Add hb_nonnull_ptr_t

Towards fixing https://github.com/harfbuzz/harfbuzz/issues/1146

src/hb-null.hh

@@ -103,4 +103,32 @@ struct CrapOrNull<const Type> {
 #define CrapOrNull(Type) CrapOrNull<Type>::get ()
 
 
+/*
+ * hb_nonnull_ptr_t
+ */
+
+template <typename P>
+struct hb_nonnull_ptr_t
+{
+  typedef typename hb_remove_pointer<P>::value T;
+
+  inline hb_nonnull_ptr_t (T *v_ = nullptr) : v (v_) {}
+  inline T * operator = (T *v_) { return v = v_; }
+  inline T * operator -> (void) { return get (); }
+  inline const T * operator -> (void) const { return get (); }
+  inline T & operator * (void) { return *get (); }
+  inline const T & operator * (void) const { return *get (); }
+  inline T ** operator & (void) { return &v; }
+  inline const T ** operator & (void) const { return &v; }
+  inline operator T * (void) { return get (); }
+  inline operator const T * (void) const { return get (); }
+  inline T * get (void) { return v ? v : const_cast<T *> (&Null(T)); }
+  inline const T * get (void) const { return v ? v : const_cast<T *> (&Null(T)); }
+  inline T * get_raw (void) { return v; }
+  inline const T * get_raw (void) const { return v; }
+
+  T *v;
+};
+
+
 #endif /* HB_NULL_HH */