htable: htable_pick helper to select a random entry.

[ccan] / ccan / htable / htable.h

diff --git a/ccan/htable/htable.h b/ccan/htable/htable.h
index 0ecae726c0bd560a5a1ba598e4d544d7480041a4..eac57e37a326612226f6cd7907c04bcbc589c360 100644 (file)
--- a/ccan/htable/htable.h
+++ b/ccan/htable/htable.h
@@ -267,6 +267,19 @@ void *htable_prev_(const struct htable *htable, struct htable_iter *i);
        htable_delval_(htable_debug(htable, HTABLE_LOC), i)
 void htable_delval_(struct htable *ht, struct htable_iter *i);
 
+/**
+ * htable_pick - set iterator to a random valid entry.
+ * @ht: the htable
+ * @seed: a random number to use.
+ * @i: the htable_iter which is output (or NULL).
+ *
+ * Usually used with htable_delval to delete a random entry.  Returns
+ * NULL iff the table is empty, otherwise a random entry.
+ */
+#define htable_pick(htable, seed, i)                                   \
+       htable_pick_(htable_debug(htable, HTABLE_LOC), seed, i)
+void *htable_pick_(const struct htable *ht, size_t seed, struct htable_iter *i);
+
 /**
  * htable_set_allocator - set calloc/free functions.
  * @alloc: allocator to use, must zero memory!