//! Unix user, group, and process identifiers.

//!

//! # Safety

//!

//! The `Uid`, `Gid`, and `Pid` types can be constructed from raw integers,

//! which is marked unsafe because actual OS's assign special meaning to some

//! integer values.

#![allow(unsafe_code)]

use crate::{backend, io};

#[cfg(feature = "alloc")]

use alloc::vec::Vec;

#[cfg(linux_kernel)]

use backend::process::types::RawCpuid;

pub use crate::pid::{Pid, RawPid};

pub use crate::ugid::{Gid, RawGid, RawUid, Uid};

/// A Linux CPU ID.

#[cfg(linux_kernel)]

#[repr(transparent)]

#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]

pub struct Cpuid(RawCpuid);

#[cfg(linux_kernel)]

impl Cpuid {

    /// Converts a `RawCpuid` into a `Cpuid`.

    ///

    /// # Safety

    ///

    /// `raw` must be the value of a valid Linux CPU ID.

    #[inline]

    pub const unsafe fn from_raw(raw: RawCpuid) -> Self {

        Self(raw)

    }

    /// Converts a `Cpuid` into a `RawCpuid`.

    #[inline]

    pub const fn as_raw(self) -> RawCpuid {

        self.0

    }

}

/// `getuid()`—Returns the process' real user ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getuid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getuid.2.html

#[inline]

#[must_use]

pub fn getuid() -> Uid {

    backend::ugid::syscalls::getuid()

}

/// `geteuid()`—Returns the process' effective user ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/geteuid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/geteuid.2.html

#[inline]

#[must_use]

pub fn geteuid() -> Uid {

    backend::ugid::syscalls::geteuid()

}

/// `getgid()`—Returns the process' real group ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getgid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getgid.2.html

#[inline]

#[must_use]

pub fn getgid() -> Gid {

    backend::ugid::syscalls::getgid()

}

/// `getegid()`—Returns the process' effective group ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getegid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getegid.2.html

#[inline]

#[must_use]

pub fn getegid() -> Gid {

    backend::ugid::syscalls::getegid()

}

/// `getpid()`—Returns the process' ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getpid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getpid.2.html

#[inline]

#[must_use]

pub fn getpid() -> Pid {

    backend::pid::syscalls::getpid()

}

/// `getppid()`—Returns the parent process' ID.

///

/// This will return `None` if the current process has no parent (or no parent accessible in the

/// current PID namespace), such as if the current process is an init process (PID 1).

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getppid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getppid.2.html

#[inline]

#[must_use]

pub fn getppid() -> Option<Pid> {

    backend::process::syscalls::getppid()

}

/// `getpgid(pid)`—Returns the process group ID of the given process.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getpgid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getpgid.2.html

#[inline]

pub fn getpgid(pid: Option<Pid>) -> io::Result<Pid> {

    backend::process::syscalls::getpgid(pid)

}

/// `setpgid(pid, pgid)`—Sets the process group ID of the given process.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/setpgid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/setpgid.2.html

#[inline]

pub fn setpgid(pid: Option<Pid>, pgid: Option<Pid>) -> io::Result<()> {

    backend::process::syscalls::setpgid(pid, pgid)

}

/// `getpgrp()`—Returns the process' group ID.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getpgrp.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getpgrp.2.html

#[inline]

#[must_use]

pub fn getpgrp() -> Pid {

    backend::process::syscalls::getpgrp()

}

/// `getsid(pid)`—Get the session ID of the given process.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getsid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getsid.2.html

#[cfg(not(target_os = "redox"))]

#[inline]

pub fn getsid(pid: Option<Pid>) -> io::Result<Pid> {

    backend::process::syscalls::getsid(pid)

}

/// `setsid()`—Create a new session.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/setsid.html

/// [Linux]: https://man7.org/linux/man-pages/man2/setsid.2.html

#[inline]

pub fn setsid() -> io::Result<Pid> {

    backend::process::syscalls::setsid()

}

/// `getgroups()`—Return a list of the current user's groups.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getgroups.html

/// [Linux]: https://man7.org/linux/man-pages/man2/getgroups.2.html

#[cfg(feature = "alloc")]

pub fn getgroups() -> io::Result<Vec<Gid>> {

    // This code would benefit from having a better way to read into

    // uninitialized memory, but that requires `unsafe`.

    let mut buffer = Vec::with_capacity(0);

    let ngroups = backend::process::syscalls::getgroups(&mut buffer)?;

    buffer.resize(ngroups, Gid::ROOT);

    backend::process::syscalls::getgroups(&mut buffer)?;

    Ok(buffer)

}