From: David Lamparter <equinox@diac24.net>
Date: Sun, 12 May 2019 10:05:14 +0000 (+0200)
Subject: lib: add dedicated pop() to DECLARE_SKIPLIST
X-Git-Tag: base_7.2~319^2~10
X-Git-Url: https://git.puffer.fish/?a=commitdiff_plain;h=01734da376d0ed6ce355f27e4d19b5496f8ae94f;p=matthieu%2Ffrr.git

lib: add dedicated pop() to DECLARE_SKIPLIST

The skiplist code was previously falling back to the del() code path for
a pop() on a skiplist.  This is unneeded complexity, a pop() can be done
more efficiently.

Signed-off-by: David Lamparter <equinox@diac24.net>
---

diff --git a/lib/typesafe.c b/lib/typesafe.c
index bd269e9b54..4b07c482e8 100644
--- a/lib/typesafe.c
+++ b/lib/typesafe.c
@@ -375,3 +375,35 @@ void typesafe_skiplist_del(struct sskip_head *head, struct sskip_item *item,
 	}
 	memset(item, 0, sizeof(*item));
 }
+
+struct sskip_item *typesafe_skiplist_pop(struct sskip_head *head)
+{
+	size_t level = SKIPLIST_MAXDEPTH;
+	struct sskip_item *prev = &head->hitem, *next, *item;
+
+	item = sl_level_get(prev, 0);
+	if (!item)
+		return NULL;
+
+	do {
+		level--;
+
+		next = sl_level_get(prev, level);
+		if (next != item)
+			continue;
+
+		sl_level_set(prev, level, sl_level_get(item, level));
+	} while (level);
+
+	head->count--;
+
+	if ((uintptr_t)item->next[SKIPLIST_OVERFLOW] & 1) {
+		uintptr_t ptrval = (uintptr_t)item->next[SKIPLIST_OVERFLOW];
+		ptrval &= UINTPTR_MAX - 3;
+		struct sskip_overflow *oflow = (struct sskip_overflow *)ptrval;
+		XFREE(MTYPE_SKIPLIST_OFLOW, oflow);
+	}
+	memset(item, 0, sizeof(*item));
+
+	return item;
+}
diff --git a/lib/typesafe.h b/lib/typesafe.h
index 94002da599..c08a222091 100644
--- a/lib/typesafe.h
+++ b/lib/typesafe.h
@@ -538,11 +538,8 @@ macro_inline void prefix ## _del(struct prefix##_head *h, type *item)          \
 }                                                                              \
 macro_inline type *prefix ## _pop(struct prefix##_head *h)                     \
 {                                                                              \
-	struct sskip_item *sitem = h->sh.hitem.next[0];                        \
-	if (!sitem)                                                            \
-		return NULL;                                                   \
-	typesafe_skiplist_del(&h->sh, sitem, cmpfn_uq);                        \
-	return container_of(sitem, type, field.si);                            \
+	struct sskip_item *sitem = typesafe_skiplist_pop(&h->sh);              \
+	return container_of_null(sitem, type, field.si);                       \
 }                                                                              \
 macro_pure type *prefix ## _first(struct prefix##_head *h)                     \
 {                                                                              \
@@ -636,6 +633,7 @@ extern void typesafe_skiplist_del(struct sskip_head *head,
 		struct sskip_item *item, int (*cmpfn)(
 			const struct sskip_item *a,
 			const struct sskip_item *b));
+extern struct sskip_item *typesafe_skiplist_pop(struct sskip_head *head);
 
 /* this needs to stay at the end because both files include each other.
  * the resolved order is typesafe.h before typerb.h