moved all stdout up to the top

src/main.rs

@@ -3,16 +3,19 @@ use std::{
     borrow::Cow,
     fs,
     io::{Read as _, Write as _},
+    rc::Rc,
 };
 
 fn main() -> Result<()> {
-    let app = App::try_new()?;
+    let mut app = App::try_new()?;
     app.run()
 }
 
 struct App {
     is_terminal: bool,
+    lk: Option<Lk>,
     paths: Vec<Cow<'static, str>>,
+    path_index: usize,
 }
 
 impl App {
@@ -32,20 +35,32 @@ impl App {
             paths
         };
 
-        Ok(App { is_terminal, paths })
+        Ok(App { is_terminal, lk: None, paths, path_index: 0 })
     }
 
-    fn run(&self) -> Result<()> {
-        for path in &self.paths {
-            let metadata = fs::metadata(&**path)?;
-            let mut lk = if metadata.is_dir() {
-                Lk::try_new_ls(path)?
-            } else {
-                Lk::try_new_cat(path)?
-            };
-            while let Some(buf) = lk.poll()? {
-                std::io::stdout().write_all(&buf)?;
+    fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
+        loop {
+            if self.path_index >= self.paths.len() {
+                return Ok(None);
             }
+            let path = &self.paths[self.path_index];
+            match self.lk.as_mut() {
+                Some(lk) => if let Some(buf) = lk.poll()? {
+                    return Ok(Some(buf));
+                } else {
+                    self.lk = None;
+                    self.path_index += 1;
+                }
+                None => {
+                    self.lk = Some(Lk::try_new(path)?);
+                }
+            };
+        }
+    }
+
+    fn run(&mut self) -> Result<()> {
+        while let Some(buf) = self.poll()? {
+            std::io::stdout().write_all(&buf)?;
         }
         Ok(())
     }
@@ -57,6 +72,15 @@ enum Lk {
 }
 
 impl Lk {
+    fn try_new(path: &str) -> Result<Self> {
+        let metadata = fs::metadata(path)?;
+        if metadata.is_dir() {
+            Self::try_new_ls(path)
+        } else {
+            Self::try_new_cat(path)
+        }
+    }
+
     fn try_new_cat(path: &str) -> Result<Self> {
         Ok(Self::Cat(Cat::try_new(path)?))
     }
@@ -65,7 +89,7 @@ impl Lk {
         Ok(Self::Ls(Ls::try_new(path)?))
     }
 
-    fn poll(&mut self) -> Result<Option<Cow<[u8]>>> {
+    fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
         match self {
             Lk::Cat(x) => x.poll(),
             Lk::Ls(x) => x.poll(),
@@ -85,7 +109,7 @@ impl Cat {
         Ok(Self { f, buf })
     }
 
-    fn poll(&mut self) -> Result<Option<Cow<[u8]>>> {
+    fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
         let bytes_read = self.f.read(&mut self.buf)?;
         let buf = &self.buf[0..bytes_read];
         if bytes_read == 0 {
@@ -105,7 +129,7 @@ impl Ls {
         Ok(Self { d })
     }
 
-    fn poll(&mut self) -> Result<Option<Cow<[u8]>>> {
+    fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
         let Some(entry) = self.d.next() else {
             return Ok(None);
         };