path: root/calendar/gui/alarm-notify/alarm.c

/* Evolution calendar - Low-level alarm timer mechanism
 *
 * Copyright (C) 2000 Helix Code, Inc.
 *
 * Authors: Miguel de Icaza <miguel@helixcode.com>
 *          Federico Mena-Quintero <federico@helixcode.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */

#include <config.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/time.h>
#include <gdk/gdk.h>
#include "alarm.h"



/* Whether the timer system has been initialized */
static gboolean alarm_inited;

/* The pipes used to notify about an alarm */
static int alarm_pipes [2];

/* The list of pending alarms */
static GList *alarms;

/* A queued alarm structure */
typedef struct {
    time_t             trigger;
    AlarmFunction      alarm_fn;
    gpointer           data;
    AlarmDestroyNotify destroy_notify_fn;
} AlarmRecord;



/* SIGALRM handler.  Notifies the callback about the alarm. */
static void
alarm_signal (int arg)
{
    char c = 0;

    write (alarm_pipes [1], &c, 1);
}

/* Sets up an itimer and returns a success code */
static gboolean
setup_itimer (time_t diff)
{
    struct itimerval itimer;
    int v;

    itimer.it_interval.tv_sec = 0;
    itimer.it_interval.tv_usec = 0;
    itimer.it_value.tv_sec = diff;
    itimer.it_value.tv_usec = 0;

    v = setitimer (ITIMER_REAL, &itimer, NULL);

    return (v == 0) ? TRUE : FALSE;
}

/* Clears the itimer we have pending */
static gboolean
clear_itimer (void)
{
    return setup_itimer (0);
}

/* Removes the head alarm, returns it, and schedules the next alarm in the
 * queue.
 */
static AlarmRecord *
pop_alarm (void)
{
    AlarmRecord *ar;
    GList *l;

    if (!alarms)
        return NULL;

    ar = alarms->data;

    l = alarms;
    alarms = g_list_remove_link (alarms, l);
    g_list_free_1 (l);

    if (alarms) {
        time_t now;
        AlarmRecord *new_ar;

        now = time (NULL);
        new_ar = alarms->data;

        if (!setup_itimer (new_ar->trigger - now)) {
            g_message ("pop_alarm(): Could not reset the timer!  "
                   "Weird things will happen.");

            /* FIXME: should we free the alarm list?  What
             * about further alarm removal requests that
             * will fail?
             */
        }
    } else
        if (!clear_itimer ())
            g_message ("pop_alarm(): Could not clear the timer!  "
                   "Weird things may happen.");

    return ar;
}

/* Input handler for our own alarm notification pipe */
static void
alarm_ready (gpointer data, gint fd, GdkInputCondition cond)
{
    AlarmRecord *ar;
    char c;

    if (read (alarm_pipes [0], &c, 1) != 1) {
        g_message ("alarm_ready(): Uh?  Could not read from notification pipe.");
        return;
    }

    g_assert (alarms != NULL);
    ar = pop_alarm ();

    g_print ("alarm_ready(): Notifying about alarm on %s\n", ctime (&ar->trigger));

    (* ar->alarm_fn) (ar, ar->trigger, ar->data);

    if (ar->destroy_notify_fn)
        (* ar->destroy_notify_fn) (ar, ar->data);

    g_free (ar);
}

static int
compare_alarm_by_time (gconstpointer a, gconstpointer b)
{
    const AlarmRecord *ara = a;
    const AlarmRecord *arb = b;
    time_t diff;

    diff = ara->trigger - arb->trigger;
    return (diff < 0) ? -1 : (diff > 0) ? 1 : 0;
}

/* Adds an alarm to the queue and sets up the timer */
static gboolean
queue_alarm (time_t now, AlarmRecord *ar)
{
    time_t diff;
    AlarmRecord *old_head;

    if (alarms)
        old_head = alarms->data;
    else
        old_head = NULL;

    alarms = g_list_insert_sorted (alarms, ar, compare_alarm_by_time);

    if (old_head == alarms->data)
        return TRUE;

    /* Set the timer for removal upon activation */

    diff = ar->trigger - now;
    if (!setup_itimer (diff)) {
        GList *l;

        g_message ("queue_alarm(): Could not set up timer!  Not queueing alarm.");

        l = g_list_find (alarms, ar);
        g_assert (l != NULL);

        alarms = g_list_remove_link (alarms, l);
        g_list_free_1 (l);
        return FALSE;
    }

    return TRUE;
}

/**
 * alarm_add:
 * @trigger: Time at which alarm will trigger.
 * @alarm_fn: Callback for trigger.
 * @data: Closure data for callback.
 *
 * Adds an alarm to trigger at the specified time.  The @alarm_fn will be called
 * with the provided data and the alarm will be removed from the trigger list.
 *
 * Return value: An identifier for this alarm; it can be used to remove the
 * alarm later with alarm_remove().  If the trigger time occurs in the past, then
 * the alarm will not be queued and the function will return NULL.
 **/
gpointer
alarm_add (time_t trigger, AlarmFunction alarm_fn, gpointer data,
       AlarmDestroyNotify destroy_notify_fn)
{
    time_t now;
    AlarmRecord *ar;

    g_return_val_if_fail (alarm_inited, NULL);
    g_return_val_if_fail (trigger != -1, NULL);
    g_return_val_if_fail (alarm_fn != NULL, NULL);

    now = time (NULL);
    if (trigger < now)
        return NULL;

    ar = g_new (AlarmRecord, 1);
    ar->trigger = trigger;
    ar->alarm_fn = alarm_fn;
    ar->data = data;
    ar->destroy_notify_fn = destroy_notify_fn;

    g_print ("alarm_add(): Adding alarm for %s\n", ctime (&trigger));

    if (!queue_alarm (now, ar)) {
        g_free (ar);
        ar = NULL;
    }

    return ar;
}

/**
 * alarm_remove:
 * @alarm: A queued alarm identifier.
 * 
 * Removes an alarm from the alarm queue.
 **/
void
alarm_remove (gpointer alarm)
{
    AlarmRecord *ar;
    AlarmRecord *old_head;
    GList *l;

    g_return_if_fail (alarm_inited);
    g_return_if_fail (alarm != NULL);

    ar = alarm;

    l = g_list_find (alarms, ar);
    if (!l) {
        g_message ("alarm_remove(): Requested removal of nonexistent alarm!");
        return;
    }

    old_head = alarms->data;

    if (old_head == ar)
        pop_alarm ();
    else {
        alarms = g_list_remove_link (alarms, l);
        g_list_free_1 (l);
    }

    if (ar->destroy_notify_fn)
        (* ar->destroy_notify_fn) (ar, ar->data);

    g_free (ar);
}

/**
 * alarm_init:
 *
 * Initializes the alarm timer mechanism.  This must be called near the
 * beginning of the program.
 **/
void
alarm_init (void)
{
    struct sigaction sa;
    int flags;

    g_return_if_fail (alarm_inited == FALSE);

    pipe (alarm_pipes);

    /* set non blocking mode */
    flags = 0;
    fcntl (alarm_pipes [0], F_GETFL, &flags);
    fcntl (alarm_pipes [0], F_SETFL, flags | O_NONBLOCK);
    gdk_input_add (alarm_pipes [0], GDK_INPUT_READ, alarm_ready, NULL);

    /* Setup the signal handler */
    sa.sa_handler = alarm_signal;
    sigemptyset (&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    sigaction (SIGALRM, &sa, NULL);

    alarm_inited = TRUE;
}

/**
 * alarm_done:
 * 
 * Terminates the alarm timer mechanism.  This should be called at the end of
 * the program.
 **/
void
alarm_done (void)
{
    GList *l;

    g_return_if_fail (alarm_inited);

    if (!clear_itimer ())
        g_message ("alarm_done(): Could not clear the timer!  "
               "Weird things may happen.");

    for (l = alarms; l; l = l->next) {
        AlarmRecord *ar;

        ar = l->data;

        if (ar->destroy_notify_fn)
            (* ar->destroy_notify_fn) (ar, ar->data);

        g_free (ar);
    }

    g_list_free (alarms);
    alarms = NULL;

    if (close (alarm_pipes[0]) != 0)
        g_message ("alarm_done(): Could not close the input pipe for notification");

    alarm_pipes[0] = -1;

    if (close (alarm_pipes[1]) != 0)
        g_message ("alarm_done(): Could not close the output pipe for notification");

    alarm_pipes[1] = -1;

    alarm_inited = FALSE;
}