lang/python/ CTypesModule

Trivial Example

The c

#include <stdio.h>
#include <stdlib.h>

// compile with gcc -o a.so a.c

typedef struct {
  int x;
} X;

X* create() {
  X *x = (X*)malloc(sizeof(X));
  x->x = 42;
  return x;
}
int set(X* x, int y) {
  x->x = y;
}
int get(X* x) {
  return x->x;
}
void destroy(X* x) {
  free(x);
}

The pyton

import ctypes
dll = ctypes.cdll.LoadLibrary("./a.so")
print(dll)
class X:
  def __init__(self):
    self.a = dll.create() # void* pointers are just integers in Python
  def destroy(self):
    dll.destroy(self.a)
  def set(self,x): # we should be putting on type annotations in real code
    x = int(x)
    dll.set(self.a,x)
  def get(self):
    return dll.get(self.a)
x = X()
print(x.get())