#include <string.h>
#include <stdio.h>
#include <pthread.h>

struct shared_data {
  pthread_mutex_t mutex;
  int counter;
};

struct thread_args {
  const char *name;
  struct shared_data *shared;
};

void *thread_callback(void *p) {
  struct thread_args *args = p;
  struct shared_data *data = args->shared;

  for (int i = 0; i < 100000; i++) {
    if (pthread_mutex_lock(&data->mutex) != 0) {
      perror("pthread_mutex_lock");
    }

    data->counter++;

    if (pthread_mutex_unlock(&data->mutex) != 0) {
      perror("pthread_mutex_unlock");
    }
  }

  return NULL;
}

int main() {
  struct shared_data shared_data = { 0 };

  if (pthread_mutex_init(&shared_data.mutex, NULL) < 0) {
    printf("Failed to initialise mutex\n");
    return -1;
  }

  pthread_t thread1;
  struct thread_args args1 = { "Thread 1", &shared_data };
  pthread_create(&thread1, NULL, thread_callback, &args1);

  pthread_t thread2;
  struct thread_args args2 = { "Thread 2", &shared_data };
  pthread_create(&thread2, NULL, thread_callback, &args2);

  pthread_join(thread1, NULL);
  pthread_join(thread2, NULL);

  printf("Counter is %d\n", shared_data.counter);
}