fs/io/BufferedReader: new class to replace class TextFile

The new class is pluggable, to prepare for gzipped database files.

For now, the TextFile class remains, and will be refactored away
later.

src/PlaylistFile.cxx

@@ -116,6 +116,29 @@ spl_map_to_fs(const char *name_utf8, Error &error)
 	return path_fs;
 }
 
+gcc_pure
+static bool
+IsNotFoundError(const Error &error)
+{
+#ifdef WIN32
+	return error.IsDomain(win32_domain) &&
+		error.GetCode() == ERROR_FILE_NOT_FOUND;
+#else
+	return error.IsDomain(errno_domain) &&
+		error.GetCode() == ENOENT;
+#endif
+}
+
+static void
+TranslatePlaylistError(Error &error)
+{
+	if (IsNotFoundError(error)) {
+		error.Clear();
+		error.Set(playlist_domain, int(PlaylistResult::NO_SUCH_LIST),
+			  "No such playlist");
+	}
+}
+
 /**
  * Create an #Error for the current errno.
  */
@@ -228,9 +251,9 @@ LoadPlaylistFile(const char *utf8path, Error &error)
 	if (path_fs.IsNull())
 		return contents;
 
-	TextFile file(path_fs);
+	TextFile file(path_fs, error);
 	if (file.HasFailed()) {
-		playlist_errno(error);
+		TranslatePlaylistError(error);
 		return contents;
 	}