uucore, cat: move unbounded splice code

src/uu/cat/src/splice.rs

@@ -22,16 +22,10 @@ pub(super) fn write_fast_using_splice<R: FdReadable, S: AsRawFd + AsFd + Write>(
     write_fd: &mut S,
 ) -> CatResult<bool> {
     if splice(&handle.reader, &write_fd, MAX_ROOTLESS_PIPE_SIZE).is_ok() {
-        // fcntl improves throughput
-        // todo: avoid fcntl overhead for small input, but don't fcntl inside of the loop
-        let _ = rustix::pipe::fcntl_setpipe_size(&mut *write_fd, MAX_ROOTLESS_PIPE_SIZE);
-        loop {
-            match splice(&handle.reader, &write_fd, MAX_ROOTLESS_PIPE_SIZE) {
-                Ok(1..) => {}
-                Ok(0) => return Ok(might_fuse(&handle.reader)),
-                Err(_) => return Ok(true),
-            }
-        }
+        Ok(
+            uucore::pipes::splice_unbounded(&handle.reader, write_fd)?
+                || might_fuse(&handle.reader),
+        )
     } else {
         Ok(
             uucore::pipes::splice_unbounded_broker(&handle.reader, write_fd)?

src/uucore/src/lib/features/pipes.rs

@@ -86,6 +86,31 @@ pub fn might_fuse(source: &impl AsFd) -> bool {
     rustix::fs::fstatfs(source).map_or(true, |stats| stats.f_type == 0x6573_5546) // FUSE magic number, too many platform specific clippy warning with const
 }
 
+/// splice all of source to dest
+/// return true if we need read/write fallback
+/// fails if one of in/output should be pipe
+#[inline]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn splice_unbounded<R, S>(source: &R, dest: &mut S) -> std::io::Result<bool>
+where
+    R: Read + AsFd,
+    S: AsFd + std::io::Write,
+{
+    // improve throughput
+    // todo: avoid fcntl overhead for small input, but don't fcntl inside of the loop
+    // no need to increase pipe size of input fd since
+    // - sender with splice probably increased size already
+    // - sender without splice is bottleneck
+    let _ = fcntl_setpipe_size(&mut *dest, MAX_ROOTLESS_PIPE_SIZE);
+    loop {
+        match splice(&source, &dest, MAX_ROOTLESS_PIPE_SIZE) {
+            Ok(1..) => {}
+            Ok(0) => return Ok(false),
+            Err(_) => return Ok(true),
+        }
+    }
+}
+
 /// force-splice source to dest even both of them are not pipe
 /// return true if we need read/write fallback
 ///