fcfs.c

#define _POSIX_C_SOURCE 200809L
#include <stdio.h>
#include <stdlib.h>
#include "scheduler.h"
#include "utils.h"

/*
 * FCFS scheduling:
 * - Sort by arrival time
 * - Execute each process in arrival order; if CPU is idle, advance time to next arrival
 */
void fcfs_schedule(const Process proc_list[], size_t n) {
    if (n == 0) {
        printf("No processes to schedule.\n");
        return;
    }

    Process *proc = malloc(sizeof(Process) * n);
    if (!proc) {
        perror("malloc");
        return;
    }
    copy_processes(proc_list, proc, n);
    sort_by_arrival(proc, n);

    GanttEntry *gantt = malloc(sizeof(GanttEntry) * n);
    size_t gcount = 0;

    int time = 0;
    for (size_t i = 0; i < n; ++i) {
        if (time < proc[i].arrival_time) {
            /* CPU idle until arrival */
            time = proc[i].arrival_time;
        }
        proc[i].start_time = time;
        proc[i].completion_time = time + proc[i].burst_time;
        proc[i].turnaround_time = proc[i].completion_time - proc[i].arrival_time;
        proc[i].waiting_time = proc[i].start_time - proc[i].arrival_time;
        proc[i].finished = 1;

        /* Gantt entry */
        gantt[gcount].pid = proc[i].pid;
        gantt[gcount].start = proc[i].start_time;
        gantt[gcount].end = proc[i].completion_time;
        ++gcount;

        time = proc[i].completion_time;
    }

    printf("\n--- First Come First Serve (FCFS) ---\n");
    print_process_table(proc, n);
    print_gantt_chart(gantt, gcount);
    calculate_and_print_averages(proc, n);

    free(proc);
    free(gantt);
}