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Implement From<RawFd> for Stdio #50

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Implement From<RawFd> for Stdio #50

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13 changes: 13 additions & 0 deletions daemonize/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@ use std::fs::File;
use std::mem::transmute;
use std::os::unix::ffi::OsStringExt;
use std::os::unix::io::AsRawFd;
use std::os::unix::io::RawFd;
use std::path::{Path, PathBuf};
use std::process::exit;

Expand Down Expand Up @@ -135,6 +136,7 @@ impl From<u32> for Mask {
enum StdioImpl {
Devnull,
RedirectToFile(File),
RedirectToRawFd(RawFd),
Keep,
}

Expand Down Expand Up @@ -166,6 +168,14 @@ impl From<File> for Stdio {
}
}

impl From<RawFd> for Stdio {
fn from(fd: RawFd) -> Self {
Self {
inner: StdioImpl::RedirectToRawFd(fd),
}
}
}
Comment on lines +171 to +177
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You may want to look at preferring the safe equivalents that are available now? sunfishcode/io-lifetimes#38

If a type implements AsRawFd, FromRawFd, and/or IntoRawFd, it usually wants AsFd, From<OwnedFd>, and/or From<T> for OwnedFd, respectively.

Since Rust 1.63.0 (Aug 2022), OwnedFd became available, which provides as_fd() and as_raw_fd() if you need to get BorrowedFd or RawFd types (original RFC for further context).

Suggested change
impl From<RawFd> for Stdio {
fn from(fd: RawFd) -> Self {
Self {
inner: StdioImpl::RedirectToRawFd(fd),
}
}
}
impl From<OwnedFd> for Stdio {
fn from(fd: OwnedFd) -> Self {
Self {
inner: StdioImpl::RedirectToFd(fd),
}
}
}
  • You would also need to change the import from use std::os::unix::io::RawFd; to use std::os::fd::OwnedFd;
  • There's also a AsRawFd import and a as_raw_fd() call for the RedirectToFile enum variant, that can get an OwnedFd since 1.63.0 in a similar way.

That said, I'm not quite sure why Stdio struct exists here instead of using the std::process::Stdio one? It already supports From for file and fd, while there is a separate function call null() for getting the equivalent /dev/null and the Keep enum variant seems to be for a No-op.

Ah.. so this is for redirection of the streams handled in the redirect_standard_streams() call further down. So at the time Rust didn't have an equivalent built-in for Stdio but it does now since Rust 1.74 (Nov 2023). So if raising the MSRV were viable, one could switch to that to simplify 😎


/// Parent process execution outcome.
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
#[non_exhaustive]
Expand Down Expand Up @@ -457,6 +467,9 @@ unsafe fn redirect_standard_streams(
let raw_fd = file.as_raw_fd();
check_err(libc::dup2(raw_fd, fd), ErrorKind::RedirectStreams)?;
}
StdioImpl::RedirectToRawFd(raw_fd) => {
check_err(libc::dup2(raw_fd, fd), ErrorKind::RedirectStreams)?;
}
StdioImpl::Keep => (),
};
Ok(())
Expand Down