MT#62181 RegisterCache: add entries_by_time

Add an ordered set of all AorEntry objects, ordered by expire time.
Amend modifier methods to update the set whenever some expire time is
updated or an entry or binding removed.

Change-Id: I2afe5becfa2124dbc8c33b38fe1a3e6d4b8a20d5

apps/sbc/RegisterCache.h

@@ -183,6 +183,22 @@ public:
   void dump_elmt(const string& alias, const AliasEntry& ae) const;
 };
 
+template<> struct std::less<unordered_map<string, AorEntry>::iterator>
+{
+  bool operator()(const unordered_map<string, AorEntry>::iterator& a,
+      const unordered_map<string, AorEntry>::iterator& b) const
+  {
+    auto lowest_a = a->second.get_lowest_expire();
+    auto lowest_b = b->second.get_lowest_expire();
+    if (lowest_a < lowest_b)
+      return true;
+    if (lowest_a > lowest_b)
+      return false;
+    // for identical set we compare the pointer values of the original object
+    return &a->second < &b->second;
+  }
+};
+
 /**
  * AoR hash table:
  *   AoR -> AorEntry
@@ -190,13 +206,24 @@ public:
 class AorHash
   : public unordered_hash_map<string, AorEntry>
 {
+  set<iterator> entries_by_time;
+
 public:
   void set_expire(const iterator& aor_it, const AorEntry::iterator& binding_it, long int expire) {
+    entries_by_time.erase(aor_it);
     aor_it->second.set_expire(binding_it, expire);
+    entries_by_time.insert(aor_it);
   }
 
   void erase_binding(const iterator& aor_it, const AorEntry::iterator& binding_it) {
+    entries_by_time.erase(aor_it);
     aor_it->second.erase(binding_it);
+    entries_by_time.insert(aor_it);
+  }
+
+  void erase(const iterator& aor_it) {
+    entries_by_time.erase(aor_it);
+    unordered_hash_map<string, AorEntry>::erase(aor_it);
   }
 
   /* Maintenance stuff */