[filesystem] Moved generic methods to platform independent code

src/xenia/base/filesystem.cc

@@ -24,5 +24,29 @@ bool CreateParentFolder(const std::filesystem::path& path) {
   return true;
 }
 
+std::vector<FileInfo> ListDirectories(const std::filesystem::path& path) {
+  std::vector<FileInfo> files = ListFiles(path);
+  std::vector<FileInfo> directories = {};
+
+  std::copy_if(files.cbegin(), files.cend(), std::back_inserter(directories),
+               [](const FileInfo& file) {
+                 return file.type == FileInfo::Type::kDirectory;
+               });
+
+  return std::move(directories);
+}
+
+std::vector<FileInfo> FilterByName(const std::vector<FileInfo>& files,
+                                   const std::regex pattern) {
+  std::vector<FileInfo> filtered_entries = {};
+
+  std::copy_if(
+      files.cbegin(), files.cend(), std::back_inserter(filtered_entries),
+      [pattern](const FileInfo& file) {
+        return std::regex_match(file.name.filename().string(), pattern);
+      });
+  return std::move(filtered_entries);
+}
+
 }  // namespace filesystem
 }  // namespace xe