xxHashSharp.cs

/*
HashToInt32 - A SQLCLR implementation of xxHashSharp
A big "Thank You" to Seok-Ju for the pure C# implementation of xxHashSharp that made it possible to create this SQLCLR version.

Changes made to the original xxHashSharp code:
* Created HashToInt32 method that takes a SqlBinary input and returns a SqlInt32.
* Removed all code not used by HashToInt32.
* Remaining public accessors changed to private.
* xxHashSharp namespace removed, but class name changed from xxHash to xxHashSharp to preserve lineage.

Compare output with https://www.coderstool.com/xxh-hash-generator
*/

/*
xxHashSharp - A pure C# implementation of xxhash
Copyright (C) 2014, Seok-Ju, Yun. (https://github.com/noricube/xxHashSharp)
Original C Implementation Copyright (C) 2012-2014, Yann Collet. (https://code.google.com/p/xxhash/)
BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   * 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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS 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 THE COPYRIGHT
OWNER OR CONTRIBUTORS 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.
*/

using Microsoft.SqlServer.Server;
using System;
using System.Data.SqlTypes;

public class xxHashSharp
{
    const uint PRIME32_1 = 2654435761U;
    const uint PRIME32_2 = 2246822519U;
    const uint PRIME32_3 = 3266489917U;
    const uint PRIME32_4 = 668265263U;
    const uint PRIME32_5 = 374761393U;

    public xxHashSharp() { }
        
    [Microsoft.SqlServer.Server.SqlFunction(IsDeterministic = true, IsPrecise = true, DataAccess = DataAccessKind.None)]
    public static SqlInt32 HashToInt32(SqlBinary data)
    {
        // null in, null out
        if (data.IsNull)
        {
            return SqlInt32.Null;
        }

        // hash it!
        var hash = CalculateHash(data.Value);

        // return the hash
        return new SqlInt32((int)hash);
    }

    private static uint CalculateHash(byte[] buf, int len = -1, uint seed = 0)
    {
        uint h32;
        int index = 0;
        if (len == -1)
        {
            len = buf.Length;
        }


        if (len >= 16)
        {
            int limit = len - 16;
            uint v1 = seed + PRIME32_1 + PRIME32_2;
            uint v2 = seed + PRIME32_2;
            uint v3 = seed + 0;
            uint v4 = seed - PRIME32_1;

            do
            {
                v1 = CalcSubHash(v1, buf, index);
                index += 4;
                v2 = CalcSubHash(v2, buf, index);
                index += 4;
                v3 = CalcSubHash(v3, buf, index);
                index += 4;
                v4 = CalcSubHash(v4, buf, index);
                index += 4;
            } while (index <= limit);

            h32 = RotateLeft(v1, 1) + RotateLeft(v2, 7) + RotateLeft(v3, 12) + RotateLeft(v4, 18);
        }
        else
        {
            h32 = seed + PRIME32_5;
        }

        h32 += (uint)len;

        while (index <= len - 4)
        {
            h32 += BitConverter.ToUInt32(buf, index) * PRIME32_3;
            h32 = RotateLeft(h32, 17) * PRIME32_4;
            index += 4;
        }

        while (index < len)
        {
            h32 += buf[index] * PRIME32_5;
            h32 = RotateLeft(h32, 11) * PRIME32_1;
            index++;
        }

        h32 ^= h32 >> 15;
        h32 *= PRIME32_2;
        h32 ^= h32 >> 13;
        h32 *= PRIME32_3;
        h32 ^= h32 >> 16;

        return h32;
    }

    private static uint CalcSubHash(uint value, byte[] buf, int index)
    {
        uint read_value = BitConverter.ToUInt32(buf, index);
        value += read_value * PRIME32_2;
        value = RotateLeft(value, 13);
        value *= PRIME32_1;
        return value;
    }

    private static uint RotateLeft(uint value, int count)
    {
        return (value << count) | (value >> (32 - count));
    }

}