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     if (a->fn < b->fn)
  45         return -1;
  46     else if (a->fn > b->fn)
  47         return +1;
  48
  49     if (a->ctx < b->ctx)
  50         return -1;
  51     else if (a->ctx > b->ctx)
  52         return +1;
  53
  54     /*
  55      * Failing _that_, the two entries genuinely are equal, and we
  56      * never have a need to store them separately in the tree.
  57      */
  58     return 0;
  59 }
  60
  61 static int compare_timer_contexts(void *av, void *bv)
  62 {
  63     char *a = (char *)av;
  64     char *b = (char *)bv;
  65     if (a < b)
  66         return -1;
  67     else if (a > b)
  68         return +1;
  69     return 0;
  70 }
  71
  72 static void init_timers(void)
  73 {
  74     if (!timers) {
  75         timers = newtree234(compare_timers);
  76         timer_contexts = newtree234(compare_timer_contexts);
  77         now = GETTICKCOUNT();
  78     }
  79 }
  80
  81 long schedule_timer(int ticks, timer_fn_t fn, void *ctx)
  82 {
  83     long when;
  84     struct timer *t, *first;
  85
  86     init_timers();
  87
  88     when = ticks + GETTICKCOUNT();
  89     assert(when - now > 0);
  90
  91     t = snew(struct timer);
  92     t->fn = fn;
  93     t->ctx = ctx;
  94     t->now = when;
  95
  96     if (t != add234(timers, t)) {
  97         sfree(t);                      /* identical timer already exists */
  98     } else {
  99         add234(timer_contexts, t->ctx);/* don't care if this fails */
 100     }
 101
 102     first = (struct timer *)index234(timers, 0);
 103     if (first == t) {
 104         /*
 105          * This timer is the very first on the list, so we must
 106          * notify the front end.
 107          */
 108         timer_change_notify(first->now);
 109     }
 110
 111     return when;
 112 }
 113
 114 /*
 115  * Call to run any timers whose time has reached the present.
 116  * Returns the time (in ticks) expected until the next timer after
 117  * that triggers.
 118  */
 119 int run_timers(long anow, long *next)
 120 {
 121     struct timer *first;
 122
 123     init_timers();
 124
 125     now = anow;
 126
 127     while (1) {
 128         first = (struct timer *)index234(timers, 0);
 129
 130         if (!first)
 131             return FALSE;              /* no timers remaining */
 132
 133         if (find234(timer_contexts, first->ctx, NULL) == NULL) {
 134             /*
 135              * This timer belongs to a context that has been
 136              * expired. Delete it without running.
 137              */
 138             delpos234(timers, 0);
 139             sfree(first);
 140         } else if (first->now - now <= 0) {
 141             /*
 142              * This timer is active and has reached its running
 143              * time. Run it.
 144              */
 145             delpos234(timers, 0);
 146             first->fn(first->ctx, first->now);
 147             sfree(first);
 148         } else {
 149             /*
 150              * This is the first still-active timer that is in the
 151              * future. Return how long it has yet to go.
 152              */
 153             *next = first->now;
 154             return TRUE;
 155         }
 156     }
 157 }
 158
 159 /*
 160  * Call to expire all timers associated with a given context.
 161  */
 162 void expire_timer_context(void *ctx)
 163 {
 164     init_timers();
 165
 166     /*
 167      * We don't bother to check the return value; if the context
 168      * already wasn't in the tree (presumably because no timers
 169      * ever actually got scheduled for it) then that's fine and we
 170      * simply don't need to do anything.
 171      */
 172     del234(timer_contexts, ctx);
 173 }