rightkit-process 0.3.1

use std::{
    io,
    process::ExitStatus,
    sync::{Arc, Mutex, MutexGuard},
    time::{Duration, SystemTime},
};
#[cfg(unix)]
type PlatformChild = std::process::Child;
#[cfg(windows)]
type PlatformChild = crate::spawn_windows::WindowsChild;
#[cfg(unix)]
use std::{thread, time::Instant};

/// An independent exit reader. On Unix it shares std's cached reap state;
/// on Windows it owns a duplicated process handle, never a borrowed handle value.
/// Keeping this reader alive does not keep an owned process tree alive.
#[derive(Debug)]
pub struct ProcessHandle {
    #[cfg(unix)]
    child: Arc<Mutex<PlatformChild>>,
    #[cfg(unix)]
    pid: u32,
    #[cfg(windows)]
    handle: std::os::windows::io::OwnedHandle,
    creation_time: Option<SystemTime>,
    #[cfg(windows)]
    creation_time_ticks: Option<u64>,
}

pub(crate) fn lock_child<T>(child: &Mutex<T>) -> MutexGuard<'_, T> {
    child.lock().unwrap_or_else(|poison| poison.into_inner())
}

impl ProcessHandle {
    pub(crate) fn new(
        child: &Arc<Mutex<PlatformChild>>,
        spawned_at: SystemTime,
    ) -> io::Result<Self> {
        #[cfg(unix)]
        {
            #[cfg(target_os = "macos")]
            let creation_time = macos_creation_time(lock_child(child).id());
            #[cfg(not(target_os = "macos"))]
            let creation_time = Some(spawned_at);
            let _ = spawned_at;
            Ok(Self {
                child: Arc::clone(child),
                pid: lock_child(child).id(),
                creation_time,
            })
        }
        #[cfg(windows)]
        {
            use std::os::windows::io::AsHandle;
            let handle = lock_child(child).as_handle().try_clone_to_owned()?;
            let ticks = windows_creation_time(&handle);
            let creation_time = ticks.and_then(|ticks| {
                // FILETIME epoch precedes Unix by 11,644,473,600 seconds.
                let ticks = ticks.checked_sub(116_444_736_000_000_000)?;
                SystemTime::UNIX_EPOCH.checked_add(Duration::new(
                    ticks / 10_000_000,
                    ((ticks % 10_000_000) * 100) as u32,
                ))
            });
            let _ = spawned_at;
            Ok(Self {
                handle,
                creation_time,
                creation_time_ticks: ticks,
            })
        }
    }

    pub fn try_clone(&self) -> io::Result<Self> {
        Ok(Self {
            #[cfg(unix)]
            child: Arc::clone(&self.child),
            #[cfg(unix)]
            pid: self.pid,
            #[cfg(windows)]
            handle: self.handle.try_clone()?,
            creation_time: self.creation_time,
            #[cfg(windows)]
            creation_time_ticks: self.creation_time_ticks,
        })
    }

    /// Native creation time on Windows/macOS; spawn observation time on other Unix hosts.
    pub fn creation_time(&self) -> Option<SystemTime> {
        self.creation_time
    }

    /// Native Windows FILETIME, in 100 ns ticks since 1601-01-01 UTC.
    #[cfg(windows)]
    pub fn creation_time_ticks(&self) -> Option<u64> {
        self.creation_time_ticks
    }

    pub fn try_wait(&self) -> io::Result<Option<ExitStatus>> {
        #[cfg(unix)]
        {
            lock_child(&self.child).try_wait()
        }
        #[cfg(windows)]
        {
            self.windows_wait(0)
        }
    }

    pub fn wait(&self) -> io::Result<ExitStatus> {
        #[cfg(unix)]
        {
            #[cfg(any(
                target_os = "linux",
                target_os = "android",
                target_os = "macos",
                target_os = "ios",
                target_os = "freebsd",
                target_os = "openbsd",
                target_os = "netbsd",
                target_os = "dragonfly",
                target_os = "solaris",
                target_os = "illumos"
            ))]
            {
                if let Some(status) = self.try_wait()? {
                    return Ok(status);
                }
                loop {
                    let mut info = std::mem::MaybeUninit::<nix::libc::siginfo_t>::uninit();
                    // Block without reaping or holding the std-child lock. std's
                    // waitpid below remains the sole reap/cache owner. This lets
                    // concurrent timeouts & detached-drop stdio cleanup proceed.
                    if unsafe {
                        nix::libc::waitid(
                            nix::libc::P_PID,
                            self.pid as nix::libc::id_t,
                            info.as_mut_ptr(),
                            nix::libc::WEXITED | nix::libc::WNOWAIT,
                        )
                    } == 0
                    {
                        return self.try_wait()?.ok_or_else(|| {
                            io::Error::other("completed process wait had no exit status")
                        });
                    }
                    let error = io::Error::last_os_error();
                    if error.raw_os_error() == Some(nix::libc::EINTR) {
                        continue;
                    }
                    // Another reader may have reaped & cached status while waitid
                    // was waking, causing ECHILD despite a valid cached result.
                    if let Some(status) = self.try_wait()? {
                        return Ok(status);
                    }
                    return Err(error);
                }
            }
            #[cfg(not(any(
                target_os = "linux",
                target_os = "android",
                target_os = "macos",
                target_os = "ios",
                target_os = "freebsd",
                target_os = "openbsd",
                target_os = "netbsd",
                target_os = "dragonfly",
                target_os = "solaris",
                target_os = "illumos"
            )))]
            {
                // Other Unix hosts use std's blocking waitpid & shared cache.
                let mut child = lock_child(&self.child);
                // An independent reader must not close owner stdin. OwnedChild::wait
                // already closes it explicitly, matching std Child::wait.
                let stdin = child.stdin.take();
                let result = child.wait();
                child.stdin = stdin;
                result
            }
        }
        #[cfg(windows)]
        {
            self.windows_wait(u32::MAX)?
                .ok_or_else(|| io::Error::other("infinite process wait unexpectedly timed out"))
        }
    }

    pub fn wait_timeout(&self, timeout: Duration) -> io::Result<Option<ExitStatus>> {
        #[cfg(windows)]
        {
            let started = std::time::Instant::now();
            loop {
                let remaining = timeout.saturating_sub(started.elapsed());
                // Round up sub-millisecond waits; reserve INFINITE for wait().
                let millis = remaining.as_millis()
                    + u128::from(!remaining.subsec_nanos().is_multiple_of(1_000_000));
                let millis = millis.min(u128::from(u32::MAX - 1)) as u32;
                if let Some(status) = self.windows_wait(millis)? {
                    return Ok(Some(status));
                }
                if started.elapsed() >= timeout {
                    return Ok(None);
                }
            }
        }
        #[cfg(unix)]
        {
            let started = Instant::now();
            loop {
                if let Some(status) = self.try_wait()? {
                    return Ok(Some(status));
                }
                if started.elapsed() >= timeout {
                    return Ok(None);
                }
                thread::sleep(
                    Duration::from_millis(5).min(timeout.saturating_sub(started.elapsed())),
                );
            }
        }
    }

    #[cfg(windows)]
    fn windows_wait(&self, millis: u32) -> io::Result<Option<ExitStatus>> {
        use std::os::windows::{io::AsRawHandle, process::ExitStatusExt};
        use windows::Win32::{
            Foundation::{HANDLE, WAIT_OBJECT_0, WAIT_TIMEOUT},
            System::Threading::{GetExitCodeProcess, WaitForSingleObject},
        };
        let handle = HANDLE(self.handle.as_raw_handle() as _);
        match unsafe { WaitForSingleObject(handle, millis) } {
            WAIT_TIMEOUT => Ok(None),
            WAIT_OBJECT_0 => {
                let mut code = 0;
                unsafe { GetExitCodeProcess(handle, &mut code) }
                    .map_err(crate::process_windows::os_error)?;
                Ok(Some(ExitStatus::from_raw(code)))
            }
            _ => Err(io::Error::last_os_error()),
        }
    }
}

#[cfg(windows)]
impl std::os::windows::io::AsHandle for ProcessHandle {
    fn as_handle(&self) -> std::os::windows::io::BorrowedHandle<'_> {
        std::os::windows::io::AsHandle::as_handle(&self.handle)
    }
}

#[cfg(windows)]
fn windows_creation_time(handle: &std::os::windows::io::OwnedHandle) -> Option<u64> {
    use std::os::windows::io::AsRawHandle;
    use windows::Win32::{
        Foundation::{FILETIME, HANDLE},
        System::Threading::GetProcessTimes,
    };
    let (mut creation, mut exit, mut kernel, mut user) = (
        FILETIME::default(),
        FILETIME::default(),
        FILETIME::default(),
        FILETIME::default(),
    );
    unsafe {
        GetProcessTimes(
            HANDLE(handle.as_raw_handle() as _),
            &mut creation,
            &mut exit,
            &mut kernel,
            &mut user,
        )
    }
    .ok()?;
    Some((u64::from(creation.dwHighDateTime) << 32) | u64::from(creation.dwLowDateTime))
}

#[cfg(target_os = "macos")]
fn macos_creation_time(pid: u32) -> Option<SystemTime> {
    use nix::libc;
    let mut info = std::mem::MaybeUninit::<libc::proc_bsdinfo>::zeroed();
    let size = std::mem::size_of::<libc::proc_bsdinfo>();
    // libproc writes exactly proc_bsdinfo for this flavor; check size before reading it.
    let written = unsafe {
        libc::proc_pidinfo(
            pid as i32,
            libc::PROC_PIDTBSDINFO,
            0,
            info.as_mut_ptr().cast(),
            size as i32,
        )
    };
    if written != size as i32 {
        return None;
    }
    let info = unsafe { info.assume_init() };
    SystemTime::UNIX_EPOCH
        .checked_add(Duration::from_secs(info.pbi_start_tvsec))?
        .checked_add(Duration::from_micros(info.pbi_start_tvusec))
}