Enum CopyState

Used as a part of copy specialization to communicate how many bytes were copied, and whether copying is done.

• Ended(n) indicates copying completed, moving a total of n bytes.
• Fallback(n) indicates copying is might not be complete, and so far n bytes have been copied using specialization. The remaining must be copied using a fallback implementation.

If a particular Read and Write combination do not implement a specialized copy routine, the specialized function will return Fallback(0).