/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Statically sized hash table implementation
 * (C) 2012  Sasha Levin <levinsasha928@gmail.com>
 */

#ifndef _LINUX_HASHTABLE_H
#define _LINUX_HASHTABLE_H

#include <math.h>
#include <stdint.h>
#include <stdbool.h>
#include <linux/hlist.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/compiler.h>

#include "../lib/util/util.h"

#define HASH_GOLDEN_RATIO_32 0x61C88647
#define HASH_GOLDEN_RATIO_64 0x61C8864680B583EBull

#if (__SIZEOF_LONG__ * __CHAR_BIT__) == 32
#define HASH_GOLDEN_RATIO_PRIME HASH_GOLDEN_RATIO_32
#define hash_long(val, bits) hash_32(val, bits)
#elif (__SIZEOF_LONG__ * __CHAR_BIT__) == 64
#define hash_long(val, bits) hash_64(val, bits)
#define HASH_GOLDEN_RATIO_PRIME HASH_GOLDEN_RATIO_64
#else
#error "Wordsize not 32 or 64"
#endif

static inline uint32_t __hash_32(uint32_t val)
{
	return val * HASH_GOLDEN_RATIO_32;
}

static inline uint32_t hash_32(uint32_t val, unsigned int bits)
{
	/* High bits are more random, so use them. */
	return __hash_32(val) >> (32 - bits);
}

static inline uint32_t hash_64(uint64_t val, unsigned int bits)
{
#if LONG_TYPE_SIZE * CHAR_BIT == 64
	/* 64x64-bit multiply is efficient on all 64-bit processors */
	return val * HASH_GOLDEN_RATIO_64 >> (64 - bits);
#else
	/* Hash 64 bits using only 32x32-bit multiply. */
	return hash_32((uint32_t)val ^ __hash_32(val >> 32), bits);
#endif
}

#define DEFINE_HASHTABLE(name, bits)						\
	struct hlist_head name[1 << (bits)] =					\
			{ [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }

#define DECLARE_HASHTABLE(name, bits)                                   	\
	struct hlist_head name[1 << (bits)]

#define HASH_SIZE(name) (ARRAY_SIZE(name))
#define HASH_BITS(name) ilogb(HASH_SIZE(name))

/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
#define hash_min(val, bits)							\
	(sizeof(val) <= 4 ? hash_32((uint32_t)val, bits) : hash_long((uint64_t)val, bits))

static inline void __hash_init(struct hlist_head *ht, unsigned int sz)
{
	unsigned int i;

	for (i = 0; i < sz; i++)
		INIT_HLIST_HEAD(&ht[i]);
}

/**
 * hash_init - initialize a hash table
 * @hashtable: hashtable to be initialized
 *
 * Calculates the size of the hashtable from the given parameter, otherwise
 * same as hash_init_size.
 *
 * This has to be a macro since HASH_BITS() will not work on pointers since
 * it calculates the size during preprocessing.
 */
#define hash_init(hashtable) __hash_init(hashtable, HASH_SIZE(hashtable))

/**
 * hash_add - add an object to a hashtable
 * @hashtable: hashtable to add to
 * @node: the &struct hlist_node of the object to be added
 * @key: the key of the object to be added
 */
#define hash_add(hashtable, node, key)						\
	hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))])

/**
 * hash_hashed - check whether an object is in any hashtable
 * @node: the &struct hlist_node of the object to be checked
 */
static inline bool hash_hashed(struct hlist_node *node)
{
	return !hlist_unhashed(node);
}

static inline bool __hash_empty(struct hlist_head *ht, unsigned int sz)
{
	unsigned int i;

	for (i = 0; i < sz; i++)
		if (!hlist_empty(&ht[i]))
			return false;

	return true;
}

/**
 * hash_empty - check whether a hashtable is empty
 * @hashtable: hashtable to check
 *
 * This has to be a macro since HASH_BITS() will not work on pointers since
 * it calculates the size during preprocessing.
 */
#define hash_empty(hashtable) __hash_empty(hashtable, HASH_SIZE(hashtable))

/**
 * hash_del - remove an object from a hashtable
 * @node: &struct hlist_node of the object to remove
 */
static inline void hash_del(struct hlist_node *node)
{
	hlist_del_init(node);
}

/**
 * hash_for_each - iterate over a hashtable
 * @name: hashtable to iterate
 * @bkt: integer to use as bucket loop cursor
 * @obj: the type * to use as a loop cursor for each entry
 * @member: the name of the hlist_node within the struct
 */
#define hash_for_each(name, bkt, obj, member)				\
	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
			(bkt)++)\
		hlist_for_each_entry(obj, &name[bkt], member)

/**
 * hash_for_each_safe - iterate over a hashtable safe against removal of
 * hash entry
 * @name: hashtable to iterate
 * @bkt: integer to use as bucket loop cursor
 * @tmp: a &struct used for temporary storage
 * @obj: the type * to use as a loop cursor for each entry
 * @member: the name of the hlist_node within the struct
 */
#define hash_for_each_safe(name, bkt, tmp, obj, member)			\
	for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
			(bkt)++)\
		hlist_for_each_entry_safe(obj, tmp, &name[bkt], member)

/**
 * hash_for_each_possible - iterate over all possible objects hashing to the
 * same bucket
 * @name: hashtable to iterate
 * @obj: the type * to use as a loop cursor for each entry
 * @member: the name of the hlist_node within the struct
 * @key: the key of the objects to iterate over
 */
#define hash_for_each_possible(name, obj, member, key)			\
	hlist_for_each_entry(obj, &name[hash_min(key, HASH_BITS(name))], member)

/**
 * hash_for_each_possible_safe - iterate over all possible objects hashing to the
 * same bucket safe against removals
 * @name: hashtable to iterate
 * @obj: the type * to use as a loop cursor for each entry
 * @tmp: a &struct used for temporary storage
 * @member: the name of the hlist_node within the struct
 * @key: the key of the objects to iterate over
 */
#define hash_for_each_possible_safe(name, obj, tmp, member, key)	\
	hlist_for_each_entry_safe(obj, tmp,\
		&name[hash_min(key, HASH_BITS(name))], member)


#endif