girepository: Use constant time calculation for sections after Object fields

Add "n_field_callbacks" to ObjectBlob which represents the number of object
fields which are also callbacks. This a allows a constant time computation
for accessing sections after fields. Track writing of this field by passing
an extra argument through the girnode writers recursive call structure. This
essentally reverts a portion of commit 7027bb256d0d1ab which added a linear
time computation for accessing sections after fields.
Update typelib validator to also ensure n_field_callbacks is properly set.

https://bugzilla.gnome.org/show_bug.cgi?id=700338

1 files changed, 3 insertions, 2 deletions

diff --git a/girepository/gitypelib-internal.h b/girepository/gitypelib-internal.h
index 5ccff719..0f105127 100644
--- a/girepository/gitypelib-internal.h
+++ b/girepository/gitypelib-internal.h
@@ -1051,7 +1051,8 @@ typedef struct {
  * @n_constants: The lengths of the arrays.Up to 16bits of padding may be
  *   inserted between the arrays to ensure that they start on a 32bit
  *   boundary.
- * @reserved2: Reserved for future use.
+ * @n_field_callbacks: The number of n_fields which are also callbacks.
+ *   This is used to calculate the fields section size in constant time.
  * @ref_func: String pointing to a function which can be called to increase
  *   the reference count for an instance of this object type.
  * @unref_func: String pointing to a function which can be called to decrease
@@ -1088,7 +1089,7 @@ typedef struct {
   guint16   n_signals;
   guint16   n_vfuncs;
   guint16   n_constants;
-  guint16   reserved2;
+  guint16   n_field_callbacks;
 
   guint32   ref_func;
   guint32   unref_func;