wc: reduce lines of code

Author: oech3

src/uu/wc/src/count_fast.rs

@@ -40,20 +40,18 @@ const BUF_SIZE: usize = 64 * 1024;
 #[cfg(any(target_os = "linux", target_os = "android"))]
 fn count_bytes_using_splice(fd: &impl AsFd) -> Result<usize, usize> {
     let null_file = uucore::pipes::dev_null().ok_or(0_usize)?;
-    let mut byte_count = 0;
-    if let Ok(res) = splice(fd, &null_file, MAX_ROOTLESS_PIPE_SIZE) {
-        byte_count += res;
+    if let Ok(mut byte_count) = splice(fd, &null_file, MAX_ROOTLESS_PIPE_SIZE) {
         // no need to increase pipe size of input fd since
         // - sender with splice probably increased size already
         // - sender without splice is bottleneck of our wc -c
         loop {
-            match splice(fd, &null_file, MAX_ROOTLESS_PIPE_SIZE) {
-                Ok(0) => return Ok(byte_count),
-                Ok(res) => byte_count += res,
-                Err(_) => return Err(byte_count),
+            match splice(fd, &null_file, MAX_ROOTLESS_PIPE_SIZE).map_err(|_| byte_count)? {
+                0 => return Ok(byte_count),
+                res => byte_count += res,
             }
         }
     } else {
+        let mut byte_count = 0;
         // input is not pipe. needs broker to use splice() with additional cost
         let (pipe_rd, pipe_wr) = pipe::<false>(MAX_ROOTLESS_PIPE_SIZE).map_err(|_| 0_usize)?;
         loop {