path: root/include/erofs/hashtable.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Original code taken from 'linux/include/linux/hash{,table}.h'
 */
#ifndef __EROFS_HASHTABLE_H
#define __EROFS_HASHTABLE_H

#ifdef __cplusplus
extern "C"
{
#endif

/*
 * Fast hashing routine for ints,  longs and pointers.
 * (C) 2002 Nadia Yvette Chambers, IBM
 */

/*
 * Statically sized hash table implementation
 * (C) 2012  Sasha Levin <levinsasha928@gmail.com>
 */

#include "defs.h"

/*
 * The "GOLDEN_RATIO_PRIME" is used in ifs/btrfs/brtfs_inode.h and
 * fs/inode.c.  It's not actually prime any more (the previous primes
 * were actively bad for hashing), but the name remains.
 */
#if BITS_PER_LONG == 32
#define GOLDEN_RATIO_PRIME GOLDEN_RATIO_32
#define hash_long(val, bits) hash_32(val, bits)
#elif BITS_PER_LONG == 64
#define hash_long(val, bits) hash_64(val, bits)
#define GOLDEN_RATIO_PRIME GOLDEN_RATIO_64
#else
#error Wordsize not 32 or 64
#endif

/*
 * This hash multiplies the input by a large odd number and takes the
 * high bits.  Since multiplication propagates changes to the most
 * significant end only, it is essential that the high bits of the
 * product be used for the hash value.
 *
 * Chuck Lever verified the effectiveness of this technique:
 * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
 *
 * Although a random odd number will do, it turns out that the golden
 * ratio phi = (sqrt(5)-1)/2, or its negative, has particularly nice
 * properties.  (See Knuth vol 3, section 6.4, exercise 9.)
 *
 * These are the negative, (1 - phi) = phi**2 = (3 - sqrt(5))/2,
 * which is very slightly easier to multiply by and makes no
 * difference to the hash distribution.
 */
#define GOLDEN_RATIO_32 0x61C88647
#define GOLDEN_RATIO_64 0x61C8864680B583EBull

struct hlist_head {
	struct hlist_node *first;
};

struct hlist_node {
	struct hlist_node *next, **pprev;
};

/*
 * Architectures might want to move the poison pointer offset
 * into some well-recognized area such as 0xdead000000000000,
 * that is also not mappable by user-space exploits:
 */
#ifdef CONFIG_ILLEGAL_POINTER_VALUE
# define POISON_POINTER_DELTA _AC(CONFIG_ILLEGAL_POINTER_VALUE, UL)
#else
# define POISON_POINTER_DELTA 0
#endif

/*
 * These are non-NULL pointers that will result in page faults
 * under normal circumstances, used to verify that nobody uses
 * non-initialized list entries.
 */
#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)

/*
 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */

#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void INIT_HLIST_NODE(struct hlist_node *h)
{
	h->next = NULL;
	h->pprev = NULL;
}

static inline int hlist_unhashed(const struct hlist_node *h)
{
	return !h->pprev;
}

static inline int hlist_empty(const struct hlist_head *h)
{
	return !h->first;
}

static inline void __hlist_del(struct hlist_node *n)
{
	struct hlist_node *next = n->next;
	struct hlist_node **pprev = n->pprev;

	*pprev = next;
	if (next)
		next->pprev = pprev;
}

static inline void hlist_del(struct hlist_node *n)
{
	__hlist_del(n);
	n->next = LIST_POISON1;
	n->pprev = LIST_POISON2;
}

static inline void hlist_del_init(struct hlist_node *n)
{
	if (!hlist_unhashed(n)) {
		__hlist_del(n);
		INIT_HLIST_NODE(n);
	}
}

static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{
	struct hlist_node *first = h->first;

	n->next = first;
	if (first)
		first->pprev = &n->next;
	h->first = n;
	n->pprev = &h->first;
}

/* next must be != NULL */
static inline void hlist_add_before(struct hlist_node *n,
					struct hlist_node *next)
{
	n->pprev = next->pprev;
	n->next = next;
	next->pprev = &n->next;
	*(n->pprev) = n;
}

static inline void hlist_add_behind(struct hlist_node *n,
				    struct hlist_node *prev)
{
	n->next = prev->next;
	prev->next = n;
	n->pprev = &prev->next;

	if (n->next)
		n->next->pprev  = &n->next;
}

/* after that we'll appear to be on some hlist and hlist_del will work */
static inline void hlist_add_fake(struct hlist_node *n)
{
	n->pprev = &n->next;
}

/*
 * Move a list from one list head to another. Fixup the pprev
 * reference of the first entry if it exists.
 */
static inline void hlist_move_list(struct hlist_head *old,
				   struct hlist_head *new)
{
	new->first = old->first;
	if (new->first)
		new->first->pprev = &new->first;
	old->first = NULL;
}

#define hlist_entry(ptr, type, member) container_of(ptr, type, member)

#define hlist_for_each(pos, head) \
	for (pos = (head)->first; pos; pos = pos->next)

#define hlist_for_each_safe(pos, n, head) \
	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
	     pos = n)

#define hlist_entry_safe(ptr, type, member) \
	({ typeof(ptr) ____ptr = (ptr); \
	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
	})

/**
 * hlist_for_each_entry	- iterate over list of given type
 * @pos:the type * to use as a loop cursor.
 * @head:the head for your list.
 * @member:the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(pos, head, member)				\
	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
	     pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_continue
 * iterate over a hlist continuing after current point
 * @pos:the type * to use as a loop cursor.
 * @member:the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(pos, member)			\
	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
	     pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_from
 * iterate over a hlist continuing from current point
 * @pos:	the type * to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(pos, member)				\
	for (; pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_safe
 * iterate over list of given type safe against removal of list entry
 * @pos:the type * to use as a loop cursor.
 * @n:another &struct hlist_node to use as temporary storage
 * @head:the head for your list.
 * @member:the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(pos, n, head, member)			\
	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
		pos && ({ n = pos->member.next; 1; });			\
		pos = hlist_entry_safe(n, typeof(*pos), member))

static inline u32 __hash_32(u32 val)
{
	return val * GOLDEN_RATIO_32;
}

static inline u32 hash_32(u32 val, unsigned int bits)
{
	/* High bits are more random, so use them. */
	return __hash_32(val) >> (32 - bits);
}

static inline u32 hash_64(u64 val, unsigned int bits)
{
#if BITS_PER_LONG == 64
	/* 64x64-bit multiply is efficient on all 64-bit processors */
	return val * GOLDEN_RATIO_64 >> (64 - bits);
#else
	/* Hash 64 bits using only 32x32-bit multiply. */
	return hash_32((u32)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) ilog2(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(val, bits) : hash_long(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)

#ifdef __cplusplus
}
#endif

#endif