279 lines
9.6 KiB
C#
279 lines
9.6 KiB
C#
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// Zlib.cs
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// ------------------------------------------------------------------
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//
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// Copyright (c) 2009 Dino Chiesa and Microsoft Corporation.
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// All rights reserved.
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//
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// This code module is part of DotNetZip, a zipfile class library.
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//
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// ------------------------------------------------------------------
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//
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// This code is licensed under the Microsoft Public License.
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// See the file License.txt for the license details.
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// More info on: http://dotnetzip.codeplex.com
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//
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// ------------------------------------------------------------------
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//
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// last saved (in emacs):
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// Time-stamp: <2009-November-07 05:26:55>
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//
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// ------------------------------------------------------------------
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//
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// This module defines classes for ZLIB compression and
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// decompression. This code is derived from the jzlib implementation of
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// zlib, but significantly modified. The object model is not the same,
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// and many of the behaviors are new or different. Nonetheless, in
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// keeping with the license for jzlib, the copyright to that code is
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// included below.
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//
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// ------------------------------------------------------------------
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//
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// Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in
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// the documentation and/or other materials provided with the distribution.
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//
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// 3. The names of the authors may not be used to endorse or promote products
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// derived from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
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// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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// FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
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// INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
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// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// -----------------------------------------------------------------------
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//
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// This program is based on zlib-1.1.3; credit to authors
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// Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
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// and contributors of zlib.
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//
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// -----------------------------------------------------------------------
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namespace SharpCompress.Compressor.Deflate
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{
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/// <summary>
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/// The compression level to be used when using a DeflateStream or ZlibStream with CompressionMode.Compress.
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/// </summary>
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internal enum CompressionLevel
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{
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/// <summary>
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/// None means that the data will be simply stored, with no change at all.
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/// If you are producing ZIPs for use on Mac OSX, be aware that archives produced with CompressionLevel.None
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/// cannot be opened with the default zip reader. Use a different CompressionLevel.
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/// </summary>
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None = 0,
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/// <summary>
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/// Same as None.
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/// </summary>
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Level0 = 0,
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/// <summary>
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/// The fastest but least effective compression.
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/// </summary>
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BestSpeed = 1,
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/// <summary>
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/// A synonym for BestSpeed.
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/// </summary>
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Level1 = 1,
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/// <summary>
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/// A little slower, but better, than level 1.
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/// </summary>
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Level2 = 2,
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/// <summary>
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/// A little slower, but better, than level 2.
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/// </summary>
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Level3 = 3,
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/// <summary>
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/// A little slower, but better, than level 3.
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/// </summary>
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Level4 = 4,
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/// <summary>
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/// A little slower than level 4, but with better compression.
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/// </summary>
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Level5 = 5,
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/// <summary>
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/// The default compression level, with a good balance of speed and compression efficiency.
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/// </summary>
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Default = 6,
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/// <summary>
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/// A synonym for Default.
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/// </summary>
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Level6 = 6,
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/// <summary>
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/// Pretty good compression!
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/// </summary>
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Level7 = 7,
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/// <summary>
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/// Better compression than Level7!
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/// </summary>
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Level8 = 8,
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/// <summary>
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/// The "best" compression, where best means greatest reduction in size of the input data stream.
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/// This is also the slowest compression.
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/// </summary>
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BestCompression = 9,
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/// <summary>
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/// A synonym for BestCompression.
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/// </summary>
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Level9 = 9,
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}
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/// <summary>
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/// Describes options for how the compression algorithm is executed. Different strategies
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/// work better on different sorts of data. The strategy parameter can affect the compression
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/// ratio and the speed of compression but not the correctness of the compresssion.
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/// </summary>
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internal enum CompressionStrategy
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{
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/// <summary>
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/// The default strategy is probably the best for normal data.
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/// </summary>
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Default = 0,
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/// <summary>
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/// The <c>Filtered</c> strategy is intended to be used most effectively with data produced by a
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/// filter or predictor. By this definition, filtered data consists mostly of small
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/// values with a somewhat random distribution. In this case, the compression algorithm
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/// is tuned to compress them better. The effect of <c>Filtered</c> is to force more Huffman
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/// coding and less string matching; it is a half-step between <c>Default</c> and <c>HuffmanOnly</c>.
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/// </summary>
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Filtered = 1,
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/// <summary>
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/// Using <c>HuffmanOnly</c> will force the compressor to do Huffman encoding only, with no
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/// string matching.
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/// </summary>
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HuffmanOnly = 2,
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}
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/// <summary>
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/// A general purpose exception class for exceptions in the Zlib library.
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/// </summary>
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internal class ZlibException : System.Exception
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{
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/// <summary>
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/// The ZlibException class captures exception information generated
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/// by the Zlib library.
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/// </summary>
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public ZlibException()
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: base()
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{
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}
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/// <summary>
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/// This ctor collects a message attached to the exception.
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/// </summary>
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/// <param name="s"></param>
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public ZlibException(System.String s)
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: base(s)
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{
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}
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}
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/// <summary>
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/// Computes an Adler-32 checksum.
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/// </summary>
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/// <remarks>
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/// The Adler checksum is similar to a CRC checksum, but faster to compute, though less
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/// reliable. It is used in producing RFC1950 compressed streams. The Adler checksum
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/// is a required part of the "ZLIB" standard. Applications will almost never need to
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/// use this class directly.
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/// </remarks>
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internal sealed class Adler
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{
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// largest prime smaller than 65536
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private static readonly int BASE = 65521;
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// NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
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private static readonly int NMAX = 5552;
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internal static uint Adler32(uint adler, byte[] buf, int index, int len)
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{
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if (buf == null)
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return 1;
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int s1 = (int) (adler & 0xffff);
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int s2 = (int) ((adler >> 16) & 0xffff);
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while (len > 0)
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{
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int k = len < NMAX ? len : NMAX;
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len -= k;
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while (k >= 16)
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{
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//s1 += (buf[index++] & 0xff); s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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s1 += buf[index++];
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s2 += s1;
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k -= 16;
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}
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if (k != 0)
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{
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do
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{
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s1 += buf[index++];
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s2 += s1;
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} while (--k != 0);
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}
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s1 %= BASE;
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s2 %= BASE;
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}
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return (uint) ((s2 << 16) | s1);
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}
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}
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}
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