How to pass array pointer to Numba function?

Question

I\'d like to create a Numba-compiled function that takes a pointer or the memory address of an array as an argument and does calculations on it, e.g., modifies the underlyin

Answer 1

Thanks to the great @stuartarchibald, I now have a working solution:

import ctypes
import numba as nb
import numpy as np

arr = np.arange(5).astype(np.double)  # create arbitrary numpy array
print(arr)

@nb.extending.intrinsic
def address_as_void_pointer(typingctx, src):
    """ returns a void pointer from a given memory address """
    from numba.core import types, cgutils
    sig = types.voidptr(src)

    def codegen(cgctx, builder, sig, args):
        return builder.inttoptr(args[0], cgutils.voidptr_t)
    return sig, codegen

addr = arr.ctypes.data

@nb.njit
def modify_data():
    """ a function taking the memory address of an array to modify it """
    data = nb.carray(address_as_void_pointer(addr), arr.shape, dtype=arr.dtype)
    data += 2

modify_data()
print(arr)

The key is the new address_as_void_pointer function that turns a memory address (given as an int) into a pointer that is usable by numba.carray.