json: string_view without char* as intermediate step

Enables reuse of already available string length info

Author: mmd-osm

include/cgimap/json_writer.hpp

@@ -34,7 +34,6 @@ class json_writer : public output_writer {
   ~json_writer() noexcept override;
 
   void start_object();
-  void object_key(const char* s);
   void object_key(std::string_view sv);
   void end_object();
 
@@ -49,8 +48,14 @@ class json_writer : public output_writer {
     yajl_gen_integer(gen, i);
   }
 
-  void entry(const char* s);
-  void entry(std::string_view sv);
+  template <typename T,
+            std::enable_if_t<std::is_convertible_v<T&&, std::string_view>,
+                             bool> = true>
+  void entry(T&& s)
+  {
+    auto sv = std::string_view(s);
+    yajl_gen_string(gen, (const unsigned char *)sv.data(), sv.size());
+  }
 
   template <typename TKey, typename TValue>
   void property(TKey&& key, TValue&& val) {

include/cgimap/output_formatter.hpp

@@ -40,7 +40,8 @@ enum class action_type {
 
 namespace {
 
-const char* element_type_name(element_type elt) {
+template <typename T = const char *>
+T element_type_name(element_type elt) noexcept {
 
   switch (elt) {
   case element_type::node:

src/json_formatter.cpp

@@ -157,7 +157,7 @@ void json_formatter::write_relation(const element_info &elem,
       writer->start_array();
       for (const auto & member : members) {
 	  writer->start_object();
-	  writer->property("type", element_type_name(member.type));
+	  writer->property("type", element_type_name<std::string_view>(member.type));
 	  writer->property("ref",  member.ref);
 	  writer->property("role", member.role);
 	  writer->end_object();

src/json_writer.cpp

@@ -63,10 +63,6 @@ void json_writer::start_object() {
   yajl_gen_map_open(gen);
 }
 
-void json_writer::object_key(const char* s) {
-  entry(s);
-}
-
 void json_writer::object_key(std::string_view sv) {
   entry(sv);
 }
@@ -102,14 +98,6 @@ void json_writer::entry(double d) {
   yajl_gen_number(gen, str, len);
 }
 
-void json_writer::entry(const char* s) {
-  entry(std::string_view(s));
-}
-
-void json_writer::entry(std::string_view sv) {
-  yajl_gen_string(gen, (const unsigned char *)sv.data(), sv.size());
-}
-
 void json_writer::start_array() {
   yajl_gen_array_open(gen);
 }