rpcs3/Utilities/hash.h

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#pragma once
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#include "util/types.hpp"
namespace rpcs3
{
constexpr usz fnv_seed = 14695981039346656037ull;
constexpr usz fnv_prime = 1099511628211ull;
template<typename T>
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static usz hash_base(T value)
{
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return static_cast<usz>(value);
}
template<typename T, typename = std::enable_if_t<std::is_integral<T>::value, bool>>
static inline usz hash64(usz hash_value, const T data)
{
hash_value ^= data;
hash_value *= fnv_prime;
return hash_value;
}
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template<typename T, typename U>
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static usz hash_struct_base(const T& value)
{
// FNV 64-bit
usz result = fnv_seed;
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const U *bits = reinterpret_cast<const U*>(&value);
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for (usz n = 0; n < (sizeof(T) / sizeof(U)); ++n)
{
result = hash64(result, bits[n]);
}
return result;
}
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template<typename T>
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static usz hash_struct(const T& value)
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{
static constexpr auto block_sz = sizeof(T);
if constexpr ((block_sz & 0x7) == 0)
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{
return hash_struct_base<T, u64>(value);
}
if constexpr ((block_sz & 0x3) == 0)
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{
return hash_struct_base<T, u32>(value);
}
if constexpr ((block_sz & 0x1) == 0)
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{
return hash_struct_base<T, u16>(value);
}
return hash_struct_base<T, u8>(value);
}
}