KyleJohnstonAssigment3.cpp

// COSC 3360
// Dr. Jehan-Francois Paris
// Spring 2016
// The University of Houston

// Assignment 3
// Kyle Johnston
// kjjohnston@uh.edu

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string>
#include <iostream>
#include <unistd.h>
#include <sys/wait.h>
#include <dirent.h>

using namespace std;

int main(int argc, char const *argv[]) {
	//Base variables
	string family, name;
	int arrivalTime, stayTime, balance;
	int numberOfProcesses = 0;
	bool waitingForNumbers;
	pid_t pid;


	//Shared Memory
	long memoryKeyM, memoryKeyC;
	int memorySidM, memorySidC;
	int *nMontagues, *nCapulets;

	memoryKeyM = rand();
	memoryKeyC = rand();

	memorySidM = shmget(memoryKeyM, sizeof(int), 0600 | IPC_CREAT);
	memorySidC = shmget(memoryKeyC, sizeof(int), 0600 | IPC_CREAT);

	if (memoryKeyM == -1) {
			perror("Cannot get shared segment for Montagues");
			exit(3);
	}
	if (memoryKeyC == -1) {
			perror("Cannot get shared segment for Capulets");
			exit(3);
	}

	nMontagues = (int *) shmat(memorySidM, NULL, 0);
	nCapulets = (int *) shmat(memorySidC, NULL, 0);

	if (nMontagues == NULL) {
			perror("Cannot get address of shared segment for the Montagues");
			exit(24);
	}
	if (nCapulets == NULL) {
			perror("Cannot get address of shared segment for the Capulets");
			exit(24);
	}

	*nMontagues = *nCapulets = 0;

	//Semaphores for Mutual Exclusion on Shared Memory
	sem_t *montague, *capulet, *numbers;
	char semMontague[] = "KyleJohnston-Montague";
	char semCapulet[] = "KyleJohnston-Capulet";
	char semNumbers[] = "KyleJohnston-Numbers";
	int semValue;

	montague = sem_open(semMontague, O_CREAT, 0600, 1);
	capulet = sem_open(semCapulet, O_CREAT, 0600, 1);
	numbers = sem_open(semNumbers, O_CREAT, 0600, 0);
	sem_post(montague);
	sem_post(capulet);
	sem_post(numbers);

	if (montague == SEM_FAILED) {
		perror("Unable to create the montague semaphore.");
		sem_unlink(semMontague);
		exit(1);
	}
	if (capulet == SEM_FAILED) {
		perror("Unable to create the capulet semaphore.");
		sem_unlink(semCapulet);
		exit(1);
	}

	//Loop, reading input and creating child processes from it.
	while (cin >> family >> name >> arrivalTime >> stayTime) {
		//cout <<"Family: "<<family<<"   \tName: "<<name<<"\t\tEntry Time: "<<arrivalTime<<"   \tStay Time: "<<stayTime<<endl;
		numberOfProcesses++;
		pid = fork();
		if (pid == 0) { //If 0 this is the child process
			sleep(arrivalTime);
			cout<<name<<" "<<family<<" arrives at time "<<arrivalTime<<"."<<endl;
			//cout<<"There are now "<<*nMontagues<<" Montague(s) and "<<*nCapulets<<" Capulet(s) in the piazza."<<endl;
			//Try to Enter

			//Queue by family
			if (family == "Montague") {
				//sem_getvalue(montague, &semValue);
				//cout<<"\t\t"<<name<<" "<<family<<" is waiting in the Montague queue, which currently has a value of "<<semValue<<endl;
				sem_wait(montague);
				//cout<<"\t\t"<<name<<" "<<family<<" has reached the front of the Montauge queue"<<endl;
			} else if (family == "Capulet") {
				//sem_getvalue(montague, &semValue);
				//cout<<"\t\t"<<name<<" "<<family<<" is waiting in the Capulet queue, which currently has a value of "<<semValue<<endl;
				sem_wait(capulet);
				//cout<<"\t\t"<<name<<" "<<family<<" has reached the front of the Capulet queue"<<endl;
			} else {
				cout<<"Family: "<<family<<" is not recognized."<<endl;
				_exit(0);
			}

			//cout<<name<<" "<<family<<" is trying to enter the piazza."<<endl;
			//Wait till ballance allows entry
			waitingForNumbers = true;
			while (true) {
				sem_wait(numbers);
				balance = *nMontagues - *nCapulets;
				//cout<<"\t\t"<<name<<" "<<family<<" checks the ballance: "<<balance<<endl;
				if (family == "Montague" && balance <= 0) {
					*nMontagues += 1;
					waitingForNumbers = false;
				} else if (family == "Capulet" && balance >= 0) {
					*nCapulets += 1;
					waitingForNumbers = false;
				}
				if (!waitingForNumbers) {
					break;
				}
				sem_post(numbers);
			}

			cout<<name<<" "<<family<<" enters the piazza."<<endl<<"There are now "<<*nMontagues<<" Montague(s) and "<<*nCapulets<<" Capulet(s) in the piazza."<<endl;
			sem_post(numbers);

			if (family == "Montague") {
				sem_post(montague);
			} else if (family == "Capulet") {
				sem_post(capulet);
			}

			sleep(stayTime);
			//cout<<name<<" "<<family<<" wants to leave the piazza."<<endl;

			//Wait till the ballance allows exiting
			waitingForNumbers = true;
			while (true) {
				sem_wait(numbers);
				balance = *nMontagues - *nCapulets;
				//cout<<name<<" "<<family<<" checks the balance "<<balance<<endl;
				if (family == "Montague" && balance >= 0) {
					*nMontagues -= 1;
					waitingForNumbers = false;
				} else if (family == "Capulet" && balance <= 0) {
					*nCapulets -= 1;
					waitingForNumbers = false;
				}
				if (!waitingForNumbers) {
					break;
				}
				sem_post(numbers);
			}

			cout<<name<<" "<<family<<" leaves the piazza."<<endl<<"There are now "<<*nMontagues<<" Montague(s) and "<<*nCapulets<<" Capulet(s) in the piazza."<<endl;
			sem_post(numbers);
			_exit(0);
		}
	}

	while (numberOfProcesses>0) {
		wait(0);
		numberOfProcesses--;
	}

	sem_unlink(semMontague);
	sem_unlink(semCapulet);
	sem_unlink(semNumbers);

	shmdt(nMontagues);
	shmdt(nCapulets);

	shmctl(memorySidM, 0, IPC_RMID);
	shmctl(memorySidC, 0, IPC_RMID);

	return 0;
}