Add InTransaction(), fix param storage

request.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <functional>
 #include <mutex>
 #include <unordered_map>
 
@@ -22,7 +23,7 @@ class Request {
 	void AddParam(const std::string_view& key, const std::string_view& value);
 	void SetBody(const std::string_view& in);
 
-	const std::string_view& GetParam(const std::string& key);
+	const std::string_view& GetParam(const std::string_view& key);
 	const std::string_view& GetBody();
 
 	void WriteHeader(const std::string_view& name, const std::string_view& value);
@@ -33,6 +34,9 @@ class Request {
 	template<typename...Args>
 	void WriteBody(const std::string_view& first, Args... more);
 
+	template<typename T>
+	T InTransaction(const std::function<T()>& callback);
+
   private:
 	Header OutputHeader();
 	iovec OutputVec();
@@ -55,4 +59,10 @@ void Request::WriteBody(const std::string_view& first, Args... more) {
 	WriteBody(more...);
 }
 
+template<typename T>
+T Request::InTransaction(const std::function<T()>& callback) {
+	std::lock_guard<std::recursive_mutex> l(output_mu_);
+	return callback();
+}
+
 } // namespace firecgi