[chip-tool] In interactive server mode when a response is sent over t…

…he wire it keeps creating new strings instead of concatening to the already existing strings (#27006)

examples/chip-tool/commands/interactive/InteractiveCommands.cpp

@@ -153,50 +153,56 @@ struct InteractiveServerResult
  {
  auto lock = ScopedLock(mMutex);
 
- std::string resultsStr;
+ std::stringstream content;
+ content << "{";
+
+ content << " \"results\": [";
  if (mResults.size())
  {
  for (const auto & result : mResults)
  {
- resultsStr = resultsStr + result + ",";
+ content << result << ",";
  }
 
  // Remove last comma.
- resultsStr.pop_back();
+ content.seekp(-1, std::ios_base::end);
  }
 
  if (mStatus != EXIT_SUCCESS)
  {
- if (resultsStr.size())
+ if (mResults.size())
  {
- resultsStr = resultsStr + ",";
+ content << ",";
  }
- resultsStr = resultsStr + "{ \"error\": \"FAILURE\" }";
+ content << "{ \"error\": \"FAILURE\" }";
  }
+ content << "],";
 
- std::string logsStr;
+ content << "\"logs\": [";
  if (mLogs.size())
  {
  for (const auto & log : mLogs)
  {
- logsStr = logsStr + "{";
- logsStr = logsStr + " \"module\": \"" + log.module + "\",";
- logsStr = logsStr + " \"category\": \"" + log.messageType + "\",";
- logsStr = logsStr + " \"message\": \"" + log.message + "\"";
- logsStr = logsStr + "},";
+ content << "{"
+ " \"module\": \"" +
+ log.module +
+ "\","
+ " \"category\": \"" +
+ log.messageType +
+ "\","
+ " \"message\": \"" +
+ log.message +
+ "\""
+ "},";
  }
 
  // Remove last comma.
- logsStr.pop_back();
+ content.seekp(-1, std::ios_base::end);
  }
+ content << "]";
 
- std::string jsonLog;
- jsonLog = jsonLog + "{";
- jsonLog = jsonLog + " \"results\": [" + resultsStr + "],";
- jsonLog = jsonLog + " \"logs\": [" + logsStr + "]";
- jsonLog = jsonLog + "}";
-
- return jsonLog;
+ content << "}";
+ return content.str();
  }
 };