From 118a9053f04d0e215bb3fe20562990cc73ae69a2 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Fri, 31 May 2024 11:55:50 -0400
Subject: list: New SLIST_SPLICE() macro

---
 src/list.h    | 24 ++++++++++++++++++++----
 src/prelude.h |  2 +-
 2 files changed, 21 insertions(+), 5 deletions(-)

(limited to 'src')

diff --git a/src/list.h b/src/list.h
index 61d0e5b..d95483f 100644
--- a/src/list.h
+++ b/src/list.h
@@ -323,6 +323,25 @@
 #define SLIST_PREPEND_(list, item, ...) \
 	LIST_VOID_(SLIST_INSERT_(list, &(list)->head, item, __VA_ARGS__))
 
+/**
+ * Splice a singly-linked list into another.
+ *
+ * @param dest
+ *         The destination list.
+ * @param cursor
+ *         A pointer to the item to splice after, e.g. &list->head or list->tail.
+ * @param src
+ *         The source list.
+ */
+#define SLIST_SPLICE(dest, cursor, src) \
+	LIST_VOID_(SLIST_SPLICE_((dest), (cursor), (src)))
+
+#define SLIST_SPLICE_(dest, cursor, src) \
+	*src->tail = *cursor, \
+	*cursor = src->head, \
+	dest->tail = *dest->tail ? src->tail : dest->tail, \
+	SLIST_INIT(src)
+
 /**
  * Add an entire singly-linked list to the tail of another.
  *
@@ -332,10 +351,7 @@
  *         The source list.
  */
 #define SLIST_EXTEND(dest, src) \
-	SLIST_EXTEND_((dest), (src))
-
-#define SLIST_EXTEND_(dest, src) \
-	(src->head ? (*dest->tail = src->head, dest->tail = src->tail, SLIST_INIT(src)) : (void)0)
+	SLIST_SPLICE(dest, (dest)->tail, src)
 
 /**
  * Remove an item from a singly-linked list.
diff --git a/src/prelude.h b/src/prelude.h
index c4edcb2..0944df1 100644
--- a/src/prelude.h
+++ b/src/prelude.h
@@ -137,7 +137,7 @@ extern const char bfs_version[];
 /**
  * Get the length of an array.
  */
-#define countof(array) (sizeof(array) / sizeof(0[array]))
+#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))
 
 /**
  * False sharing/destructive interference/largest cache line size.
-- 
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