//! The `CWD` and `ABS` constants, representing the current working directory //! and absolute-only paths, respectively. //! //! # Safety //! //! This file uses `AT_FDCWD`, which is a raw file descriptor, but which is //! always valid, and `-EBADF`, which is an undocumented by commonly used //! convention of passing a value which will always fail if the accompanying //! path isn't absolute. #![allow(unsafe_code)] use crate::backend; use backend::c; use backend::fd::{BorrowedFd, RawFd}; /// `AT_FDCWD`—A handle representing the current working directory. /// /// This is a file descriptor which refers to the process current directory /// which can be used as the directory argument in `*at` functions such as /// [`openat`]. /// /// # References /// - [POSIX] /// /// [`openat`]: crate::fs::openat /// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fcntl.h.html // SAFETY: `AT_FDCWD` is a reserved value that is never dynamically // allocated, so it'll remain valid for the duration of `'static`. #[doc(alias = "AT_FDCWD")] pub const CWD: BorrowedFd<'static> = unsafe { BorrowedFd::<'static>::borrow_raw(c::AT_FDCWD as RawFd) }; /// `-EBADF`—A handle that requires paths to be absolute. /// /// This is a file descriptor which refers to no directory, which can be used /// as the directory argument in `*at` functions such as [`openat`], which /// causes them to fail with [`BADF`] if the accompanying path is not absolute. /// /// This corresponds to the undocumented by commonly used convention of /// passing `-EBADF` as the `dirfd` argument, which is ignored if the path /// is absolute, and evokes an `EBADF` error otherwise. /// /// [`openat`]: crate::fs::openat /// [`BADF`]: crate::io::Errno::BADF // SAFETY: This `-EBADF` convention is commonly used, such as in lxc, so OS's // aren't going to break it. pub const ABS: BorrowedFd<'static> = unsafe { BorrowedFd::<'static>::borrow_raw(c::EBADF.wrapping_neg() as RawFd) }; #[cfg(test)] mod tests { use super::*; use crate::fd::AsRawFd; #[test] fn test_cwd() { assert!(CWD.as_raw_fd() != -1); #[cfg(linux_kernel)] #[cfg(feature = "io_uring")] assert!(CWD.as_raw_fd() != linux_raw_sys::io_uring::IORING_REGISTER_FILES_SKIP); } #[test] fn test_abs() { assert!(ABS.as_raw_fd() < 0); assert!(ABS.as_raw_fd() != -1); assert!(ABS.as_raw_fd() != c::AT_FDCWD); #[cfg(linux_kernel)] #[cfg(feature = "io_uring")] assert!(ABS.as_raw_fd() != linux_raw_sys::io_uring::IORING_REGISTER_FILES_SKIP); } }