list.h

/*
 * Taken from Linux kernel.
 * Some parts:
 * Copyright Neil Brown ©2015-2023 <neil@brown.name>
 * May be distributed under terms of GPLv2 - see file:COPYING
 *
 */
#ifndef __LIST_H__
#define __LIST_H__

#include "safe.h"

#define ASSERT(x) do { if (!(x)) abort();} while (0)

/*Taken from various places in linux kernel */

#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif
/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:	the pointer to the member.
 * @type:	the type of the container struct this is embedded in.
 * @member:	the name of the member within the struct.
 *
 */
#define container_of(ptr, type, member) ({			\
	const typeof( ((type *)0)->member ) *__mptr safe = (ptr);	\
	(type * safe)( (char *)__mptr - offsetof(type,member) );})
#define container_of_array(ptr, type, member, index) ({			\
	const typeof( ((type *)0)->member[index] ) *__mptr safe = (ptr);	\
	(type * safe)( (char *)__mptr - offsetof(type,member[index]) );})

/*
 * 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.
 */

struct list_head {
	struct list_head *next safe, *prev safe;
};

#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 safe,
			      struct list_head *prev safe,
			      struct list_head *next safe)
{
	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
 * list_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_add(struct list_head *new safe, struct list_head *head safe)
{
	__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 safe, struct list_head *head safe)
{
	__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 safe, struct list_head *next safe)
{
	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_del(struct list_head *entry safe)
{
	__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 safe)
{
	__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 safe, struct list_head *head safe)
{
	__list_del(list->prev, list->next);
	list_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 safe,
				  struct list_head *head safe)
{
	__list_del(list->prev, list->next);
	list_add_tail(list, head);
}

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

/**
 * 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_head 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_head 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_first_entry_or_null - 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_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) \
	(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)

/**
 * list_next_entry - get the next element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
	list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
	list_entry((pos)->member.prev, typeof(*(pos)), member)

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

/**
 * list_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 list_head within the struct.
 */
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_first_entry(head, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_reverse - iterate backwards 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 list_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)			\
	for (pos = list_last_entry(head, typeof(*pos), member);		\
	     &pos->member != (head);					\
	     pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_safe	-	iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @n:		&struct list_node temp pointer.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_first_entry(head, typeof(*pos), member);	\
	     &pos->member != (head) && ({n = pos->member.next; 1;});	\
	     pos = list_entry(n, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration 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 list_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member)			\
	for (pos = list_next_entry(pos, member);			\
	     &pos->member != (head);					\
	     pos = list_next_entry(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_head within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member)			\
	for (; pos && &pos->member != (head);				\
	     pos = list_next_entry(pos, member))

/* 'first' has lsb set so the start of the list can be recognised
 * with passing the head around.
 */
struct hlist_head {
	struct hlist_node *vfirst;
};
#define	HLIST_PTR(_h) ((struct hlist_node *)(((unsigned long)_h) & ~1UL))
#define	HLIST_HEAD_PTR(_h) ((void*)(((unsigned long)_h) | 1UL))
#define	HLIST_IS_HEAD(_h) (((unsigned long)(*(_h))) & 1UL)

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

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

static inline int hlist_unhashed(const struct hlist_node *h safe)
{
	return h->pprev == &h->next;
}

static inline int hlist_empty(const struct hlist_head *h safe)
{
#ifndef __CHECKER__
	return !HLIST_PTR(h->vfirst);
#else
	return (h->vfirst == NULL || h->vfirst == (struct hlist_node*)1);
#endif
}

static inline void __hlist_del(struct hlist_node *n safe)
{
	struct hlist_node *next = n->next;
	struct hlist_node **pprev = n->pprev;
	if (HLIST_IS_HEAD(pprev))
		*pprev= HLIST_HEAD_PTR(next);
	else
		*pprev = next;
	if (next)
		next->pprev = pprev;
}

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

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

static inline void hlist_add_head(struct hlist_node *n safe, struct hlist_head *h safe)
{
	struct hlist_node *first = HLIST_PTR(h->vfirst);
	n->next = first;
	if (first)
		first->pprev = &n->next;
	h->vfirst = HLIST_HEAD_PTR(n);
	n->pprev = &h->vfirst;
}

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

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

	if(next->next)
		next->next->pprev  = &next->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 safe,
				   struct hlist_head *new safe)
{
	new->vfirst = old->vfirst;
	if (!hlist_empty(new))
		HLIST_PTR(new->vfirst)->pprev = &new->vfirst;
	INIT_HLIST_HEAD(old);
}

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

#define hlist_next_entry(ptr, member) \
	hlist_entry((ptr)->member.next, typeof(*(ptr)), member)
#define hlist_first_entry(head, type, member)			\
	hlist_entry((head)->vfirst, type, member)
#define hlist_prev(ptr) container_of((ptr)->pprev, struct hlist_node, next)
#define hlist_prev_entry(ptr, member) \
	({struct hlist_node *__hln = hlist_prev(&(ptr)->member); \
		hlist_entry(__hln, typeof(*(ptr)), member); })

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

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

/**
 * 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_empty(head) ? NULL : hlist_first_entry(head, typeof(*pos), member); \
	     pos ;							\
	     pos = pos->member.next ? hlist_next_entry(pos, member) : NULL)
/**
 * 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 = (pos)->member.next ? hlist_next_entry(pos, member) : NULL;	\
	     pos ;							\
	     pos = pos->member.next ? hlist_next_entry(pos, member) : NULL)

/**
 * hlist_for_each_entry_continue_reverse - iterate backwards 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_reverse(pos, member)		 \
	for (pos = HLIST_IS_HEAD(pos->member.pprev) ? NULL : hlist_prev_entry(pos, member); \
	     pos ;						\
	     pos = HLIST_IS_HEAD(pos->member.pprev) ? NULL : hlist_prev_entry(pos, member ))

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
 * @tpos:	the type * to use as a loop cursor.
 * @pos:	the &struct hlist_node to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#if 0
#define hlist_for_each_entry_from(tpos, pos, member)			\
	for (; pos &&							\
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = pos->next)
#endif
/**
 * 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 cursor.
 * @pos:	the &struct hlist_node 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.
 */
#if 0
#define hlist_for_each_entry_safe(tpos, pos, n, head, member)		\
	for (pos = HLIST_PTR((head)->first);				\
	     pos && ({ n = pos->next; 1; }) &&				\
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = n)
#endif

/*
 * tlists are lists with types.
 * The lsbs of each of the two pointers provide 2 bits of type
 * information.  This is useful when different fields in different
 * structures can all be on the same list
 */
struct tlist_head {
	struct tlist_head *next safe, *prev safe;
};

#define TLIST_PTR(p) ((struct tlist_head * safe)(((unsigned long)(p)) & ~1UL))
#define __TLIST_TYPE(p,n) ((((unsigned long)(p)) & 1)<<1 | (((unsigned long)(n)) & 1))
#define TLIST_TYPE(e) __TLIST_TYPE((e)->prev, (e)->next)
#define TLIST_PREV(p,t) ((struct tlist_head * safe)((((t)>>1)&1)|(unsigned long)(p)))
#define TLIST_NEXT(n,t) ((struct tlist_head * safe)(((t)&1)|(unsigned long)(n)))

#define TLIST_HEAD_INIT(name, type) { TLIST_NEXT(&(name),(type)),	\
				      TLIST_PREV(&(name),(type)) }
#define INIT_TLIST_HEAD(ptr, type) do {		\
	(ptr)->next = TLIST_NEXT((ptr),(type));	\
	(ptr)->prev = TLIST_PREV((ptr),(type));	\
} while (0)

/**
 * tlist_empty - tests whether a tlist is empty
 * @head: the list to test.
 */
static inline int tlist_empty(struct tlist_head *head safe)
{
	return TLIST_PTR(head->next) == head;
}
/*
 * 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 __tlist_add(struct tlist_head *new safe, int type,
			       struct tlist_head *prev safe,
			       struct tlist_head *next safe)
{
	next->prev = TLIST_PREV(new, __TLIST_TYPE(next->prev, NULL));
	new->next = TLIST_NEXT(next, type);
	new->prev = TLIST_PREV(prev, type);
	prev->next = TLIST_NEXT(new, __TLIST_TYPE(NULL, prev->next));
}

/**
 * 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_head within the struct.
 */
#define tlist_entry(ptr, type, member) \
	container_of(TLIST_PTR(ptr), type, member)

/**
 * tlist_add - add a new entry
 * @new: new entry to be added
 * @type: type of location
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void tlist_add(struct tlist_head *new safe, int type, struct tlist_head *head safe)
{
	__tlist_add(new, type, head, TLIST_PTR(head->next));
}

/**
 * tlist_add_tail - add a new entry
 * @new: new entry to be added
 * @type: type of location
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void tlist_add_tail(struct tlist_head *new safe, int type,
				  struct tlist_head *head safe)
{
	__tlist_add(new, type, TLIST_PTR(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 __tlist_del(struct tlist_head *prev safe, struct tlist_head *next safe)
{
	int nt = TLIST_TYPE(next);
	int pt = TLIST_TYPE(prev);
	next->prev = TLIST_PREV(TLIST_PTR(prev), nt);
	prev->next = TLIST_NEXT(TLIST_PTR(next), pt);
}

/**
 * tlist_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 tlist_del(struct tlist_head *entry safe)
{
	__tlist_del(TLIST_PTR(entry->prev), TLIST_PTR(entry->next));
	entry->next = LIST_POISON1;
	entry->prev = LIST_POISON2;
}

/**
 * tlist_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void tlist_del_init(struct tlist_head *entry safe)
{
	int type = TLIST_TYPE(entry);
	__tlist_del(TLIST_PTR(entry->prev), TLIST_PTR(entry->next));
	INIT_TLIST_HEAD(entry, type);
}

/**
 * tlist_next_entry - get the next element in list
 * @pos:	the type * to cursor
 * @member:	the name of the tlist_head within the struct.
 */
#define tlist_next_entry(pos, member) \
	tlist_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * tlist_prev_entry - get the prev element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define tlist_prev_entry(pos, member) \
	tlist_entry((pos)->member.prev, typeof(*(pos)), member)

/**
 * tlist_for_each	-	iterate over a tlist
 * @pos:	the &struct tlist_head to use as a loop cursor.
 * @head:	the head for your tlist.
 */
#define tlist_for_each(pos, head) \
	for (pos = TLIST_PTR((head)->next); pos != (head); pos = TLIST_PTR(pos->next))

/**
 * tlist_for_each_continue - continue iteration over tlist
 * @pos:	the struct tlist_head * to use as a loop cursor.
 * @head_typef:	the the type of the head for your list.
 *
 * Continue to iterate over tlist, continuing after
 * the current position.
 */
#define tlist_for_each_continue(pos, head_type)			\
	for (pos = TLIST_PTR(pos->next);			\
	     TLIST_TYPE(pos) != (head_type);			\
	     pos = TLIST_PTR(pos->next))

/**
 * list_for_each_continue_reverse - iterate backwards from the given point
 * @pos:	the struct tlist_head * to use as a loop cursor.
 * @head:	the type of the head for your list.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define tlist_for_each_continue_reverse(pos, head_type)		\
	for (pos = TLIST_PTR(pos->prev);			\
	     TLIST_TYPE(pos) != (head_type);			\
	     pos = TLIST_PTR(pos->prev))

/**
 * tlist_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 tlist_head within the struct.
 *
 * Iterate over list of given type.
 */
#define tlist_for_each_entry(pos, head, member)		\
	for (pos = list_entry((head)->next, typeof(*(pos)), member);	\
	     &pos->member != (head);					\
	     pos = tlist_next_entry(pos, member))

/**
 * tlist_for_each_entry_continue - continue iteration over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head_type:	type of pointer in the head for your list.
 * @member:	the name of the tlist_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define tlist_for_each_entry_continue(pos, head_type, member)		\
	for (pos = tlist_next_entry(pos, member);			\
	     TLIST_TYPE(&pos->member) != (head_type);			\
	     pos = tlist_next_entry(pos, member))

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

/* Natural merge sort of the linked list */
static inline void sort_list(struct list_head *lst safe,
			     char * (*key)(struct list_head *le, const void *data),
			     const void *data)
{
	struct list_head *de[2];
	struct list_head *l;

	if (list_empty(lst))
		return;
	/* Convert to NULL terminated singly-linked list for sorting */
	lst->prev->next = safe_cast NULL;

	de[0] = lst->next;
	de[1] = NULL;

	do {
		struct list_head ** safe dep[2];
		struct list_head *d[2];
		int curr = 0;
		char *prev = "";
		int next = 0;

		dep[0] = &de[0];
		dep[1] = &de[1];
		d[0] = de[0];
		d[1] = de[1];

		/* d[0] and d[1] are two lists to be merged and split.
		 * The results will be put in de[0] and de[1].
		 * dep[0] and dep[1] are end pointers to de[0] and de[1] so far.
		 *
		 * Take least of d[0] and d[1].
		 * If it is larger than prev, add to
		 * dep[curr], else swap curr then add
		 */
		while (d[0] || d[1]) {
			char *kn = key(d[next], data);
			char *kp = key(d[1-next], data);
			if (kn == NULL ||
			    (kp != NULL &&
			     !((strcmp(prev, kp) <= 0)
			       ^(strcmp(kp, kn) <= 0)
			       ^(strcmp(kn, prev) <= 0)))
			) {
				char *t = kn;
				kn = kp;
				kp = t;
				next = 1 - next;
			}

			if (!d[next] || !kn)
				break;
			if (strcmp(kn, prev) < 0)
				curr = 1 - curr;
			prev = kn;
			*dep[curr] = d[next];
			dep[curr] = &d[next]->next;
			d[next] = d[next]->next;
		}
		*dep[0] = NULL;
		*dep[1] = NULL;
	} while (de[0] && de[1]);

	/* Now re-assemble the doublely-linked list */
	if (de[0])
		lst->next = de[0];
	else
		lst->next = safe_cast de[1];
	l = lst;

	while ((void*)l->next) {
		l->next->prev = l;
		l = l->next;
	}
	l->next = lst;
	lst->prev = l;
}
#endif /* __LIST_H__ */