/*
  This program spawns NUM_THREADS threads, each of which count from 0 to LOOP_NUM (exclusive)
  For example, when NUM_THREADS = 4 and LOOP_NUM = 5, 4 threads will be spawned and the output
  of each thread will be counting from 0 to 4.

  Don't forget to compile with the -pthread flag!
*/


#include <pthread.h>
#include <iostream>

using std::cout;
using std::cerr;
using std::endl;

const int NUM_THREADS = 4;
const int LOOP_NUM = 5;

// This is the routine that is executed by each of the threads spawned by main().
// Counts from 0 to LOOP_NUM (exclusive).
// Parameter arg is a pointer to an int representing the thread number.
void *thread_main(void *arg) {
  int *num = reinterpret_cast<int*>(arg);

  for (int i = 0; i < LOOP_NUM; i++) {
    cout << "[cthread: " << *num << "] " << i << endl;
  }

  delete num;
  return nullptr;
}

// Main spawns each thread with pthread_create() and tells them to execute thread_main()
int main(int argc, char** argv) {

  // an array of all of our threads
  pthread_t thds[NUM_THREADS];

  // spawn threads
  for (int i = 0; i < NUM_THREADS; i++) {
    int *num = new int(i);

    // create new thread and tell it to execute thread_main() with argument num 
    if (pthread_create(&thds[i], nullptr, &thread_main, num) != 0) {
      cerr << "pthread_create failed" << endl;
    }
  }

  // by calling pthread_exit, if main() finishes before the threads
  // it will not terminate the execution of the threads
  pthread_exit(nullptr);
  
  // because we call pthread_exit, we should not see this statement printed
  cout << "Unreachable statement" << endl;
  return 0;
}