Prepare convert function

src/Tools/tool_helper/src/lib.rs

@@ -1,6 +1,7 @@
-use std::{boxed::Box, io::Write, path::PathBuf};
+use std::{boxed::Box, io::{Read, Write}, path::PathBuf};
 
 pub type Output    = Box<dyn Write>;
+pub type Input     = Box<dyn Read>;
 pub type Result<T> = std::result::Result<T, Error>;
 
 pub struct Error {
@@ -30,9 +31,16 @@ impl Error {
     }
 }
 
-pub fn open_output(input_file: Option<PathBuf>) -> Result<Output> {
+pub fn open_output(output_file: Option<PathBuf>) -> Result<Output> {
+    match output_file {
+        Some(output_path) => Ok(Box::new(Error::from_io_result(std::fs::File::create(output_path))?)),
+        None              => Ok(Box::new(std::io::stdout())),
+    }
+}
+
+pub fn open_input(input_file: Option<PathBuf>) -> Result<Input> {
     match input_file {
-        Some(input_path) => Ok(Box::new(Error::from_io_result(std::fs::File::create(input_path))?)),
-        None             => Ok(Box::new(std::io::stdout())),
+        Some(input_path) => Ok(Box::new(Error::from_io_result(std::fs::File::open(input_path))?)),
+        None             => Ok(Box::new(std::io::stdin())),
     }
 }