From ff93b402bb0fcc86e59a892da6e2ad48c2615b83 Mon Sep 17 00:00:00 2001
From: oech3 <79379754+oech3@users.noreply.github.com>
Date: Sun, 10 May 2026 16:43:29 +0900
Subject: [PATCH] cat: dedup print_unbuffered

---
 src/uu/cat/src/cat.rs         | 27 +++++----------------------
 src/uucore/src/lib/mods/io.rs | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/src/uu/cat/src/cat.rs b/src/uu/cat/src/cat.rs
index 7d643bbed1a..66bd69dfc85 100644
--- a/src/uu/cat/src/cat.rs
+++ b/src/uu/cat/src/cat.rs
@@ -497,31 +497,13 @@ fn print_fast<R: FdReadable>(handle: &mut InputHandle<R>) -> CatResult<()> {
 }
 
 #[cfg_attr(any(target_os = "linux", target_os = "android"), inline(never))] // splice fast-path does not require this allocation
-#[cfg(any(unix, target_os = "wasi"))]
-fn print_unbuffered<R: FdReadable>(
-    handle: &mut InputHandle<R>,
-    stdout: io::Stdout,
-) -> CatResult<()> {
-    // todo: since there is no cost by 0-fill, we could use larger heap buffer for throughput
-    let mut buf = [std::mem::MaybeUninit::<u8>::uninit(); 1024 * 64];
-    // use raw syscall to remove buffering
-    loop {
-        match rustix::io::read(&handle.reader, &mut buf) {
-            Ok(([], _)) => return Ok(()),
-            Ok((filled, _)) => {
-                uucore::io::write_all_raw(&stdout, filled).inspect_err(handle_broken_pipe)?;
-            }
-            Err(e) if e.kind() != ErrorKind::Interrupted => return Err(e.into()),
-            _ => {}
-        }
-    }
-}
-
-#[cfg(not(any(unix, target_os = "wasi")))]
 fn print_unbuffered<R: FdReadable>(
     handle: &mut InputHandle<R>,
     stdout: io::Stdout,
 ) -> CatResult<()> {
+    #[cfg(any(unix, target_os = "wasi"))]
+    let mut stdout = uucore::io::RawWriter(stdout); // use raw syscall to remove buffering
+    #[cfg(not(any(unix, target_os = "wasi")))]
     let mut stdout = stdout.lock();
     let mut buf = [0; 1024 * 64];
     loop {
@@ -531,8 +513,9 @@ fn print_unbuffered<R: FdReadable>(
                 stdout
                     .write_all(&buf[..n])
                     .inspect_err(handle_broken_pipe)?;
-                // we cannot use rustix::io on Windows
+                // cannot use rustix::io on Windows
                 // really bad workaround for unbuffered write <https://github.com/uutils/coreutils/issues/12188>
+                #[cfg(not(any(unix, target_os = "wasi")))]
                 stdout.flush().inspect_err(handle_broken_pipe)?;
             }
             Err(e) if e.kind() != ErrorKind::Interrupted => return Err(e.into()),
diff --git a/src/uucore/src/lib/mods/io.rs b/src/uucore/src/lib/mods/io.rs
index b3fcb938956..9d7fe889a3f 100644
--- a/src/uucore/src/lib/mods/io.rs
+++ b/src/uucore/src/lib/mods/io.rs
@@ -30,7 +30,20 @@ type NativeType = OwnedHandle;
 #[cfg(not(windows))]
 type NativeType = OwnedFd;
 
-// io::write_all but no buffering
+// create stdout without buffering
+#[cfg(any(unix, target_os = "wasi"))]
+pub struct RawWriter(pub io::Stdout);
+#[cfg(any(unix, target_os = "wasi"))]
+impl io::Write for RawWriter {
+    fn write(&mut self, b: &[u8]) -> io::Result<usize> {
+        rustix::io::write(&self.0, b).map_err(Into::into)
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+// io::write_all but no buffering (deprecated?)
 #[inline]
 #[cfg(any(unix, target_os = "wasi"))]
 pub fn write_all_raw(output: impl AsFd, buf: &[u8]) -> io::Result<()> {