Test FFI on Python

ffi_test.c

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

#include "ffi_test.h"

const char greeting_format[] = "%s, %s, you old %s, you!";

/* get species name */
char *get_species(Species species) {

  switch (species) {
    case HUMAN:
      return "human";
    case CANINE:
      return "dog";
    default:
      return "entity";
  }

}

/* get greeting */
char *get_greeting(Greeting greeting) {

  switch (greeting) {
    case HELLO:
      return "Hello";
    case HI:
      return "Hi";
    case YO:
      return "Yo";
    default:
      return "Hello";
  }

}

/* generate greeting */
char *greet(const Being being) {

  char *s = get_species(being.species);
  char *g = get_greeting(being.greeting);

  char *result = malloc(
    snprintf(NULL, 0, greeting_format, g, being.name, s) + 1
  );

  sprintf(result, greeting_format, g, being.name, s);

  return result;

}

/* generate random numbers to fill array */
void randn(int n, float *array) {

  for (int i = 0; i < n; i++) {
    array[i] = (float) rand() / RAND_MAX;
  }

}

ffi_test.h

#ifndef FFI_TEST
#define FFI_TEST

typedef enum Species {
  HUMAN, CANINE
} Species;
typedef enum Greeting {
  HELLO, HI, YO
} Greeting;
typedef struct Being {
  char name[1024];
  Species species;
  Greeting greeting;
} Being;

char *greet(const Being being);

void randn(int n, float *array);

#endif

ffi_test.py

#!/usr/bin/env python

import time
import os.path
import cffi

PATH = os.path.split(__file__)[0]

# define the API
ffi = cffi.FFI()
ffi.cdef("""
    void free(void *);
    void srand(unsigned seed);

    typedef enum Species {
      HUMAN, CANINE
    } Species;
    typedef enum Greeting {
      HELLO, HI, YO
    } Greeting;
    typedef struct Being {
      char name[1024];
      Species species;
      Greeting greeting;
    } Being;

    char *greet(const Being being);
    void randn(int n, float *array);
""")

# load the library. performs compilation if necessary
lib = ffi.verify("""
    #include <ffi_test.h>
    #include <stdlib.h>
""", sources=[os.path.join(PATH, 'ffi_test.c')], include_dirs=[PATH])

# arrays
seed = int((time.time() % 1) * 1e6)
lib.srand(seed)

array = ffi.new('float[10000]')
lib.randn(10000, array)
print sum(array)

# structs
beings = ffi.new("Being[]", [
    ('Josh', lib.HUMAN, lib.YO),
    ('Ziggy', lib.CANINE, lib.HI),
])

for being in beings:
    print being
    salutation = ffi.gc(lib.greet(being), lib.free)
    print ffi.string(salutation)