cleanup nu-command, remove redundant code (#5208)

crates/nu-command/src/filesystem/util.rs

@@ -7,6 +7,7 @@ use nu_protocol::ShellError;
 
 use dialoguer::Input;
 use std::error::Error;
+use std::io::{BufRead, BufReader, Read};
 
 #[derive(Default)]
 pub struct FileStructure {
@@ -120,3 +121,37 @@ pub fn get_interactive_confirmation(prompt: String) -> Result<bool, Box<dyn Erro
         Ok(false)
     }
 }
+
+pub struct BufferedReader<R: Read> {
+    pub input: BufReader<R>,
+}
+
+impl<R: Read> BufferedReader<R> {
+    pub fn new(input: BufReader<R>) -> Self {
+        Self { input }
+    }
+}
+
+impl<R: Read> Iterator for BufferedReader<R> {
+    type Item = Result<Vec<u8>, ShellError>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let buffer = self.input.fill_buf();
+        match buffer {
+            Ok(s) => {
+                let result = s.to_vec();
+
+                let buffer_len = s.len();
+
+                if buffer_len == 0 {
+                    None
+                } else {
+                    self.input.consume(buffer_len);
+
+                    Some(Ok(result))
+                }
+            }
+            Err(e) => Some(Err(ShellError::IOError(e.to_string()))),
+        }
+    }
+}