/* * timing.c * * This module tracks any timers set up by schedule_timer(). It * keeps all the currently active timers in a list; it informs the * front end of when the next timer is due to go off if that * changes; and, very importantly, it tracks the context pointers * passed to schedule_timer(), so that if a context is freed all * the timers associated with it can be immediately annulled. */ #include <assert.h> #include <stdio.h> #include "putty.h" #include "tree234.h" struct timer { timer_fn_t fn; void *ctx; long now; }; static tree234 *timers = NULL; static tree234 *timer_contexts = NULL; static long now = 0L; static int compare_timers(void *av, void *bv) { struct timer *a = (struct timer *)av; struct timer *b = (struct timer *)bv; long at = a->now - now; long bt = b->now - now; if (at < bt) return -1; else if (at > bt) return +1; /* * Failing that, compare on the other two fields, just so that * we don't get unwanted equality. */ #ifdef __LCC__ /* lcc won't let us compare function pointers. Legal, but annoying. */ { int c = memcmp(&a->fn, &b->fn, sizeof(a->fn)); if (c < 0) return -1; else if (c > 0) return +1; } #else if (a->fn < b->fn) return -1; else if (a->fn > b->fn) return +1; #endif if (a->ctx < b->ctx) return -1; else if (a->ctx > b->ctx) return +1; /* * Failing _that_, the two entries genuinely are equal, and we * never have a need to store them separately in the tree. */ return 0; } static int compare_timer_contexts(void *av, void *bv) { char *a = (char *)av; char *b = (char *)bv; if (a < b) return -1; else if (a > b) return +1; return 0; } static void init_timers(void) { if (!timers) { timers = newtree234(compare_timers); timer_contexts = newtree234(compare_timer_contexts); now = GETTICKCOUNT(); } } long schedule_timer(int ticks, timer_fn_t fn, void *ctx) { long when; struct timer *t, *first; init_timers(); when = ticks + GETTICKCOUNT(); /* * Just in case our various defences against timing skew fail * us: if we try to schedule a timer that's already in the * past, we instead schedule it for the immediate future. */ if (when - now <= 0) when = now + 1; t = snew(struct timer); t->fn = fn; t->ctx = ctx; t->now = when; if (t != add234(timers, t)) { sfree(t); /* identical timer already exists */ } else { add234(timer_contexts, t->ctx);/* don't care if this fails */ } first = (struct timer *)index234(timers, 0); if (first == t) { /* * This timer is the very first on the list, so we must * notify the front end. */ timer_change_notify(first->now); } return when; } /* * Call to run any timers whose time has reached the present. * Returns the time (in ticks) expected until the next timer after * that triggers. */ int run_timers(long anow, long *next) { struct timer *first; init_timers(); #ifdef TIMING_SYNC /* * In this ifdef I put some code which deals with the * possibility that `anow' disagrees with GETTICKCOUNT by a * significant margin. Our strategy for dealing with it differs * depending on platform, because on some platforms * GETTICKCOUNT is more likely to be right whereas on others * `anow' is a better gold standard. */ { long tnow = GETTICKCOUNT(); if (tnow + TICKSPERSEC/50 - anow < 0 || anow + TICKSPERSEC/50 - tnow < 0 ) { #if defined TIMING_SYNC_ANOW /* * If anow is accurate and the tick count is wrong, * this is likely to be because the tick count is * derived from the system clock which has changed (as * can occur on Unix). Therefore, we resolve this by * inventing an offset which is used to adjust all * future output from GETTICKCOUNT. * * A platform which defines TIMING_SYNC_ANOW is * expected to have also defined this offset variable * in (its platform-specific adjunct to) putty.h. * Therefore we can simply reference it here and assume * that it will exist. */ tickcount_offset += anow - tnow; #elif defined TIMING_SYNC_TICKCOUNT /* * If the tick count is more likely to be accurate, we * simply use that as our time value, which may mean we * run no timers in this call (because we got called * early), or alternatively it may mean we run lots of * timers in a hurry because we were called late. */ anow = tnow; #else /* * Any platform which defines TIMING_SYNC must also define one of the two * auxiliary symbols TIMING_SYNC_ANOW and TIMING_SYNC_TICKCOUNT, to * indicate which measurement to trust when the two disagree. */ #error TIMING_SYNC definition incomplete #endif } } #endif now = anow; while (1) { first = (struct timer *)index234(timers, 0); if (!first) return FALSE; /* no timers remaining */ if (find234(timer_contexts, first->ctx, NULL) == NULL) { /* * This timer belongs to a context that has been * expired. Delete it without running. */ delpos234(timers, 0); sfree(first); } else if (first->now - now <= 0) { /* * This timer is active and has reached its running * time. Run it. */ delpos234(timers, 0); first->fn(first->ctx, first->now); sfree(first); } else { /* * This is the first still-active timer that is in the * future. Return how long it has yet to go. */ *next = first->now; return TRUE; } } } /* * Call to expire all timers associated with a given context. */ void expire_timer_context(void *ctx) { init_timers(); /* * We don't bother to check the return value; if the context * already wasn't in the tree (presumably because no timers * ever actually got scheduled for it) then that's fine and we * simply don't need to do anything. */ del234(timer_contexts, ctx); }