ilist.c

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/*-------------------------------------------------------------------------
 *
 * ilist.c
 *    support for integrated/inline doubly- and singly- linked lists
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/lib/ilist.c
 *
 * NOTES
 *    This file only contains functions that are too big to be considered
 *    for inlining.  See ilist.h for most of the goodies.
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "lib/ilist.h"
 
/*
 * Delete 'node' from list.
 *
 * It is not allowed to delete a 'node' which is not in the list 'head'
 *
 * Caution: this is O(n); consider using slist_delete_current() instead.
 */
void
slist_delete(slist_head *head, const slist_node *node)
{
    slist_node *last = &head->head;
    slist_node *cur;
    bool        found PG_USED_FOR_ASSERTS_ONLY = false;
 
    while ((cur = last->next) != NULL)
    {
        if (cur == node)
        {
            last->next = cur->next;
#ifdef USE_ASSERT_CHECKING
            found = true;
#endif
            break;
        }
        last = cur;
    }
    Assert(found);
 
    slist_check(head);
}
 
#ifdef ILIST_DEBUG
/*
 * dlist_member_check
 *      Validate that 'node' is a member of 'head'
 */
void
dlist_member_check(const dlist_head *head, const dlist_node *node)
{
    const dlist_node *cur;
 
    /* iteration open-coded to due to the use of const */
    for (cur = head->head.next; cur != &head->head; cur = cur->next)
    {
        if (cur == node)
            return;
    }
    elog(ERROR, "double linked list member check failure");
}
 
/*
 * Verify integrity of a doubly linked list
 */
void
dlist_check(const dlist_head *head)
{
    dlist_node *cur;
 
    if (head == NULL)
        elog(ERROR, "doubly linked list head address is NULL");
 
    if (head->head.next == NULL && head->head.prev == NULL)
        return;                 /* OK, initialized as zeroes */
 
    /* iterate in forward direction */
    for (cur = head->head.next; cur != &head->head; cur = cur->next)
    {
        if (cur == NULL ||
            cur->next == NULL ||
            cur->prev == NULL ||
            cur->prev->next != cur ||
            cur->next->prev != cur)
            elog(ERROR, "doubly linked list is corrupted");
    }
 
    /* iterate in backward direction */
    for (cur = head->head.prev; cur != &head->head; cur = cur->prev)
    {
        if (cur == NULL ||
            cur->next == NULL ||
            cur->prev == NULL ||
            cur->prev->next != cur ||
            cur->next->prev != cur)
            elog(ERROR, "doubly linked list is corrupted");
    }
}
 
/*
 * Verify integrity of a singly linked list
 */
void
slist_check(const slist_head *head)
{
    slist_node *cur;
 
    if (head == NULL)
        elog(ERROR, "singly linked list head address is NULL");
 
    /*
     * there isn't much we can test in a singly linked list except that it
     * actually ends sometime, i.e. hasn't introduced a cycle or similar
     */
    for (cur = head->head.next; cur != NULL; cur = cur->next)
        ;
}
 
#endif                          /* ILIST_DEBUG */