From a933ee38bbb8dffbc48a3363a94ff6f2a9f7964d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 16 Nov 2000 22:30:52 +0000
Subject: Change SearchSysCache coding conventions so that a reference count is
 maintained for each cache entry.  A cache entry will not be freed until the
 matching ReleaseSysCache call has been executed.  This eliminates worries
 about cache entries getting dropped while still in use.  See my posting to
 pg-hackers of even date for more info.

---
 src/backend/lib/dllist.c | 98 ++++++++++++++++--------------------------------
 1 file changed, 32 insertions(+), 66 deletions(-)

(limited to 'src/backend/lib/dllist.c')

diff --git a/src/backend/lib/dllist.c b/src/backend/lib/dllist.c
index f38251934c4..175c02c3e7c 100644
--- a/src/backend/lib/dllist.c
+++ b/src/backend/lib/dllist.c
@@ -2,7 +2,6 @@
  *
  * dllist.c
  *	  this is a simple doubly linked list implementation
- *	  replaces the old simplelists stuff
  *	  the elements of the lists are void*
  *
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
@@ -10,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/lib/dllist.c,v 1.18 2000/06/08 22:37:05 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/lib/dllist.c,v 1.19 2000/11/16 22:30:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,25 +32,33 @@ DLNewList(void)
 {
 	Dllist	   *l;
 
-	l = malloc(sizeof(Dllist));
+	l = (Dllist *) malloc(sizeof(Dllist));
 	l->dll_head = 0;
 	l->dll_tail = 0;
 
 	return l;
 }
 
-/* free up a list and all the nodes in it --- but *not* whatever the nodes
+void
+DLInitList(Dllist *list)
+{
+	list->dll_head = 0;
+	list->dll_tail = 0;
+}
+
+/*
+ * free up a list and all the nodes in it --- but *not* whatever the nodes
  * might point to!
  */
 void
-DLFreeList(Dllist *l)
+DLFreeList(Dllist *list)
 {
 	Dlelem	   *curr;
 
-	while ((curr = DLRemHead(l)) != 0)
+	while ((curr = DLRemHead(list)) != 0)
 		free(curr);
 
-	free(l);
+	free(list);
 }
 
 Dlelem *
@@ -59,7 +66,7 @@ DLNewElem(void *val)
 {
 	Dlelem	   *e;
 
-	e = malloc(sizeof(Dlelem));
+	e = (Dlelem *) malloc(sizeof(Dlelem));
 	e->dle_next = 0;
 	e->dle_prev = 0;
 	e->dle_val = val;
@@ -68,59 +75,18 @@ DLNewElem(void *val)
 }
 
 void
-DLFreeElem(Dlelem *e)
-{
-	free(e);
-}
-
-Dlelem *
-DLGetHead(Dllist *l)
-{
-	return l ? l->dll_head : 0;
-}
-
-/* get the value stored in the first element */
-#ifdef NOT_USED
-void *
-DLGetHeadVal(Dllist *l)
+DLInitElem(Dlelem *e, void *val)
 {
-	Dlelem	   *e = DLGetHead(l);
-
-	return e ? e->dle_val : 0;
-}
-
-#endif
-
-Dlelem *
-DLGetTail(Dllist *l)
-{
-	return l ? l->dll_tail : 0;
-}
-
-/* get the value stored in the last element */
-#ifdef NOT_USED
-void *
-DLGetTailVal(Dllist *l)
-{
-	Dlelem	   *e = DLGetTail(l);
-
-	return e ? e->dle_val : 0;
-}
-
-#endif
-
-#ifdef NOT_USED
-Dlelem *
-DLGetPred(Dlelem *e)			/* get predecessor */
-{
-	return e ? e->dle_prev : 0;
+	e->dle_next = 0;
+	e->dle_prev = 0;
+	e->dle_val = val;
+	e->dle_list = 0;
 }
-#endif
 
-Dlelem *
-DLGetSucc(Dlelem *e)			/* get successor */
+void
+DLFreeElem(Dlelem *e)
 {
-	return e ? e->dle_next : 0;
+	free(e);
 }
 
 void
@@ -131,16 +97,16 @@ DLRemove(Dlelem *e)
 	if (e->dle_prev)
 		e->dle_prev->dle_next = e->dle_next;
 	else
-/* must be the head element */
 	{
+		/* must be the head element */
 		Assert(e == l->dll_head);
 		l->dll_head = e->dle_next;
 	}
 	if (e->dle_next)
 		e->dle_next->dle_prev = e->dle_prev;
 	else
-/* must be the tail element */
 	{
+		/* must be the tail element */
 		Assert(e == l->dll_tail);
 		l->dll_tail = e->dle_prev;
 	}
@@ -194,12 +160,12 @@ DLRemHead(Dllist *l)
 
 	l->dll_head = result->dle_next;
 
-	result->dle_next = 0;
-	result->dle_list = 0;
-
 	if (result == l->dll_tail)	/* if the head is also the tail */
 		l->dll_tail = 0;
 
+	result->dle_next = 0;
+	result->dle_list = 0;
+
 	return result;
 }
 
@@ -217,12 +183,12 @@ DLRemTail(Dllist *l)
 
 	l->dll_tail = result->dle_prev;
 
-	result->dle_prev = 0;
-	result->dle_list = 0;
-
 	if (result == l->dll_head)	/* if the tail is also the head */
 		l->dll_head = 0;
 
+	result->dle_prev = 0;
+	result->dle_list = 0;
+
 	return result;
 }
 
@@ -241,8 +207,8 @@ DLMoveToFront(Dlelem *e)
 	if (e->dle_next)
 		e->dle_next->dle_prev = e->dle_prev;
 	else
-/* must be the tail element */
 	{
+		/* must be the tail element */
 		Assert(e == l->dll_tail);
 		l->dll_tail = e->dle_prev;
 	}
-- 
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