[buffer/set/map] Move immutable check only to C API boundary

The immutable objects are a concept only enforced by the C API.
So move checks only to that region.

This does assume that the rest of the code is careful not getting
into these internal methods on immutable objects, which something
we do, but have no way of enforcing (currently).

.

src/hb-buffer.cc

@@ -218,9 +218,6 @@ hb_buffer_t::get_scratch_buffer (unsigned int *size)
 void
 hb_buffer_t::reset ()
 {
-  if (unlikely (hb_object_is_immutable (this)))
-    return;
-
   hb_unicode_funcs_destroy (unicode);
   unicode = hb_unicode_funcs_reference (hb_unicode_funcs_get_default ());
   flags = HB_BUFFER_FLAG_DEFAULT;
@@ -233,9 +230,6 @@ hb_buffer_t::reset ()
 void
 hb_buffer_t::clear ()
 {
-  if (unlikely (hb_object_is_immutable (this)))
-    return;
-
   hb_segment_properties_t default_props = HB_SEGMENT_PROPERTIES_DEFAULT;
   props = default_props;
   scratch_flags = HB_BUFFER_SCRATCH_FLAG_DEFAULT;
@@ -290,9 +284,6 @@ hb_buffer_t::add_info (const hb_glyph_info_t &glyph_info)
 void
 hb_buffer_t::remove_output ()
 {
-  if (unlikely (hb_object_is_immutable (this)))
-    return;
-
   have_output = false;
   have_positions = false;
 
@@ -303,9 +294,6 @@ hb_buffer_t::remove_output ()
 void
 hb_buffer_t::clear_output ()
 {
-  if (unlikely (hb_object_is_immutable (this)))
-    return;
-
   have_output = true;
   have_positions = false;
 
@@ -316,9 +304,6 @@ hb_buffer_t::clear_output ()
 void
 hb_buffer_t::clear_positions ()
 {
-  if (unlikely (hb_object_is_immutable (this)))
-    return;
-
   have_output = false;
   have_positions = true;
 
@@ -1226,6 +1211,9 @@ hb_buffer_get_invisible_glyph (hb_buffer_t    *buffer)
 void
 hb_buffer_reset (hb_buffer_t *buffer)
 {
+  if (unlikely (hb_object_is_immutable (buffer)))
+    return;
+
   buffer->reset ();
 }
 
@@ -1241,6 +1229,9 @@ hb_buffer_reset (hb_buffer_t *buffer)
 void
 hb_buffer_clear_contents (hb_buffer_t *buffer)
 {
+  if (unlikely (hb_object_is_immutable (buffer)))
+    return;
+
   buffer->clear ();
 }
 

src/hb-map.cc

@@ -253,6 +253,9 @@ hb_map_has (const hb_map_t *map,
 void
 hb_map_clear (hb_map_t *map)
 {
+  if (unlikely (hb_object_is_immutable (map)))
+    return;
+
   return map->clear ();
 }
 

src/hb-map.hh

@@ -97,8 +97,6 @@ struct hb_hashmap_t
 
   void reset ()
   {
-    if (unlikely (hb_object_is_immutable (this)))
-      return;
     successful = true;
     clear ();
   }
@@ -171,8 +169,6 @@ struct hb_hashmap_t
 
   void clear ()
   {
-    if (unlikely (hb_object_is_immutable (this)))
-      return;
     if (items)
       for (auto &_ : hb_iter (items, mask + 1))
 	_.clear ();

src/hb-set.cc

@@ -183,6 +183,9 @@ hb_set_allocation_successful (const hb_set_t  *set)
 void
 hb_set_clear (hb_set_t *set)
 {
+  if (unlikely (hb_object_is_immutable (set)))
+    return;
+
   set->clear ();
 }
 

src/hb-set.hh

@@ -256,17 +256,12 @@ struct hb_set_t
 
   void reset ()
   {
-    if (unlikely (hb_object_is_immutable (this)))
-      return;
     successful = true;
     clear ();
   }
 
   void clear ()
   {
-    if (unlikely (hb_object_is_immutable (this)))
-      return;
-
     if (resize (0))
       population = 0;
   }