physxCAPI/physxCDLL/include/foundation/PxHash.h

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#ifndef PX_HASH_H
#define PX_HASH_H

#include "foundation/PxBasicTemplates.h"
#include "foundation/PxString.h"

#if PX_VC
#pragma warning(push)
#pragma warning(disable : 4302)
#endif

#if PX_LINUX
#include "foundation/PxSimpleTypes.h"
#endif

/*!
Central definition of hash functions
*/

#if !PX_DOXYGEN
namespace physx
{
#endif
// Hash functions

// Thomas Wang's 32 bit mix
// http://www.cris.com/~Ttwang/tech/inthash.htm
PX_FORCE_INLINE uint32_t PxComputeHash(const uint32_t key)
{
	uint32_t k = key;
	k += ~(k << 15);
	k ^= (k >> 10);
	k += (k << 3);
	k ^= (k >> 6);
	k += ~(k << 11);
	k ^= (k >> 16);
	return uint32_t(k);
}

PX_FORCE_INLINE uint32_t PxComputeHash(const int32_t key)
{
	return PxComputeHash(uint32_t(key));
}

// Thomas Wang's 64 bit mix
// http://www.cris.com/~Ttwang/tech/inthash.htm
PX_FORCE_INLINE uint32_t PxComputeHash(const uint64_t key)
{
	uint64_t k = key;
	k += ~(k << 32);
	k ^= (k >> 22);
	k += ~(k << 13);
	k ^= (k >> 8);
	k += (k << 3);
	k ^= (k >> 15);
	k += ~(k << 27);
	k ^= (k >> 31);
	return uint32_t(UINT32_MAX & k);
}

#if PX_APPLE_FAMILY
// hash for size_t, to make gcc happy
PX_INLINE uint32_t PxComputeHash(const size_t key)
{
#if PX_P64_FAMILY
	return PxComputeHash(uint64_t(key));
#else
	return PxComputeHash(uint32_t(key));
#endif
}
#endif

// Hash function for pointers
PX_INLINE uint32_t PxComputeHash(const void* ptr)
{
#if PX_P64_FAMILY
	return PxComputeHash(uint64_t(ptr));
#else
	return PxComputeHash(uint32_t(UINT32_MAX & size_t(ptr)));
#endif
}

// Hash function for pairs
template <typename F, typename S>
PX_INLINE uint32_t PxComputeHash(const PxPair<F, S>& p)
{
	uint32_t seed = 0x876543;
	uint32_t m = 1000007;
	return PxComputeHash(p.second) ^ (m * (PxComputeHash(p.first) ^ (m * seed)));
}

// hash object for hash map template parameter
template <class Key>
struct PxHash
{
	uint32_t operator()(const Key& k) const
	{
		return PxComputeHash(k);
	}
	bool equal(const Key& k0, const Key& k1) const
	{
		return k0 == k1;
	}
};

// specialization for strings
template <>
struct PxHash<const char*>
{
  public:
	uint32_t operator()(const char* _string) const
	{
		// "DJB" string hash
		const uint8_t* string = reinterpret_cast<const uint8_t*>(_string);
		uint32_t h = 5381;
		for(const uint8_t* ptr = string; *ptr; ptr++)
			h = ((h << 5) + h) ^ uint32_t(*ptr);
		return h;
	}
	bool equal(const char* string0, const char* string1) const
	{
		return !Pxstrcmp(string0, string1);
	}
};

#if !PX_DOXYGEN
} // namespace physx
#endif

#if PX_VC
#pragma warning(pop)
#endif

#endif