HashCombine.h File Reference

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Macros
#define	JPH_MAKE_HASH_STRUCT(type, name, ...)
#define	JPH_MAKE_HASHABLE(type, ...)

Functions
JPH_NAMESPACE_BEGIN uint64	HashBytes (const void *inData, uint inSize, uint64 inSeed=0xcbf29ce484222325UL)
uint64	Hash64 (uint64 inValue)
template<typename T >
void	HashCombineHelper (size_t &ioSeed, const T &inValue)
	Helper function that hashes a single value into ioSeed Taken from: https://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x.
template<typename... Values>
void	HashCombine (std::size_t &ioSeed, Values... inValues)

Macro Definition Documentation

JPH_MAKE_HASH_STRUCT

#define JPH_MAKE_HASH_STRUCT	(		type,
			name,
			... )

Value:

    struct [[nodiscard]] name                               \
    {                                                       \
        std::size_t operator()(const type &t) const         \
        {                                                   \
            std::size_t ret = 0;                            \
            ::JPH::HashCombine(ret, __VA_ARGS__);           \
            return ret;                                     \
        }                                                   \
    };

JPH_MAKE_HASHABLE

#define JPH_MAKE_HASHABLE	(		type,
			... )

Value:

    JPH_SUPPRESS_WARNING_PUSH								\
	JPH_SUPPRESS_WARNINGS									\
    namespace std                                           \
    {                                                       \
        template<>											\
		JPH_MAKE_HASH_STRUCT(type, hash<type>, __VA_ARGS__)   \
    }                                                       \
    JPH_SUPPRESS_WARNING_POP

Function Documentation

Hash64()

uint64 Hash64 ( uint64 inValue )

inline

A 64 bit hash function by Thomas Wang, Jan 1997 See: http://web.archive.org/web/20071223173210/http://www.concentric.net/~Ttwang/tech/inthash.htm

Parameters

inValue

Value to hash

Returns

Hash

HashBytes()

JPH_NAMESPACE_BEGIN uint64 HashBytes ( const void * inData, uint inSize, uint64 inSeed = 0xcbf29ce484222325UL )

inline

Implements the FNV-1a hash algorithm

See also

https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function

Parameters

inData	Data block of bytes
inSize	Number of bytes
inSeed	Seed of the hash (can be used to pass in the hash of a previous operation, otherwise leave default)

Returns

Hash

HashCombine()

template<typename... Values>

void HashCombine ( std::size_t & ioSeed, Values... inValues )

inline

Hash combiner to use a custom struct in an unordered map or set

Usage:

struct SomeHashKey
{
    std::string key1;
    std::string key2;
    bool key3;
};

JPH_MAKE_HASHABLE(SomeHashKey, t.key1, t.key2, t.key3) 

HashCombineHelper()

template<typename T >

void HashCombineHelper ( size_t & ioSeed, const T & inValue )

inline

Helper function that hashes a single value into ioSeed Taken from: https://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x.