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/*-------------------------------------------------------------------------
*
* dllist.h
* simple doubly linked list primitives
* the elements of the list are void* so the lists can contain anything
* Dlelem can only be in one list at a time
*
*
* Here's a small example of how to use Dllists:
*
* Dllist *lst;
* Dlelem *elt;
* void *in_stuff; -- stuff to stick in the list
* void *out_stuff
*
* lst = DLNewList(); -- make a new dllist
* DLAddHead(lst, DLNewElem(in_stuff)); -- add a new element to the list
* with in_stuff as the value
* ...
* elt = DLGetHead(lst); -- retrieve the head element
* out_stuff = (void*)DLE_VAL(elt); -- get the stuff out
* DLRemove(elt); -- removes the element from its list
* DLFreeElem(elt); -- free the element since we don't
* use it anymore
*
*
* It is also possible to use Dllist objects that are embedded in larger
* structures instead of being separately malloc'd. To do this, use
* DLInitElem() to initialize a Dllist field within a larger object.
* Don't forget to DLRemove() each field from its list (if any) before
* freeing the larger object!
*
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/lib/dllist.h,v 1.29 2009/01/01 17:23:59 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef DLLIST_H
#define DLLIST_H
struct Dllist;
struct Dlelem;
typedef struct Dlelem
{
struct Dlelem *dle_next; /* next element */
struct Dlelem *dle_prev; /* previous element */
void *dle_val; /* value of the element */
struct Dllist *dle_list; /* what list this element is in */
} Dlelem;
typedef struct Dllist
{
Dlelem *dll_head;
Dlelem *dll_tail;
} Dllist;
extern Dllist *DLNewList(void); /* allocate and initialize a list header */
extern void DLInitList(Dllist *list); /* init a header alloced by caller */
extern void DLFreeList(Dllist *list); /* free up a list and all the nodes in
* it */
extern Dlelem *DLNewElem(void *val);
extern void DLInitElem(Dlelem *e, void *val);
extern void DLFreeElem(Dlelem *e);
extern void DLRemove(Dlelem *e); /* removes node from list */
extern void DLAddHead(Dllist *list, Dlelem *node);
extern void DLAddTail(Dllist *list, Dlelem *node);
extern Dlelem *DLRemHead(Dllist *list); /* remove and return the head */
extern Dlelem *DLRemTail(Dllist *list);
extern void DLMoveToFront(Dlelem *e); /* move node to front of its list */
/* These are macros for speed */
#define DLGetHead(list) ((list)->dll_head)
#define DLGetTail(list) ((list)->dll_tail)
#define DLGetSucc(elem) ((elem)->dle_next)
#define DLGetPred(elem) ((elem)->dle_prev)
#define DLGetListHdr(elem) ((elem)->dle_list)
#define DLE_VAL(elem) ((elem)->dle_val)
#endif /* DLLIST_H */
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