Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * ilist.c
       4             :  *    support for integrated/inline doubly- and singly- linked lists
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/lib/ilist.c
      12             :  *
      13             :  * NOTES
      14             :  *    This file only contains functions that are too big to be considered
      15             :  *    for inlining.  See ilist.h for most of the goodies.
      16             :  *
      17             :  *-------------------------------------------------------------------------
      18             :  */
      19             : #include "postgres.h"
      20             : 
      21             : #include "lib/ilist.h"
      22             : 
      23             : /*
      24             :  * Delete 'node' from list.
      25             :  *
      26             :  * It is not allowed to delete a 'node' which is not in the list 'head'
      27             :  *
      28             :  * Caution: this is O(n); consider using slist_delete_current() instead.
      29             :  */
      30             : void
      31        8134 : slist_delete(slist_head *head, const slist_node *node)
      32             : {
      33        8134 :     slist_node *last = &head->head;
      34             :     slist_node *cur;
      35        8134 :     bool        found PG_USED_FOR_ASSERTS_ONLY = false;
      36             : 
      37       27120 :     while ((cur = last->next) != NULL)
      38             :     {
      39       27120 :         if (cur == node)
      40             :         {
      41        8134 :             last->next = cur->next;
      42             : #ifdef USE_ASSERT_CHECKING
      43             :             found = true;
      44             : #endif
      45        8134 :             break;
      46             :         }
      47       18986 :         last = cur;
      48             :     }
      49             :     Assert(found);
      50             : 
      51             :     slist_check(head);
      52        8134 : }
      53             : 
      54             : #ifdef ILIST_DEBUG
      55             : /*
      56             :  * dlist_member_check
      57             :  *      Validate that 'node' is a member of 'head'
      58             :  */
      59             : void
      60             : dlist_member_check(const dlist_head *head, const dlist_node *node)
      61             : {
      62             :     const dlist_node *cur;
      63             : 
      64             :     /* iteration open-coded to due to the use of const */
      65             :     for (cur = head->head.next; cur != &head->head; cur = cur->next)
      66             :     {
      67             :         if (cur == node)
      68             :             return;
      69             :     }
      70             :     elog(ERROR, "double linked list member check failure");
      71             : }
      72             : 
      73             : /*
      74             :  * Verify integrity of a doubly linked list
      75             :  */
      76             : void
      77             : dlist_check(const dlist_head *head)
      78             : {
      79             :     dlist_node *cur;
      80             : 
      81             :     if (head == NULL)
      82             :         elog(ERROR, "doubly linked list head address is NULL");
      83             : 
      84             :     if (head->head.next == NULL && head->head.prev == NULL)
      85             :         return;                 /* OK, initialized as zeroes */
      86             : 
      87             :     /* iterate in forward direction */
      88             :     for (cur = head->head.next; cur != &head->head; cur = cur->next)
      89             :     {
      90             :         if (cur == NULL ||
      91             :             cur->next == NULL ||
      92             :             cur->prev == NULL ||
      93             :             cur->prev->next != cur ||
      94             :             cur->next->prev != cur)
      95             :             elog(ERROR, "doubly linked list is corrupted");
      96             :     }
      97             : 
      98             :     /* iterate in backward direction */
      99             :     for (cur = head->head.prev; cur != &head->head; cur = cur->prev)
     100             :     {
     101             :         if (cur == NULL ||
     102             :             cur->next == NULL ||
     103             :             cur->prev == NULL ||
     104             :             cur->prev->next != cur ||
     105             :             cur->next->prev != cur)
     106             :             elog(ERROR, "doubly linked list is corrupted");
     107             :     }
     108             : }
     109             : 
     110             : /*
     111             :  * Verify integrity of a singly linked list
     112             :  */
     113             : void
     114             : slist_check(const slist_head *head)
     115             : {
     116             :     slist_node *cur;
     117             : 
     118             :     if (head == NULL)
     119             :         elog(ERROR, "singly linked list head address is NULL");
     120             : 
     121             :     /*
     122             :      * there isn't much we can test in a singly linked list except that it
     123             :      * actually ends sometime, i.e. hasn't introduced a cycle or similar
     124             :      */
     125             :     for (cur = head->head.next; cur != NULL; cur = cur->next)
     126             :         ;
     127             : }
     128             : 
     129             : #endif                          /* ILIST_DEBUG */