yes: Add zero copy fast-path

Author: oech3

.vscode/cspell.dictionaries/workspace.wordlist.txt

@@ -8,6 +8,7 @@ advapi32-sys
 aho-corasick
 backtrace
 blake2b_simd
+rustix
 
 # * uutils project
 uutils

Cargo.lock

@@ -428,6 +428,7 @@ rlimit = "0.11.0"
 rstest = "0.26.0"
 rustc-hash = "2.1.1"
 rust-ini = "0.21.0"
+rustix = { version = "1.1.4", features = ["fs", "param", "pipe"] }
 same-file = "1.0.6"
 self_cell = "1.0.4"
 selinux = "=0.6.0"

Cargo.toml

@@ -22,6 +22,7 @@ path = "src/yes.rs"
 clap = { workspace = true }
 itertools = { workspace = true }
 fluent = { workspace = true }
+rustix = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]
 uucore = { workspace = true, features = ["pipes", "signals"] }

src/uu/yes/Cargo.toml

@@ -111,6 +111,7 @@ fn prepare_buffer(buf: &mut Vec<u8>) {
     }
 }
 
+#[cfg(not(target_os = "linux"))]
 pub fn exec(bytes: &[u8]) -> io::Result<()> {
     let stdout = io::stdout();
     let mut stdout = stdout.lock();
@@ -120,6 +121,29 @@ pub fn exec(bytes: &[u8]) -> io::Result<()> {
     }
 }
 
+#[cfg(target_os = "linux")]
+pub fn exec(bytes: &[u8]) -> io::Result<()> {
+    use rustix::fd::BorrowedFd;
+    use rustix::param::page_size;
+    use rustix::pipe::{IoSliceRaw, SpliceFlags, vmsplice};
+    use std::os::unix::io::AsRawFd;
+
+    let stdout = io::stdout();
+    //zero copy fast-path
+    //todo: we should align instead of giving up fast-path
+    let aligned = bytes.len().is_multiple_of(page_size());
+    if aligned {
+        let fd_raw = stdout.as_raw_fd();
+        let fd = unsafe { BorrowedFd::borrow_raw(fd_raw) };
+        let iovec = [IoSliceRaw::from_slice(bytes)];
+        while unsafe { vmsplice(fd, &iovec, SpliceFlags::empty()) }.is_ok() {}
+    }
+    let mut stdout = stdout.lock();
+    loop {
+        stdout.write_all(bytes)?;
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;