98 lines
2.9 KiB
C++
98 lines
2.9 KiB
C++
// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
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// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
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// SPDX-License-Identifier: MIT
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#pragma once
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JPH_NAMESPACE_BEGIN
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/// Implements the FNV-1a hash algorithm
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/// @see https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
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/// @param inData Data block of bytes
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/// @param inSize Number of bytes
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/// @param inSeed Seed of the hash (can be used to pass in the hash of a previous operation, otherwise leave default)
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/// @return Hash
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inline uint64 HashBytes(const void *inData, uint inSize, uint64 inSeed = 0xcbf29ce484222325UL)
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{
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uint64 hash = inSeed;
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for (const uint8 *data = reinterpret_cast<const uint8 *>(inData); data < reinterpret_cast<const uint8 *>(inData) + inSize; ++data)
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{
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hash = hash ^ uint64(*data);
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hash = hash * 0x100000001b3UL;
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}
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return hash;
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}
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/// A 64 bit hash function by Thomas Wang, Jan 1997
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/// See: http://web.archive.org/web/20071223173210/http://www.concentric.net/~Ttwang/tech/inthash.htm
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/// @param inValue Value to hash
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/// @return Hash
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inline uint64 Hash64(uint64 inValue)
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{
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uint64 hash = inValue;
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hash = (~hash) + (hash << 21); // hash = (hash << 21) - hash - 1;
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hash = hash ^ (hash >> 24);
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hash = (hash + (hash << 3)) + (hash << 8); // hash * 265
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hash = hash ^ (hash >> 14);
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hash = (hash + (hash << 2)) + (hash << 4); // hash * 21
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hash = hash ^ (hash >> 28);
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hash = hash + (hash << 31);
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return hash;
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}
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/// @brief Helper function that hashes a single value into ioSeed
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/// Taken from: https://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x
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template <typename T>
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inline void HashCombineHelper(size_t &ioSeed, const T &inValue)
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{
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std::hash<T> hasher;
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ioSeed ^= hasher(inValue) + 0x9e3779b9 + (ioSeed << 6) + (ioSeed >> 2);
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}
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/// Hash combiner to use a custom struct in an unordered map or set
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///
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/// Usage:
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///
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/// struct SomeHashKey
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/// {
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/// std::string key1;
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/// std::string key2;
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/// bool key3;
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/// };
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///
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/// JPH_MAKE_HASHABLE(SomeHashKey, t.key1, t.key2, t.key3)
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template <typename... Values>
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inline void HashCombine(std::size_t &ioSeed, Values... inValues)
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{
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// Hash all values together using a fold expression
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(HashCombineHelper(ioSeed, inValues), ...);
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}
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JPH_NAMESPACE_END
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JPH_SUPPRESS_WARNING_PUSH
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JPH_CLANG_SUPPRESS_WARNING("-Wc++98-compat-pedantic")
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#define JPH_MAKE_HASH_STRUCT(type, name, ...) \
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struct [[nodiscard]] name \
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{ \
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std::size_t operator()(const type &t) const \
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{ \
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std::size_t ret = 0; \
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::JPH::HashCombine(ret, __VA_ARGS__); \
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return ret; \
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} \
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};
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#define JPH_MAKE_HASHABLE(type, ...) \
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JPH_SUPPRESS_WARNING_PUSH \
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JPH_SUPPRESS_WARNINGS \
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namespace std \
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{ \
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template<> \
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JPH_MAKE_HASH_STRUCT(type, hash<type>, __VA_ARGS__) \
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} \
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JPH_SUPPRESS_WARNING_POP
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JPH_SUPPRESS_WARNING_POP
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