1996-07-09 08:22:35 +02:00
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/*-------------------------------------------------------------------------
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*
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* dllist.c--
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* this is a simple doubly linked list implementation
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* replaces the old simplelists stuff
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* the elements of the lists are void*
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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1997-08-19 23:40:56 +02:00
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* $Header: /cvsroot/pgsql/src/backend/lib/dllist.c,v 1.5 1997/08/19 21:31:16 momjian Exp $
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1996-07-09 08:22:35 +02:00
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*
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*-------------------------------------------------------------------------
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*/
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1996-11-06 09:27:16 +01:00
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#include <postgres.h>
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1996-10-31 11:26:33 +01:00
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1996-11-06 09:27:16 +01:00
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#include <lib/dllist.h>
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1996-07-09 08:22:35 +02:00
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Dllist*
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1996-11-10 04:06:38 +01:00
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DLNewList(void)
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1996-07-09 08:22:35 +02:00
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{
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Dllist* l;
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l = malloc(sizeof(Dllist));
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l->dll_head = 0;
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l->dll_tail = 0;
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return l;
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}
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/* free up a list and all the nodes in it*/
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void
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DLFreeList(Dllist* l)
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{
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Dlelem* curr;
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while ( (curr = DLRemHead(l)) != 0)
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free(curr);
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free(l);
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}
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Dlelem*
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DLNewElem(void* val)
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{
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Dlelem* e;
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e = malloc(sizeof(Dlelem));
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e->dle_next = 0;
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e->dle_prev = 0;
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e->dle_val = val;
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e->dle_list = 0;
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return e;
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}
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void
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DLFreeElem(Dlelem* e)
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{
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free(e);
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}
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Dlelem*
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DLGetHead(Dllist* l)
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{
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return (l ? l->dll_head : 0);
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}
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/* get the value stored in the first element */
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1997-08-19 23:40:56 +02:00
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#ifdef NOT_USED
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1996-07-09 08:22:35 +02:00
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void*
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DLGetHeadVal(Dllist* l)
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{
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Dlelem* e = DLGetHead(l);
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return (e ? e->dle_val : 0);
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}
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1997-08-19 23:40:56 +02:00
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#endif
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1996-07-09 08:22:35 +02:00
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Dlelem*
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DLGetTail(Dllist* l)
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{
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return (l ? l->dll_tail : 0);
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}
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/* get the value stored in the first element */
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1997-08-19 23:40:56 +02:00
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#ifdef NOT_USED
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1996-07-09 08:22:35 +02:00
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void*
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DLGetTailVal(Dllist* l)
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{
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Dlelem* e = DLGetTail(l);
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return (e ? e->dle_val : 0);
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}
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1997-08-19 23:40:56 +02:00
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#endif
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1996-07-09 08:22:35 +02:00
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Dlelem*
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DLGetPred(Dlelem* e) /* get predecessor */
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{
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return (e ? e->dle_prev : 0);
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}
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Dlelem*
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DLGetSucc(Dlelem* e) /* get successor */
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{
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return (e ? e->dle_next : 0);
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}
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void
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DLRemove(Dlelem* e)
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{
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Dllist* l;
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if (e->dle_prev)
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e->dle_prev->dle_next = e->dle_next;
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if (e->dle_next)
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e->dle_next->dle_prev = e->dle_prev;
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/* check to see if we're removing the head or tail */
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l = e->dle_list;
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if (e == l->dll_head)
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DLRemHead(l);
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if (e == l->dll_tail)
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DLRemTail(l);
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}
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void
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DLAddHead(Dllist* l, Dlelem* e)
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{
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e->dle_list = l;
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if (l->dll_head) {
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l->dll_head->dle_prev = e;
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e->dle_next = l->dll_head;
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}
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e->dle_prev = 0;
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l->dll_head = e;
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if (l->dll_tail == 0) /* if this is first element added */
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l->dll_tail = l->dll_head;
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}
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void
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DLAddTail(Dllist* l, Dlelem* e)
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{
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e->dle_list = l;
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if (l->dll_tail) {
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l->dll_tail->dle_next = e;
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e->dle_prev = l->dll_tail;
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}
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e->dle_next = 0;
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l->dll_tail = e;
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if (l->dll_head == 0) /* if this is first element added */
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l->dll_head = l->dll_tail;
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}
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Dlelem*
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DLRemHead(Dllist* l)
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{
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/* remove and return the head */
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Dlelem* result;
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if (l->dll_head == 0)
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return 0;
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result = l->dll_head;
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if (l->dll_head->dle_next) {
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l->dll_head->dle_next->dle_prev = 0;
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}
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l->dll_head = l->dll_head->dle_next;
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result->dle_next = 0;
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result->dle_list = 0;
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if (result == l->dll_tail) /* if the head is also the tail */
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l->dll_tail = 0;
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return result;
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}
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Dlelem*
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DLRemTail(Dllist* l)
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{
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/* remove and return the tail */
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Dlelem* result;
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if (l->dll_tail == 0 )
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return 0;
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result = l->dll_tail;
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if (l->dll_tail->dle_prev) {
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l->dll_tail->dle_prev->dle_next = 0;
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}
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l->dll_tail = l->dll_tail->dle_prev;
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result->dle_prev = 0;
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result->dle_list = 0;
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if (result == l->dll_head) /* if the tail is also the head */
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l->dll_head = 0;
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return result;
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}
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