This little library allows us to check if to bigarray share same memory area:

                    ba2
            ba1    .-------.
           .------|.        |
          |       | |       |
0x000800: [-------###-------]
                  | |
		   .
		  ba3

In this example, ba1 and ba2 share a small area and bigarray-overlap can
returns this small area to you as a new ba3 value.

open Bigarray

let () =
  let ba = Array1.create Char Bigarray.c_layout 17 in
  let ba1 = Array1.sub ba 0 10 in
  let ba2 = Array1.sub ba 7 17 in
  match Overlap.array1 ba1 ba2 with
  | Some (len, x, _y) ->
    let ba3 = Array1.sub ba x len in
    ...
  | None -> ...

overlap returns the length of the shared area, the x point from ba1 and
the y point from ba2.

A js_of_ocaml support

overlap is compatible with js_of_ocaml but it lies about expected results.
Indeed, we are not able to know the position in memory of given bigarray in
the JS world. By this fact, Overlap with js_of_ocaml will always returns
None.