//! Functions which operate on file descriptors.

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

use crate::fs::Mode;

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

use crate::fs::{Gid, Uid};

use crate::fs::{OFlags, SeekFrom, Timespec};

use crate::{backend, io};

use backend::fd::{AsFd, BorrowedFd};

#[cfg(not(any(

    netbsdlike,

    target_os = "dragonfly",

    target_os = "espidf",

    target_os = "nto",

    target_os = "redox",

    target_os = "vita",

)))]

use backend::fs::types::FallocateFlags;

#[cfg(not(any(

    target_os = "espidf",

    target_os = "solaris",

    target_os = "vita",

    target_os = "wasi"

)))]

use backend::fs::types::FlockOperation;

#[cfg(linux_kernel)]

use backend::fs::types::FsWord;

use backend::fs::types::Stat;

#[cfg(not(any(

    solarish,

    target_os = "espidf",

    target_os = "haiku",

    target_os = "netbsd",

    target_os = "nto",

    target_os = "redox",

    target_os = "vita",

    target_os = "wasi",

)))]

use backend::fs::types::StatFs;

#[cfg(not(any(target_os = "haiku", target_os = "redox", target_os = "wasi")))]

use backend::fs::types::StatVfs;

use core::fmt;

/// Timestamps used by [`utimensat`] and [`futimens`].

///

/// [`utimensat`]: crate::fs::utimensat

/// [`futimens`]: crate::fs::futimens

// This is `repr(C)` and specifically laid out to match the representation used

// by `utimensat` and `futimens`, which expect 2-element arrays of timestamps.

#[repr(C)]

#[derive(Clone)]

pub struct Timestamps {

    /// The timestamp of the last access to a filesystem object.

    pub last_access: Timespec,

    /// The timestamp of the last modification of a filesystem object.

    pub last_modification: Timespec,

}

impl fmt::Debug for Timestamps {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        f.debug_struct("Timestamps")

            .field("last_access.tv_sec", &self.last_access.tv_sec)

            .field("last_access.tv_nsec", &self.last_access.tv_nsec)

            .field("last_modification.tv_sec", &self.last_modification.tv_sec)

            .field("last_modification.tv_nsec", &self.last_modification.tv_nsec)

            .finish()

    }

}

/// The filesystem magic number for procfs.

///

/// See [the `fstatfs` manual page] for more information.

///

/// [the `fstatfs` manual page]: https://man7.org/linux/man-pages/man2/fstatfs.2.html#DESCRIPTION

#[cfg(linux_kernel)]

pub const PROC_SUPER_MAGIC: FsWord = backend::c::PROC_SUPER_MAGIC as FsWord;

/// The filesystem magic number for NFS.

///

/// See [the `fstatfs` manual page] for more information.

///

/// [the `fstatfs` manual page]: https://man7.org/linux/man-pages/man2/fstatfs.2.html#DESCRIPTION

#[cfg(linux_kernel)]

pub const NFS_SUPER_MAGIC: FsWord = backend::c::NFS_SUPER_MAGIC as FsWord;

/// `lseek(fd, offset, whence)`—Repositions a file descriptor within a file.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[inline]

#[doc(alias = "lseek")]

pub fn seek<Fd: AsFd>(fd: Fd, pos: SeekFrom) -> io::Result<u64> {

    backend::fs::syscalls::seek(fd.as_fd(), pos)

}

/// `lseek(fd, 0, SEEK_CUR)`—Returns the current position within a file.

///

/// Return the current position of the file descriptor. This is a subset of

/// the functionality of `seek`, but this interface makes it easier for users

/// to declare their intent not to mutate any state.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[inline]

#[doc(alias = "lseek")]

pub fn tell<Fd: AsFd>(fd: Fd) -> io::Result<u64> {

    backend::fs::syscalls::tell(fd.as_fd())

}

/// `fchmod(fd, mode)`—Sets open file or directory permissions.

///

/// This implementation does not support [`OFlags::PATH`] file descriptors,

/// even on platforms where the host libc emulates it.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

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

#[inline]

pub fn fchmod<Fd: AsFd>(fd: Fd, mode: Mode) -> io::Result<()> {

    backend::fs::syscalls::fchmod(fd.as_fd(), mode)

}

/// `fchown(fd, owner, group)`—Sets open file or directory ownership.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

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

#[inline]

pub fn fchown<Fd: AsFd>(fd: Fd, owner: Option<Uid>, group: Option<Gid>) -> io::Result<()> {

    backend::fs::syscalls::fchown(fd.as_fd(), owner, group)

}

/// `fstat(fd)`—Queries metadata for an open file or directory.

///

/// [`Mode::from_raw_mode`] and [`FileType::from_raw_mode`] may be used to

/// interpret the `st_mode` field.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

/// [`Mode::from_raw_mode`]: Mode::from_raw_mode

/// [`FileType::from_raw_mode`]: crate::fs::FileType::from_raw_mode

#[inline]

pub fn fstat<Fd: AsFd>(fd: Fd) -> io::Result<Stat> {

    backend::fs::syscalls::fstat(fd.as_fd())

}

/// `fstatfs(fd)`—Queries filesystem statistics for an open file or directory.

///

/// Compared to [`fstatvfs`], this function often provides more information,

/// though it's less portable.

///

/// # References

///  - [Linux]

///

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

#[cfg(not(any(

    solarish,

    target_os = "espidf",

    target_os = "haiku",

    target_os = "netbsd",

    target_os = "nto",

    target_os = "redox",

    target_os = "vita",

    target_os = "wasi",

)))]

#[inline]

pub fn fstatfs<Fd: AsFd>(fd: Fd) -> io::Result<StatFs> {

    backend::fs::syscalls::fstatfs(fd.as_fd())

}

/// `fstatvfs(fd)`—Queries filesystem statistics for an open file or

/// directory, POSIX version.

///

/// Compared to [`fstatfs`], this function often provides less information,

/// but it is more portable. But even so, filesystems are very diverse and not

/// all the fields are meaningful for every filesystem. And `f_fsid` doesn't

/// seem to have a clear meaning anywhere.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[cfg(not(any(target_os = "haiku", target_os = "redox", target_os = "wasi")))]

#[inline]

pub fn fstatvfs<Fd: AsFd>(fd: Fd) -> io::Result<StatVfs> {

    backend::fs::syscalls::fstatvfs(fd.as_fd())

}

/// `futimens(fd, times)`—Sets timestamps for an open file or directory.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[cfg(not(any(target_os = "espidf", target_os = "vita")))]

#[inline]

pub fn futimens<Fd: AsFd>(fd: Fd, times: &Timestamps) -> io::Result<()> {

    backend::fs::syscalls::futimens(fd.as_fd(), times)

}

/// `fallocate(fd, mode, offset, len)`—Adjusts file allocation.

///

/// This is a more general form of `posix_fallocate`, adding a `mode` argument

/// which modifies the behavior. On platforms which only support

/// `posix_fallocate` and not the more general form, no `FallocateFlags` values

/// are defined so it will always be empty.

///

/// # References

///  - [POSIX]

///  - [Linux `fallocate`]

///  - [Linux `posix_fallocate`]

///

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

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

/// [Linux `posix_fallocate`]: https://man7.org/linux/man-pages/man3/posix_fallocate.3.html

#[cfg(not(any(

    netbsdlike,

    target_os = "dragonfly",

    target_os = "espidf",

    target_os = "nto",

    target_os = "redox",

    target_os = "vita",

)))] // not implemented in libc for netbsd yet

#[inline]

#[doc(alias = "posix_fallocate")]

pub fn fallocate<Fd: AsFd>(fd: Fd, mode: FallocateFlags, offset: u64, len: u64) -> io::Result<()> {

    backend::fs::syscalls::fallocate(fd.as_fd(), mode, offset, len)

}

/// `fcntl(fd, F_GETFL) & O_ACCMODE`

///

/// Returns a pair of booleans indicating whether the file descriptor is

/// readable and/or writable, respectively. This is only reliable on files; for

/// example, it doesn't reflect whether sockets have been shut down; for

/// general I/O handle support, use [`io::is_read_write`].

#[inline]

pub fn is_file_read_write<Fd: AsFd>(fd: Fd) -> io::Result<(bool, bool)> {

    _is_file_read_write(fd.as_fd())

}

pub(crate) fn _is_file_read_write(fd: BorrowedFd<'_>) -> io::Result<(bool, bool)> {

    let mode = backend::fs::syscalls::fcntl_getfl(fd)?;

    // Check for `O_PATH`.

    #[cfg(any(linux_kernel, target_os = "emscripten", target_os = "fuchsia"))]

    if mode.contains(OFlags::PATH) {

        return Ok((false, false));

    }

    // Use `RWMODE` rather than `ACCMODE` as `ACCMODE` may include `O_PATH`.

    // We handled `O_PATH` above.

    match mode & OFlags::RWMODE {

        OFlags::RDONLY => Ok((true, false)),

        OFlags::RDWR => Ok((true, true)),

        OFlags::WRONLY => Ok((false, true)),

        _ => unreachable!(),

    }

}

/// `fsync(fd)`—Ensures that file data and metadata is written to the

/// underlying storage device.

///

/// On iOS and macOS this isn't sufficient to ensure that data has reached

/// persistent storage; use [`fcntl_fullfsync`] to ensure that.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

/// [`fcntl_fullfsync`]: https://docs.rs/rustix/*/x86_64-apple-darwin/rustix/fs/fn.fcntl_fullfsync.html

#[inline]

pub fn fsync<Fd: AsFd>(fd: Fd) -> io::Result<()> {

    backend::fs::syscalls::fsync(fd.as_fd())

}

/// `fdatasync(fd)`—Ensures that file data is written to the underlying

/// storage device.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[cfg(not(any(

    apple,

    target_os = "dragonfly",

    target_os = "espidf",

    target_os = "haiku",

    target_os = "redox",

    target_os = "vita",

)))]

#[inline]

pub fn fdatasync<Fd: AsFd>(fd: Fd) -> io::Result<()> {

    backend::fs::syscalls::fdatasync(fd.as_fd())

}

/// `ftruncate(fd, length)`—Sets the length of a file.

///

/// # References

///  - [POSIX]

///  - [Linux]

///

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

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

#[inline]

pub fn ftruncate<Fd: AsFd>(fd: Fd, length: u64) -> io::Result<()> {

    backend::fs::syscalls::ftruncate(fd.as_fd(), length)

}

/// `flock(fd, operation)`—Acquire or release an advisory lock on an open file.

///

/// # References

///  - [Linux]

///

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

#[cfg(not(any(

    target_os = "espidf",

    target_os = "solaris",

    target_os = "vita",

    target_os = "wasi"

)))]

#[inline]

pub fn flock<Fd: AsFd>(fd: Fd, operation: FlockOperation) -> io::Result<()> {

    backend::fs::syscalls::flock(fd.as_fd(), operation)

}

/// `syncfs(fd)`—Flush cached filesystem data.

///

/// # References

///  - [Linux]

///

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

#[cfg(linux_kernel)]

#[inline]

pub fn syncfs<Fd: AsFd>(fd: Fd) -> io::Result<()> {

    backend::fs::syscalls::syncfs(fd.as_fd())

}