comm-central/third_party/rust/tokio/src/fs/open_options.rs

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use crate::fs::{asyncify, File};
use std::io;
use std::path::Path;
#[cfg(test)]
mod mock_open_options;
#[cfg(test)]
use mock_open_options::MockOpenOptions as StdOpenOptions;
#[cfg(not(test))]
use std::fs::OpenOptions as StdOpenOptions;
#[cfg(unix)]
use std::os::unix::fs::OpenOptionsExt;
#[cfg(windows)]
use std::os::windows::fs::OpenOptionsExt;
/// Options and flags which can be used to configure how a file is opened.
///
/// This builder exposes the ability to configure how a [`File`] is opened and
/// what operations are permitted on the open file. The [`File::open`] and
/// [`File::create`] methods are aliases for commonly used options using this
/// builder.
///
/// Generally speaking, when using `OpenOptions`, you'll first call [`new`],
/// then chain calls to methods to set each option, then call [`open`], passing
/// the path of the file you're trying to open. This will give you a
/// [`io::Result`] with a [`File`] inside that you can further operate
/// on.
///
/// This is a specialized version of [`std::fs::OpenOptions`] for usage from
/// the Tokio runtime.
///
/// `From<std::fs::OpenOptions>` is implemented for more advanced configuration
/// than the methods provided here.
///
/// [`new`]: OpenOptions::new
/// [`open`]: OpenOptions::open
/// [`File`]: File
/// [`File::open`]: File::open
/// [`File::create`]: File::create
///
/// # Examples
///
/// Opening a file to read:
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .read(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
///
/// Opening a file for both reading and writing, as well as creating it if it
/// doesn't exist:
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .read(true)
/// .write(true)
/// .create(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
#[derive(Clone, Debug)]
pub struct OpenOptions(StdOpenOptions);
impl OpenOptions {
/// Creates a blank new set of options ready for configuration.
///
/// All options are initially set to `false`.
///
/// This is an async version of [`std::fs::OpenOptions::new`][std]
///
/// [std]: std::fs::OpenOptions::new
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
///
/// let mut options = OpenOptions::new();
/// let future = options.read(true).open("foo.txt");
/// ```
pub fn new() -> OpenOptions {
OpenOptions(StdOpenOptions::new())
}
/// Sets the option for read access.
///
/// This option, when true, will indicate that the file should be
/// `read`-able if opened.
///
/// This is an async version of [`std::fs::OpenOptions::read`][std]
///
/// [std]: std::fs::OpenOptions::read
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .read(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn read(&mut self, read: bool) -> &mut OpenOptions {
self.0.read(read);
self
}
/// Sets the option for write access.
///
/// This option, when true, will indicate that the file should be
/// `write`-able if opened.
///
/// This is an async version of [`std::fs::OpenOptions::write`][std]
///
/// [std]: std::fs::OpenOptions::write
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn write(&mut self, write: bool) -> &mut OpenOptions {
self.0.write(write);
self
}
/// Sets the option for the append mode.
///
/// This option, when true, means that writes will append to a file instead
/// of overwriting previous contents. Note that setting
/// `.write(true).append(true)` has the same effect as setting only
/// `.append(true)`.
///
/// For most filesystems, the operating system guarantees that all writes are
/// atomic: no writes get mangled because another process writes at the same
/// time.
///
/// One maybe obvious note when using append-mode: make sure that all data
/// that belongs together is written to the file in one operation. This
/// can be done by concatenating strings before passing them to [`write()`],
/// or using a buffered writer (with a buffer of adequate size),
/// and calling [`flush()`] when the message is complete.
///
/// If a file is opened with both read and append access, beware that after
/// opening, and after every write, the position for reading may be set at the
/// end of the file. So, before writing, save the current position (using
/// [`seek`]`(`[`SeekFrom`]`::`[`Current`]`(0))`), and restore it before the next read.
///
/// This is an async version of [`std::fs::OpenOptions::append`][std]
///
/// [std]: std::fs::OpenOptions::append
///
/// ## Note
///
/// This function doesn't create the file if it doesn't exist. Use the [`create`]
/// method to do so.
///
/// [`write()`]: crate::io::AsyncWriteExt::write
/// [`flush()`]: crate::io::AsyncWriteExt::flush
/// [`seek`]: crate::io::AsyncSeekExt::seek
/// [`SeekFrom`]: std::io::SeekFrom
/// [`Current`]: std::io::SeekFrom::Current
/// [`create`]: OpenOptions::create
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .append(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn append(&mut self, append: bool) -> &mut OpenOptions {
self.0.append(append);
self
}
/// Sets the option for truncating a previous file.
///
/// If a file is successfully opened with this option set it will truncate
/// the file to 0 length if it already exists.
///
/// The file must be opened with write access for truncate to work.
///
/// This is an async version of [`std::fs::OpenOptions::truncate`][std]
///
/// [std]: std::fs::OpenOptions::truncate
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .truncate(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn truncate(&mut self, truncate: bool) -> &mut OpenOptions {
self.0.truncate(truncate);
self
}
/// Sets the option for creating a new file.
///
/// This option indicates whether a new file will be created if the file
/// does not yet already exist.
///
/// In order for the file to be created, [`write`] or [`append`] access must
/// be used.
///
/// This is an async version of [`std::fs::OpenOptions::create`][std]
///
/// [std]: std::fs::OpenOptions::create
/// [`write`]: OpenOptions::write
/// [`append`]: OpenOptions::append
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .create(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn create(&mut self, create: bool) -> &mut OpenOptions {
self.0.create(create);
self
}
/// Sets the option to always create a new file.
///
/// This option indicates whether a new file will be created. No file is
/// allowed to exist at the target location, also no (dangling) symlink.
///
/// This option is useful because it is atomic. Otherwise between checking
/// whether a file exists and creating a new one, the file may have been
/// created by another process (a TOCTOU race condition / attack).
///
/// If `.create_new(true)` is set, [`.create()`] and [`.truncate()`] are
/// ignored.
///
/// The file must be opened with write or append access in order to create a
/// new file.
///
/// This is an async version of [`std::fs::OpenOptions::create_new`][std]
///
/// [std]: std::fs::OpenOptions::create_new
/// [`.create()`]: OpenOptions::create
/// [`.truncate()`]: OpenOptions::truncate
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .create_new(true)
/// .open("foo.txt")
/// .await?;
///
/// Ok(())
/// }
/// ```
pub fn create_new(&mut self, create_new: bool) -> &mut OpenOptions {
self.0.create_new(create_new);
self
}
/// Opens a file at `path` with the options specified by `self`.
///
/// This is an async version of [`std::fs::OpenOptions::open`][std]
///
/// [std]: std::fs::OpenOptions::open
///
/// # Errors
///
/// This function will return an error under a number of different
/// circumstances. Some of these error conditions are listed here, together
/// with their [`ErrorKind`]. The mapping to [`ErrorKind`]s is not part of
/// the compatibility contract of the function, especially the `Other` kind
/// might change to more specific kinds in the future.
///
/// * [`NotFound`]: The specified file does not exist and neither `create`
/// or `create_new` is set.
/// * [`NotFound`]: One of the directory components of the file path does
/// not exist.
/// * [`PermissionDenied`]: The user lacks permission to get the specified
/// access rights for the file.
/// * [`PermissionDenied`]: The user lacks permission to open one of the
/// directory components of the specified path.
/// * [`AlreadyExists`]: `create_new` was specified and the file already
/// exists.
/// * [`InvalidInput`]: Invalid combinations of open options (truncate
/// without write access, no access mode set, etc.).
/// * [`Other`]: One of the directory components of the specified file path
/// was not, in fact, a directory.
/// * [`Other`]: Filesystem-level errors: full disk, write permission
/// requested on a read-only file system, exceeded disk quota, too many
/// open files, too long filename, too many symbolic links in the
/// specified path (Unix-like systems only), etc.
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let file = OpenOptions::new().open("foo.txt").await?;
/// Ok(())
/// }
/// ```
///
/// [`ErrorKind`]: std::io::ErrorKind
/// [`AlreadyExists`]: std::io::ErrorKind::AlreadyExists
/// [`InvalidInput`]: std::io::ErrorKind::InvalidInput
/// [`NotFound`]: std::io::ErrorKind::NotFound
/// [`Other`]: std::io::ErrorKind::Other
/// [`PermissionDenied`]: std::io::ErrorKind::PermissionDenied
pub async fn open(&self, path: impl AsRef<Path>) -> io::Result<File> {
let path = path.as_ref().to_owned();
let opts = self.0.clone();
let std = asyncify(move || opts.open(path)).await?;
Ok(File::from_std(std))
}
/// Returns a mutable reference to the underlying `std::fs::OpenOptions`
pub(super) fn as_inner_mut(&mut self) -> &mut StdOpenOptions {
&mut self.0
}
}
feature! {
#![unix]
impl OpenOptions {
/// Sets the mode bits that a new file will be created with.
///
/// If a new file is created as part of an `OpenOptions::open` call then this
/// specified `mode` will be used as the permission bits for the new file.
/// If no `mode` is set, the default of `0o666` will be used.
/// The operating system masks out bits with the system's `umask`, to produce
/// the final permissions.
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut options = OpenOptions::new();
/// options.mode(0o644); // Give read/write for owner and read for others.
/// let file = options.open("foo.txt").await?;
///
/// Ok(())
/// }
/// ```
pub fn mode(&mut self, mode: u32) -> &mut OpenOptions {
self.as_inner_mut().mode(mode);
self
}
/// Passes custom flags to the `flags` argument of `open`.
///
/// The bits that define the access mode are masked out with `O_ACCMODE`, to
/// ensure they do not interfere with the access mode set by Rusts options.
///
/// Custom flags can only set flags, not remove flags set by Rusts options.
/// This options overwrites any previously set custom flags.
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
/// use std::io;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut options = OpenOptions::new();
/// options.write(true);
/// if cfg!(unix) {
/// options.custom_flags(libc::O_NOFOLLOW);
/// }
/// let file = options.open("foo.txt").await?;
///
/// Ok(())
/// }
/// ```
pub fn custom_flags(&mut self, flags: i32) -> &mut OpenOptions {
self.as_inner_mut().custom_flags(flags);
self
}
}
}
cfg_windows! {
impl OpenOptions {
/// Overrides the `dwDesiredAccess` argument to the call to [`CreateFile`]
/// with the specified value.
///
/// This will override the `read`, `write`, and `append` flags on the
/// `OpenOptions` structure. This method provides fine-grained control over
/// the permissions to read, write and append data, attributes (like hidden
/// and system), and extended attributes.
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
///
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
/// // Open without read and write permission, for example if you only need
/// // to call `stat` on the file
/// let file = OpenOptions::new().access_mode(0).open("foo.txt").await?;
/// # Ok(())
/// # }
/// ```
///
pub fn access_mode(&mut self, access: u32) -> &mut OpenOptions {
self.as_inner_mut().access_mode(access);
self
}
/// Overrides the `dwShareMode` argument to the call to [`CreateFile`] with
/// the specified value.
///
/// By default `share_mode` is set to
/// `FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE`. This allows
/// other processes to read, write, and delete/rename the same file
/// while it is open. Removing any of the flags will prevent other
/// processes from performing the corresponding operation until the file
/// handle is closed.
///
/// # Examples
///
/// ```no_run
/// use tokio::fs::OpenOptions;
///
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
/// // Do not allow others to read or modify this file while we have it open
/// // for writing.
/// let file = OpenOptions::new()
/// .write(true)
/// .share_mode(0)
/// .open("foo.txt").await?;
/// # Ok(())
/// # }
/// ```
///
pub fn share_mode(&mut self, share: u32) -> &mut OpenOptions {
self.as_inner_mut().share_mode(share);
self
}
/// Sets extra flags for the `dwFileFlags` argument to the call to
/// [`CreateFile2`] to the specified value (or combines it with
/// `attributes` and `security_qos_flags` to set the `dwFlagsAndAttributes`
/// for [`CreateFile`]).
///
/// Custom flags can only set flags, not remove flags set by Rust's options.
/// This option overwrites any previously set custom flags.
///
/// # Examples
///
/// ```no_run
/// use windows_sys::Win32::Storage::FileSystem::FILE_FLAG_DELETE_ON_CLOSE;
/// use tokio::fs::OpenOptions;
///
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
/// let file = OpenOptions::new()
/// .create(true)
/// .write(true)
/// .custom_flags(FILE_FLAG_DELETE_ON_CLOSE)
/// .open("foo.txt").await?;
/// # Ok(())
/// # }
/// ```
///
pub fn custom_flags(&mut self, flags: u32) -> &mut OpenOptions {
self.as_inner_mut().custom_flags(flags);
self
}
/// Sets the `dwFileAttributes` argument to the call to [`CreateFile2`] to
/// the specified value (or combines it with `custom_flags` and
/// `security_qos_flags` to set the `dwFlagsAndAttributes` for
/// [`CreateFile`]).
///
/// If a _new_ file is created because it does not yet exist and
/// `.create(true)` or `.create_new(true)` are specified, the new file is
/// given the attributes declared with `.attributes()`.
///
/// If an _existing_ file is opened with `.create(true).truncate(true)`, its
/// existing attributes are preserved and combined with the ones declared
/// with `.attributes()`.
///
/// In all other cases the attributes get ignored.
///
/// # Examples
///
/// ```no_run
/// use windows_sys::Win32::Storage::FileSystem::FILE_ATTRIBUTE_HIDDEN;
/// use tokio::fs::OpenOptions;
///
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .create(true)
/// .attributes(FILE_ATTRIBUTE_HIDDEN)
/// .open("foo.txt").await?;
/// # Ok(())
/// # }
/// ```
///
pub fn attributes(&mut self, attributes: u32) -> &mut OpenOptions {
self.as_inner_mut().attributes(attributes);
self
}
/// Sets the `dwSecurityQosFlags` argument to the call to [`CreateFile2`] to
/// the specified value (or combines it with `custom_flags` and `attributes`
/// to set the `dwFlagsAndAttributes` for [`CreateFile`]).
///
/// By default `security_qos_flags` is not set. It should be specified when
/// opening a named pipe, to control to which degree a server process can
/// act on behalf of a client process (security impersonation level).
///
/// When `security_qos_flags` is not set, a malicious program can gain the
/// elevated privileges of a privileged Rust process when it allows opening
/// user-specified paths, by tricking it into opening a named pipe. So
/// arguably `security_qos_flags` should also be set when opening arbitrary
/// paths. However the bits can then conflict with other flags, specifically
/// `FILE_FLAG_OPEN_NO_RECALL`.
///
/// For information about possible values, see [Impersonation Levels] on the
/// Windows Dev Center site. The `SECURITY_SQOS_PRESENT` flag is set
/// automatically when using this method.
///
/// # Examples
///
/// ```no_run
/// use windows_sys::Win32::Storage::FileSystem::SECURITY_IDENTIFICATION;
/// use tokio::fs::OpenOptions;
///
/// # #[tokio::main]
/// # async fn main() -> std::io::Result<()> {
/// let file = OpenOptions::new()
/// .write(true)
/// .create(true)
///
/// // Sets the flag value to `SecurityIdentification`.
/// .security_qos_flags(SECURITY_IDENTIFICATION)
///
/// .open(r"\\.\pipe\MyPipe").await?;
/// # Ok(())
/// # }
/// ```
///
/// [Impersonation Levels]:
pub fn security_qos_flags(&mut self, flags: u32) -> &mut OpenOptions {
self.as_inner_mut().security_qos_flags(flags);
self
}
}
}
impl From<StdOpenOptions> for OpenOptions {
fn from(options: StdOpenOptions) -> OpenOptions {
OpenOptions(options)
}
}
impl Default for OpenOptions {
fn default() -> Self {
Self::new()
}
}