Fix multiplication overflow bug.

The `snapshot_sync_day_factors` array is sorted
ascendingly, so find() will return on the first
iteration that is at least equal to the requested
interval.

However, the last value in the array is u64::max,
which means that multiplying it with DAY_SECONDS
will overflow. To avoid that, we use saturating_mul.

diff --git a/src/snapshot.rs b/src/snapshot.rs
index a27eafdfe0de702cb57db02048e1fd0d02a45532..65f6fad03823b56cedd249c2eff87e137dcc56b9 100644 (file)
--- a/src/snapshot.rs
+++ b/src/snapshot.rs
@@ -115,11 +115,27 @@ impl<L: Deref + Clone> Snapshotter<L> where L::Target: Logger {
                                        // special-case 0 to always refer to a full/initial sync
                                        u64::MAX
                                } else {
+                                       /*
+                                       We have snapshots for 6-day- and 7-day-intervals, but the next interval is
+                                       14 days. So if somebody requests an update with a timestamp that is 10 days old,
+                                       there is no longer a snapshot for that specific interval.
+
+                                       The correct snapshot will be the next highest interval, i. e. for 14 days.
+
+                                       The `snapshot_sync_day_factors` array is sorted ascendingly, so find() will
+                                       return on the first iteration that is at least equal to the requested interval.
+
+                                       Note, however, that the last value in the array is u64::max, which means that
+                                       multiplying it with DAY_SECONDS will overflow. To avoid that, we use
+                                       saturating_mul.
+                                        */
+
                                        // find min(x) in snapshot_sync_day_factors where x >= i
                                        snapshot_sync_day_factors.iter().find(|x| {
-                                               *x * DAY_SECONDS >= i * config::SNAPSHOT_CALCULATION_INTERVAL as u64
+                                               DAY_SECONDS.saturating_mul(**x) >= i * config::SNAPSHOT_CALCULATION_INTERVAL as u64
                                        }).unwrap().clone()
                                };
+                               log_info!(self.logger, "i: {}, referenced day range: {}", i, referenced_day_range);
 
                                let snapshot_filename = snapshot_filenames_by_day_range.get(&referenced_day_range).unwrap();
                                let relative_snapshot_path = format!("{}/{}", relative_symlink_to_snapshot_path, snapshot_filename);