Job scheduling from input file - c++

Question

I'm working on a simulated process scheduler for my operating systems class and am having trouble figuring out the best way to extract the data from the file to process. The input file will look like this:
5
1 3 10
2 4 15
3 6 8
4 7 3
5 9 12
Where the first number is the number of processes and each line contains: (1) The job number, (2)The Arrival Time, and (3)The CPU Cycle time.
I have to process the jobs using FCFS, SJF, SRT, and Round Robin.
This is part of what i have so far, but I'm having trouble figuring out how to get the data from the file in a way that I could process it more easily (or at all, I'm a little stuck).
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
struct job
{
int id, arrTime, cpuTime;
};
int main()
{
fstream input;
job job1, job2, job3, job4, job5, job6, job7,job8, job9, job10;
char n, *id, *at, *cpu;
int proc;
input.open("input.txt");
input.get(n);
proc = n;
return 0;
}
I was considering taking each bit of information from the 10 jobs given and putting it into the 10 job class objects. Also, is there a good way to implement the code in a way that will allow for any number of jobs?

Answer 1

Use a container like std::vector to store your jobs. Good I/O is hard and tedious to do:
For example:
// container to hold jobs
// remember to #include <vector>
std::vector<job> myJobs;
And then read them in:
// read in number of jobs:
// going to need #include <fstream> and <sstream>
ifstream input("input.txt");
if (!input)
{
std::cerr << "Failed to open input file! Cannot continue\n";
exit(1);
}
int numJobs = 0;
if (input >> numJobs)
{
myJobs.reserve(numJobs);
}
else
{
std::cerr << "Failed to read number of jobs. Cannot continue\n";
exit(1);
}
std::string nextline;
for (int i=0;i<numJobs && std::getline(input >> std::ws, nextLine); ++i)
{
std::stringstream inStream(nextLine);
job nextJob;
nextLine >> nextJob.id >> nextJob.arrTime >> nextJob.cpuTime;
if (!inStream)
{
std::cerr << "Error reading next job\n";
break;
}
myJobs.push_back(nextJob);
}
input.close();
std::cout << "Was supposed to read in " << numJobs << " jobs. Successfully read in " << myJobs.size() << " jobs.";
And then do what you will with the container:
// Now you can do what you want with them
// Let's sort them from smallest cpuTime to largest!
// remember to #include<algorithm>
std::sort(std::begin(myJobs), std::end(myJobs), [](const job& lhs, const job& rhs){return lhs.cputime < rhs.cputime;});
cout << "Jobs sorted by cputime: \n";
for (auto&& j : myJobs)
{
cout << j.id << " " << j.arrTime << " " << j.cpuTime << std::endl;
}
Edit I used a bit of C++11 in this post, so it will not compile if you're only using C++98/03