move secondary context out of main

src/basic/io.rs

@@ -0,0 +1,25 @@
+/*
+ * srx: The fast Symbol Ranking based compressor.
+ * Copyright (C) 2023  Mai Thanh Minh (a.k.a. thanhminhmr)
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either  version 3 of the  License,  or (at your option) any later
+ * version.
+ *
+ * This program  is distributed in the hope  that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR  A PARTICULAR PURPOSE. See  the  GNU  General  Public   License  for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+use crate::basic::AnyResult;
+
+// -----------------------------------------------
+
+pub trait Closable<T> {
+    fn close(self) -> AnyResult<T>;
+}

src/basic/mod.rs

@@ -17,5 +17,7 @@
  */
 
 mod error;
+mod io;
 
 pub use self::error::*;
+pub use self::io::*;