[map] Add hb_map_copy()

New API:
+ hb_map_copy()

docs/harfbuzz-sections.txt

@@ -453,6 +453,7 @@ hb_icu_script_to_script
 HB_MAP_VALUE_INVALID
 hb_map_allocation_successful
 hb_map_clear
+hb_map_copy
 hb_map_create
 hb_map_del
 hb_map_destroy

src/hb-map.cc

@@ -172,6 +172,25 @@ hb_map_allocation_successful (const hb_map_t  *map)
   return map->successful;
 }
 
+/**
+ * hb_map_copy:
+ * @map: A map
+ *
+ * Allocate a copy of @map.
+ *
+ * Return value: Newly-allocated map.
+ *
+ * Since: REPLACEME
+ **/
+hb_map_t *
+hb_map_copy (const hb_map_t *map)
+{
+  hb_map_t *copy = hb_map_create ();
+  if (unlikely (!copy)) return nullptr;
+  copy->resize (map->population);
+  hb_copy (*map, *copy);
+  return copy;
+}
 
 /**
  * hb_map_set:

src/hb-map.h

@@ -82,6 +82,9 @@ hb_map_get_user_data (hb_map_t           *map,
 HB_EXTERN hb_bool_t
 hb_map_allocation_successful (const hb_map_t *map);
 
+HB_EXTERN hb_map_t *
+hb_map_copy (const hb_map_t *map);
+
 HB_EXTERN void
 hb_map_clear (hb_map_t *map);
 

src/hb-set.cc

@@ -186,6 +186,7 @@ hb_set_t *
 hb_set_copy (const hb_set_t *set)
 {
   hb_set_t *copy = hb_set_create ();
+  if (unlikely (!copy)) return nullptr;
   copy->set (*set);
   return copy;
 }