New timing infrastructure. There's a new function schedule_timer()

[u/mdw/putty] / timing.c

diff --git a/timing.c b/timing.c
new file mode 100644 (file)
index 0000000..a87be89
--- /dev/null
+++ b/timing.c
@@ -0,0 +1,173 @@
+/*
+ * 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.
+     */
+    if (a->fn < b->fn)
+       return -1;
+    else if (a->fn > b->fn)
+       return +1;
+
+    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();
+    assert(when - now > 0);
+
+    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();
+
+    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);
+}