Issue-108. Track recent packets in unordered_set

Check individual packets seen recently for expiry - and purge.
Otherwise - only scan all of recentPackets for expired once
fill > 75% (of MAX_NUM_NODES).

src/mesh/PacketHistory.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include "Router.h"
-#include <queue>
 #include <unordered_set>
 
 /// We clear our old flood record five minute after we see the last of it
@@ -24,37 +23,15 @@ class PacketRecordHashFunction
     size_t operator()(const PacketRecord &p) const { return (std::hash<NodeNum>()(p.sender)) ^ (std::hash<PacketId>()(p.id)); }
 };
 
-/// Order packet records by arrival time, we want the oldest packets to be in the front of our heap
-class PacketRecordOrderFunction
-{
-  public:
-    size_t operator()(const PacketRecord &p1, const PacketRecord &p2) const
-    {
-        // If the timer ticks have rolled over the difference between times will be _enormous_.  Handle that case specially
-        uint32_t t1 = p1.rxTimeMsec, t2 = p2.rxTimeMsec;
-
-        if (t1 - t2 > UINT32_MAX / 2) {
-            // time must have rolled over, swap them because the new little number is 'bigger' than the old big number
-            t1 = t2;
-            t2 = p1.rxTimeMsec;
-        }
-
-        return t1 > t2;
-    }
-};
-
 /**
  * This is a mixin that adds a record of past packets we have seen
  */
 class PacketHistory
 {
   private:
-    /** FIXME: really should be a std::unordered_set with the key being sender,id.
-     * This would make checking packets in wasSeenRecently faster.
-     */
-    std::vector<PacketRecord> recentPackets;
-    // priority_queue<PacketRecord, vector<PacketRecord>, PacketRecordOrderFunction> arrivalTimes;
-    // unordered_set<PacketRecord, PacketRecordHashFunction> recentPackets;
+    std::unordered_set<PacketRecord, PacketRecordHashFunction> recentPackets;
+
+    void clearExpiredRecentPackets(); // clear all recentPackets older than FLOOD_EXPIRE_TIME
 
   public:
     PacketHistory();