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 getdate, 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 getdate ();
  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   now = time ((time_t *) NULL);
 128
 129   for (ep = events; ep < events + num_events; ep++)
 130     /* Are any events ready to fire?  */
 131     if (ep->reply_at <= now)
 132       {
 133         fputs (ep->token, stdout);
 134         putc ('\n', stdout);
 135         fflush (stdout);
 136         free (ep->token);
 137
 138         /* We now have a hole in the event array; fill it with the last
 139            event.  */
 140         ep->token = events[num_events].token;
 141         ep->reply_at = events[num_events].reply_at;
 142         num_events--;
 143
 144         /* We ought to scan this event again.  */
 145         ep--;
 146       }
 147     else
 148       {
 149         /* next timeout should be the soonest of any remaining */
 150         if ((tdiff = ep->reply_at - now) < waitfor || waitfor < 0)
 151           waitfor = (long)tdiff;
 152       }
 153
 154   /* If there are no more events, we needn't bother setting an alarm.  */
 155   if (num_events > 0)
 156     alarm (waitfor);
 157 }
 158
 159 void
 160 getevent ()
 161 {
 162   int i;
 163   char *buf;
 164   int buf_size;
 165
 166   /* In principle the itimer should be disabled on entry to this
 167      function, but it really doesn't make any important difference
 168      if it isn't.  */
 169
 170   buf_size = 80;
 171   buf = (char *) malloc (buf_size);
 172
 173   /* Read a line from standard input, expanding buf if it is too short
 174      to hold the line.  */
 175   for (i = 0; ; i++)
 176     {
 177       int c;
 178
 179       if (i >= buf_size)
 180         {
 181           buf_size *= 2;
 182           buf = (char *) realloc (buf, buf_size);
 183
 184           /* If we're out of memory, toss this event.  */
 185           do
 186             {
 187               c = getchar ();
 188             }
 189           while (c != '\n' && c != EOF);
 190
 191           return;
 192         }
 193
 194       c = getchar ();
 195
 196       if (c == EOF)
 197         exit (0);
 198
 199       if (c == '\n')
 200         {
 201           buf[i] = '\0';
 202           break;
 203         }
 204
 205       buf[i] = c;
 206     }
 207
 208   /* Register the event.  */
 209   schedule (buf);
 210   free (buf);
 211
 212   /* Who knows what this interrupted, or if it said "now"? */
 213   notify ();
 214 }
 215
 216 SIGTYPE
 217 sigcatch (sig)
 218      int sig;
 219 /* dispatch on incoming signal, then restore it */
 220 {
 221   struct event *ep;
 222
 223   switch (sig)
 224     {
 225     case SIGALRM:
 226       notify ();
 227       break;
 228     case SIGIO:
 229       getevent ();
 230       break;
 231     case SIGTERM:
 232       fprintf (stderr, "Events still queued:\n");
 233       for (ep = events; ep < events + num_events; ep++)
 234         fprintf (stderr, "%d = %ld @ %s\n",
 235                  ep - events, ep->reply_at, ep->token);
 236       exit (0);
 237       break;
 238     }
 239
 240   /* required on older UNIXes; harmless on newer ones */
 241   signal (sig, sigcatch);
 242 }
 243
 244 /*ARGSUSED*/
 245 int
 246 main (argc, argv)
 247      int argc;
 248      char **argv;
 249 {
 250   for (pname = argv[0] + strlen (argv[0]);
 251        *pname != '/' && pname != argv[0];
 252        pname--);
 253   if (*pname == '/')
 254     pname++;
 255
 256   events_size = 16;
 257   events = ((struct event *) malloc (events_size * sizeof (*events)));
 258   num_events = 0;
 259
 260   signal (SIGIO, sigcatch);
 261   signal (SIGALRM, sigcatch);
 262   signal (SIGTERM, sigcatch);
 263
 264 #ifndef USG
 265   if (fcntl (0, F_SETOWN, getpid ()) == -1)
 266     {
 267       fprintf (stderr, "%s: can't set ownership of stdin\n", pname);
 268       fprintf (stderr, "%s\n", sys_errlist[errno]);
 269       exit (1);
 270     }
 271   if (fcntl (0, F_SETFL, fcntl (0, F_GETFL, 0) | FASYNC) == -1)
 272     {
 273       fprintf (stderr, "%s: can't request asynchronous I/O on stdin\n", pname);
 274       fprintf (stderr, "%s\n", sys_errlist[errno]);
 275       exit (1);
 276     }
 277 #endif /* USG */
 278
 279   while (1) pause ();
 280 }
 281
 282 /* timer.c ends here */