git.distorted.org.uk Git - u/mdw/putty/blob - timing.c

   1 /*
   2  * timing.c
   3  *
   4  * This module tracks any timers set up by schedule_timer(). It
   5  * keeps all the currently active timers in a list; it informs the
   6  * front end of when the next timer is due to go off if that
   7  * changes; and, very importantly, it tracks the context pointers
   8  * passed to schedule_timer(), so that if a context is freed all
   9  * the timers associated with it can be immediately annulled.
  10  */
  11
  12 #include <assert.h>
  13 #include <stdio.h>
  14
  15 #include "putty.h"
  16 #include "tree234.h"
  17
  18 struct timer {
  19     timer_fn_t fn;
  20     void *ctx;
  21     long now;
  22 };
  23
  24 static tree234 *timers = NULL;
  25 static tree234 *timer_contexts = NULL;
  26 static long now = 0L;
  27
  28 static int compare_timers(void *av, void *bv)
  29 {
  30     struct timer *a = (struct timer *)av;
  31     struct timer *b = (struct timer *)bv;
  32     long at = a->now - now;
  33     long bt = b->now - now;
  34
  35     if (at < bt)
  36         return -1;
  37     else if (at > bt)
  38         return +1;
  39
  40     /*
  41      * Failing that, compare on the other two fields, just so that
  42      * we don't get unwanted equality.
  43      */
  44 #ifdef __LCC__
  45     /* lcc won't let us compare function pointers. Legal, but annoying. */
  46     {
  47         int c = memcmp(&a->fn, &b->fn, sizeof(a->fn));
  48         if (c < 0)
  49             return -1;
  50         else if (c > 0)
  51             return +1;
  52     }
  53 #else
  54     if (a->fn < b->fn)
  55         return -1;
  56     else if (a->fn > b->fn)
  57         return +1;
  58 #endif
  59
  60     if (a->ctx < b->ctx)
  61         return -1;
  62     else if (a->ctx > b->ctx)
  63         return +1;
  64
  65     /*
  66      * Failing _that_, the two entries genuinely are equal, and we
  67      * never have a need to store them separately in the tree.
  68      */
  69     return 0;
  70 }
  71
  72 static int compare_timer_contexts(void *av, void *bv)
  73 {
  74     char *a = (char *)av;
  75     char *b = (char *)bv;
  76     if (a < b)
  77         return -1;
  78     else if (a > b)
  79         return +1;
  80     return 0;
  81 }
  82
  83 static void init_timers(void)
  84 {
  85     if (!timers) {
  86         timers = newtree234(compare_timers);
  87         timer_contexts = newtree234(compare_timer_contexts);
  88         now = GETTICKCOUNT();
  89     }
  90 }
  91
  92 long schedule_timer(int ticks, timer_fn_t fn, void *ctx)
  93 {
  94     long when;
  95     struct timer *t, *first;
  96
  97     init_timers();
  98
  99     when = ticks + GETTICKCOUNT();
 100     assert(when - now > 0);
 101
 102     t = snew(struct timer);
 103     t->fn = fn;
 104     t->ctx = ctx;
 105     t->now = when;
 106
 107     if (t != add234(timers, t)) {
 108         sfree(t);                      /* identical timer already exists */
 109     } else {
 110         add234(timer_contexts, t->ctx);/* don't care if this fails */
 111     }
 112
 113     first = (struct timer *)index234(timers, 0);
 114     if (first == t) {
 115         /*
 116          * This timer is the very first on the list, so we must
 117          * notify the front end.
 118          */
 119         timer_change_notify(first->now);
 120     }
 121
 122     return when;
 123 }
 124
 125 /*
 126  * Call to run any timers whose time has reached the present.
 127  * Returns the time (in ticks) expected until the next timer after
 128  * that triggers.
 129  */
 130 int run_timers(long anow, long *next)
 131 {
 132     struct timer *first;
 133
 134     init_timers();
 135
 136     now = anow;
 137
 138     while (1) {
 139         first = (struct timer *)index234(timers, 0);
 140
 141         if (!first)
 142             return FALSE;              /* no timers remaining */
 143
 144         if (find234(timer_contexts, first->ctx, NULL) == NULL) {
 145             /*
 146              * This timer belongs to a context that has been
 147              * expired. Delete it without running.
 148              */
 149             delpos234(timers, 0);
 150             sfree(first);
 151         } else if (first->now - now <= 0) {
 152             /*
 153              * This timer is active and has reached its running
 154              * time. Run it.
 155              */
 156             delpos234(timers, 0);
 157             first->fn(first->ctx, first->now);
 158             sfree(first);
 159         } else {
 160             /*
 161              * This is the first still-active timer that is in the
 162              * future. Return how long it has yet to go.
 163              */
 164             *next = first->now;
 165             return TRUE;
 166         }
 167     }
 168 }
 169
 170 /*
 171  * Call to expire all timers associated with a given context.
 172  */
 173 void expire_timer_context(void *ctx)
 174 {
 175     init_timers();
 176
 177     /*
 178      * We don't bother to check the return value; if the context
 179      * already wasn't in the tree (presumably because no timers
 180      * ever actually got scheduled for it) then that's fine and we
 181      * simply don't need to do anything.
 182      */
 183     del234(timer_contexts, ctx);
 184 }