MinecraftConsoles/Minecraft.World/JavaIntHash.h

#pragma once

#include <cstdint>

// Java doesn't have a default hash value for ints, however, the hashmap itself does some "supplemental" hashing, so
// our ints actually get hashed by code as implemented below. std templates *do* have a standard hash for ints, but it
// would appear to be a bit expensive so matching the java one for now anyway. This code implements the supplemental
// hashing that happens in java so we can match what their maps are doing with ints.

struct IntKeyHash
{
	inline int operator()(const int &k) const
	{
		int h = k;
        h += ~(h << 9);
        h ^=  (((unsigned int)h) >> 14);
        h +=  (h << 4);
        h ^=  (((unsigned int)h) >> 10);
		return h;
	}
};

struct IntKeyEq
{
	inline bool operator()(const int &x, const int &y) const
	{ return x==y; }
};

// This hash functor is taken from the IntHashMap java class used by the game, so that we can use a standard std hashmap with this hash rather
// than implement the class itself
struct IntKeyHash2
{
	inline int operator()(const int &k) const
	{
		unsigned int h = static_cast<unsigned int>(k);
        h ^= (h >> 20) ^ (h >> 12);
        return static_cast<int>(h ^ (h >> 7) ^ (h >> 4));
	}
};


// This hash functor is taken from the LongHashMap java class used by the game, so that we can use a standard std hashmap with this hash rather
// than implement the class itself
struct LongKeyHash
{
	inline int hash(const int &k) const
	{
		unsigned int h = static_cast<unsigned int>(k);
        h ^= (h >> 20) ^ (h >> 12);
        return static_cast<int>(h ^ (h >> 7) ^ (h >> 4));
	}

	inline int operator()(const int64_t &k) const
	{
		return hash(static_cast<int>(k ^ ((static_cast<uint64_t>(k)) >> 32)));
	}
};

struct LongKeyEq
{
	inline bool operator() (const int64_t &x, const int64_t &y) const 
	{ return x == y; }
};

enum eINSTANCEOF;
struct eINSTANCEOFKeyHash
{
	int operator()(const eINSTANCEOF &k) const
	{
		unsigned int h = static_cast<unsigned int>(k);
        h ^= (h >> 20) ^ (h >> 12);
        return static_cast<int>(h ^ (h >> 7) ^ (h >> 4));
	}
};

struct eINSTANCEOFKeyEq
{
	inline bool operator()(const eINSTANCEOF &x, const eINSTANCEOF &y) const
	{ return x == y; }
};