ck_hs: Add ck_hs_move operation.

This operation moves ownership from one hash set object
to another and re-assigns callback functions to developer-specified
values. This allows for dynamic configuration of allocation
callbacks and is necessary for use-cases involving executable code
which may be unmapped underneath the hash set.

The developer is responsible for enforcing barriers and enforcing
the visibility of the new hash set.

include/ck_hs.h

@@ -88,6 +88,8 @@ typedef struct ck_hs_iterator ck_hs_iterator_t;
 
 void ck_hs_iterator_init(ck_hs_iterator_t *);
 bool ck_hs_next(ck_hs_t *, ck_hs_iterator_t *, void **);
+bool ck_hs_move(ck_hs_t *, ck_hs_t *, ck_hs_hash_cb_t *,
+    ck_hs_compare_cb_t *, struct ck_malloc *);
 bool ck_hs_init(ck_hs_t *, unsigned int, ck_hs_hash_cb_t *,
     ck_hs_compare_cb_t *, struct ck_malloc *, unsigned long, unsigned long);
 void ck_hs_destroy(ck_hs_t *);

src/ck_hs.c

@@ -582,6 +582,26 @@ ck_hs_remove(struct ck_hs *hs,
 	return object;
 }
 
+bool
+ck_hs_move(struct ck_hs *hs,
+    struct ck_hs *source,
+    ck_hs_hash_cb_t *hf,
+    ck_hs_compare_cb_t *compare,
+    struct ck_malloc *m)
+{
+
+	if (m == NULL || m->malloc == NULL || m->free == NULL || hf == NULL)
+		return false;
+
+	hs->mode = source->mode;
+	hs->seed = source->seed;
+	hs->map = source->map;
+	hs->m = m;
+	hs->hf = hf;
+	hs->compare = compare;
+	return true;
+}
+
 bool
 ck_hs_init(struct ck_hs *hs,
     unsigned int mode,