tee: improve stdout performance

Author: xtqqczze

src/uu/tee/src/tee.rs

@@ -80,7 +80,7 @@ fn tee(options: &Options) -> Result<()> {
         0,
         NamedWriter {
             name: translate!("tee-standard-output").into(),
-            inner: Writer::Stdout(stdout()),
+            inner: Writer::stdout_raw(),
         },
     );
 
@@ -251,21 +251,39 @@ fn process_error(
 
 enum Writer {
     File(std::fs::File),
-    Stdout(std::io::Stdout),
+    StdoutRaw(core::mem::ManuallyDrop<std::fs::File>),
+}
+
+impl Writer {
+    #[cfg(not(windows))]
+    fn stdout_raw() -> Self {
+        let fd = std::os::fd::AsRawFd::as_raw_fd(&stdout());
+        Self::StdoutRaw(core::mem::ManuallyDrop::new(unsafe {
+            std::os::fd::FromRawFd::from_raw_fd(fd)
+        }))
+    }
+
+    #[cfg(windows)]
+    fn stdout_raw() -> Self {
+        let handle = std::os::windows::io::AsRawHandle::as_raw_handle(&stdout());
+        Self::StdoutRaw(core::mem::ManuallyDrop::new(unsafe {
+            std::os::windows::io::FromRawHandle::from_raw_handle(handle)
+        }))
+    }
 }
 
 impl Write for Writer {
     fn write(&mut self, buf: &[u8]) -> Result<usize> {
         match self {
             Self::File(f) => f.write(buf),
-            Self::Stdout(s) => s.write(buf),
+            Self::StdoutRaw(s) => s.write(buf),
         }
     }
 
     fn flush(&mut self) -> Result<()> {
         match self {
             Self::File(f) => f.flush(),
-            Self::Stdout(s) => s.flush(),
+            Self::StdoutRaw(s) => s.flush(),
         }
     }
 }