#include "stdafx.h"
#include "windows.h"

#include <process.h>
#include <time.h> 
#include <stdlib.h> 
#include <stdio.h> 

#include <iostream>

using namespace std;

const unsigned int PHILOSOPHER_NUM=5;
const char THINKING=1;
const char HUNGRY=2;
const char DINING=3;

// each fork has a semaphore
HANDLE semph[PHILOSOPHER_NUM];

// Mutex for printing
HANDLE mutex;

void philosopherProc(void* param);

int main(int argc, char* argv[])
{
 int i;
 srand(time(0));

 mutex = CreateMutex(NULL, false, NULL);
 for (i=0; i<PHILOSOPHER_NUM; i++)
 {
  semph[i] = CreateSemaphore(NULL, 1, 1, NULL);
  _beginthread(philosopherProc, 0, (void*)&i);
  Sleep(10);
 }

 Sleep(2000);
 return 0;
}

void philosopherProc(void* param)
{
 int myid;
 char idStr[128];
 char stateStr[128];
 char mystate;
 int ret;
 unsigned int leftFork;
 unsigned int rightFork;

 myid = *((int*)(param));
 itoa(myid, idStr, 10);

 //cout << "philosopher " << myid << " begin......" << endl;
 Sleep(10);

 // initial state is THINKING
 mystate = THINKING;
 leftFork = (myid) % PHILOSOPHER_NUM;
 rightFork = (myid + 1) % PHILOSOPHER_NUM;

 while (true)
 {
  switch(mystate)
  {
  case THINKING:
   // changing my state
   mystate = HUNGRY;
   strcpy(stateStr, "HUNGRY");
   break;

  case HUNGRY:
   strcpy(stateStr, "HUNGRY");
   // first test the left fork ...
   ret = WaitForSingleObject(semph[leftFork], 0);
   if (ret == WAIT_OBJECT_0)
   {
    // left fork is ok, take it up !
    // then test the right fork ...
    ret = WaitForSingleObject(semph[rightFork], 0);
    if (ret == WAIT_OBJECT_0)
    {
     // right fork is also ok !
     // changing my state
     mystate = DINING;
     strcpy(stateStr, "DINING");
    }
    else
    {
     // right fork is being used by others, so I must put down
     // the left fork.
     ReleaseSemaphore(semph[leftFork], 1, NULL);
    }
   }
   break;

  case DINING:
   // put down both the left and right fork
   ReleaseSemaphore(semph[leftFork], 1, NULL);
   ReleaseSemaphore(semph[rightFork], 1, NULL);

   // changing my state
   mystate = THINKING;
   strcpy(stateStr, "THINKING");
   break;
  }

  // print my state
  WaitForSingleObject(mutex, INFINITE);
  cout << "philosopher " << myid << " is : " << stateStr << endl;  
  ReleaseMutex(mutex);
  
  // sleep a random time : between 1 - 5 s
  int sleepTime; 
  sleepTime = 1 + (int)(5.0*rand()/(RAND_MAX+1.0)); 
  Sleep(sleepTime*10);
 }
}