1 files changed, 126 insertions, 0 deletions
diff --git a/src/or/periodic.c b/src/or/periodic.c
new file mode 100644
index 0000000000..057fcf672e
--- /dev/null
+++ b/src/or/periodic.c
@@ -0,0 +1,126 @@
+/* Copyright (c) 2015-2016, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file periodic.c
+ *
+ * \brief Generic backend for handling periodic events.
+ */
+
+#include "or.h"
+#include "compat_libevent.h"
+#include "config.h"
+#include "periodic.h"
+
+#ifdef HAVE_EVENT2_EVENT_H
+#include <event2/event.h>
+#else
+#include <event.h>
+#endif
+
+/** We disable any interval greater than this number of seconds, on the
+ * grounds that it is probably an absolute time mistakenly passed in as a
+ * relative time.
+ */
+static const int MAX_INTERVAL = 10 * 365 * 86400;
+
+/** Set the event <b>event</b> to run in <b>next_interval</b> seconds from
+ * now. */
+static void
+periodic_event_set_interval(periodic_event_item_t *event,
+                            time_t next_interval)
+{
+  tor_assert(next_interval < MAX_INTERVAL);
+  struct timeval tv;
+  tv.tv_sec = next_interval;
+  tv.tv_usec = 0;
+  event_add(event->ev, &tv);
+}
+
+/** Wraps dispatches for periodic events, <b>data</b> will be a pointer to the
+ * event that needs to be called */
+static void
+periodic_event_dispatch(evutil_socket_t fd, short what, void *data)
+{
+  (void)fd;
+  (void)what;
+  periodic_event_item_t *event = data;
+
+  time_t now = time(NULL);
+  const or_options_t *options = get_options();
+//  log_debug(LD_GENERAL, "Dispatching %s", event->name);
+  int r = event->fn(now, options);
+  int next_interval = 0;
+
+  /* update the last run time if action was taken */
+  if (r==0) {
+    log_err(LD_BUG, "Invalid return value for periodic event from %s.",
+                      event->name);
+    tor_assert(r != 0);
+  } else if (r > 0) {
+    event->last_action_time = now;
+    /* If the event is meant to happen after ten years, that's likely
+     * a bug, and somebody gave an absolute time rather than an interval.
+     */
+    tor_assert(r < MAX_INTERVAL);
+    next_interval = r;
+  } else {
+    /* no action was taken, it is likely a precondition failed,
+     * we should reschedule for next second incase the precondition
+     * passes then */
+    next_interval = 1;
+  }
+
+//  log_debug(LD_GENERAL, "Scheduling %s for %d seconds", event->name,
+//           next_interval);
+  struct timeval tv = { next_interval , 0 };
+  event_add(event->ev, &tv);
+}
+
+/** Schedules <b>event</b> to run as soon as possible from now. */
+void
+periodic_event_reschedule(periodic_event_item_t *event)
+{
+  periodic_event_set_interval(event, 1);
+}
+
+/** Initializes the libevent backend for a periodic event. */
+void
+periodic_event_setup(periodic_event_item_t *event)
+{
+  if (event->ev) { /* Already setup? This is a bug */
+    log_err(LD_BUG, "Initial dispatch should only be done once.");
+    tor_assert(0);
+  }
+
+  event->ev = tor_event_new(tor_libevent_get_base(),
+                            -1, 0,
+                            periodic_event_dispatch,
+                            event);
+  tor_assert(event->ev);
+}
+
+/** Handles initial dispatch for periodic events. It should happen 1 second
+ * after the events are created to mimic behaviour before #3199's refactor */
+void
+periodic_event_launch(periodic_event_item_t *event)
+{
+  if (! event->ev) { /* Not setup? This is a bug */
+    log_err(LD_BUG, "periodic_event_launch without periodic_event_setup");
+    tor_assert(0);
+  }
+
+  // Initial dispatch
+  periodic_event_dispatch(-1, EV_TIMEOUT, event);
+}
+
+/** Release all storage associated with <b>event</b> */
+void
+periodic_event_destroy(periodic_event_item_t *event)
+{
+  if (!event)
+    return;
+  tor_event_free(event->ev);
+  event->last_action_time = 0;
+}
+