More descriptive event data

src/event.rs

@@ -12,26 +12,30 @@
 /// Though processing power varies across nodes, the network gives priority to the
 /// fastest processor. Duration should therefore be estimated by assuming that the hash
 /// was generated by the fastest processor at the time the entry was logged.
-///
-/// When 'data' is None, the event represents a simple "tick", and exists for the
+pub struct Event {
+    pub num_hashes: u64,
+    pub end_hash: u64,
+    pub data: EventData,
+}
+
+/// When 'data' is Tick, the event represents a simple "tick", and exists for the
 /// sole purpose of improving the performance of event log verification. A tick can
 /// be generated in 'num_hashes' hashes and verified in 'num_hashes' hashes.  By logging a hash alongside
 /// the tick, each tick and be verified in parallel using the 'end_hash' of the preceding
 /// tick to seed its hashing.
-pub struct Event {
-    pub end_hash: u64,
-    pub num_hashes: u64,
-    pub data: Option<u64>,
+pub enum EventData {
+    Tick,
+    UserDataKey(u64),
 }
 
 impl Event {
     /// Creates an Event from the number of hashes 'num_hashes' since the previous event
     /// and that resulting 'end_hash'.
-    pub fn new(end_hash: u64, num_hashes: u64) -> Self {
-        let data = None;
+    pub fn new(num_hashes: u64, end_hash: u64) -> Self {
+        let data = EventData::Tick;
         Event {
-            end_hash,
             num_hashes,
+            end_hash,
             data,
         }
     }
@@ -51,7 +55,7 @@ impl Event {
             hash.hash(&mut hasher);
             hash = hasher.finish();
         }
-        Self::new(hash, num_hashes)
+        Self::new(num_hashes, hash)
     }
     /// Verifies self.end_hash is the result of hashing a 'start_hash' 'self.num_hashes' times.
     ///