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Use rustix instead of libc #10

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Use rustix instead of libc #10

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0d3898b
Use rustix instead of libc
notgull Apr 29, 2023
6af3c20
Merge branch 'main' into rustix
swsnr May 10, 2023
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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ categories = ["os", "api-bindings"]
rust-version = "1.64"

[target.'cfg(not(windows))'.dependencies]
libc = "0.2.141"
rustix = { version = "0.37.17", default-features = false, features = ["std", "process"] }

[target.'cfg(windows)'.dependencies]
windows = { version = "0.48.0", features = [
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43 changes: 21 additions & 22 deletions src/lib.rs
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Expand Up @@ -60,29 +60,28 @@ pub fn gethostname() -> OsString {
#[cfg(unix)]
#[inline]
fn gethostname_impl() -> OsString {
use libc::{c_char, sysconf, _SC_HOST_NAME_MAX};
use std::os::unix::ffi::OsStringExt;
// Get the maximum size of host names on this system, and account for the
// trailing NUL byte.
let hostname_max = unsafe { sysconf(_SC_HOST_NAME_MAX) };
let mut buffer = vec![0; (hostname_max as usize) + 1];
let returncode = unsafe { libc::gethostname(buffer.as_mut_ptr() as *mut c_char, buffer.len()) };
if returncode != 0 {
// There are no reasonable failures, so lets panic
panic!(
"gethostname failed: {}
Please report an issue to <https://github.com/swsnr/gethostname.rs/issues>!",
std::io::Error::last_os_error()
);
}
// We explicitly search for the trailing NUL byte and cap at the buffer
// length: If the buffer's too small (which shouldn't happen since we
// explicitly use the max hostname size above but just in case) POSIX
// doesn't specify whether there's a NUL byte at the end, so if we didn't
// check we might read from memory that's not ours.
let end = buffer.iter().position(|&b| b == 0).unwrap_or(buffer.len());
buffer.resize(end, 0);
OsString::from_vec(buffer)

// libc::gethostname() is implemented in both musl and glibc by calling uname() and copying
// the nodename field into the buffer.
//
// glibc:
// https://github.com/lattera/glibc/blob/895ef79e04a953cac1493863bcae29ad85657ee1/sysdeps/posix/gethostname.c#L32-L36
// musl:
// https://github.com/cloudius-systems/musl/blob/00733dd1cf791d13ff6155509cf139a5f7b2eecb/src/unistd/gethostname.c#L4-L13
//
// On FreeBSD, libc::gethostname() is a sysctl call to KERN_HOSTNAME. uname() fetches the nodename
// using the same strategy.
//
// freebsd gethostname:
// https://github.com/FreeBSDDesktop/freebsd-base/blob/de1aa3dab23c06fec962a14da3e7b4755c5880cf/lib/libc/gen/gethostname.c#L47-L54
// freebsd uname:
// https://github.com/FreeBSDDesktop/freebsd-base/blob/de1aa3dab23c06fec962a14da3e7b4755c5880cf/lib/libc/gen/__xuname.c#L73-L83
//
// OpenBSD uses the same strategy, so I doubt that other implementations of uname() among the BSDs
// stray too far from this pattern.
let bytes = rustix::process::uname().nodename().to_bytes().to_vec();
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OsString::from_vec(bytes)
}

#[cfg(windows)]
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