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use crate::fs::{asyncify, File}; use std::io; use std::path::Path; /// 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`][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 /// [result]: std::io::Result /// [`File`]: File /// [`File::open`]: File::open /// [`File::create`]: File::create /// [`std::fs::OpenOptions`]: std::fs::OpenOptions /// /// # 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(std::fs::OpenOptions); 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(std::fs::OpenOptions::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 std::fs::OpenOptions { &mut self.0 } } impl From<std::fs::OpenOptions> for OpenOptions { fn from(options: std::fs::OpenOptions) -> OpenOptions { OpenOptions(options) } } impl Default for OpenOptions { fn default() -> Self { Self::new() } }