Cache UTF-16 strings on Windows during sorting

Converting between UTF-8 and UTF-16 is surprisingly slow, this improves
sorting performance by 16%.

src/api/helpers/text.cpp

@@ -182,11 +182,21 @@ std::string FromWinWide(const std::wstring& wstr) {
 
 int CompareFilenames(const std::string& lhs, const std::string& rhs) {
 #ifdef _WIN32
-  // On Windows, use CompareStringOrdinal as that will perform case conversion
+  return CompareFilenames(ToWinWide(lhs), ToWinWide(rhs));
+#else
+  auto unicodeLhs = icu::UnicodeString::fromUTF8(lhs);
+  auto unicodeRhs = icu::UnicodeString::fromUTF8(rhs);
+  return unicodeLhs.caseCompare(unicodeRhs, U_FOLD_CASE_DEFAULT);
+#endif
+}
+
+#ifdef _WIN32
+int CompareFilenames(const std::wstring& lhs, const std::wstring& rhs) {
+  // Use CompareStringOrdinal as that will perform case conversion
   // using the operating system uppercase table information, which (I think)
   // will give results that match the filesystem, and is not locale-dependent.
   int result = CompareStringOrdinal(
-      ToWinWide(lhs).c_str(), -1, ToWinWide(rhs).c_str(), -1, true);
+      lhs.c_str(), -1, rhs.c_str(), -1, true);
   switch (result) {
     case CSTR_LESS_THAN:
       return -1;
@@ -198,12 +208,8 @@ int CompareFilenames(const std::string& lhs, const std::string& rhs) {
       throw std::invalid_argument(
           "One of the filenames to compare was invalid.");
   }
-#else
-  auto unicodeLhs = icu::UnicodeString::fromUTF8(lhs);
-  auto unicodeRhs = icu::UnicodeString::fromUTF8(rhs);
-  return unicodeLhs.caseCompare(unicodeRhs, U_FOLD_CASE_DEFAULT);
-#endif
 }
+#endif
 
 std::string NormalizeFilename(const std::string& filename) {
 #ifdef _WIN32

src/api/helpers/text.h

@@ -46,6 +46,12 @@ std::optional<std::string> ExtractVersion(const std::string& text);
 // locale-invariant.
 int CompareFilenames(const std::string& lhs, const std::string& rhs);
 
+#ifdef _WIN32
+std::wstring ToWinWide(const std::string& str);
+
+int CompareFilenames(const std::wstring& lhs, const std::wstring& rhs);
+#endif
+
 // Normalize the given filename in a way that is locale-invariant. On Windows,
 // this uppercases the filename according to the same case mapping rules as used
 // by the filesystem. On Linux, case folding is used and gives results that are

src/api/sorting/plugin_graph.cpp

@@ -590,6 +590,19 @@ void PathsCache::CachePath(const vertex_t& fromVertex,
   }
 }
 
+#if _WIN32
+const std::wstring& WideStringsCache::GetOrInsert(
+    const std::string& narrowString) {
+  auto vertexNameIt = wideStringsCache_.find(narrowString);
+  if (vertexNameIt == wideStringsCache_.end()) {
+    vertexNameIt =
+        wideStringsCache_.emplace(narrowString, ToWinWide(narrowString)).first;
+  }
+
+  return vertexNameIt->second;
+}
+#endif
+
 size_t PluginGraph::CountVertices() const {
   return boost::num_vertices(graph_);
 }
@@ -601,7 +614,16 @@ std::pair<vertex_it, vertex_it> PluginGraph::GetVertices() const {
 std::optional<vertex_t> PluginGraph::GetVertexByName(
     const std::string& name) const {
   for (const auto& vertex : boost::make_iterator_range(GetVertices())) {
-    if (CompareFilenames(GetPlugin(vertex).GetName(), name) == 0) {
+#if _WIN32
+    auto& wideVertexName =
+        wideStringCache_.GetOrInsert(GetPlugin(vertex).GetName());
+    auto& wideName = wideStringCache_.GetOrInsert(name);
+      
+    int comparison = CompareFilenames(wideVertexName, wideName);
+#else
+    int comparison = CompareFilenames(GetPlugin(vertex).GetName(), name);
+#endif
+    if (comparison == 0) {
       return vertex;
     }
   }

src/api/sorting/plugin_graph.h

@@ -55,6 +55,16 @@ private:
   std::unordered_map<vertex_t, std::unordered_set<vertex_t>> pathsCache_;
 };
 
+#if _WIN32
+class WideStringsCache {
+public:
+  const std::wstring& GetOrInsert(const std::string& narrowString);
+
+private:
+  std::unordered_map<std::string, std::wstring> wideStringsCache_;
+};
+#endif
+
 class PluginGraph {
 public:
   size_t CountVertices() const;
@@ -99,6 +109,9 @@ public:
 private:
   RawPluginGraph graph_;
   PathsCache pathsCache_;
+#if _WIN32
+  mutable WideStringsCache wideStringCache_;
+#endif
 };
 }