Refactor gnc-features.

* type aliases to gnc-features.h
* string_views to avoid copying (all of the strings are static)
* qof_book_get_unknown_features returns a FeatureSet

libgnucash/engine/gnc-features.cpp

@@ -69,7 +69,7 @@ gchar *gnc_features_test_unknown (QofBook *book)
     if (unknowns.empty())
         return nullptr;
 
-    auto accum = [](const auto& a, const auto& b){ return a + "\n* " + b; };
+    auto accum = [](const auto& a, const auto& b){ return a + "\n* " + b.second.data(); };
     auto msg {std::accumulate (unknowns.begin(), unknowns.end(),
                                    std::string (_(header)), accum)};
     return g_strdup (msg.c_str());
@@ -88,7 +88,7 @@ void gnc_features_set_used (QofBook *book, const gchar *feature)
         return;
     }
 
-    qof_book_set_feature (book, feature, iter->second.c_str());
+    qof_book_set_feature (book, feature, iter->second.data());
 }
 
 

libgnucash/engine/gnc-features.h

@@ -36,9 +36,15 @@
 #ifndef GNC_FEATURES_H
 #define GNC_FEATURES_H
 
-#include "qof.h"
-
 #ifdef __cplusplus
+#include <string_view>
+#include <unordered_map>
+#include <vector>
+
+using Feature = std::pair<std::string_view, std::string_view>;
+using FeaturesTable = std::unordered_map<std::string_view, std::string_view>;
+using FeatureSet = std::vector<Feature>;
+
 extern "C" {
 #endif
 

libgnucash/engine/qofbook.cpp

@@ -1267,14 +1267,14 @@ qof_book_set_feature (QofBook *book, const gchar *key, const gchar *descr)
     }
 }
 
-std::vector<std::string>
+FeatureSet
 qof_book_get_unknown_features (QofBook *book, const FeaturesTable& features)
 {
-    std::vector<std::string> rv;
+    FeatureSet rv;
     auto test_feature = [&](const KvpFrameImpl::map_type::value_type& feature)
     {
         if (features.find (feature.first) == features.end ())
-            rv.push_back (feature.second->get<const char*>());
+            rv.emplace_back (feature.first, feature.second->get<const char*>());
     };
     auto frame = qof_instance_get_slots (QOF_INSTANCE (book));
     auto slot = frame->get_slot({GNC_FEATURES});

libgnucash/engine/qofbook.hpp

@@ -26,10 +26,9 @@
 #include <string>
 
 #include "qof.h"
+#include "gnc-features.h"
 
-using FeaturesTable = std::unordered_map<std::string,std::string>;
-
-std::vector<std::string>
+FeatureSet
 qof_book_get_unknown_features (QofBook *book, const FeaturesTable& features);
 bool qof_book_test_feature (QofBook*, const char*);