+class file_not_found: public std::runtime_error
+{
+public:
+ file_not_found(const std::string &fn): std::runtime_error(fn) { }
+ ~file_not_found() throw() { }
+};
+
+class file_already_exists: public std::runtime_error
+{
+public:
+ file_already_exists(const std::string &fn): std::runtime_error(fn) { }
+ ~file_already_exists() throw() { }
+};
+
+