#ifndef __USER_LIST_H
#define __USER_LIST_H

#include <sys/types.h>
#include <unistd.h>

#define DEBUG_LIST

#ifdef DEBUG_LIST
#include <sys/types.h>
#include <signal.h>
#ifndef LIST_BUG
#define LIST_BUG() do { printf(">>>>> list bug <<<< at %d\n",__LINE__); kill(getpid(),SIGSEGV); } while(0)
#endif
#define __LIST_MAGIC 0xdeabbeef
#define __LIST_MAGIC_POISON 0xbeefdead
#define __LIST_MAGIC_COMMA , __LIST_MAGIC
#define __LIST_MAGIC_ASSIGN(x) (x).magic = __LIST_MAGIC;
#else
#define __LIST_MAGIC
#define __LIST_MAGIC_COMMA
#define __LIST_MAGIC_ASSIGN(x) 
#endif

#define __LIST_POISON ((struct list_head *)-1)

struct list_head {
	struct list_head *next;
	struct list_head *prev;
#ifdef DEBUG_LIST
	int magic;
#endif
};

#define LIST_HEAD_INIT(x) { &x, &x __LIST_MAGIC_COMMA}
#define LIST_HEAD_DECLARE(x) struct list_head x = LIST_HEAD_INIT(x)
#define INIT_LIST_HEAD(x) do { (x).next = &x; (x).prev = &x; __LIST_MAGIC_ASSIGN(x)} while (0)

#define list_for_each(p,list) for(p=(list)->next; p != list; p=p->next)
#define list_for_each_reverse(p,list) for(p=(list)->prev; p != list; p=p->prev)
#define list_for_each_safe(p,n,list) for(p=(list)->next,n=p->next; p != list; p=n,n=p->next)

#ifdef DEBUG_LIST
static inline void list_check(struct list_head *x)
{
	struct list_head *p;
	list_for_each_reverse(p,x) { if (p->magic != __LIST_MAGIC) LIST_BUG(); }
	list_for_each(p,x) { if (p->magic != __LIST_MAGIC) LIST_BUG(); }
}
#endif

static inline void list_add(struct list_head *x,struct list_head *list)
{
#ifdef DEBUG_LIST
	if (x->magic == __LIST_MAGIC_POISON && 
	    (x->next != __LIST_POISON || x->prev != __LIST_POISON))
		LIST_BUG();
#endif
	x->next = list->next;
	x->prev = list;
	list->next->prev = x;
	list->next = x;
#ifdef DEBUG_LIST
	x->magic = __LIST_MAGIC;
	list_check(list);
#endif
}

static inline void list_add_tail(struct list_head *x, struct list_head *list)
{
#ifdef DEBUG_LIST
	if (x->magic == __LIST_MAGIC && 
	    (x->next != __LIST_POISON || x->prev != __LIST_POISON))
		LIST_BUG();
#endif
	x->prev = list->prev;
	x->next = list;
	list->prev->next = x;
	list->prev = x;
#ifdef DEBUG_LIST
	x->magic = __LIST_MAGIC;
	list_check(list);
#endif
}

#define list_entry(p,type,list) ((type*)(((char*)(p))-((char*)&(((type*)NULL)->list))))

#define list_empty(list) ((list)->next == (list))
#define list_head(list) ((list)->next)

static inline void list_del(struct list_head *x)
{
#ifdef DEBUG_LIST
	if (x->magic != __LIST_MAGIC)
		LIST_BUG();
	list_check(x);
	x->magic = __LIST_MAGIC_POISON;
#endif
	x->prev->next = x->next;
	x->next->prev = x->prev;
	x->next = __LIST_POISON;
	x->prev = __LIST_POISON;
}

static inline struct list_head * pop_list_head(struct list_head *head)
{
	struct list_head *p;
	if (list_empty(head))
		return NULL;
	p = head->next;
	list_del(p);
#ifdef DEBUG_LIST
	list_check(head);
#endif
	return p;
}

#endif /* __USER_LIST_H */