HashTraits.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "uLang/Common/Common.h"
 
namespace uLang
{
// Default hash function for pointers.
inline uint32_t GetTypeHash(const void* Key)
{
    const uintptr_t PtrInt = reinterpret_cast<uintptr_t>(Key) >> 4;
    uint32_t Hash = static_cast<uint32_t>(PtrInt);    
    Hash ^= Hash >> 16;
    Hash *= 0x85ebca6b;
    Hash ^= Hash >> 13;
    Hash *= 0xc2b2ae35;
    Hash ^= Hash >> 16;
    return Hash;
}
 
inline uint32_t MurmurFinalize32(uint32_t Hash)
{
    Hash ^= Hash >> 16;
    Hash *= 0x85ebca6b;
    Hash ^= Hash >> 13;
    Hash *= 0xc2b2ae35;
    Hash ^= Hash >> 16;
    return Hash;
}
 
[[nodiscard]] inline constexpr uint32_t HashCombineFast(uint32_t A, uint32_t B)
{
    return A ^ (B + 0x9e3779b9 + (A << 6) + (A >> 2));
}
 
inline uint32_t GetTypeHash(uint32_t I)
{
    return MurmurFinalize32(I);
}
 
inline uint32_t GetTypeHash(int32_t I)
{
    return MurmurFinalize32(static_cast<uint32_t>(I));
}
 
inline uint32_t GetTypeHash(uint64_t I)
{
    return HashCombineFast(MurmurFinalize32(static_cast<uint32_t>(I)), MurmurFinalize32(static_cast<uint32_t>(I >> 32)));
}
 
inline uint32_t GetTypeHash(int64_t I)
{
    return HashCombineFast(MurmurFinalize32(static_cast<uint32_t>(I)), MurmurFinalize32(static_cast<uint32_t>(static_cast<uint64_t>(I) >> 32)));
}
 
template<class KeyType>
struct TDefaultHashTraits
{
    static uint32_t GetKeyHash(const KeyType& Key) { return GetTypeHash(Key); }
};
}