OK Sorry @szekelyisz, my idea was to use the printable help class but that is also not available, so no go.
I guess would allocate my arrays one bigger and stuff a zero past the end of the data then.
I would also urge you to reconsider using String at all here. Allocating and deallocating large Strings can be problematic for heap fragmentation and cause weird crashes. If you can stuff the zero past the end, then you can just use char* and static allocation.