File: Add misc useful API from C++17.

firmware/application/file.cpp

@@ -251,6 +251,10 @@ path& path::replace_extension(const path& replacement) {
 	return *this;
 }
 
+bool operator<(const path& lhs, const path& rhs) {
+	return lhs.native() < rhs.native();
+}
+
 bool operator>(const path& lhs, const path& rhs) {
 	return lhs.native() > rhs.native();
 }
@@ -276,6 +280,10 @@ directory_iterator& directory_iterator::operator++() {
 	return *this;
 }
 
+bool is_directory(const file_status s) {
+	return (s & AM_DIR);
+}
+
 bool is_regular_file(const file_status s) {
 	return !(s & AM_DIR);
 }

firmware/application/file.hpp

@@ -158,6 +158,7 @@ private:
 	string_type _s;
 };
 
+bool operator<(const path& lhs, const path& rhs);
 bool operator>(const path& lhs, const path& rhs);
 
 using file_status = BYTE;
@@ -178,6 +179,10 @@ struct directory_entry : public FILINFO {
 		return fattrib;
 	}
 
+	std::uintmax_t size() const {
+		return fsize;
+	};
+
 	const std::filesystem::path path() const noexcept { return { fname }; };
 };
 
@@ -221,6 +226,7 @@ inline directory_iterator end(const directory_iterator&) noexcept { return { };
 
 inline bool operator!=(const directory_iterator& lhs, const directory_iterator& rhs) { return lhs.impl != rhs.impl; };
 
+bool is_directory(const file_status s);
 bool is_regular_file(const file_status s);
 
 space_info space(const path& p);