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c#windows-phone-8hashstreamwindows-phone-8.1

Hashing Streams on Windows Phone


I am trying to create an extension method that will hash a stream on Windows Phone. It was easy for iOS and Android because I can just call something like this:

var hasher = MD5.Create();
var hashBytes = hasher.ComputeHash(stream);
var hash = Convert.ToBase64String(hashBytes);

But on Windows Phone, that API is not available so I am working to create my own and I need this method to be synchronous so I need to figure out a way to call inputStream.ReadAsync() synchronously but there is no Result property or Wait() method. I also found that nothing get placed into buffer.

This is what I have so far:

/// <summary>
/// Hashes the stream.
/// </summary>
/// <param name="stream">The stream.</param>
/// <param name="algorithm">The hash algorithm. Defaults to MD5.</param>
/// <returns>The hexadecimal hash value of the stream.</returns>
public static string Hash(this Stream stream, string algorithm = null)
{
    if (stream == null)
        return string.Empty;

    var streamPositionBeforeHashing = stream.Position;
    stream.Position = 0;

    var alg = HashAlgorithmProvider.OpenAlgorithm(algorithm ?? HashAlgorithmNames.Md5);
    var inputStream = stream.AsInputStream();
    uint capacity = (uint) Math.Min(stream.Length, 100000000);
    var buffer = new Buffer(capacity);
    var hash = alg.CreateHash();

    while (true)
    {
        var result = inputStream.ReadAsync(buffer, capacity, InputStreamOptions.None);

        if (buffer.Length > 0)
            hash.Append(buffer);
        else
            break;
    }

    var hashText = CryptographicBuffer.EncodeToHexString(hash.GetValueAndReset())
        .Replace("=", string.Empty)
        .Replace("\\", string.Empty)
        .Replace("/", string.Empty);

    inputStream.Dispose();
    stream.Position = streamPositionBeforeHashing;
    return hashText;
}

Solution

  • I ended up using a cross-platform implementation of MD5 crypto service provider to get a similar hash method to the one found on iOS and Android.

    https://raw.githubusercontent.com/XLabs/Xamarin-Forms-Labs/master/src/Cryptography/XLabs.Cryptography/MD5.cs

    using System;
    using System.IO;
    using System.Text;
    
    namespace XLabs.Cryptography
    {
        /// <summary>
        /// Summary description for MD5.
        /// </summary>
        public class MD5 : IDisposable
        {
            /// <summary>
            /// Creates the specified hash name.
            /// </summary>
            /// <param name="hashName">Name of the hash.</param>
            /// <returns>MD5.</returns>
            /// <exception cref="System.NotSupportedException"></exception>
            static public MD5 Create(string hashName)
            {
                if (hashName == "MD5")
                    return new MD5();
                else
                    throw new NotSupportedException();
            }
    
            /// <summary>
            /// Gets the MD5 string.
            /// </summary>
            /// <param name="source">The source.</param>
            /// <returns>System.String.</returns>
            static public string GetMd5String(String source)
            {
                var md = Create();
                var hash = md.ComputeHash(Encoding.UTF8.GetBytes(source));
    
                var sb = new StringBuilder();
                foreach (byte b in hash) sb.Append(b.ToString("x2"));
                return sb.ToString();
            }
    
            /// <summary>
            /// Creates this instance.
            /// </summary>
            /// <returns>MD5.</returns>
            static public MD5 Create()
            {
                return new MD5();
            }
    
            #region base implementation of the MD5
            #region constants
            /// <summary>
            /// The S11
            /// </summary>
            private const byte S11 = 7;
            /// <summary>
            /// The S12
            /// </summary>
            private const byte S12 = 12;
            /// <summary>
            /// The S13
            /// </summary>
            private const byte S13 = 17;
            /// <summary>
            /// The S14
            /// </summary>
            private const byte S14 = 22;
            /// <summary>
            /// The S21
            /// </summary>
            private const byte S21 = 5;
            /// <summary>
            /// The S22
            /// </summary>
            private const byte S22 = 9;
            /// <summary>
            /// The S23
            /// </summary>
            private const byte S23 = 14;
            /// <summary>
            /// The S24
            /// </summary>
            private const byte S24 = 20;
            /// <summary>
            /// The S31
            /// </summary>
            private const byte S31 = 4;
            /// <summary>
            /// The S32
            /// </summary>
            private const byte S32 = 11;
            /// <summary>
            /// The S33
            /// </summary>
            private const byte S33 = 16;
            /// <summary>
            /// The S34
            /// </summary>
            private const byte S34 = 23;
            /// <summary>
            /// The S41
            /// </summary>
            private const byte S41 = 6;
            /// <summary>
            /// The S42
            /// </summary>
            private const byte S42 = 10;
            /// <summary>
            /// The S43
            /// </summary>
            private const byte S43 = 15;
            /// <summary>
            /// The S44
            /// </summary>
            private const byte S44 = 21;
            /// <summary>
            /// The padding
            /// </summary>
            static private readonly byte[] Padding = {
                0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
            };
            #endregion
    
            #region F, G, H and I are basic MD5 functions.
            /// <summary>
            /// fs the specified x.
            /// </summary>
            /// <param name="x">The x.</param>
            /// <param name="y">The y.</param>
            /// <param name="z">The z.</param>
            /// <returns>System.UInt32.</returns>
            static private uint F(uint x, uint y, uint z)
            {
                return (((x) & (y)) | ((~x) & (z)));
            }
            /// <summary>
            /// gs the specified x.
            /// </summary>
            /// <param name="x">The x.</param>
            /// <param name="y">The y.</param>
            /// <param name="z">The z.</param>
            /// <returns>System.UInt32.</returns>
            static private uint G(uint x, uint y, uint z)
            {
                return (((x) & (z)) | ((y) & (~z)));
            }
            /// <summary>
            /// hes the specified x.
            /// </summary>
            /// <param name="x">The x.</param>
            /// <param name="y">The y.</param>
            /// <param name="z">The z.</param>
            /// <returns>System.UInt32.</returns>
            static private uint H(uint x, uint y, uint z)
            {
                return ((x) ^ (y) ^ (z));
            }
            /// <summary>
            /// is the specified x.
            /// </summary>
            /// <param name="x">The x.</param>
            /// <param name="y">The y.</param>
            /// <param name="z">The z.</param>
            /// <returns>System.UInt32.</returns>
            static private uint I(uint x, uint y, uint z)
            {
                return ((y) ^ ((x) | (~z)));
            }
            #endregion
    
            #region rotates x left n bits.
            /// <summary>
            /// rotates x left n bits.
            /// </summary>
            /// <param name="x">The x.</param>
            /// <param name="n">The n.</param>
            /// <returns>System.UInt32.</returns>
            static private uint ROTATE_LEFT(uint x, byte n)
            {
                return (((x) << (n)) | ((x) >> (32 - (n))));
            }
            #endregion
    
            #region FF, GG, HH, and II transformations
            /// <summary>
            /// Ffs the specified a.
            /// </summary>
            /// <param name="a">a.</param>
            /// <param name="b">The b.</param>
            /// <param name="c">The c.</param>
            /// <param name="d">The d.</param>
            /// <param name="x">The x.</param>
            /// <param name="s">The s.</param>
            /// <param name="ac">The ac.</param>
            /// FF, GG, HH, and II transformations
            /// for rounds 1, 2, 3, and 4.
            /// Rotation is separate from addition to prevent recomputation.
            static private void FF(ref uint a, uint b, uint c, uint d, uint x, byte s, uint ac)
            {
                (a) += F((b), (c), (d)) + (x) + (uint)(ac);
                (a) = ROTATE_LEFT((a), (s));
                (a) += (b);
            }
            /// <summary>
            /// Ggs the specified a.
            /// </summary>
            /// <param name="a">a.</param>
            /// <param name="b">The b.</param>
            /// <param name="c">The c.</param>
            /// <param name="d">The d.</param>
            /// <param name="x">The x.</param>
            /// <param name="s">The s.</param>
            /// <param name="ac">The ac.</param>
            static private void GG(ref uint a, uint b, uint c, uint d, uint x, byte s, uint ac)
            {
                (a) += G((b), (c), (d)) + (x) + (uint)(ac);
                (a) = ROTATE_LEFT((a), (s));
                (a) += (b);
            }
            /// <summary>
            /// Hhes the specified a.
            /// </summary>
            /// <param name="a">a.</param>
            /// <param name="b">The b.</param>
            /// <param name="c">The c.</param>
            /// <param name="d">The d.</param>
            /// <param name="x">The x.</param>
            /// <param name="s">The s.</param>
            /// <param name="ac">The ac.</param>
            static private void HH(ref uint a, uint b, uint c, uint d, uint x, byte s, uint ac)
            {
                (a) += H((b), (c), (d)) + (x) + (uint)(ac);
                (a) = ROTATE_LEFT((a), (s));
                (a) += (b);
            }
            /// <summary>
            /// Iis the specified a.
            /// </summary>
            /// <param name="a">a.</param>
            /// <param name="b">The b.</param>
            /// <param name="c">The c.</param>
            /// <param name="d">The d.</param>
            /// <param name="x">The x.</param>
            /// <param name="s">The s.</param>
            /// <param name="ac">The ac.</param>
            static private void II(ref uint a, uint b, uint c, uint d, uint x, byte s, uint ac)
            {
                (a) += I((b), (c), (d)) + (x) + (uint)(ac);
                (a) = ROTATE_LEFT((a), (s));
                (a) += (b);
            }
            #endregion
    
            #region context info
            /// <summary>
            /// state (ABCD)
            /// </summary>
            readonly uint[] state = new uint[4];
    
            /// <summary>
            /// number of bits, modulo 2^64 (lsb first)
            /// </summary>
            readonly uint[] count = new uint[2];
    
            /// <summary>
            /// input buffer
            /// </summary>
            readonly byte[] buffer = new byte[64];
            #endregion
    
            /// <summary>
            /// Initializes a new instance of the <see cref="MD5"/> class.
            /// </summary>
            internal MD5()
            {
                Initialize();
            }
    
            /// <summary>
            /// MD5 initialization. Begins an MD5 operation, writing a new context.
            /// </summary>
            /// <remarks>The RFC named it "MD5Init"</remarks>
            public virtual void Initialize()
            {
                this.count[0] = this.count[1] = 0;
    
                // Load magic initialization constants.
                this.state[0] = 0x67452301;
                this.state[1] = 0xefcdab89;
                this.state[2] = 0x98badcfe;
                this.state[3] = 0x10325476;
            }
    
            /// <summary>
            /// MD5 block update operation. Continues an MD5 message-digest
            /// operation, processing another message block, and updating the
            /// context.
            /// </summary>
            /// <param name="input">The input.</param>
            /// <param name="offset">The offset.</param>
            /// <param name="count">The count.</param>
            /// <remarks>The RFC Named it MD5Update</remarks>
            protected virtual void HashCore(byte[] input, int offset, int count)
            {
                int i;
                int index;
                int partLen;
    
                // Compute number of bytes mod 64
                index = (int)((this.count[0] >> 3) & 0x3F);
    
                // Update number of bits
                if ((this.count[0] += (uint)((uint)count << 3)) < ((uint)count << 3))
                    this.count[1]++;
                this.count[1] += ((uint)count >> 29);
    
                partLen = 64 - index;
    
                // Transform as many times as possible.
                if (count >= partLen)
                {
                    Buffer.BlockCopy(input, offset, this.buffer, index, partLen);
                    Transform(this.buffer, 0);
    
                    for (i = partLen; i + 63 < count; i += 64)
                        Transform(input, offset + i);
    
                    index = 0;
                }
                else
                    i = 0;
    
                // Buffer remaining input 
                Buffer.BlockCopy(input, offset + i, this.buffer, index, count - i);
            }
    
            /// <summary>
            /// MD5 finalization. Ends an MD5 message-digest operation, writing the
            /// the message digest and zeroizing the context.
            /// </summary>
            /// <returns>message digest</returns>
            /// <remarks>The RFC named it MD5Final</remarks>
            protected virtual byte[] HashFinal()
            {
                byte[] digest = new byte[16];
                byte[] bits = new byte[8];
                int index, padLen;
    
                // Save number of bits
                Encode(bits, 0, this.count, 0, 8);
    
                // Pad out to 56 mod 64.
                index = (int)((uint)(this.count[0] >> 3) & 0x3f);
                padLen = (index < 56) ? (56 - index) : (120 - index);
                HashCore(Padding, 0, padLen);
    
                // Append length (before padding)
                HashCore(bits, 0, 8);
    
                // Store state in digest 
                Encode(digest, 0, this.state, 0, 16);
    
                // Zeroize sensitive information.
                this.count[0] = this.count[1] = 0;
                this.state[0] = 0;
                this.state[1] = 0;
                this.state[2] = 0;
                this.state[3] = 0;
    
                // initialize again, to be ready to use
                Initialize();
    
                return digest;
            }
    
            /// <summary>
            /// MD5 basic transformation. Transforms state based on 64 bytes block.
            /// </summary>
            /// <param name="block">The block.</param>
            /// <param name="offset">The offset.</param>
            private void Transform(byte[] block, int offset)
            {
                uint a = this.state[0], b = this.state[1], c = this.state[2], d = this.state[3];
                uint[] x = new uint[16];
                Decode(x, 0, block, offset, 64);
    
                // Round 1
                FF(ref a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */
                FF(ref d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */
                FF(ref c, d, a, b, x[2], S13, 0x242070db); /* 3 */
                FF(ref b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */
                FF(ref a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */
                FF(ref d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */
                FF(ref c, d, a, b, x[6], S13, 0xa8304613); /* 7 */
                FF(ref b, c, d, a, x[7], S14, 0xfd469501); /* 8 */
                FF(ref a, b, c, d, x[8], S11, 0x698098d8); /* 9 */
                FF(ref d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */
                FF(ref c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
                FF(ref b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
                FF(ref a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
                FF(ref d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
                FF(ref c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
                FF(ref b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
    
                // Round 2
                GG(ref a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */
                GG(ref d, a, b, c, x[6], S22, 0xc040b340); /* 18 */
                GG(ref c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
                GG(ref b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */
                GG(ref a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */
                GG(ref d, a, b, c, x[10], S22, 0x2441453); /* 22 */
                GG(ref c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
                GG(ref b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */
                GG(ref a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */
                GG(ref d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
                GG(ref c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */
                GG(ref b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */
                GG(ref a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
                GG(ref d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */
                GG(ref c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */
                GG(ref b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
    
                // Round 3
                HH(ref a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */
                HH(ref d, a, b, c, x[8], S32, 0x8771f681); /* 34 */
                HH(ref c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
                HH(ref b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
                HH(ref a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */
                HH(ref d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */
                HH(ref c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */
                HH(ref b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
                HH(ref a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
                HH(ref d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */
                HH(ref c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */
                HH(ref b, c, d, a, x[6], S34, 0x4881d05); /* 44 */
                HH(ref a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */
                HH(ref d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
                HH(ref c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
                HH(ref b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */
    
                // Round 4
                II(ref a, b, c, d, x[0], S41, 0xf4292244); /* 49 */
                II(ref d, a, b, c, x[7], S42, 0x432aff97); /* 50 */
                II(ref c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
                II(ref b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */
                II(ref a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
                II(ref d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */
                II(ref c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
                II(ref b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */
                II(ref a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */
                II(ref d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
                II(ref c, d, a, b, x[6], S43, 0xa3014314); /* 59 */
                II(ref b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
                II(ref a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */
                II(ref d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
                II(ref c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */
                II(ref b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */
    
                this.state[0] += a;
                this.state[1] += b;
                this.state[2] += c;
                this.state[3] += d;
    
                // Zeroize sensitive information.
                for (int i = 0; i < x.Length; i++)
                    x[i] = 0;
            }
    
            /// <summary>
            /// Encodes input (uint) into output (byte). Assumes len is
            /// multiple of 4.
            /// </summary>
            /// <param name="output">The output.</param>
            /// <param name="outputOffset">The output offset.</param>
            /// <param name="input">The input.</param>
            /// <param name="inputOffset">The input offset.</param>
            /// <param name="count">The count.</param>
            private static void Encode(byte[] output, int outputOffset, uint[] input, int inputOffset, int count)
            {
                int i, j;
                int end = outputOffset + count;
                for (i = inputOffset, j = outputOffset; j < end; i++, j += 4)
                {
                    output[j] = (byte)(input[i] & 0xff);
                    output[j + 1] = (byte)((input[i] >> 8) & 0xff);
                    output[j + 2] = (byte)((input[i] >> 16) & 0xff);
                    output[j + 3] = (byte)((input[i] >> 24) & 0xff);
                }
            }
    
            /// <summary>
            /// Decodes input (byte) into output (uint). Assumes len is
            /// a multiple of 4.
            /// </summary>
            /// <param name="output">The output.</param>
            /// <param name="outputOffset">The output offset.</param>
            /// <param name="input">The input.</param>
            /// <param name="inputOffset">The input offset.</param>
            /// <param name="count">The count.</param>
            static private void Decode(uint[] output, int outputOffset, byte[] input, int inputOffset, int count)
            {
                int i, j;
                int end = inputOffset + count;
                for (i = outputOffset, j = inputOffset; j < end; i++, j += 4)
                    output[i] = input[j] | (((uint)input[j + 1]) << 8) | (((uint)input[j + 2]) << 16) | (((uint)input[j + 3]) << 24);
            }
            #endregion
    
            #region expose the same interface as the regular MD5 object
    
            /// <summary>
            /// The hash value
            /// </summary>
            protected byte[] HashValue;
            /// <summary>
            /// The state
            /// </summary>
            protected int State;
            /// <summary>
            /// Gets a value indicating whether this instance can reuse transform.
            /// </summary>
            /// <value><c>true</c> if this instance can reuse transform; otherwise, <c>false</c>.</value>
            public virtual bool CanReuseTransform
            {
                get
                {
                    return true;
                }
            }
    
            /// <summary>
            /// Gets a value indicating whether this instance can transform multiple blocks.
            /// </summary>
            /// <value><c>true</c> if this instance can transform multiple blocks; otherwise, <c>false</c>.</value>
            public virtual bool CanTransformMultipleBlocks
            {
                get
                {
                    return true;
                }
            }
            /// <summary>
            /// Gets the hash.
            /// </summary>
            /// <value>The hash.</value>
            /// <exception cref="System.InvalidOperationException"></exception>
            public virtual byte[] Hash
            {
                get
                {
                    if (this.State != 0)
                        throw new InvalidOperationException();
                    return (byte[])this.HashValue.Clone();
                }
            }
            /// <summary>
            /// Gets the size of the hash.
            /// </summary>
            /// <value>The size of the hash.</value>
            public virtual int HashSize
            {
                get
                {
                    return this.HashSizeValue;
                }
            }
            /// <summary>
            /// The hash size value
            /// </summary>
            protected int HashSizeValue = 128;
    
            /// <summary>
            /// Gets the size of the input block.
            /// </summary>
            /// <value>The size of the input block.</value>
            public virtual int InputBlockSize
            {
                get
                {
                    return 1;
                }
            }
            /// <summary>
            /// Gets the size of the output block.
            /// </summary>
            /// <value>The size of the output block.</value>
            public virtual int OutputBlockSize
            {
                get
                {
                    return 1;
                }
            }
    
            /// <summary>
            /// Clears this instance.
            /// </summary>
            public void Clear()
            {
                Dispose(true);
            }
    
            /// <summary>
            /// Computes the hash.
            /// </summary>
            /// <param name="buffer">The buffer.</param>
            /// <returns>System.Byte[].</returns>
            public byte[] ComputeHash(byte[] buffer)
            {
                return ComputeHash(buffer, 0, buffer.Length);
            }
            /// <summary>
            /// Computes the hash.
            /// </summary>
            /// <param name="buffer">The buffer.</param>
            /// <param name="offset">The offset.</param>
            /// <param name="count">The count.</param>
            /// <returns>System.Byte[].</returns>
            public byte[] ComputeHash(byte[] buffer, int offset, int count)
            {
                Initialize();
                HashCore(buffer, offset, count);
                this.HashValue = HashFinal();
                return (byte[])this.HashValue.Clone();
            }
    
            /// <summary>
            /// Computes the hash.
            /// </summary>
            /// <param name="inputStream">The input stream.</param>
            /// <returns>System.Byte[].</returns>
            public byte[] ComputeHash(Stream inputStream)
            {
                Initialize();
                int count;
                byte[] buffer = new byte[4096];
                while (0 < (count = inputStream.Read(buffer, 0, 4096)))
                {
                    HashCore(buffer, 0, count);
                }
                this.HashValue = HashFinal();
                return (byte[])this.HashValue.Clone();
            }
    
            /// <summary>
            /// Transforms the block.
            /// </summary>
            /// <param name="inputBuffer">The input buffer.</param>
            /// <param name="inputOffset">The input offset.</param>
            /// <param name="inputCount">The input count.</param>
            /// <param name="outputBuffer">The output buffer.</param>
            /// <param name="outputOffset">The output offset.</param>
            /// <returns>System.Int32.</returns>
            /// <exception cref="System.ArgumentNullException">inputBuffer</exception>
            /// <exception cref="System.ArgumentOutOfRangeException">
            /// inputOffset
            /// or
            /// inputOffset
            /// </exception>
            /// <exception cref="System.ArgumentException">inputCount</exception>
            public int TransformBlock(
                byte[] inputBuffer,
                int inputOffset,
                int inputCount,
                byte[] outputBuffer,
                int outputOffset
            )
            {
                if (inputBuffer == null)
                {
                    throw new ArgumentNullException("inputBuffer");
                }
                if (inputOffset < 0)
                {
                    throw new ArgumentOutOfRangeException("inputOffset");
                }
                if ((inputCount < 0) || (inputCount > inputBuffer.Length))
                {
                    throw new ArgumentException("inputCount");
                }
                if ((inputBuffer.Length - inputCount) < inputOffset)
                {
                    throw new ArgumentOutOfRangeException("inputOffset");
                }
                if (this.State == 0)
                {
                    Initialize();
                    this.State = 1;
                }
    
                HashCore(inputBuffer, inputOffset, inputCount);
                if ((inputBuffer != outputBuffer) || (inputOffset != outputOffset))
                {
                    Buffer.BlockCopy(inputBuffer, inputOffset, outputBuffer, outputOffset, inputCount);
                }
                return inputCount;
            }
            /// <summary>
            /// Transforms the final block.
            /// </summary>
            /// <param name="inputBuffer">The input buffer.</param>
            /// <param name="inputOffset">The input offset.</param>
            /// <param name="inputCount">The input count.</param>
            /// <returns>System.Byte[].</returns>
            /// <exception cref="System.ArgumentNullException">inputBuffer</exception>
            /// <exception cref="System.ArgumentOutOfRangeException">
            /// inputOffset
            /// or
            /// inputOffset
            /// </exception>
            /// <exception cref="System.ArgumentException">inputCount</exception>
            public byte[] TransformFinalBlock(
                byte[] inputBuffer,
                int inputOffset,
                int inputCount
            )
            {
                if (inputBuffer == null)
                {
                    throw new ArgumentNullException("inputBuffer");
                }
                if (inputOffset < 0)
                {
                    throw new ArgumentOutOfRangeException("inputOffset");
                }
                if ((inputCount < 0) || (inputCount > inputBuffer.Length))
                {
                    throw new ArgumentException("inputCount");
                }
                if ((inputBuffer.Length - inputCount) < inputOffset)
                {
                    throw new ArgumentOutOfRangeException("inputOffset");
                }
                if (this.State == 0)
                {
                    Initialize();
                }
                HashCore(inputBuffer, inputOffset, inputCount);
                this.HashValue = HashFinal();
                byte[] buffer = new byte[inputCount];
                Buffer.BlockCopy(inputBuffer, inputOffset, buffer, 0, inputCount);
                this.State = 0;
                return buffer;
            }
            #endregion
    
            /// <summary>
            /// Releases unmanaged and - optionally - managed resources.
            /// </summary>
            /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
            protected virtual void Dispose(bool disposing)
            {
                if (!disposing)
                    Initialize();
            }
            /// <summary>
            /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
            /// </summary>
            public void Dispose()
            {
                Dispose(true);
            }
        }
    }