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Add detached node functions to ilist

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These allow to test whether an element is in a list by checking whether
prev/next are NULL. Needed to replace SHMQueueIsDetached() when converting
from SHM_QUEUE to ilist.h style lists.

Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/20221120055930.t6kl3tyivzhlrzu2@awork3.anarazel.de
Discussion: https://postgr.es/m/20200211042229.msv23badgqljrdg2@alap3.anarazel.de
This commit is contained in:
Andres Freund 2023-01-18 11:41:14 -08:00
parent 2b16208753
commit 51384cc40c
1 changed files with 63 additions and 0 deletions
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63
src/include/lib/ilist.h
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@ -316,6 +316,17 @@ dlist_init(dlist_head *head)
head->head.next = head->head.prev = &head->head; head->head.next = head->head.prev = &head->head;
} }
/*
* Initialize a doubly linked list element.
*
* This is only needed when dlist_node_is_detached() may be needed.
*/
static inline void
dlist_node_init(dlist_node *node)
{
node->next = node->prev = NULL;
}
/* /*
* Is the list empty? * Is the list empty?
* *
@ -397,6 +408,19 @@ dlist_delete(dlist_node *node)
node->next->prev = node->prev; node->next->prev = node->prev;
} }
/*
* Like dlist_delete(), but also sets next/prev to NULL to signal not being in
* a list.
*/
static inline void
dlist_delete_thoroughly(dlist_node *node)
{
node->prev->next = node->next;
node->next->prev = node->prev;
node->next = NULL;
node->prev = NULL;
}
/* /*
* Same as dlist_delete, but performs checks in ILIST_DEBUG builds to ensure * Same as dlist_delete, but performs checks in ILIST_DEBUG builds to ensure
* that 'node' belongs to 'head'. * that 'node' belongs to 'head'.
@ -408,6 +432,17 @@ dlist_delete_from(dlist_head *head, dlist_node *node)
dlist_delete(node); dlist_delete(node);
} }
/*
* Like dlist_delete_from, but also sets next/prev to NULL to signal not
* being in a list.
*/
static inline void
dlist_delete_from_thoroughly(dlist_head *head, dlist_node *node)
{
dlist_member_check(head, node);
dlist_delete_thoroughly(node);
}
/* /*
* Remove and return the first node from a list (there must be one). * Remove and return the first node from a list (there must be one).
*/ */
@ -480,6 +515,21 @@ dlist_has_prev(const dlist_head *head, const dlist_node *node)
return node->prev != &head->head; return node->prev != &head->head;
} }
/*
* Check if node is detached. A node is only detached if it either has been
* initialized with dlist_init_node(), or deleted with
* dlist_delete_thoroughly() / dlist_delete_from_thoroughly() /
* dclist_delete_from_thoroughly().
*/
static inline bool
dlist_node_is_detached(const dlist_node *node)
{
Assert((node->next == NULL && node->prev == NULL) ||
(node->next != NULL && node->prev != NULL));
return node->next == NULL;
}
/* /*
* Return the next node in the list (there must be one). * Return the next node in the list (there must be one).
*/ */
@ -718,6 +768,19 @@ dclist_delete_from(dclist_head *head, dlist_node *node)
head->count--; head->count--;
} }
/*
* Like dclist_delete_from(), but also sets next/prev to NULL to signal not
* being in a list.
*/
static inline void
dclist_delete_from_thoroughly(dclist_head *head, dlist_node *node)
{
Assert(head->count > 0);
dlist_delete_from_thoroughly(&head->dlist, node);
head->count--;
}
/* /*
* dclist_pop_head_node * dclist_pop_head_node
* Remove and return the first node from a list (there must be one). * Remove and return the first node from a list (there must be one).