safe and efficient copying between blocks of memory

There are several ways of storing and accessing blocks of memory in an OCaml program, including

• bytes and string values for mutable and immutable strings that reside in the OCaml heap
• bigarray values for reference-counted blocks that reside in the OCaml heaps
• Ctypes ptr values that can be used to address arbitrary addresses using typed descriptions of the memory layout.
• Ctypes array values that provide bounds-checked access to ptr-addressed memory.

The Memcpy module provides functions for safely and efficiently copying blocks of memory between these different representations.