// Compiler call:		gccc aufgabe1.c -lpthread
#include <pthread.h>
#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>

#define LOOPCOUNT 200
void* reader_function(void*);
void writer_function(void);

int buffer_a, buffer_b;
pthread_mutex_t mutex_a, mutex_b;

int main(int argc, char* argv[]) {
  pthread_mutexattr_t mutex_attr;
  pthread_attr_t attr;
  pthread_t reader;

  if (pthread_mutexattr_init(&mutex_attr) == 0) {
    if (pthread_mutex_init(&mutex_a, &mutex_attr) == 0) {
      if (pthread_mutex_init(&mutex_b, &mutex_attr) == 0) {
        if (pthread_attr_init(&attr) == 0) {
          if (pthread_create(&reader, &attr, reader_function, 0) == 0) {
            writer_function();
            pthread_join(reader, 0);
          }
        }
        pthread_mutex_destroy(&mutex_b);
      }
      pthread_mutex_destroy(&mutex_a);
    }
  }
  printf("Main thread finished!\n");
  return 0;
}

void writer_function(void) {
  int i;
  for (i = 0; i < LOOPCOUNT; i++) {
    pthread_mutex_lock(&mutex_a);
    buffer_a = i;
    printf("Writer: Buffer a is : %d,\n", buffer_a);
    pthread_mutex_lock(&mutex_b);
    buffer_b = buffer_a;
    printf("Writer: Buffer b is : %d,\n", buffer_b);
    pthread_mutex_unlock(&mutex_b);
    pthread_mutex_unlock(&mutex_a);
  }
}

void* reader_function(void* ptr) {
  int i;
  for (i = 0; i < LOOPCOUNT; i++) {
    pthread_mutex_lock(&mutex_a);
    printf("Reader: Buffer a+b is : %d,\n", buffer_b + buffer_a);
    pthread_mutex_unlock(&mutex_a);
    pthread_mutex_lock(&mutex_b);
    printf("Reader: Buffer a is : %d,\n", buffer_a);
    pthread_mutex_unlock(&mutex_b);
  }
  printf("Reader thread finished\n");
  return 0;
}