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This will enable us to query for the current system's hostname in both Unix and Windows environments. We could have pulled in the 'gethostname' crate for this, but: 1. I'm not a huge fan of micro-crates. 2. The 'gethostname' crate panics if an error occurs. (Which, to be fair, an error should never occur, but it seems plausible on borked systems? ripgrep runs in a lot of places, so I'd rather not take the chance of a panic bringing down ripgrep for an optional convenience feature.) 3. The 'gethostname' crate uses the 'windows-targets' crate from Microsoft. This is arguably the "right" thing to do, but ripgrep doesn't use them yet and they appear high-churn. So I just added a safe wrapper to do this to winapi-util[1] and then inlined the Unix version here. This brings in no extra dependencies and the routine is fallible so that callers can recover from potentially strange failures. [1]: BurntSushi/winapi-util#14
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use std::{ffi::OsString, io}; | ||
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/// Returns the hostname of the current system. | ||
/// | ||
/// It is unusual, although technically possible, for this routine to return | ||
/// an error. It is difficult to list out the error conditions, but one such | ||
/// possibility is platform support. | ||
/// | ||
/// # Platform specific behavior | ||
/// | ||
/// On Windows, this currently uses the "physical DNS hostname" computer name. | ||
/// This may change in the future. | ||
/// | ||
/// On Unix, this returns the result of the `gethostname` function from the | ||
/// `libc` linked into the program. | ||
pub fn hostname() -> io::Result<OsString> { | ||
#[cfg(windows)] | ||
{ | ||
use winapi_util::sysinfo::{get_computer_name, ComputerNameKind}; | ||
get_computer_name(ComputerNameKind::PhysicalDnsHostname) | ||
} | ||
#[cfg(unix)] | ||
{ | ||
gethostname() | ||
} | ||
#[cfg(not(any(windows, unix)))] | ||
{ | ||
io::Error::new( | ||
io::ErrorKind::Other, | ||
"hostname could not be found on unsupported platform", | ||
) | ||
} | ||
} | ||
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||
#[cfg(unix)] | ||
fn gethostname() -> io::Result<OsString> { | ||
use std::os::unix::ffi::OsStringExt; | ||
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||
// SAFETY: There don't appear to be any safety requirements for calling | ||
// sysconf. | ||
let limit = unsafe { libc::sysconf(libc::_SC_HOST_NAME_MAX) }; | ||
if limit == -1 { | ||
// It is in theory possible for sysconf to return -1 for a limit but | ||
// *not* set errno, in which case, io::Error::last_os_error is | ||
// indeterminate. But untangling that is super annoying because std | ||
// doesn't expose any unix-specific APIs for inspecting the errno. (We | ||
// could do it ourselves, but it just doesn't seem worth doing?) | ||
return Err(io::Error::last_os_error()); | ||
} | ||
let Ok(maxlen) = usize::try_from(limit) else { | ||
let msg = format!("host name max limit ({}) overflowed usize", limit); | ||
return Err(io::Error::new(io::ErrorKind::Other, msg)); | ||
}; | ||
// maxlen here includes the NUL terminator. | ||
let mut buf = vec![0; maxlen]; | ||
// SAFETY: The pointer we give is valid as it is derived directly from a | ||
// Vec. Similarly, `maxlen` is the length of our Vec, and is thus valid | ||
// to write to. | ||
let rc = unsafe { | ||
libc::gethostname(buf.as_mut_ptr().cast::<libc::c_char>(), maxlen) | ||
}; | ||
if rc == -1 { | ||
return Err(io::Error::last_os_error()); | ||
} | ||
// POSIX says that if the hostname is bigger than `maxlen`, then it may | ||
// write a truncate name back that is not necessarily NUL terminated (wtf, | ||
// lol). So if we can't find a NUL terminator, then just give up. | ||
let Some(zeropos) = buf.iter().position(|&b| b == 0) else { | ||
let msg = "could not find NUL terminator in hostname"; | ||
return Err(io::Error::new(io::ErrorKind::Other, msg)); | ||
}; | ||
buf.truncate(zeropos); | ||
buf.shrink_to_fit(); | ||
Ok(OsString::from_vec(buf)) | ||
} | ||
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#[cfg(test)] | ||
mod tests { | ||
use super::*; | ||
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#[test] | ||
fn print_hostname() { | ||
println!("{:?}", hostname().unwrap()); | ||
} | ||
} |
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