fix: feat: implement the command SAdd (OpenAtomFoundation#106)

* bug fix:sadd

* format

* fix: only the increased size is returned

fix:only the increased size is returned

src/cmd_set.cc

@@ -39,6 +39,8 @@ bool SAddCmd::DoInitial(PClient* client) {
   client->SetKey(client->argv_[1]);
   return true;
 }
+// Integer reply: the number of elements that were added to the set,
+// not including all the elements already present in the set.
 void SAddCmd::DoCmd(PClient* client) {
   PObject* value = nullptr;
   PError err = PSTORE.GetValueByType(client->Key(), value, kPTypeSet);
@@ -51,11 +53,11 @@ void SAddCmd::DoCmd(PClient* client) {
     }
   }
   auto set = value->CastSet();
-  auto resPair = set->emplace(client->argv_[2]);
-  if (resPair.second) {
-    client->AppendInteger(1);
-  } else {
-    client->AppendInteger(0);
+  const auto oldSize = set->size();
+  for (int i = 2; i < client->argv_.size(); ++i) {
+    set->insert(client->argv_[i]);
   }
+  // new size is bigger than old size , avoid the risk
+  client->AppendInteger(set->size() - oldSize);
 }
 }  // namespace pikiwidb