97 lines
3.2 KiB
C#
97 lines
3.2 KiB
C#
namespace Standart.Hash.xxHash
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{
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public static partial class xxHash32
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{
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private const uint p1 = 2654435761U;
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private const uint p2 = 2246822519U;
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private const uint p3 = 3266489917U;
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private const uint p4 = 668265263U;
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private const uint p5 = 374761393U;
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/// <summary>d
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/// Compute xxHash for the data byte array
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/// </summary>
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/// <param name="data">The source of data</param>
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/// <param name="length">The length of the data for hashing</param>
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/// <param name="seed">The seed number</param>
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/// <returns>hash</returns>
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public static unsafe uint ComputeHash(byte[] data, int length, uint seed = 0)
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{
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fixed (byte* pData = &data[0])
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{
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byte* ptr = pData;
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byte* end = pData + length;
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uint h32;
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if (length >= 16)
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{
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byte* limit = end - 16;
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uint v1 = seed + p1 + p2;
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uint v2 = seed + p2;
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uint v3 = seed + 0;
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uint v4 = seed - p1;
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do
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{
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v1 += *((uint*)ptr) * p2;
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v1 = (v1 << 13) | (v1 >> (32 - 13)); // rotl 13
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v1 *= p1;
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ptr += 4;
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v2 += *((uint*)ptr) * p2;
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v2 = (v2 << 13) | (v2 >> (32 - 13)); // rotl 13
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v2 *= p1;
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ptr += 4;
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v3 += *((uint*)ptr) * p2;
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v3 = (v3 << 13) | (v3 >> (32 - 13)); // rotl 13
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v3 *= p1;
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ptr += 4;
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v4 += *((uint*)ptr) * p2;
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v4 = (v4 << 13) | (v4 >> (32 - 13)); // rotl 13
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v4 *= p1;
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ptr += 4;
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} while (ptr <= limit);
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h32 = ((v1 << 1) | (v1 >> (32 - 1))) + // rotl 1
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((v2 << 7) | (v2 >> (32 - 7))) + // rotl 7
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((v3 << 12) | (v3 >> (32 - 12))) + // rotl 12
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((v4 << 18) | (v4 >> (32 - 18))); // rotl 18
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}
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else
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{
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h32 = seed + p5;
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}
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h32 += (uint) length;
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// finalize
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while (ptr <= end - 4)
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{
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h32 += *((uint*)ptr) * p3;
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h32 = ((h32 << 17) | (h32 >> (32 - 17))) * p4; // (rotl 17) * p4
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ptr += 4;
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}
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while (ptr < end)
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{
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h32 += *((byte*)ptr) * p5;
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h32 = ((h32 << 11) | (h32 >> (32 - 11))) * p1; // (rotl 11) * p1
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ptr += 1;
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}
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// avalanche
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h32 ^= h32 >> 15;
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h32 *= p2;
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h32 ^= h32 >> 13;
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h32 *= p3;
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h32 ^= h32 >> 16;
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return h32;
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}
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}
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}
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} |