lib-src/timer.c

   1 /* timer.c --- daemon to provide a tagged interval timer service
   2
   3    This little daemon runs forever waiting for signals.  SIGIO (or
   4    SIGUSR1) causes it to read an event spec from stdin; that is, a
   5    date followed by colon followed by an event label.  SIGALRM causes
   6    it to check its queue for events attached to the current second; if
   7    one is found, its label is written to stdout.  SIGTERM causes it to
   8    terminate, printing a list of pending events.
   9
  10    This program is intended to be used with the lisp package called
  11    timer.el.  It was written anonymously in 1990.  This version was
  12    documented and rewritten for portability by esr@snark.thyrsus.com,
  13    Aug 7 1992.  */
  14
  15 #include <stdio.h>
  16 #include <signal.h>
  17 #include <fcntl.h>      /* FASYNC */
  18 #include <sys/types.h>  /* time_t */
  19
  20 #include "../src/config.h"
  21 #ifdef USG
  22 #undef SIGIO
  23 #define SIGIO   SIGUSR1
  24 #endif
  25
  26 extern int errno;
  27 extern char *sys_errlist[], *malloc ();
  28 extern time_t time ();
  29
  30 /*
  31  * The field separator for input.  This character shouldn't be legal in a date,
  32  * and should be printable so event strings are readable by people.  Was
  33  * originally ';', then got changed to bogus `\001'.
  34  */
  35 #define FS '@'
  36
  37 struct event
  38   {
  39     char *token;
  40     time_t reply_at;
  41   };
  42 int events_size;                /* How many slots have we allocated?  */
  43 int num_events;                 /* How many are actually scheduled?  */
  44 struct event *events;           /* events[0 .. num_events-1] are the
  45                                    valid events.  */
  46
  47 char *pname;      /* programme name for error messages */
  48
  49 /* Accepts a string of two fields seperated by FS.
  50    First field is string for get_date, saying when to wake-up.
  51    Second field is a token to identify the request.  */
  52 void
  53 schedule (str)
  54      char *str;
  55 {
  56   extern time_t get_date ();
  57   extern char *strcpy ();
  58   time_t now;
  59   register char *p;
  60   static struct event *ep;
  61
  62   /* check entry format */
  63   for (p = str; *p && *p != FS; p++)
  64     continue;
  65   if (!*p)
  66     {
  67       fprintf (stderr, "%s: bad input format: %s\n", pname, str);
  68       return;
  69     }
  70   *p++ = 0;
  71
  72   /* allocate an event slot */
  73   ep = events + num_events;
  74
  75   /* If the event array is full, stretch it.  After stretching, we know
  76      that ep will be pointing to an available event spot.  */
  77   if (ep == events + events_size)
  78     {
  79       int old_size = events_size;
  80
  81       events_size *= 2;
  82       events = ((struct event *)
  83                 realloc (events, events_size * sizeof (struct event)));
  84       if (! events)
  85         {
  86           fprintf (stderr, "%s: virtual memory exhausted.\n", pname);
  87
  88           /* Should timer exit now?  Well, we've still got other
  89              events in the queue, and more memory might become
  90              available in the future, so we'll just toss this event.
  91              This will screw up whoever scheduled the event, but
  92              maybe someone else will survive.  */
  93           return;
  94         }
  95
  96       while (old_size < events_size)
  97         events[old_size++].token = NULL;
  98     }
  99
 100   /* Don't allow users to schedule events in past time.  */
 101   ep->reply_at = get_date (str, NULL);
 102   if (ep->reply_at - time (&now) < 0)
 103     {
 104       fprintf (stderr, "%s: bad time spec: %s%c%s\n", pname, str, FS, p);
 105       return;
 106     }
 107
 108   /* save the event description */
 109   ep->token = (char *) malloc ((unsigned) strlen (p) + 1);
 110   if (! ep->token)
 111     {
 112       fprintf (stderr, "%s: malloc %s: %s%c%s\n",
 113                pname, sys_errlist[errno], str, FS, p);
 114       return;
 115     }
 116
 117   strcpy (ep->token, p);
 118   num_events++;
 119 }
 120
 121 void
 122 notify ()
 123 {
 124   time_t now, tdiff, waitfor = -1;
 125   register struct event *ep;
 126
 127   /* If an alarm timer runs out while this function is executing,
 128      it could get called recursively.  This would be bad, because
 129      it's not re-entrant.  So we must try to suspend the signal. */
 130 #ifdef sigmask
 131   sighold(SIGIO);
 132 #endif
 133
 134   now = time ((time_t *) NULL);
 135
 136   for (ep = events; ep < events + num_events; ep++)
 137     /* Are any events ready to fire?  */
 138     if (ep->reply_at <= now)
 139       {
 140         fputs (ep->token, stdout);
 141         putc ('\n', stdout);
 142         fflush (stdout);
 143         free (ep->token);
 144
 145         /* We now have a hole in the event array; fill it with the last
 146            event.  */
 147         ep->token = events[num_events - 1].token;
 148         ep->reply_at = events[num_events - 1].reply_at;
 149         num_events--;
 150
 151         /* We ought to scan this event again.  */
 152         ep--;
 153       }
 154     else
 155       {
 156         /* next timeout should be the soonest of any remaining */
 157         if ((tdiff = ep->reply_at - now) < waitfor || waitfor < 0)
 158           waitfor = (long)tdiff;
 159       }
 160
 161   /* If there are no more events, we needn't bother setting an alarm.  */
 162   if (num_events > 0)
 163     alarm (waitfor);
 164
 165 #ifdef sigmask
 166   sigrelse(SIGIO);
 167 #endif
 168 }
 169
 170 void
 171 getevent ()
 172 {
 173   int i;
 174   char *buf;
 175   int buf_size;
 176
 177   /* In principle the itimer should be disabled on entry to this
 178      function, but it really doesn't make any important difference
 179      if it isn't.  */
 180
 181   buf_size = 80;
 182   buf = (char *) malloc (buf_size);
 183
 184   /* Read a line from standard input, expanding buf if it is too short
 185      to hold the line.  */
 186   for (i = 0; ; i++)
 187     {
 188       int c;
 189
 190       if (i >= buf_size)
 191         {
 192           buf_size *= 2;
 193           buf = (char *) realloc (buf, buf_size);
 194
 195           /* If we're out of memory, toss this event.  */
 196           do
 197             {
 198               c = getchar ();
 199             }
 200           while (c != '\n' && c != EOF);
 201
 202           return;
 203         }
 204
 205       c = getchar ();
 206
 207       if (c == EOF)
 208         exit (0);
 209
 210       if (c == '\n')
 211         {
 212           buf[i] = '\0';
 213           break;
 214         }
 215
 216       buf[i] = c;
 217     }
 218
 219   /* Register the event.  */
 220   schedule (buf);
 221   free (buf);
 222
 223   /* Who knows what this interrupted, or if it said "now"? */
 224   notify ();
 225 }
 226
 227 SIGTYPE
 228 sigcatch (sig)
 229      int sig;
 230 /* dispatch on incoming signal, then restore it */
 231 {
 232   struct event *ep;
 233
 234   switch (sig)
 235     {
 236     case SIGALRM:
 237       notify ();
 238       break;
 239     case SIGIO:
 240       getevent ();
 241       break;
 242     case SIGTERM:
 243       fprintf (stderr, "Events still queued:\n");
 244       for (ep = events; ep < events + num_events; ep++)
 245         fprintf (stderr, "%d = %ld @ %s\n",
 246                  ep - events, ep->reply_at, ep->token);
 247       exit (0);
 248       break;
 249     }
 250
 251   /* required on older UNIXes; harmless on newer ones */
 252   signal (sig, sigcatch);
 253 }
 254
 255 /*ARGSUSED*/
 256 int
 257 main (argc, argv)
 258      int argc;
 259      char **argv;
 260 {
 261   for (pname = argv[0] + strlen (argv[0]);
 262        *pname != '/' && pname != argv[0];
 263        pname--);
 264   if (*pname == '/')
 265     pname++;
 266
 267   events_size = 16;
 268   events = ((struct event *) malloc (events_size * sizeof (*events)));
 269   num_events = 0;
 270
 271   signal (SIGIO, sigcatch);
 272   signal (SIGALRM, sigcatch);
 273   signal (SIGTERM, sigcatch);
 274
 275 #ifndef USG
 276   if (fcntl (0, F_SETOWN, getpid ()) == -1)
 277     {
 278       fprintf (stderr, "%s: can't set ownership of stdin\n", pname);
 279       fprintf (stderr, "%s\n", sys_errlist[errno]);
 280       exit (1);
 281     }
 282   if (fcntl (0, F_SETFL, fcntl (0, F_GETFL, 0) | FASYNC) == -1)
 283     {
 284       fprintf (stderr, "%s: can't request asynchronous I/O on stdin\n", pname);
 285       fprintf (stderr, "%s\n", sys_errlist[errno]);
 286       exit (1);
 287     }
 288 #endif /* USG */
 289
 290   for (;;)
 291       pause ();
 292 }
 293
 294 /* timer.c ends here */