I have a python script that creates a set of ctype input arguments to pass to scipy.LowLevelCallable(see the notes section) and uses it to make a call to scipy.generic_filter that only executes a single iteration for testing purposes. I also define an extra argument and pass it to the user_data void pointer as following:
from scipy import LowLevelCallable, ndimage
import numpy as np
import ctypes
clib = ctypes.cdll.LoadLibrary('path_to_my_file/my_filter.so')
clib.max_filter.restype = ctypes.c_int
clib.max_filter.argtypes = (
ctypes.POINTER(ctypes.c_double),
ctypes.c_long,
ctypes.POINTER(ctypes.c_double),
ctypes.c_void_p)
my_user_data = ctypes.c_double(12345)
ptr = ctypes.cast(ctypes.pointer(my_user_data), ctypes.c_void_p)
max_filter_llc = LowLevelCallable(clib.max_filter,ptr)
#this part only executes the LowLevelCallable function once and has no special meaning
image = np.random.random((1, 1))
footprint = np.array([[0, 1, 0],
[1, 1, 1],
[0, 1, 0]], dtype=bool)
mask = ndimage.generic_filter(image, max_filter_llc, footprint=footprint)
path_to_my_file/my_filter.so corresponds to the scipy.LowLevelCallable function argument structure and simply prints the user_data variable:
#include <math.h>
#include <stdint.h>
#include <stdio.h>
int my_filter(
double * buffer,
intptr_t filter_size,
double * return_value,
void * user_data
) {
double x;
x = *(double *)(user_data);
printf("my user_data input is: %ld", x);
return 1;
}
This prints out my user_data input is: 0, even though I defined my_user_data as 12345 in my python script. How can I change my scripts so I can access the extra argument in my c program?
