Timerix/DTLib.XXHash
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Code refactoring

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This commit is contained in:
Alexander Melnik
2018-10-01 12:55:20 +03:00
parent d801b9996b
commit 462293ee0e
14 changed files with 730 additions and 630 deletions
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129
src/Standart.Hash.xxHash/xxHash32.cs
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namespace Standart.Hash.xxHash
{
using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
public static partial class xxHash32
{
private const uint p1 = 2654435761U;
private const uint p2 = 2246822519U;
private const uint p3 = 3266489917U;
private const uint p4 = 668265263U;
private const uint p5 = 374761393U;
/// <summary>
/// Compute xxHash for the data byte array
/// </summary>
/// <param name="data">The source of data</param>
/// <param name="length">The length of the data for hashing</param>
/// <param name="seed">The seed number</param>
/// <returns>hash</returns>
public static unsafe uint ComputeHash(byte[] data, int length, uint seed = 0)
{
Debug.Assert(data != null);
Debug.Assert(length >= 0);
Debug.Assert(length <= data.Length);
fixed (byte* pData = &data[0])
{
return UnsafeComputeHash(pData, length, seed);
}
}
/// <summary>
/// Compute xxHash for the data byte span
/// </summary>
/// <param name="data">The source of data</param>
/// <param name="length">The length of the data for hashing</param>
/// <param name="seed">The seed number</param>
/// <returns>hash</returns>
public static unsafe uint ComputeHash(Span<byte> data, int length, uint seed = 0)
{
Debug.Assert(data != null);
Debug.Assert(length >= 0);
Debug.Assert(length <= data.Length);
fixed (byte* pData = &data[0])
{
return UnsafeComputeHash(pData, length, seed);
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static unsafe uint UnsafeComputeHash(byte* ptr, int length, uint seed)
{
byte* end = ptr + length;
uint h32;
if (length >= 16)
{
byte* limit = end - 16;
uint v1 = seed + p1 + p2;
uint v2 = seed + p2;
uint v3 = seed + 0;
uint v4 = seed - p1;
do
{
v1 += *((uint*)ptr) * p2;
v1 = (v1 << 13) | (v1 >> (32 - 13)); // rotl 13
v1 *= p1;
ptr += 4;
v2 += *((uint*)ptr) * p2;
v2 = (v2 << 13) | (v2 >> (32 - 13)); // rotl 13
v2 *= p1;
ptr += 4;
v3 += *((uint*)ptr) * p2;
v3 = (v3 << 13) | (v3 >> (32 - 13)); // rotl 13
v3 *= p1;
ptr += 4;
v4 += *((uint*)ptr) * p2;
v4 = (v4 << 13) | (v4 >> (32 - 13)); // rotl 13
v4 *= p1;
ptr += 4;
} while (ptr <= limit);
h32 = ((v1 << 1) | (v1 >> (32 - 1))) + // rotl 1
((v2 << 7) | (v2 >> (32 - 7))) + // rotl 7
((v3 << 12) | (v3 >> (32 - 12))) + // rotl 12
((v4 << 18) | (v4 >> (32 - 18))); // rotl 18
}
else
{
h32 = seed + p5;
}
h32 += (uint) length;
// finalize
while (ptr <= end - 4)
{
h32 += *((uint*)ptr) * p3;
h32 = ((h32 << 17) | (h32 >> (32 - 17))) * p4; // (rotl 17) * p4
ptr += 4;
}
while (ptr < end)
{
h32 += *((byte*)ptr) * p5;
h32 = ((h32 << 11) | (h32 >> (32 - 11))) * p1; // (rotl 11) * p1
ptr += 1;
}
// avalanche
h32 ^= h32 >> 15;
h32 *= p2;
h32 ^= h32 >> 13;
h32 *= p3;
h32 ^= h32 >> 16;
return h32;
}
}
}