90 lines
2.6 KiB
C#
90 lines
2.6 KiB
C#
using System.IO;
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using System.Text;
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namespace Toolbox.Library.Security.Cryptography
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{
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public static class MurMurHash3
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{
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private const uint Seed = 0;
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public static uint Hash(string s)
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{
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var ss = new MemoryStream(Encoding.UTF8.GetBytes(s));
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return Hash(ss);
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}
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public static uint 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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var h1 = Seed;
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uint streamLength = 0;
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using (var reader = new BinaryReader(stream))
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{
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var chunk = reader.ReadBytes(4);
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while (chunk.Length > 0)
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{
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streamLength += (uint)chunk.Length;
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uint k1;
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switch (chunk.Length)
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{
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case 4:
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k1 = (uint)(chunk[0] | chunk[1] << 8 | chunk[2] << 16 | chunk[3] << 24);
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k1 *= c1;
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k1 = Rot(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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h1 = Rot(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) (chunk[0] | chunk[1] << 8 | chunk[2] << 16);
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k1 *= c1;
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k1 = Rot(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) (chunk[0] | chunk[1] << 8);
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k1 *= c1;
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k1 = Rot(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 = (chunk[0]);
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k1 *= c1;
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k1 = Rot(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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chunk = reader.ReadBytes(4);
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}
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}
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h1 ^= streamLength;
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h1 = Mix(h1);
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return h1;
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}
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private static uint Rot(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 Mix(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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