// Copyright Keysight Technologies 2012-2019
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, you can obtain one at http://mozilla.org/MPL/2.0/.
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/*
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This code is public domain.
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The MurmurHash3 algorithm was created by Austin Appleby and put into the public domain. See http://code.google.com/p/smhasher/
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This C# variant was authored by
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Elliott B. Edwards and was placed into the public domain as a gist
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*/
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using System.IO;
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using System.Text;
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namespace Tap.Shared
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{
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internal static class MurMurHash3
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{
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//Change to suit your needs
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const uint seed = 144;
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public static int Hash(byte[] bytes)
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{
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using (var stream = new MemoryStream(bytes))
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return Hash(stream);
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}
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public static int Hash(string uniqueString)
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{
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byte[] input = Encoding.UTF8.GetBytes(uniqueString);
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using (var stream = new MemoryStream(input))
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return Hash(stream);
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}
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public static int Hash(Stream stream)
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{
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const uint c1 = 0xcc9e2d51;
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const uint c2 = 0x1b873593;
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uint h1 = seed;
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uint k1 = 0;
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uint streamLength = 0;
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var reader = stream;
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byte[] chunk = new byte[4];
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{
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while (true)
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{
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int len = reader.Read(chunk, 0, 4);
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if (len <= 0) break;
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streamLength += (uint)len;
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switch (len)
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{
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case 4:
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/* Get four bytes from the input into an uint */
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k1 = (uint)
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(chunk[0]
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| chunk[1] << 8
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| chunk[2] << 16
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| chunk[3] << 24);
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/* bitmagic hash */
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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h1 = rotl32(h1, 13);
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h1 = h1 * 5 + 0xe6546b64;
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break;
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case 3:
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k1 = (uint)
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(chunk[0]
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| chunk[1] << 8
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| chunk[2] << 16);
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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break;
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case 2:
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k1 = (uint)
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(chunk[0]
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| chunk[1] << 8);
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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break;
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case 1:
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k1 = (uint)(chunk[0]);
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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break;
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}
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}
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}
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// finalization, magic chants to wrap it all up
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h1 ^= streamLength;
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h1 = fmix(h1);
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unchecked //ignore overflow
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{
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return (int)h1;
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}
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}
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private static uint rotl32(uint x, byte r)
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{
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return (x << r) | (x >> (32 - r));
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}
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private static uint fmix(uint h)
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{
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h ^= h >> 16;
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h *= 0x85ebca6b;
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h ^= h >> 13;
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h *= 0xc2b2ae35;
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h ^= h >> 16;
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return h;
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}
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}
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}
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