
head = new short[HASH_SIZE];
prev = new short[WSIZE];
/* We start at index 1, to avoid a implementation deficiency, that
* we cannot build a repeat pattern at index 0.
*/
blockStart = strstart = 1;
}
public void Reset()
{
huffman.Reset();
adler.Reset();
blockStart = strstart = 1;
lookahead = 0;
totalIn = 0;
prevAvailable = false;
matchLen = MIN_MATCH - 1;
for (int i = 0; i < HASH_SIZE; i++)
{
head[i] = 0;
}
for (int i = 0; i < WSIZE; i++)
{
prev[i] = 0;
}
}
public void ResetAdler()
{
adler.Reset();
}
public int Adler
{
get
{
return (int)adler.Value;
}
}
public int TotalIn
{
get
{
return totalIn;
}
}
public DeflateStrategy Strategy
{
get
{
return strategy;
}
set
{
strategy = value;
}
}
public void SetLevel(int lvl)
{
goodLength = DeflaterConstants.GOOD_LENGTH[lvl];
max_lazy = DeflaterConstants.MAX_LAZY[lvl];
niceLength = DeflaterConstants.NICE_LENGTH[lvl];
max_chain = DeflaterConstants.MAX_CHAIN[lvl];
if (DeflaterConstants.COMPR_FUNC[lvl] != comprFunc)
{
// if (DeflaterConstants.DEBUGGING) {
// //Console.WriteLine("Change from "+comprFunc +" to "
// + DeflaterConstants.COMPR_FUNC[lvl]);
// }
switch (comprFunc)
{
case DEFLATE_STORED:
if (strstart > blockStart)
{
huffman.FlushStoredBlock(window, blockStart,
strstart - blockStart, false);
blockStart = strstart;
}
UpdateHash();
break;
case DEFLATE_FAST:
if (strstart > blockStart)
{
huffman.FlushBlock(window, blockStart, strstart - blockStart,
false);
blockStart = strstart;
}
break;
case DEFLATE_SLOW:
if (prevAvailable)
{
huffman.TallyLit(window[strstart-1] & 0xff);
}
if (strstart > blockStart)
{
huffman.FlushBlock(window, blockStart, strstart - blockStart,
false);
blockStart = strstart;
}
prevAvailable = false;
matchLen = MIN_MATCH - 1;
break;
}
comprFunc = COMPR_FUNC[lvl];
}
}
private void UpdateHash()
{
// if (DEBUGGING) {
// //Console.WriteLine("updateHash: "+strstart);
// }
ins_h = (window[strstart] << HASH_SHIFT) ^ window[strstart + 1];
}
private int InsertString()
{
short match;
int hash = ((ins_h << HASH_SHIFT) ^ window[strstart + (MIN_MATCH -1)]) & HASH_MASK;
// if (DEBUGGING) {
// if (hash != (((window[strstart] << (2*HASH_SHIFT)) ^
// (window[strstart + 1] << HASH_SHIFT) ^
// (window[strstart + 2])) & HASH_MASK)) {
// throw new Exception("hash inconsistent: "+hash+"/"
// +window[strstart]+","
// +window[strstart+1]+","
// +window[strstart+2]+","+HASH_SHIFT);
// }
// }
prev[strstart & WMASK] = match = head[hash];
head[hash] = (short)strstart;
ins_h = hash;
return match & 0xffff;
}
void SlideWindow()
{
Array.Copy(window, WSIZE, window, 0, WSIZE);
matchStart -= WSIZE;
strstart -= WSIZE;
blockStart -= WSIZE;
/* Slide the hash table (could be avoided with 32 bit values
* at the expense of memory usage).
*/
for (int i = 0; i < HASH_SIZE; ++i)
{
int m = head[i] & 0xffff;
head[i] = (short)(m >= WSIZE ? (m - WSIZE) : 0);
}
/* Slide the prev table. */
for (int i = 0; i < WSIZE; i++)
{
int m = prev[i] & 0xffff;
prev[i] = (short)(m >= WSIZE ? (m - WSIZE) : 0);
}
}
public void FillWindow()
{
/* If the window is almost full and there is insufficient lookahead,
* move the upper half to the lower one to make room in the upper half.
*/
if (strstart >= WSIZE + MAX_DIST)
{
SlideWindow();
}
/* If there is not enough lookahead, but still some input left,
* read in the input
*/
while (lookahead < DeflaterConstants.MIN_LOOKAHEAD && inputOff < inputEnd)
{
int more = 2 * WSIZE - lookahead - strstart;
if (more > inputEnd - inputOff)
{
more = inputEnd - inputOff;
}
System.Array.Copy(inputBuf, inputOff, window, strstart + lookahead, more);
adler.Update(inputBuf, inputOff, more);
inputOff += more;
totalIn += more;
lookahead += more;
}
if (lookahead >= MIN_MATCH)
{
UpdateHash();
}
}
private bool FindLongestMatch(int curMatch)
{
int chainLength = this.max_chain;
int niceLength = this.niceLength;
short[] prev = this.prev;
int scan = this.strstart;
int match;
int best_end = this.strstart + matchLen;
int best_len = Math.Max(matchLen, MIN_MATCH - 1);
int limit = Math.Max(strstart - MAX_DIST, 0);
int strend = strstart + MAX_MATCH - 1;
byte scan_end1 = window[best_end - 1];
byte scan_end = window[best_end];
/* Do not waste too much time if we already have a good match: */
if (best_len >= this.goodLength)
{
chainLength >>= 2;
}
/* Do not look for matches beyond the end of the input. This is necessary
* to make deflate deterministic.
*/
if (niceLength > lookahead)
{
niceLength = lookahead;
}
if (DeflaterConstants.DEBUGGING && strstart > 2 * WSIZE - MIN_LOOKAHEAD)
{
throw new InvalidOperationException("need lookahead");
}
do
{
if (DeflaterConstants.DEBUGGING && curMatch >= strstart)
{
throw new InvalidOperationException("future match");
}
if (window[curMatch + best_len] != scan_end ||
window[curMatch + best_len - 1] != scan_end1 ||
window[curMatch] != window[scan] ||
window[curMatch + 1] != window[scan + 1])
{
continue;
}
match = curMatch + 2;
scan += 2;
/* We check for insufficient lookahead only every 8th comparison;
* the 256th check will be made at strstart+258.
*/
while (window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] &&
window[++scan] == window[++match] && scan < strend) ;
if (scan > best_end)
{
// if (DeflaterConstants.DEBUGGING && ins_h == 0)
// System.err.println("Found match: "+curMatch+"-"+(scan-strstart));
matchStart = curMatch;
best_end = scan;
best_len = scan - strstart;
if (best_len >= niceLength)
{
break;
}
scan_end1 = window[best_end - 1];
scan_end = window[best_end];
}
scan = strstart;
} while ((curMatch = (prev[curMatch & WMASK] & 0xffff)) > limit && --chainLength != 0);
matchLen = Math.Min(best_len, lookahead);
return matchLen >= MIN_MATCH;
}
public void SetDictionary(byte[] buffer, int offset, int length)
{
if (DeflaterConstants.DEBUGGING && strstart != 1)
{
throw new InvalidOperationException("strstart not 1");
}
adler.Update(buffer, offset, length);
if (length < MIN_MATCH)
{
return;
}
if (length > MAX_DIST)
{
offset += length - MAX_DIST;
length = MAX_DIST;
}
System.Array.Copy(buffer, offset, window, strstart, length);
UpdateHash();
--length;
while (--length > 0)
{
InsertString();
strstart++;
}
strstart += 2;
blockStart = strstart;
}
private bool DeflateStored(bool flush, bool finish)
{
if (!flush && lookahead == 0)
{
return false;
}
strstart += lookahead;
lookahead = 0;
int storedLen = strstart - blockStart;
if ((storedLen >= DeflaterConstants.MAX_BLOCK_SIZE) || /* Block is full */
(blockStart < WSIZE && storedLen >= MAX_DIST) || /* Block may move out of window */
flush)
{
bool lastBlock = finish;
if (storedLen > DeflaterConstants.MAX_BLOCK_SIZE)
{
storedLen = DeflaterConstants.MAX_BLOCK_SIZE;
lastBlock = false;
}
// if (DeflaterConstants.DEBUGGING) {
// //Console.WriteLine("storedBlock["+storedLen+","+lastBlock+"]");
// }
huffman.FlushStoredBlock(window, blockStart, storedLen, lastBlock);
blockStart += storedLen;
return !lastBlock;
}
return true;
}
private bool DeflateFast(bool flush, bool finish)
{
if (lookahead < MIN_LOOKAHEAD && !flush)
{
return false;
}
while (lookahead >= MIN_LOOKAHEAD || flush)
{
if (lookahead == 0)
{
/* We are flushing everything */
huffman.FlushBlock(window, blockStart, strstart - blockStart, finish);
blockStart = strstart;
return false;
}
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 hashHead;
if (lookahead >= MIN_MATCH &&
(hashHead = InsertString()) != 0 &&
strategy != DeflateStrategy.HuffmanOnly &&
strstart - hashHead <= MAX_DIST &&
FindLongestMatch(hashHead))
{
/* longestMatch sets matchStart and matchLen */
// if (DeflaterConstants.DEBUGGING) {
// for (int i = 0 ; i < matchLen; i++) {
// if (window[strstart+i] != window[matchStart + i]) {
// throw new Exception();
// }
// }
// }
huffman.TallyDist(strstart - matchStart, matchLen);
lookahead -= matchLen;
if (matchLen <= max_lazy && lookahead >= MIN_MATCH)
{
while (--matchLen > 0)
{
++strstart;
InsertString();
}
++strstart;
}
else
{
strstart += matchLen;
if (lookahead >= MIN_MATCH - 1)
{
UpdateHash();
}
}
matchLen = MIN_MATCH - 1;
continue;
}
else
{
/* No match found */
huffman.TallyLit(window[strstart] & 0xff);
++strstart;
--lookahead;
}
if (huffman.IsFull())
{
bool lastBlock = finish && lookahead == 0;
huffman.FlushBlock(window, blockStart, strstart - blockStart,
lastBlock);
blockStart = strstart;
return !lastBlock;
}
}
return true;
}
private bool DeflateSlow(bool flush, bool finish)
{
if (lookahead < MIN_LOOKAHEAD && !flush)
{
return false;
}
while (lookahead >= MIN_LOOKAHEAD || flush)
{
if (lookahead == 0)
{
if (prevAvailable)
{
huffman.TallyLit(window[strstart-1] & 0xff);
}
prevAvailable = false;
/* We are flushing everything */
if (DeflaterConstants.DEBUGGING && !flush)
{
throw new Exception("Not flushing, but no lookahead");
}
huffman.FlushBlock(window, blockStart, strstart - blockStart,
finish);
blockStart = strstart;
return false;
}
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 != DeflateStrategy.HuffmanOnly && 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 == DeflateStrategy.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 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;
}
}
}
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