Move one voting schedule fn into networkstatus.c

The 'voting_schdule_get_start_of_next_interval' function isn't
actually dirauth-specific.

2 files changed, 47 insertions, 0 deletions

diff --git a/src/feature/nodelist/networkstatus.c b/src/feature/nodelist/networkstatus.c
index d7864fa38a..6755de1a81 100644
--- a/src/feature/nodelist/networkstatus.c
+++ b/src/feature/nodelist/networkstatus.c
@@ -2765,3 +2765,47 @@ networkstatus_free_all(void)
     }
   }
 }
+
+/** Return the start of the next interval of size <b>interval</b> (in
+ * seconds) after <b>now</b>, plus <b>offset</b>. Midnight always
+ * starts a fresh interval, and if the last interval of a day would be
+ * truncated to less than half its size, it is rolled into the
+ * previous interval. */
+time_t
+voting_schedule_get_start_of_next_interval(time_t now, int interval,
+                                           int offset)
+{
+  struct tm tm;
+  time_t midnight_today=0;
+  time_t midnight_tomorrow;
+  time_t next;
+
+  tor_gmtime_r(&now, &tm);
+  tm.tm_hour = 0;
+  tm.tm_min = 0;
+  tm.tm_sec = 0;
+
+  if (tor_timegm(&tm, &midnight_today) < 0) {
+    // LCOV_EXCL_START
+    log_warn(LD_BUG, "Ran into an invalid time when trying to find midnight.");
+    // LCOV_EXCL_STOP
+  }
+  midnight_tomorrow = midnight_today + (24*60*60);
+
+  next = midnight_today + ((now-midnight_today)/interval + 1)*interval;
+
+  /* Intervals never cross midnight. */
+  if (next > midnight_tomorrow)
+    next = midnight_tomorrow;
+
+  /* If the interval would only last half as long as it's supposed to, then
+   * skip over to the next day. */
+  if (next + interval/2 > midnight_tomorrow)
+    next = midnight_tomorrow;
+
+  next += offset;
+  if (next - interval > now)
+    next -= interval;
+
+  return next;
+}
diff --git a/src/feature/nodelist/networkstatus.h b/src/feature/nodelist/networkstatus.h
index 5e8c8a9e57..c376bdd371 100644
--- a/src/feature/nodelist/networkstatus.h
+++ b/src/feature/nodelist/networkstatus.h
@@ -153,6 +153,9 @@ void vote_routerstatus_free_(vote_routerstatus_t *rs);
 void set_routerstatus_from_routerinfo(routerstatus_t *rs,
                                       const node_t *node,
                                       const routerinfo_t *ri);
+time_t voting_schedule_get_start_of_next_interval(time_t now,
+                                                  int interval,
+                                                  int offset);
 
 #ifdef NETWORKSTATUS_PRIVATE
 #ifdef TOR_UNIT_TESTS