virtualx-engine/core/templates/hashfuncs.h

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/*  hashfuncs.h                                                          */
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#ifndef HASHFUNCS_H
#define HASHFUNCS_H

#include "core/math/aabb.h"
#include "core/math/math_defs.h"
#include "core/math/math_funcs.h"
#include "core/math/rect2.h"
#include "core/math/rect2i.h"
#include "core/math/vector2.h"
#include "core/math/vector2i.h"
#include "core/math/vector3.h"
#include "core/math/vector3i.h"
#include "core/object/object_id.h"
#include "core/string/node_path.h"
#include "core/string/string_name.h"
#include "core/string/ustring.h"
#include "core/templates/rid.h"
#include "core/typedefs.h"

/**
 * Hashing functions
 */

/**
 * DJB2 Hash function
 * @param C String
 * @return 32-bits hashcode
 */
static _FORCE_INLINE_ uint32_t hash_djb2(const char *p_cstr) {
	const unsigned char *chr = (const unsigned char *)p_cstr;
	uint32_t hash = 5381;
	uint32_t c;

	while ((c = *chr++)) {
		hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
	}

	return hash;
}

static _FORCE_INLINE_ uint32_t hash_djb2_buffer(const uint8_t *p_buff, int p_len, uint32_t p_prev = 5381) {
	uint32_t hash = p_prev;

	for (int i = 0; i < p_len; i++) {
		hash = ((hash << 5) + hash) + p_buff[i]; /* hash * 33 + c */
	}

	return hash;
}

static _FORCE_INLINE_ uint32_t hash_djb2_one_32(uint32_t p_in, uint32_t p_prev = 5381) {
	return ((p_prev << 5) + p_prev) + p_in;
}

/**
 * Thomas Wang's 64-bit to 32-bit Hash function:
 * https://web.archive.org/web/20071223173210/https:/www.concentric.net/~Ttwang/tech/inthash.htm
 *
 * @param p_int - 64-bit unsigned integer key to be hashed
 * @return unsigned 32-bit value representing hashcode
 */
static _FORCE_INLINE_ uint32_t hash_one_uint64(const uint64_t p_int) {
	uint64_t v = p_int;
	v = (~v) + (v << 18); // v = (v << 18) - v - 1;
	v = v ^ (v >> 31);
	v = v * 21; // v = (v + (v << 2)) + (v << 4);
	v = v ^ (v >> 11);
	v = v + (v << 6);
	v = v ^ (v >> 22);
	return uint32_t(v);
}

// Murmurhash3 32-bit version.
// All MurmurHash versions are public domain software, and the author disclaims all copyright to their code.

static _FORCE_INLINE_ uint32_t rotl32(uint32_t x, int8_t r) {
	return (x << r) | (x >> (32 - r));
}

static _FORCE_INLINE_ uint32_t fmix32(uint32_t h) {
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;

	return h;
}

static _FORCE_INLINE_ uint32_t hash_murmur3_32(const void *key, int length, const uint32_t seed = 0x7F07C65) {
	// Although not required, this is a random prime number.
	const uint8_t *data = (const uint8_t *)key;
	const int nblocks = length / 4;

	uint32_t h1 = seed;

	const uint32_t c1 = 0xcc9e2d51;
	const uint32_t c2 = 0x1b873593;

	const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);

	for (int i = -nblocks; i; i++) {
		uint32_t k1 = blocks[i];

		k1 *= c1;
		k1 = rotl32(k1, 15);
		k1 *= c2;

		h1 ^= k1;
		h1 = rotl32(h1, 13);
		h1 = h1 * 5 + 0xe6546b64;
	}

	const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);

	uint32_t k1 = 0;

	switch (length & 3) {
		case 3:
			k1 ^= tail[2] << 16;
			[[fallthrough]];
		case 2:
			k1 ^= tail[1] << 8;
			[[fallthrough]];
		case 1:
			k1 ^= tail[0];
			k1 *= c1;
			k1 = rotl32(k1, 15);
			k1 *= c2;
			h1 ^= k1;
	};

	// Finalize with additional bit mixing.
	h1 ^= length;
	return fmix32(h1);
}

static _FORCE_INLINE_ uint32_t hash_djb2_one_float(double p_in, uint32_t p_prev = 5381) {
	union {
		double d;
		uint64_t i;
	} u;

	// Normalize +/- 0.0 and NaN values so they hash the same.
	if (p_in == 0.0f) {
		u.d = 0.0;
	} else if (Math::is_nan(p_in)) {
		u.d = NAN;
	} else {
		u.d = p_in;
	}

	return ((p_prev << 5) + p_prev) + hash_one_uint64(u.i);
}

template <class T>
static _FORCE_INLINE_ uint32_t make_uint32_t(T p_in) {
	union {
		T t;
		uint32_t _u32;
	} _u;
	_u._u32 = 0;
	_u.t = p_in;
	return _u._u32;
}

static _FORCE_INLINE_ uint64_t hash_djb2_one_float_64(double p_in, uint64_t p_prev = 5381) {
	union {
		double d;
		uint64_t i;
	} u;

	// Normalize +/- 0.0 and NaN values so they hash the same.
	if (p_in == 0.0f) {
		u.d = 0.0;
	} else if (Math::is_nan(p_in)) {
		u.d = NAN;
	} else {
		u.d = p_in;
	}

	return ((p_prev << 5) + p_prev) + u.i;
}

static _FORCE_INLINE_ uint64_t hash_djb2_one_64(uint64_t p_in, uint64_t p_prev = 5381) {
	return ((p_prev << 5) + p_prev) + p_in;
}

template <class T>
static _FORCE_INLINE_ uint64_t make_uint64_t(T p_in) {
	union {
		T t;
		uint64_t _u64;
	} _u;
	_u._u64 = 0; // in case p_in is smaller

	_u.t = p_in;
	return _u._u64;
}

template <class T>
class Ref;

struct HashMapHasherDefault {
	// Generic hash function for any type.
	template <class T>
	static _FORCE_INLINE_ uint32_t hash(const T *p_pointer) { return hash_one_uint64((uint64_t)p_pointer); }

	template <class T>
	static _FORCE_INLINE_ uint32_t hash(const Ref<T> &p_ref) { return hash_one_uint64((uint64_t)p_ref.operator->()); }

	static _FORCE_INLINE_ uint32_t hash(const String &p_string) { return p_string.hash(); }
	static _FORCE_INLINE_ uint32_t hash(const char *p_cstr) { return hash_djb2(p_cstr); }
	static _FORCE_INLINE_ uint32_t hash(const wchar_t p_wchar) { return fmix32(p_wchar); }
	static _FORCE_INLINE_ uint32_t hash(const char16_t p_uchar) { return fmix32(p_uchar); }
	static _FORCE_INLINE_ uint32_t hash(const char32_t p_uchar) { return fmix32(p_uchar); }
	static _FORCE_INLINE_ uint32_t hash(const RID &p_rid) { return hash_one_uint64(p_rid.get_id()); }
	static _FORCE_INLINE_ uint32_t hash(const StringName &p_string_name) { return p_string_name.hash(); }
	static _FORCE_INLINE_ uint32_t hash(const NodePath &p_path) { return p_path.hash(); }
	static _FORCE_INLINE_ uint32_t hash(const ObjectID &p_id) { return hash_one_uint64(p_id); }

	static _FORCE_INLINE_ uint32_t hash(const uint64_t p_int) { return hash_one_uint64(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const int64_t p_int) { return hash_one_uint64(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const float p_float) { return hash_djb2_one_float(p_float); }
	static _FORCE_INLINE_ uint32_t hash(const double p_double) { return hash_djb2_one_float(p_double); }
	static _FORCE_INLINE_ uint32_t hash(const uint32_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const int32_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const uint16_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const int16_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const uint8_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const int8_t p_int) { return fmix32(p_int); }
	static _FORCE_INLINE_ uint32_t hash(const Vector2i &p_vec) { return hash_murmur3_32(&p_vec, sizeof(Vector2i)); }
	static _FORCE_INLINE_ uint32_t hash(const Vector3i &p_vec) { return hash_murmur3_32(&p_vec, sizeof(Vector3i)); }
	static _FORCE_INLINE_ uint32_t hash(const Vector2 &p_vec) { return hash_murmur3_32(&p_vec, sizeof(Vector2)); }
	static _FORCE_INLINE_ uint32_t hash(const Vector3 &p_vec) { return hash_murmur3_32(&p_vec, sizeof(Vector3)); }
	static _FORCE_INLINE_ uint32_t hash(const Rect2i &p_rect) { return hash_murmur3_32(&p_rect, sizeof(Rect2i)); }
	static _FORCE_INLINE_ uint32_t hash(const Rect2 &p_rect) { return hash_murmur3_32(&p_rect, sizeof(Rect2)); }
	static _FORCE_INLINE_ uint32_t hash(const AABB &p_aabb) { return hash_murmur3_32(&p_aabb, sizeof(AABB)); }
};

template <typename T>
struct HashMapComparatorDefault {
	static bool compare(const T &p_lhs, const T &p_rhs) {
		return p_lhs == p_rhs;
	}
};

template <>
struct HashMapComparatorDefault<float> {
	static bool compare(const float &p_lhs, const float &p_rhs) {
		return (p_lhs == p_rhs) || (Math::is_nan(p_lhs) && Math::is_nan(p_rhs));
	}
};

template <>
struct HashMapComparatorDefault<double> {
	static bool compare(const double &p_lhs, const double &p_rhs) {
		return (p_lhs == p_rhs) || (Math::is_nan(p_lhs) && Math::is_nan(p_rhs));
	}
};

template <>
struct HashMapComparatorDefault<Vector2> {
	static bool compare(const Vector2 &p_lhs, const Vector2 &p_rhs) {
		return ((p_lhs.x == p_rhs.x) || (Math::is_nan(p_lhs.x) && Math::is_nan(p_rhs.x))) && ((p_lhs.y == p_rhs.y) || (Math::is_nan(p_lhs.y) && Math::is_nan(p_rhs.y)));
	}
};

template <>
struct HashMapComparatorDefault<Vector3> {
	static bool compare(const Vector3 &p_lhs, const Vector3 &p_rhs) {
		return ((p_lhs.x == p_rhs.x) || (Math::is_nan(p_lhs.x) && Math::is_nan(p_rhs.x))) && ((p_lhs.y == p_rhs.y) || (Math::is_nan(p_lhs.y) && Math::is_nan(p_rhs.y))) && ((p_lhs.z == p_rhs.z) || (Math::is_nan(p_lhs.z) && Math::is_nan(p_rhs.z)));
	}
};

constexpr uint32_t HASH_TABLE_SIZE_MAX = 29;

const uint32_t hash_table_size_primes[HASH_TABLE_SIZE_MAX] = {
	5,
	13,
	23,
	47,
	97,
	193,
	389,
	769,
	1543,
	3079,
	6151,
	12289,
	24593,
	49157,
	98317,
	196613,
	393241,
	786433,
	1572869,
	3145739,
	6291469,
	12582917,
	25165843,
	50331653,
	100663319,
	201326611,
	402653189,
	805306457,
	1610612741,
};

#endif // HASHFUNCS_H