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RaptorDB - The Document Store

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24 Jul 2019CPOL86 min read 2.3M   16.3K   653  
NoSql, JSON based, Document store database with compiled .net map functions and automatic hybrid bitmap indexing and LINQ query filters (now with standalone Server mode, Backup and Active Restore, Transactions, Server side queries, MonoDroid support, HQ-Branch Replication, working in Linux, .net
using System;
using System.Collections.Generic;
using System.Text;

namespace RaptorDB.Common
{
    //internal static class murmur3
    //{
    //    private static uint seed = 7878;

    //    public static uint MurmurHash3(byte[] data)
    //    {
    //        const uint c1 = 0xcc9e2d51;
    //        const uint c2 = 0x1b873593;

    //        int curLength = data.Length;    /* Current position in byte array */
    //        int length = curLength;   /* the const length we need to fix tail */
    //        uint h1 = seed;
    //        uint k1 = 0;

    //        /* body, eat stream a 32-bit int at a time */
    //        int currentIndex = 0;
    //        while (curLength >= 4)
    //        {
    //            /* Get four bytes from the input into an UInt32 */
    //            k1 = (uint)(data[currentIndex++]
    //              | data[currentIndex++] << 8
    //              | data[currentIndex++] << 16
    //              | data[currentIndex++] << 24);

    //            /* bitmagic hash */
    //            k1 *= c1;
    //            k1 = rotl32(k1, 15);
    //            k1 *= c2;

    //            h1 ^= k1;
    //            h1 = rotl32(h1, 13);
    //            h1 = h1 * 5 + 0xe6546b64;
    //            curLength -= 4;
    //        }

    //        /* tail, the reminder bytes that did not make it to a full int */
    //        /* (this switch is slightly more ugly than the C++ implementation
    //         * because we can't fall through) */
    //        switch (curLength)
    //        {
    //            case 3:
    //                k1 = (UInt32)(data[currentIndex++]
    //                  | data[currentIndex++] << 8
    //                  | data[currentIndex++] << 16);
    //                k1 *= c1;
    //                k1 = rotl32(k1, 15);
    //                k1 *= c2;
    //                h1 ^= k1;
    //                break;
    //            case 2:
    //                k1 = (UInt32)(data[currentIndex++]
    //                  | data[currentIndex++] << 8);
    //                k1 *= c1;
    //                k1 = rotl32(k1, 15);
    //                k1 *= c2;
    //                h1 ^= k1;
    //                break;
    //            case 1:
    //                k1 = (UInt32)(data[currentIndex++]);
    //                k1 *= c1;
    //                k1 = rotl32(k1, 15);
    //                k1 *= c2;
    //                h1 ^= k1;
    //                break;
    //        };

    //        // finalization, magic chants to wrap it all up
    //        h1 ^= (uint)length;
    //        h1 = fmix(h1);

    //        unchecked
    //        {
    //            return (uint)h1;
    //        }
    //    }
    //    private static uint rotl32(uint x, byte r)
    //    {
    //        return (x << r) | (x >> (32 - r));
    //    }

    //    private static uint fmix(uint h)
    //    {
    //        h ^= h >> 16;
    //        h *= 0x85ebca6b;
    //        h ^= h >> 13;
    //        h *= 0xc2b2ae35;
    //        h ^= h >> 16;
    //        return h;
    //    }
    //}

    public class MurmurHash2Unsafe
    {
        public UInt32 Hash(Byte[] data)
        {
            return Hash(data, 0xc58f1a7b);
        }
        const UInt32 m = 0x5bd1e995;
        const Int32 r = 24;

        public unsafe UInt32 Hash(Byte[] data, UInt32 seed)
        {
            Int32 length = data.Length;
            if (length == 0)
                return 0;
            UInt32 h = seed ^ (UInt32)length;
            Int32 remainingBytes = length & 3; // mod 4
            Int32 numberOfLoops = length >> 2; // div 4
            fixed (byte* firstByte = &(data[0]))
            {
                UInt32* realData = (UInt32*)firstByte;
                while (numberOfLoops != 0)
                {
                    UInt32 k = *realData;
                    k *= m;
                    k ^= k >> r;
                    k *= m;

                    h *= m;
                    h ^= k;
                    numberOfLoops--;
                    realData++;
                }
                switch (remainingBytes)
                {
                    case 3:
                        h ^= (UInt16)(*realData);
                        h ^= ((UInt32)(*(((Byte*)(realData)) + 2))) << 16;
                        h *= m;
                        break;
                    case 2:
                        h ^= (UInt16)(*realData);
                        h *= m;
                        break;
                    case 1:
                        h ^= *((Byte*)realData);
                        h *= m;
                        break;
                    default:
                        break;
                }
            }

            // Do a few final mixes of the hash to ensure the last few
            // bytes are well-incorporated.

            h ^= h >> 13;
            h *= m;
            h ^= h >> 15;

            return h;
        }
    }
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Architect -
United Kingdom United Kingdom
Mehdi first started programming when he was 8 on BBC+128k machine in 6512 processor language, after various hardware and software changes he eventually came across .net and c# which he has been using since v1.0.
He is formally educated as a system analyst Industrial engineer, but his programming passion continues.

* Mehdi is the 5th person to get 6 out of 7 Platinum's on Code-Project (13th Jan'12)
* Mehdi is the 3rd person to get 7 out of 7 Platinum's on Code-Project (26th Aug'16)

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