/* SPDX-License-Identifier: AGPL-3.0-or-later */
/*
 * Soft:        The main goal of gtp-guard is to provide robust and secure
 *              extensions to GTP protocol (GPRS Tunneling Procol). GTP is
 *              widely used for data-plane in mobile core-network. gtp-guard
 *              implements a set of 3 main frameworks:
 *              A Proxy feature for data-plane tweaking, a Routing facility
 *              to inter-connect and a Firewall feature for filtering,
 *              rewriting and redirecting.
 *
 * Authors:     Alexandre Cassen, <acassen@gmail.com>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU Affero General Public
 *              License Version 3.0 as published by the Free Software Foundation;
 *              either version 3.0 of the License, or (at your option) any later
 *              version.
 *
 * Copyright (C) 2023 Alexandre Cassen, <acassen@gmail.com>
 */

#ifndef _LIST_HEAD_H
#define _LIST_HEAD_H

#include <stdlib.h>
#include <stddef.h>

#include "container.h"

/*
 * 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)
#define LIST_POISON2  ((void *) 0x00200200)

/*
 * Simple doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */

typedef struct list_head {
	struct list_head *next, *prev;
} list_head_t;

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) \
	struct list_head name = LIST_HEAD_INIT(name)

#define INIT_LIST_HEAD(ptr) do { \
	(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head *new,
			      struct list_head *prev,
			      struct list_head *next)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
 * list_head_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_head_add(struct list_head *new, struct list_head *head)
{
	__list_add(new, head, head->next);
}

/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
	__list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
	next->prev = prev;
	prev->next = next;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void list_head_del(struct list_head *entry)
{
	__list_del(entry->prev, entry->next);
	entry->next = LIST_POISON1;
	entry->prev = LIST_POISON2;
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(struct list_head *entry)
{
	__list_del(entry->prev, entry->next);
	INIT_LIST_HEAD(entry);
}

/**
 * list_move - delete from one list and add as another's head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
	__list_del(list->prev, list->next);
	list_head_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
static inline void list_move_tail(struct list_head *list,
				  struct list_head *head)
{
	__list_del(list->prev, list->next);
	list_add_tail(list, head);
}

/**
 * list_is_first - tests whether @list is the first entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_first(const struct list_head *list,
				const struct list_head *head)
{
	return list->prev == head;
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(const struct list_head *list,
			       const struct list_head *head)
{
	return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const struct list_head *head)
{
	return head->next == head;
}

/**
 * list_copy - copy one list to another
 * @dst: the destination list
 * @src: the source list
 */
static inline void list_copy(struct list_head *dst, struct list_head *src)
{
	if (list_empty(src))
		INIT_LIST_HEAD(dst);
	else {
		*dst = *src;
		dst->next->prev = dst;
		dst->prev->next = dst;
	}
}

static inline void __list_splice(struct list_head *list,
				 struct list_head *head)
{
	struct list_head *first = list->next;
	struct list_head *last = list->prev;
	struct list_head *at = head->next;

	first->prev = head;
	head->next = first;

	last->next = at;
	at->prev = last;
}

/**
 * list_splice - join two lists
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice(struct list_head *list, struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * The list at @list is reinitialised
 */
static inline void list_splice_init(struct list_head *list,
				    struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head);
		INIT_LIST_HEAD(list);
	}
}

/**
 * list_sort - merge sort elements of a list.
 * @head: the head of the list.
 * @cmp: the function used to compare to list nodes.
 */
void list_sort(struct list_head *head,
	       int (*cmp)(struct list_head *a, struct list_head *b));

/**
 * list_entry - get the struct for this entry
 * @ptr:	the &struct list_head pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_struct within the struct.
 */
#define list_entry(ptr, type, member) \
	container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_struct within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
	list_entry((ptr)->next, type, member)

/**
 * list_last_entry - get the last element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_struct within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) \
	list_entry((ptr)->prev, type, member)


/**
 * list_for_each	-	iterate over a list
 * @pos:	the &struct list_head to use as a loop counter.
 * @head:	the head for your list.
 */
#define list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); \
		pos = pos->next)

/**
 * __list_for_each	-	iterate over a list
 * @pos:	the &struct list_head to use as a loop counter.
 * @head:	the head for your list.
 *
 * This variant differs from list_for_each() in that it's the
 * simplest possible list iteration code, no prefetching is done.
 * Use this for code that knows the list to be very short (empty
 * or 1 entry) most of the time.
 */
#define __list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev	-	iterate over a list backwards
 * @pos:	the &struct list_head to use as a loop counter.
 * @head:	the head for your list.
 */
#define list_for_each_prev(pos, head) \
	for (pos = (head)->prev; pos != (head); \
		pos = pos->prev)

/**
 * list_for_each_safe	-	iterate over a list safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop counter.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

/**
 * list_for_each_entry	-	iterate over list of given type
 * @pos:	the type * to use as a loop counter.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_entry((head)->next, typeof(*pos), member);	\
	     &pos->member != (head); 					\
	     pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:	the type * to use as a loop counter.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)			\
	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
	     &pos->member != (head); 					\
	     pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_for_each_entry_continue -	iterate over list of given type
 *			continuing after existing point
 * @pos:	the type * to use as a loop counter.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry_continue(pos, head, member) 		\
	for (pos = list_entry(pos->member.next, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)		\
	for (pos = list_entry(pos->member.prev, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member) 			\
	for (; &pos->member != (head);					\
	     pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from_reverse(pos, head, member)		\
	for (; &pos->member != (head);					\
	     pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop counter.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_entry((head)->next, typeof(*pos), member),	\
		n = list_entry(pos->member.next, typeof(*pos), member);	\
	     &pos->member != (head); 					\
	     pos = n, n = list_entry(n->member.next, typeof(*n), member))


/*
 * 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).
 */

typedef struct hlist_head {
	struct hlist_node *first;
} hlist_head_t;

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

#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
#define INIT_HLIST_NODE(ptr) ((ptr)->next = NULL, (ptr)->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 (n->pprev)  {
		__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;
}

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_after(struct hlist_node *n,
				       struct hlist_node *next)
{
	next->next = n->next;
	n->next = next;
	next->pprev = &n->next;
	if (next->next)
		next->next->pprev = &next->next;
}

#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; n = pos ? pos->next : 0, pos; \
	     pos = n)

/**
 * hlist_for_each_entry	- iterate over list of given type
 * @tpos:	the type * to use as a loop counter.
 * @pos:	the &struct hlist_node to use as a loop counter.
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(tpos, pos, head, member)			 \
	for (pos = (head)->first;					 \
	     pos &&							 \
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = pos->next)

/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing after existing point
 * @tpos:	the type * to use as a loop counter.
 * @pos:	the &struct hlist_node to use as a loop counter.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(tpos, pos, member)		 \
	for (pos = (pos)->next;						 \
	     pos &&							 \
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = pos->next)

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from existing point
 * @tpos:	the type * to use as a loop counter.
 * @pos:	the &struct hlist_node to use as a loop counter.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(tpos, pos, member)			 \
	for (; pos &&							 \
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = pos->next)

/**
 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @tpos:	the type * to use as a loop counter.
 * @pos:	the &struct hlist_node to use as a loop counter.
 * @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(tpos, pos, n, head, member) 		 \
	for (pos = (head)->first;					 \
	     pos && ({ n = pos->next; 1; }) && 				 \
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = n)

#define hlist_insert_sorted(tpos, ntpos, pos, head, smember, hmember, res)	\
	res = 0;								\
	tpos = NULL;								\
	hlist_for_each_entry(tpos, pos, (head), hmember)			\
		if (ntpos->smember <= tpos->smember)				\
			break;							\
	if (tpos) {								\
		if (ntpos->smember < tpos->smember)				\
			hlist_add_before(&ntpos->hmember, &tpos->hmember);	\
		else if (ntpos->smember > tpos->smember)			\
			hlist_add_after(&tpos->hmember, &ntpos->hmember);	\
		else								\
			res = 1;						\
	} else									\
		hlist_add_head(&ntpos->hmember, (head));

#endif /* ! _LIST_HEAD_H */
