fs/io/TextFile: add method Check()

src/fs/io/TextFile.cxx

@@ -61,3 +61,11 @@ TextFile::ReadLine()
 
 	return buffered_reader->ReadLine();
 }
+
+bool
+TextFile::Check(Error &error) const
+{
+	assert(buffered_reader != nullptr);
+
+	return buffered_reader->Check(error);
+}

src/fs/io/TextFile.hxx

@@ -56,10 +56,18 @@ public:
 	 * space.  There is a reasonable maximum line length, only to
 	 * prevent denial of service.
 	 *
+	 * Use Check() after nullptr has been returned to check
+	 * whether an error occurred or end-of-file has been reached.
+	 *
 	 * @param file the source file, opened in text mode
 	 * @return a pointer to the line, or nullptr on end-of-file or error
 	 */
 	char *ReadLine();
+
+	/**
+	 * Check whether a ReadLine() call has thrown an error.
+	 */
+	bool Check(Error &error) const;
 };
 
 #endif