/* File:  ~liux/public_html/cop460/examples/simple-semaphore.cc
   Purpose: Demonstrate how to synchronize multiple threads
            using semaphores
   Author:  Xiuwen Liu
   On the web: 
     http://www.cs.fsu.edu/~liux/cop460/examples/simple-semaphore.cc
   Command to complie (Pay attention to -lthread -lc):
         g++  -o simple-mutex simple-mutex.cc -lthread -lc
*/

#include <sys/types.h>
#include <strings.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <thread.h>
#include <stdlib.h>
#include <iostream.h>
#include <synch.h>

#define NUM_THREADS 5
thread_t tid[NUM_THREADS];      /* array of thread IDs */

int totalTransaction;
int accounts[NUM_THREADS];  /* Account balances */
int      performed_transactions[NUM_THREADS]; 

void * RandomTransaction(void *msg);
int PerformATransaction(int from, int to, int val);
int CheckRunning(void);
sema_t exclusive_sema;

int main(int argc, char *argv[])
{

  int i, sum;
  // Initialize mutex lock 
  sema_init(&exclusive_sema, (int)1, USYNC_THREAD, (void *)NULL);
  totalTransaction = 0;
  for (i=0; i < NUM_THREADS; i++) {
    accounts[i] = 1000;
    performed_transactions[i] = 0;
  }
  sum =0;
  for (i=0; i<5; i++) {
    cout << "\n\tInit account "
	 << i+1 << "'s balance: " << accounts[i];
    sum += accounts[i];
  }
  cout <<"\n\tTotal initial balance is " << sum << endl;
  for (i=0; i < NUM_THREADS; i++) {
    if (thr_create(NULL, (int)0, RandomTransaction, (char *)NULL,
		   THR_SUSPENDED, &(tid[i])) <0) {
      perror("create thread: ");
      return -1;
    }
  }
  for (i=0; i < NUM_THREADS; i++)
    thr_continue(tid[i]);
  while (thr_join((unsigned int)NULL, 
		  (unsigned int *)NULL, (void **)NULL) == 0);

  sum = 0;
  for (i=0; i<5; i++) {
    cout << "\n\tFinal account "
	 << i+1 << "'s balance: " << accounts[i];
    sum += accounts[i];
  }
  cout <<"\nTotal final balance is " << sum << endl;
  
  sema_destroy(&exclusive_sema);
  for (i=0; i < NUM_THREADS; i++) {
    cout << "\nAccount " << i+1 << " performed " 
	 << performed_transactions[i];
  }
  cout << "\n";
  return 0;
}

void * RandomTransaction(void *msg)
{
  thread_t current_thr;
  int myAcct, toAcct;
  int amount;
  current_thr = thr_self();
  for (myAcct=0; myAcct < NUM_THREADS; myAcct++) {
    if (current_thr == tid[myAcct]) break;
  }
  if (myAcct >= NUM_THREADS) {
    cerr << "Something must be wrong with the thread IDs.\n";
    return (void *)NULL;
  }
  cout << "Thread " << myAcct+1 << " is running.\n";
  do {
    /* First figure out my account number */
    do {
      toAcct = ((int)random())%NUM_THREADS;
    } while (myAcct == toAcct);
    amount = (int)(random()%10+10);
    PerformATransaction(myAcct, toAcct, amount);
  } while(CheckRunning());
  return (void *)NULL;
}

int PerformATransaction(int from, int to, int val)
{
  int i, sum;
  
  if (accounts[from] < val) {
    thr_yield();
    return -1;
  }
  performed_transactions[from]++;
  sema_wait(&exclusive_sema);
  accounts[from] -= val;
  thr_yield();
  accounts[to] += val;
  totalTransaction++;
  if ((totalTransaction %10000) == 0) {
    sum =0;
    cout << "\nNow " 
	 << totalTransaction 
	 << " transactions have been completed.";
    for (i=0; i<5; i++) {
      cout << "\n\tAccount " << i+1 
	<< "'s balance: " << accounts[i];
      sum += accounts[i];
    }
    cout << "\n\tTotal balance after " 
	 << totalTransaction
	 << " transactions is " << sum << endl;
  }
  sema_post(&exclusive_sema);
  return 0;
}


int CheckRunning(void)
{
  int i;
  sema_wait(&exclusive_sema);
  i = (int)(totalTransaction < 100000);
  sema_post(&exclusive_sema);
  return i;
}