diff options
Diffstat (limited to 'tools/plink/timing.c')
| -rw-r--r-- | tools/plink/timing.c | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/tools/plink/timing.c b/tools/plink/timing.c new file mode 100644 index 000000000..2b7b70cb9 --- /dev/null +++ b/tools/plink/timing.c @@ -0,0 +1,243 @@ +/*
+ * 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);
+}
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