interfacer.c

#include <stdio.h>

struct fish_key_store {
  void* data;
  int (*getter) (void*, const char*, char*, size_t);
  int (*setter) (void*, const char*, const char*);
};

struct fish_key_store fish_key_store_make (void* data, void* getter, void* setter) {
  return (struct fish_key_store){
      .data = data,
      .getter = (int(*)(void*, const char*, char*, size_t))getter,
      .setter = (int(*)(void*, const char*, const char*))setter,
  };
}

void f (struct fish_key_store store) {
  char buffer[1024];

  store.getter(store.data, "key", buffer, 1024);
  store.setter(store.data, "key", "value");
}


struct first_key_store { };
int first_key_store_get (struct first_key_store* a, const char* b, char* c, size_t d) { printf("getting first key %s\n", b); return -1; }
int first_key_store_set (struct first_key_store* a, const char* b, const char* c) { printf("setting first key %s: %s\n", b, c); return -1; }



struct second_key_store {};
int second_key_store_get (struct second_key_store* a, const char* b, char* c, size_t d) { printf("getting second key %s\n", b); return -1; }
int second_key_store_set (struct second_key_store* a, const char* b, const char* c) { printf("setting second key %s: %s\n", b, c); return -1; }


int main () {
  struct first_key_store first;
  f(fish_key_store_make(&first, first_key_store_get, first_key_store_set));

  struct second_key_store  second;
  f(fish_key_store_make(&second, second_key_store_get, second_key_store_set));
  return 0;
}