Signature:

  FUNCTION h5offsetof(start,end) RESULT(offset)
    USE, INTRINSIC :: ISO_C_BINDING
    USE H5GLOBAL
    IMPLICIT NONE
    INTEGER(SIZE_T) :: offset
    TYPE(C_PTR), VALUE, INTENT(IN) :: start, end

Inputs:

  start - starting pointer address
  end   - ending pointer address

Outputs:

  offset - offset