#include <semaphore.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <cstdlib>
#include <iostream>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <string>
#include <fstream>



using namespace std;

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

    fstream bufferFile;
    ifstream readFile;
    int sem1 = 1;
    int sem2 = 0;
    int aNum = 0;
    int childcount = 0;
    pid_t fork_return;

    bufferFile.open("buffer.txt.", ios::out);
    cout << "Writing to buffer file.\n";
    bufferFile << aNum;
    bufferFile.close();

    sem_t mutex;
    sem_init(&mutex,1,1);
    fork_return  = fork( );
    while(childcount < 5){
               if (fork_return == 0) {  /*in the child process*/
                                 sem_wait(&mutex);
                                    readFile.open("buffer.txt");
                                    //readFile.seekg(ios_base::beg);
                                    readFile >> aNum;
                                    readFile.close();
                                    aNum++;
                                    bufferFile.open("buffer.txt.", ios::out);
                                    bufferFile << aNum;
                                    bufferFile.close();
                                    childcount++;
                                    sem2 = 1;
                                    cout << "A. The number [ " << aNum <<"] modified by child\n";
                                 sem_post(&mutex);
               }

               else if(fork_return > 0 )  /*in the parent process*/
                     {
                            sem_wait(&mutex);
                                    readFile.open("buffer.txt");
                                    //readFile.seekg(ios_base::beg);
                                    readFile >> aNum;
                                    readFile.close();
                                    aNum++;
                                    bufferFile.open("buffer.txt.", ios::out);
                                    bufferFile << aNum;
                                    bufferFile.close();
                                    sem1 = 1;
                                    cout << "B. The number [ " << aNum <<"] modified by parent\n";
                            sem_post(&mutex);
                    }
    }//big while



   return 0;
}