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Improved comparison for GEDCOM file synchronization (#583)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,219 @@ | ||
| /* | ||
| The xxHash32 implementation is based on the code published by Yann Collet: | ||
| https://raw.githubusercontent.com/Cyan4973/xxHash/5c174cfa4e45a42f94082dc0d4539b39696afea1/xxhash.c | ||
| xxHash - Fast Hash algorithm | ||
| Copyright (C) 2012-2016, Yann Collet | ||
| BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php) | ||
| Redistribution and use in source and binary forms, with or without | ||
| modification, are permitted provided that the following conditions are | ||
| met: | ||
| * Redistributions of source code must retain the above copyright | ||
| notice, this list of conditions and the following disclaimer. | ||
| * Redistributions in binary form must reproduce the above | ||
| copyright notice, this list of conditions and the following disclaimer | ||
| in the documentation and/or other materials provided with the | ||
| distribution. | ||
| THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||
| "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||
| LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||
| A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | ||
| OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | ||
| SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | ||
| LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | ||
| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | ||
| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||
| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | ||
| OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
| You can contact the author at : | ||
| - xxHash homepage: http://www.xxhash.com | ||
| - xxHash source repository : https://github.com/Cyan4973/xxHash | ||
| */ | ||
|
|
||
| using System.Runtime.CompilerServices; | ||
|
|
||
| namespace System | ||
| { | ||
| public struct HashCode | ||
| { | ||
| private static readonly uint s_seed = GenerateGlobalSeed(); | ||
|
|
||
| private const uint Prime1 = 2654435761U; | ||
| private const uint Prime2 = 2246822519U; | ||
| private const uint Prime3 = 3266489917U; | ||
| private const uint Prime4 = 668265263U; | ||
| private const uint Prime5 = 374761393U; | ||
|
|
||
| private uint _v1, _v2, _v3, _v4; | ||
| private uint _queue1, _queue2, _queue3; | ||
| private uint _length; | ||
|
|
||
| #region Private and inlined | ||
|
|
||
| private static unsafe uint GenerateGlobalSeed() | ||
| { | ||
| var rnd = new Random(); | ||
|
|
||
| uint result; | ||
| //Interop.GetRandomBytes((byte*)&result, sizeof(uint)); | ||
| result = (uint)rnd.Next(); | ||
| return result; | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static void Initialize(out uint v1, out uint v2, out uint v3, out uint v4) | ||
| { | ||
| v1 = s_seed + Prime1 + Prime2; | ||
| v2 = s_seed + Prime2; | ||
| v3 = s_seed; | ||
| v4 = s_seed - Prime1; | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint RotateLeft(uint value, int offset) | ||
| { | ||
| return (value << offset) | (value >> (32 - offset)); | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint Round(uint hash, uint input) | ||
| { | ||
| return RotateLeft(hash + input * Prime2, 13) * Prime1; | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint QueueRound(uint hash, uint queuedValue) | ||
| { | ||
| return RotateLeft(hash + queuedValue * Prime3, 17) * Prime4; | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint MixState(uint v1, uint v2, uint v3, uint v4) | ||
| { | ||
| return RotateLeft(v1, 1) + RotateLeft(v2, 7) + RotateLeft(v3, 12) + RotateLeft(v4, 18); | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint MixEmptyState() | ||
| { | ||
| return s_seed + Prime5; | ||
| } | ||
|
|
||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| private static uint MixFinal(uint hash) | ||
| { | ||
| hash ^= hash >> 15; | ||
| hash *= Prime2; | ||
| hash ^= hash >> 13; | ||
| hash *= Prime3; | ||
| hash ^= hash >> 16; | ||
| return hash; | ||
| } | ||
|
|
||
| #endregion | ||
|
|
||
| public void AddVal<T>(T value) where T : struct | ||
| { | ||
| AddHash(value.GetHashCode()); | ||
| } | ||
|
|
||
| public void AddObj<T>(T value) where T : class | ||
| { | ||
| AddHash(value == null ? 0 : value.GetHashCode()); | ||
| } | ||
|
|
||
| public void AddHash(int value) | ||
| { | ||
| // The original xxHash works as follows: | ||
| // 0. Initialize immediately. We can't do this in a struct (no | ||
| // default ctor). | ||
| // 1. Accumulate blocks of length 16 (4 uints) into 4 accumulators. | ||
| // 2. Accumulate remaining blocks of length 4 (1 uint) into the | ||
| // hash. | ||
| // 3. Accumulate remaining blocks of length 1 into the hash. | ||
|
|
||
| // There is no need for #3 as this type only accepts ints. _queue1, | ||
| // _queue2 and _queue3 are basically a buffer so that when | ||
| // ToHashCode is called we can execute #2 correctly. | ||
|
|
||
| // We need to initialize the xxHash32 state (_v1 to _v4) lazily (see | ||
| // #0) nd the last place that can be done if you look at the | ||
| // original code is just before the first block of 16 bytes is mixed | ||
| // in. The xxHash32 state is never used for streams containing fewer | ||
| // than 16 bytes. | ||
|
|
||
| // To see what's really going on here, have a look at the Combine | ||
| // methods. | ||
|
|
||
| uint val = (uint)value; | ||
|
|
||
| // Storing the value of _length locally shaves of quite a few bytes | ||
| // in the resulting machine code. | ||
| uint previousLength = _length++; | ||
| uint position = previousLength % 4; | ||
|
|
||
| // Switch can't be inlined. | ||
|
|
||
| if (position == 0) | ||
| _queue1 = val; | ||
| else if (position == 1) | ||
| _queue2 = val; | ||
| else if (position == 2) | ||
| _queue3 = val; | ||
| else // position == 3 | ||
| { | ||
| if (previousLength == 3) | ||
| Initialize(out _v1, out _v2, out _v3, out _v4); | ||
|
|
||
| _v1 = Round(_v1, _queue1); | ||
| _v2 = Round(_v2, _queue2); | ||
| _v3 = Round(_v3, _queue3); | ||
| _v4 = Round(_v4, val); | ||
| } | ||
| } | ||
|
|
||
| public int ToHashCode() | ||
| { | ||
| // Storing the value of _length locally shaves of quite a few bytes | ||
| // in the resulting machine code. | ||
| uint length = _length; | ||
|
|
||
| // position refers to the *next* queue position in this method, so | ||
| // position == 1 means that _queue1 is populated; _queue2 would have | ||
| // been populated on the next call to Add. | ||
| uint position = length % 4; | ||
|
|
||
| // If the length is less than 4, _v1 to _v4 don't contain anything | ||
| // yet. xxHash32 treats this differently. | ||
|
|
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| uint hash = length < 4 ? MixEmptyState() : MixState(_v1, _v2, _v3, _v4); | ||
|
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||
| // _length is incremented once per Add(Int32) and is therefore 4 | ||
| // times too small (xxHash length is in bytes, not ints). | ||
|
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| hash += length * 4; | ||
|
|
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| // Mix what remains in the queue | ||
|
|
||
| // Switch can't be inlined right now, so use as few branches as | ||
| // possible by manually excluding impossible scenarios (position > 1 | ||
| // is always false if position is not > 0). | ||
| if (position > 0) { | ||
| hash = QueueRound(hash, _queue1); | ||
| if (position > 1) { | ||
| hash = QueueRound(hash, _queue2); | ||
| if (position > 2) | ||
| hash = QueueRound(hash, _queue3); | ||
| } | ||
| } | ||
|
|
||
| hash = MixFinal(hash); | ||
| return (int)hash; | ||
| } | ||
| } | ||
| } |
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