// Copyright (c) 2020 - 2025 kio@little-bat.de
// BSD-2-Clause license
// https://opensource.org/licenses/BSD-2-Clause

#pragma once
#include "kio/kio.h"


// Hash functions needed for HashMap


namespace kio
{

inline uint32 sdbm_hash(const char* key)
{
	// Calculate hash for key
	//		note: this is the sdbm algorithm:
	//		hash(i) = hash(i-1) * 65599 + str[i];
	//	see: http://www.cse.yorku.ca/~oz/hash.html
	//	https://programmers.stackexchange.com/questions/49550

	uint32 hash = 0;
	while (int c = *key++)
	{
		hash = (hash << 6) + (hash << 16) - hash + uint(c); // meistens eine Winzigkeit schneller als Multiplikation
	}

	//return hash;					// original algorithm
	return hash ^ (hash >> 16); // do some xor'ing to better support smaller required hash sizes
}

inline uint32 hash(const void* key) { return uint32(size_t(key) ^ (size_t(key) >> 12)); }

inline uint32 hash(cstr key) { return sdbm_hash(key); }

inline uint32 hash(uint32 key) { return key ^ (key >> 16); }
inline uint32 hash(int32 key) { return hash(uint32(key)); }

inline uint32 hash(uint64 key) { return hash(uint32(key) ^ uint32(key >> 32)); }
inline uint32 hash(int64 key) { return hash(uint64(key)); }

//	inline uint32 hash (uint key)		{ return key ^ (key>>16); }
//	inline uint32 hash (int key)		{ return hash(uint32(key)); }

#if !defined(_LINUX) && !defined(_CYGWIN)
  #if _sizeof_long == 8
inline uint32 hash(ulong key) { return hash(uint64(key)); }
inline uint32 hash(long key) { return hash(uint64(key)); }
  #elif _sizeof_long == 4
inline uint32 hash(ulong key) { return hash(uint32(key)); }
inline uint32 hash(long key) { return hash(uint32(key)); }
  #else
	#error
  #endif
#endif

// keys must compare what is hashed:
template<typename T>
inline bool same(T a, T b)
{
	return a == b;
}
inline bool same(cstr a, cstr b) { return eq(a, b); }
} // namespace kio