csc360-a1-shell/c/jobs.c

/*
 * A simple shell with some basic features.
 *
 * Sami Samhuri 0327342
 * January 31, 2006
 * CSC 360, Assignment 1
 *
 * jobs.c
 * $Id: jobs.c 184 2006-01-29 08:53:30Z sjs $
 */

/*#define _GNU_SOURCE*/

#include <stdio.h>
#include <string.h>

#include "jobs.h"
#include "utils.h"

#define MIN(a, b) ((a) < (b)) ? (a) : (b)

static job job_list_head = NULL;
static int num_jobs = 0;
static int next_id = 1;

static int get_next_id(void) {
    while (job_with_id(next_id))
        next_id++;
    return next_id++;
}

job add_job(pid_t pid, char **argv) {
    job i, j = (job)myxmalloc(sizeof(struct job));
    j->id = get_next_id();
    j->pid = pid;
    j->cmdline = array_cat(argv);
    j->next = NULL;
    j->prev = NULL;

    for (i = job_list_head; i && i->next; i = i->next) { /* insert jobs in job_id order */
        if (i->id > j->id) {                             /* insert BEFORE i */
            j->next = i;
            j->prev = i->prev;
            if (i->prev)
                i->prev->next = j;
            i->prev = j;

            if (job_list_head == i)
                job_list_head = j;
            break;
        }
    }

    if (i == NULL) /* empty list */
    {
        job_list_head = j;
    } else if (!i->next) /* at the end, i->next == NULL */
    {                    /* at this point, append the new job to the end of the list */
        i->next = j;
        j->prev = i;
    }
    num_jobs++;
    return j;
}

void delete_job(job j) {
    next_id = MIN(next_id, j->id); /* prefer the lower id */

    if (j == job_list_head) {
        if (j->next)
            job_list_head = j->next;
        else
            job_list_head = NULL;
    }
    if (j->prev)
        j->prev->next = j->next;
    if (j->next)
        j->next->prev = j->prev;

    xfree(j->cmdline);
    xfree(j);
    num_jobs--;
}

void free_job_list(void) {
    while (job_list_head)
        delete_job(job_list_head);
}

job job_with_id(int job_id) {
    job j;
    for (j = job_list_head; j; j = j->next) {
        if (j->id == job_id)
            return j;
    }
    return NULL;
}

job job_with_pid(pid_t pid) {
    job j;
    for (j = job_list_head; j; j = j->next) {
        if (j->pid == pid)
            return j;
    }
    return NULL;
}

job get_job_list(void) { return job_list_head; }

int get_num_jobs(void) { return num_jobs; }