// Zlib.cs
// ------------------------------------------------------------------
//
// Copyright (c) 2009-2011 Dino Chiesa and Microsoft Corporation.
// All rights reserved.
//
// This code module is part of DotNetZip, a zipfile class library.
//
// ------------------------------------------------------------------
//
// This code is licensed under the Microsoft Public License.
// See the file License.txt for the license details.
// More info on: http://dotnetzip.codeplex.com
//
// ------------------------------------------------------------------
//
// Last Saved: <2011-August-03 19:52:28>
//
// ------------------------------------------------------------------
//
// This module defines classes for ZLIB compression and
// decompression. This code is derived from the jzlib implementation of
// zlib, but significantly modified.  The object model is not the same,
// and many of the behaviors are new or different.  Nonetheless, in
// keeping with the license for jzlib, the copyright to that code is
// included below.
//
// ------------------------------------------------------------------
//
// The following notice applies to jzlib:
//
// Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the distribution.
//
// 3. The names of the authors may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
// INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// -----------------------------------------------------------------------
//
// jzlib is based on zlib-1.1.3.
//
// The following notice applies to zlib:
//
// -----------------------------------------------------------------------
//
// Copyright (C) 1995-2004 Jean-loup Gailly and Mark Adler
//
//   The ZLIB software is provided 'as-is', without any express or implied
//   warranty.  In no event will the authors be held liable for any damages
//   arising from the use of this software.
//
//   Permission is granted to anyone to use this software for any purpose,
//   including commercial applications, and to alter it and redistribute it
//   freely, subject to the following restrictions:
//
//   1. The origin of this software must not be misrepresented; you must not
//      claim that you wrote the original software. If you use this software
//      in a product, an acknowledgment in the product documentation would be
//      appreciated but is not required.
//   2. Altered source versions must be plainly marked as such, and must not be
//      misrepresented as being the original software.
//   3. This notice may not be removed or altered from any source distribution.
//
//   Jean-loup Gailly jloup@gzip.org
//   Mark Adler madler@alumni.caltech.edu
//
// -----------------------------------------------------------------------



using System;
using Interop=System.Runtime.InteropServices;

namespace BestHTTP.Decompression.Zlib
{

    /// <summary>
    /// Describes how to flush the current deflate operation.
    /// </summary>
    /// <remarks>
    /// The different FlushType values are useful when using a Deflate in a streaming application.
    /// </remarks>
    public enum FlushType
    {
        /// <summary>No flush at all.</summary>
        None = 0,

        /// <summary>Closes the current block, but doesn't flush it to
        /// the output. Used internally only in hypothetical
        /// scenarios.  This was supposed to be removed by Zlib, but it is
        /// still in use in some edge cases.
        /// </summary>
        Partial,

        /// <summary>
        /// Use this during compression to specify that all pending output should be
        /// flushed to the output buffer and the output should be aligned on a byte
        /// boundary.  You might use this in a streaming communication scenario, so that
        /// the decompressor can get all input data available so far.  When using this
        /// with a ZlibCodec, <c>AvailableBytesIn</c> will be zero after the call if
        /// enough output space has been provided before the call.  Flushing will
        /// degrade compression and so it should be used only when necessary.
        /// </summary>
        Sync,

        /// <summary>
        /// Use this during compression to specify that all output should be flushed, as
        /// with <c>FlushType.Sync</c>, but also, the compression state should be reset
        /// so that decompression can restart from this point if previous compressed
        /// data has been damaged or if random access is desired.  Using
        /// <c>FlushType.Full</c> too often can significantly degrade the compression.
        /// </summary>
        Full,

        /// <summary>Signals the end of the compression/decompression stream.</summary>
        Finish,
    }


    /// <summary>
    /// The compression level to be used when using a DeflateStream or ZlibStream with CompressionMode.Compress.
    /// </summary>
    public enum CompressionLevel
    {
        /// <summary>
        /// None means that the data will be simply stored, with no change at all.
        /// If you are producing ZIPs for use on Mac OSX, be aware that archives produced with CompressionLevel.None
        /// cannot be opened with the default zip reader. Use a different CompressionLevel.
        /// </summary>
        None= 0,
        /// <summary>
        /// Same as None.
        /// </summary>
        Level0 = 0,

        /// <summary>
        /// The fastest but least effective compression.
        /// </summary>
        BestSpeed = 1,

        /// <summary>
        /// A synonym for BestSpeed.
        /// </summary>
        Level1 = 1,

        /// <summary>
        /// A little slower, but better, than level 1.
        /// </summary>
        Level2 = 2,

        /// <summary>
        /// A little slower, but better, than level 2.
        /// </summary>
        Level3 = 3,

        /// <summary>
        /// A little slower, but better, than level 3.
        /// </summary>
        Level4 = 4,

        /// <summary>
        /// A little slower than level 4, but with better compression.
        /// </summary>
        Level5 = 5,

        /// <summary>
        /// The default compression level, with a good balance of speed and compression efficiency.
        /// </summary>
        Default = 6,
        /// <summary>
        /// A synonym for Default.
        /// </summary>
        Level6 = 6,

        /// <summary>
        /// Pretty good compression!
        /// </summary>
        Level7 = 7,

        /// <summary>
        ///  Better compression than Level7!
        /// </summary>
        Level8 = 8,

        /// <summary>
        /// The "best" compression, where best means greatest reduction in size of the input data stream.
        /// This is also the slowest compression.
        /// </summary>
        BestCompression = 9,

        /// <summary>
        /// A synonym for BestCompression.
        /// </summary>
        Level9 = 9,
    }

    /// <summary>
    /// Describes options for how the compression algorithm is executed.  Different strategies
    /// work better on different sorts of data.  The strategy parameter can affect the compression
    /// ratio and the speed of compression but not the correctness of the compresssion.
    /// </summary>
    public enum CompressionStrategy
    {
        /// <summary>
        /// The default strategy is probably the best for normal data.
        /// </summary>
        Default = 0,

        /// <summary>
        /// The <c>Filtered</c> strategy is intended to be used most effectively with data produced by a
        /// filter or predictor.  By this definition, filtered data consists mostly of small
        /// values with a somewhat random distribution.  In this case, the compression algorithm
        /// is tuned to compress them better.  The effect of <c>Filtered</c> is to force more Huffman
        /// coding and less string matching; it is a half-step between <c>Default</c> and <c>HuffmanOnly</c>.
        /// </summary>
        Filtered = 1,

        /// <summary>
        /// Using <c>HuffmanOnly</c> will force the compressor to do Huffman encoding only, with no
        /// string matching.
        /// </summary>
        HuffmanOnly = 2,
    }


    /// <summary>
    /// An enum to specify the direction of transcoding - whether to compress or decompress.
    /// </summary>
    public enum CompressionMode
    {
        /// <summary>
        /// Used to specify that the stream should compress the data.
        /// </summary>
        Compress= 0,
        /// <summary>
        /// Used to specify that the stream should decompress the data.
        /// </summary>
        Decompress = 1,
    }


    /// <summary>
    /// A general purpose exception class for exceptions in the Zlib library.
    /// </summary>
    [Interop.GuidAttribute("ebc25cf6-9120-4283-b972-0e5520d0000E")]
    internal class ZlibException : System.Exception
    {
        /// <summary>
        /// The ZlibException class captures exception information generated
        /// by the Zlib library.
        /// </summary>
        public ZlibException()
            : base()
        {
        }

        /// <summary>
        /// This ctor collects a message attached to the exception.
        /// </summary>
        /// <param name="s">the message for the exception.</param>
        public ZlibException(System.String s)
            : base(s)
        {
        }
    }


    internal class SharedUtils
    {
        /// <summary>
        /// Performs an unsigned bitwise right shift with the specified number
        /// </summary>
        /// <param name="number">Number to operate on</param>
        /// <param name="bits">Ammount of bits to shift</param>
        /// <returns>The resulting number from the shift operation</returns>
        public static int URShift(int number, int bits)
        {
            return (int)((uint)number >> bits);
        }

#if NOT
        /// <summary>
        /// Performs an unsigned bitwise right shift with the specified number
        /// </summary>
        /// <param name="number">Number to operate on</param>
        /// <param name="bits">Ammount of bits to shift</param>
        /// <returns>The resulting number from the shift operation</returns>
        public static long URShift(long number, int bits)
        {
            return (long) ((UInt64)number >> bits);
        }
#endif

        /// <summary>
        ///   Reads a number of characters from the current source TextReader and writes
        ///   the data to the target array at the specified index.
        /// </summary>
        ///
        /// <param name="sourceTextReader">The source TextReader to read from</param>
        /// <param name="target">Contains the array of characteres read from the source TextReader.</param>
        /// <param name="start">The starting index of the target array.</param>
        /// <param name="count">The maximum number of characters to read from the source TextReader.</param>
        ///
        /// <returns>
        ///   The number of characters read. The number will be less than or equal to
        ///   count depending on the data available in the source TextReader. Returns -1
        ///   if the end of the stream is reached.
        /// </returns>
        public static System.Int32 ReadInput(System.IO.TextReader sourceTextReader, byte[] target, int start, int count)
        {
            // Returns 0 bytes if not enough space in target
            if (target.Length == 0) return 0;

            char[] charArray = new char[target.Length];
            int bytesRead = sourceTextReader.Read(charArray, start, count);

            // Returns -1 if EOF
            if (bytesRead == 0) return -1;

            for (int index = start; index < start + bytesRead; index++)
                target[index] = (byte)charArray[index];

            return bytesRead;
        }


        internal static byte[] ToByteArray(System.String sourceString)
        {
            return System.Text.UTF8Encoding.UTF8.GetBytes(sourceString);
        }


        internal static char[] ToCharArray(byte[] byteArray)
        {
            return System.Text.UTF8Encoding.UTF8.GetChars(byteArray);
        }
    }

    internal static class InternalConstants
    {
        internal static readonly int MAX_BITS     = 15;
        internal static readonly int BL_CODES     = 19;
        internal static readonly int D_CODES      = 30;
        internal static readonly int LITERALS     = 256;
        internal static readonly int LENGTH_CODES = 29;
        internal static readonly int L_CODES      = (LITERALS + 1 + LENGTH_CODES);

        // Bit length codes must not exceed MAX_BL_BITS bits
        internal static readonly int MAX_BL_BITS  = 7;

        // repeat previous bit length 3-6 times (2 bits of repeat count)
        internal static readonly int REP_3_6      = 16;

        // repeat a zero length 3-10 times  (3 bits of repeat count)
        internal static readonly int REPZ_3_10    = 17;

        // repeat a zero length 11-138 times  (7 bits of repeat count)
        internal static readonly int REPZ_11_138  = 18;

    }

    internal sealed class StaticTree
    {
        internal static readonly short[] lengthAndLiteralsTreeCodes = new short[] {
            12, 8, 140, 8, 76, 8, 204, 8, 44, 8, 172, 8, 108, 8, 236, 8,
            28, 8, 156, 8, 92, 8, 220, 8, 60, 8, 188, 8, 124, 8, 252, 8,
             2, 8, 130, 8, 66, 8, 194, 8, 34, 8, 162, 8, 98, 8, 226, 8,
            18, 8, 146, 8, 82, 8, 210, 8, 50, 8, 178, 8, 114, 8, 242, 8,
            10, 8, 138, 8, 74, 8, 202, 8, 42, 8, 170, 8, 106, 8, 234, 8,
            26, 8, 154, 8, 90, 8, 218, 8, 58, 8, 186, 8, 122, 8, 250, 8,
             6, 8, 134, 8, 70, 8, 198, 8, 38, 8, 166, 8, 102, 8, 230, 8,
            22, 8, 150, 8, 86, 8, 214, 8, 54, 8, 182, 8, 118, 8, 246, 8,
            14, 8, 142, 8, 78, 8, 206, 8, 46, 8, 174, 8, 110, 8, 238, 8,
            30, 8, 158, 8, 94, 8, 222, 8, 62, 8, 190, 8, 126, 8, 254, 8,
             1, 8, 129, 8, 65, 8, 193, 8, 33, 8, 161, 8, 97, 8, 225, 8,
            17, 8, 145, 8, 81, 8, 209, 8, 49, 8, 177, 8, 113, 8, 241, 8,
             9, 8, 137, 8, 73, 8, 201, 8, 41, 8, 169, 8, 105, 8, 233, 8,
            25, 8, 153, 8, 89, 8, 217, 8, 57, 8, 185, 8, 121, 8, 249, 8,
             5, 8, 133, 8, 69, 8, 197, 8, 37, 8, 165, 8, 101, 8, 229, 8,
            21, 8, 149, 8, 85, 8, 213, 8, 53, 8, 181, 8, 117, 8, 245, 8,
            13, 8, 141, 8, 77, 8, 205, 8, 45, 8, 173, 8, 109, 8, 237, 8,
            29, 8, 157, 8, 93, 8, 221, 8, 61, 8, 189, 8, 125, 8, 253, 8,
            19, 9, 275, 9, 147, 9, 403, 9, 83, 9, 339, 9, 211, 9, 467, 9,
            51, 9, 307, 9, 179, 9, 435, 9, 115, 9, 371, 9, 243, 9, 499, 9,
            11, 9, 267, 9, 139, 9, 395, 9, 75, 9, 331, 9, 203, 9, 459, 9,
            43, 9, 299, 9, 171, 9, 427, 9, 107, 9, 363, 9, 235, 9, 491, 9,
            27, 9, 283, 9, 155, 9, 411, 9, 91, 9, 347, 9, 219, 9, 475, 9,
            59, 9, 315, 9, 187, 9, 443, 9, 123, 9, 379, 9, 251, 9, 507, 9,
             7, 9, 263, 9, 135, 9, 391, 9, 71, 9, 327, 9, 199, 9, 455, 9,
            39, 9, 295, 9, 167, 9, 423, 9, 103, 9, 359, 9, 231, 9, 487, 9,
            23, 9, 279, 9, 151, 9, 407, 9, 87, 9, 343, 9, 215, 9, 471, 9,
            55, 9, 311, 9, 183, 9, 439, 9, 119, 9, 375, 9, 247, 9, 503, 9,
            15, 9, 271, 9, 143, 9, 399, 9, 79, 9, 335, 9, 207, 9, 463, 9,
            47, 9, 303, 9, 175, 9, 431, 9, 111, 9, 367, 9, 239, 9, 495, 9,
            31, 9, 287, 9, 159, 9, 415, 9, 95, 9, 351, 9, 223, 9, 479, 9,
            63, 9, 319, 9, 191, 9, 447, 9, 127, 9, 383, 9, 255, 9, 511, 9,
             0, 7, 64, 7, 32, 7, 96, 7, 16, 7, 80, 7, 48, 7, 112, 7,
             8, 7, 72, 7, 40, 7, 104, 7, 24, 7, 88, 7, 56, 7, 120, 7,
             4, 7, 68, 7, 36, 7, 100, 7, 20, 7, 84, 7, 52, 7, 116, 7,
             3, 8, 131, 8, 67, 8, 195, 8, 35, 8, 163, 8, 99, 8, 227, 8
        };

        internal static readonly short[] distTreeCodes = new short[] {
            0, 5, 16, 5, 8, 5, 24, 5, 4, 5, 20, 5, 12, 5, 28, 5,
            2, 5, 18, 5, 10, 5, 26, 5, 6, 5, 22, 5, 14, 5, 30, 5,
            1, 5, 17, 5, 9, 5, 25, 5, 5, 5, 21, 5, 13, 5, 29, 5,
            3, 5, 19, 5, 11, 5, 27, 5, 7, 5, 23, 5 };

        internal static readonly StaticTree Literals;
        internal static readonly StaticTree Distances;
        internal static readonly StaticTree BitLengths;

        internal short[] treeCodes; // static tree or null
        internal int[] extraBits;   // extra bits for each code or null
        internal int extraBase;     // base index for extra_bits
        internal int elems;         // max number of elements in the tree
        internal int maxLength;     // max bit length for the codes

        private StaticTree(short[] treeCodes, int[] extraBits, int extraBase, int elems, int maxLength)
        {
            this.treeCodes = treeCodes;
            this.extraBits = extraBits;
            this.extraBase = extraBase;
            this.elems = elems;
            this.maxLength = maxLength;
        }
        static StaticTree()
        {
            Literals = new StaticTree(lengthAndLiteralsTreeCodes, ZTree.ExtraLengthBits, InternalConstants.LITERALS + 1, InternalConstants.L_CODES, InternalConstants.MAX_BITS);
            Distances = new StaticTree(distTreeCodes, ZTree.ExtraDistanceBits, 0, InternalConstants.D_CODES, InternalConstants.MAX_BITS);
            BitLengths = new StaticTree(null, ZTree.extra_blbits, 0, InternalConstants.BL_CODES, InternalConstants.MAX_BL_BITS);
        }
    }



    /// <summary>
    /// Computes an Adler-32 checksum.
    /// </summary>
    /// <remarks>
    /// The Adler checksum is similar to a CRC checksum, but faster to compute, though less
    /// reliable.  It is used in producing RFC1950 compressed streams.  The Adler checksum
    /// is a required part of the "ZLIB" standard.  Applications will almost never need to
    /// use this class directly.
    /// </remarks>
    ///
    /// <exclude/>
    public sealed class Adler
    {
        // largest prime smaller than 65536
        private static readonly uint BASE = 65521;
        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
        private static readonly int NMAX = 5552;


#pragma warning disable 3001
#pragma warning disable 3002

        /// <summary>
        ///   Calculates the Adler32 checksum.
        /// </summary>
        /// <remarks>
        ///   <para>
        ///     This is used within ZLIB.  You probably don't need to use this directly.
        ///   </para>
        /// </remarks>
        /// <example>
        ///    To compute an Adler32 checksum on a byte array:
        ///  <code>
        ///    var adler = Adler.Adler32(0, null, 0, 0);
        ///    adler = Adler.Adler32(adler, buffer, index, length);
        ///  </code>
        /// </example>
        public static uint Adler32(uint adler, byte[] buf, int index, int len)
        {
            if (buf == null)
                return 1;

            uint s1 = (uint) (adler & 0xffff);
            uint s2 = (uint) ((adler >> 16) & 0xffff);

            while (len > 0)
            {
                int k = len < NMAX ? len : NMAX;
                len -= k;
                while (k >= 16)
                {
                    //s1 += (buf[index++] & 0xff); s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    s1 += buf[index++]; s2 += s1;
                    k -= 16;
                }
                if (k != 0)
                {
                    do
                    {
                        s1 += buf[index++];
                        s2 += s1;
                    }
                    while (--k != 0);
                }
                s1 %= BASE;
                s2 %= BASE;
            }
            return (uint)((s2 << 16) | s1);
        }
#pragma warning restore 3001
#pragma warning restore 3002

    }

}