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//! Types for working with files. use std::fs; use std::io::{Read as _, Seek, SeekFrom, Write as _}; use std::path::Path; use std::pin::Pin; use std::sync::Mutex; use cfg_if::cfg_if; use futures::future::{self, FutureExt, TryFutureExt}; use futures::io::{AsyncRead, AsyncSeek, AsyncWrite, Initializer}; use crate::future::Future; use crate::io; use crate::task::{blocking, Context, Poll}; /// A reference to a file on the filesystem. /// /// An instance of a `File` can be read and/or written depending on what options it was opened /// with. /// /// Files are automatically closed when they go out of scope. Errors detected on closing are /// ignored by the implementation of `Drop`. Use the method [`sync_all`] if these errors must be /// manually handled. /// /// This type is an async version of [`std::fs::File`]. /// /// [`sync_all`]: struct.File.html#method.sync_all /// [`std::fs::File`]: https://doc.rust-lang.org/std/fs/struct.File.html /// /// # Examples /// /// Create a new file and write some bytes to it: /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// use async_std::prelude::*; /// /// let mut file = File::create("a.txt").await?; /// file.write_all(b"Hello, world!").await?; /// # /// # Ok(()) }) } /// ``` /// /// Read the contents of a file into a `Vec<u8>`: /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// use async_std::prelude::*; /// /// let mut file = File::open("a.txt").await?; /// let mut contents = Vec::new(); /// file.read_to_end(&mut contents).await?; /// # /// # Ok(()) }) } /// ``` #[derive(Debug)] pub struct File { mutex: Mutex<State>, #[cfg(unix)] raw_fd: std::os::unix::io::RawFd, #[cfg(windows)] raw_handle: UnsafeShared<std::os::windows::io::RawHandle>, } /// The state of an asynchronous file. /// /// The file can be either idle or busy performing an asynchronous operation. #[derive(Debug)] enum State { /// The file is idle. /// /// If the inner representation is `None`, that means the file is closed. Idle(Option<Inner>), /// The file is blocked on an asynchronous operation. /// /// Awaiting this operation will result in the new state of the file. Busy(blocking::JoinHandle<State>), } /// Inner representation of an asynchronous file. #[derive(Debug)] struct Inner { /// The blocking file handle. file: fs::File, /// The read/write buffer. buf: Vec<u8>, /// The result of the last asynchronous operation on the file. last_op: Option<Operation>, } /// Possible results of an asynchronous operation on a file. #[derive(Debug)] enum Operation { Read(io::Result<usize>), Write(io::Result<usize>), Seek(io::Result<u64>), Flush(io::Result<()>), } impl File { /// Opens a file in read-only mode. /// /// See the [`OpenOptions::open`] method for more details. /// /// # Errors /// /// This function will return an error if `path` does not already exist. /// Other errors may also be returned according to [`OpenOptions::open`]. /// /// [`OpenOptions::open`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// /// let file = File::open("a.txt").await?; /// # /// # Ok(()) }) } /// ``` pub async fn open<P: AsRef<Path>>(path: P) -> io::Result<File> { let path = path.as_ref().to_owned(); let file = blocking::spawn(async move { fs::File::open(&path) }).await?; #[cfg(unix)] let file = File { raw_fd: file.as_raw_fd(), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; #[cfg(windows)] let file = File { raw_handle: UnsafeShared(file.as_raw_handle()), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; Ok(file) } /// Opens a file in write-only mode. /// /// This function will create a file if it does not exist, and will truncate it if it does. /// /// See the [`OpenOptions::open`] function for more details. /// /// [`OpenOptions::open`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// /// let file = File::create("a.txt").await?; /// # /// # Ok(()) }) } /// ``` pub async fn create<P: AsRef<Path>>(path: P) -> io::Result<File> { let path = path.as_ref().to_owned(); let file = blocking::spawn(async move { fs::File::create(&path) }).await?; #[cfg(unix)] let file = File { raw_fd: file.as_raw_fd(), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; #[cfg(windows)] let file = File { raw_handle: UnsafeShared(file.as_raw_handle()), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; Ok(file) } /// Attempts to synchronize all OS-internal metadata to disk. /// /// This function will attempt to ensure that all in-memory data reaches the filesystem before /// returning. /// /// This can be used to handle errors that would otherwise only be caught when the `File` is /// closed. Dropping a file will ignore errors in synchronizing this in-memory data. /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// use async_std::prelude::*; /// /// let mut file = File::create("a.txt").await?; /// file.write_all(b"Hello, world!").await?; /// file.sync_all().await?; /// # /// # Ok(()) }) } /// ``` pub async fn sync_all(&self) -> io::Result<()> { future::poll_fn(|cx| { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => match opt.take() { None => return Poll::Ready(None), Some(inner) => { let (s, r) = futures::channel::oneshot::channel(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.sync_all(); let _ = s.send(res); State::Idle(Some(inner)) })); return Poll::Ready(Some(r)); } }, // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } }) .map(|opt| opt.ok_or_else(|| io_error("file closed"))) .await? .map_err(|_| io_error("blocking task failed")) .await? } /// Similar to [`sync_all`], except that it may not synchronize file metadata. /// /// This is intended for use cases that must synchronize content, but don't need the metadata /// on disk. The goal of this method is to reduce disk operations. /// /// Note that some platforms may simply implement this in terms of [`sync_all`]. /// /// [`sync_all`]: struct.File.html#method.sync_all /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// use async_std::prelude::*; /// /// let mut file = File::create("a.txt").await?; /// file.write_all(b"Hello, world!").await?; /// file.sync_data().await?; /// # /// # Ok(()) }) } /// ``` pub async fn sync_data(&self) -> io::Result<()> { future::poll_fn(|cx| { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => match opt.take() { None => return Poll::Ready(None), Some(inner) => { let (s, r) = futures::channel::oneshot::channel(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.sync_data(); let _ = s.send(res); State::Idle(Some(inner)) })); return Poll::Ready(Some(r)); } }, // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } }) .map(|opt| opt.ok_or_else(|| io_error("file closed"))) .await? .map_err(|_| io_error("blocking task failed")) .await? } /// Truncates or extends the underlying file. /// /// If the `size` is less than the current file's size, then the file will be truncated. If it /// is greater than the current file's size, then the file will be extended to `size` and have /// all of the intermediate data filled in with zeros. /// /// The file's cursor isn't changed. In particular, if the cursor was at the end and the file /// is truncated using this operation, the cursor will now be past the end. /// /// # Errors /// /// This function will return an error if the file is not opened for writing. /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// /// let file = File::create("a.txt").await?; /// file.set_len(10).await?; /// # /// # Ok(()) }) } /// ``` pub async fn set_len(&self, size: u64) -> io::Result<()> { future::poll_fn(|cx| { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => match opt.take() { None => return Poll::Ready(None), Some(inner) => { let (s, r) = futures::channel::oneshot::channel(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.set_len(size); let _ = s.send(res); State::Idle(Some(inner)) })); return Poll::Ready(Some(r)); } }, // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } }) .map(|opt| opt.ok_or_else(|| io_error("file closed"))) .await? .map_err(|_| io_error("blocking task failed")) .await? } /// Queries metadata about the file. /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// /// let file = File::open("a.txt").await?; /// let metadata = file.metadata().await?; /// # /// # Ok(()) }) } /// ``` pub async fn metadata(&self) -> io::Result<fs::Metadata> { future::poll_fn(|cx| { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => match opt.take() { None => return Poll::Ready(None), Some(inner) => { let (s, r) = futures::channel::oneshot::channel(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.metadata(); let _ = s.send(res); State::Idle(Some(inner)) })); return Poll::Ready(Some(r)); } }, // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } }) .map(|opt| opt.ok_or_else(|| io_error("file closed"))) .await? .map_err(|_| io_error("blocking task failed")) .await? } /// Changes the permissions on the underlying file. /// /// # Errors /// /// This function will return an error if the user lacks permission to change attributes on the /// underlying file, but may also return an error in other OS-specific cases. /// /// # Examples /// /// ```no_run /// # #![feature(async_await)] /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async { /// # /// use async_std::fs::File; /// /// let file = File::create("a.txt").await?; /// /// let mut perms = file.metadata().await?.permissions(); /// perms.set_readonly(true); /// file.set_permissions(perms).await?; /// # /// # Ok(()) }) } /// ``` pub async fn set_permissions(&self, perm: fs::Permissions) -> io::Result<()> { let mut perm = Some(perm); future::poll_fn(|cx| { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => match opt.take() { None => return Poll::Ready(None), Some(inner) => { let (s, r) = futures::channel::oneshot::channel(); let perm = perm.take().unwrap(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.set_permissions(perm); let _ = s.send(res); State::Idle(Some(inner)) })); return Poll::Ready(Some(r)); } }, // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } }) .map(|opt| opt.ok_or_else(|| io_error("file closed"))) .await? .map_err(|_| io_error("blocking task failed")) .await? } } impl AsyncRead for File { fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8], ) -> Poll<io::Result<usize>> { Pin::new(&mut &*self).poll_read(cx, buf) } #[inline] unsafe fn initializer(&self) -> Initializer { Initializer::nop() } } impl AsyncRead for &File { fn poll_read( mut self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8], ) -> Poll<io::Result<usize>> { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => { // Grab a reference to the inner representation of the file or return an error // if the file is closed. let inner = opt.as_mut().ok_or_else(|| io_error("file closed"))?; let mut offset = 0; // Check if the operation has completed. if let Some(Operation::Read(res)) = inner.last_op.take() { let n = res?; if n <= buf.len() { // Copy the read data into the buffer and return. buf[..n].copy_from_slice(&inner.buf[..n]); return Poll::Ready(Ok(n)); } // If more data was read than fits into the buffer, let's retry the read // operation, but first move the cursor where it was before the previous // read. offset = n; } let mut inner = opt.take().unwrap(); // Set the length of the inner buffer to the length of the provided buffer. if inner.buf.len() < buf.len() { inner.buf.reserve(buf.len() - inner.buf.len()); } unsafe { inner.buf.set_len(buf.len()); } // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { if offset > 0 { let pos = SeekFrom::Current(-(offset as i64)); let _ = Seek::seek(&mut inner.file, pos); } let res = inner.file.read(&mut inner.buf); inner.last_op = Some(Operation::Read(res)); State::Idle(Some(inner)) })); } // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } } #[inline] unsafe fn initializer(&self) -> Initializer { Initializer::nop() } } impl AsyncWrite for File { fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<io::Result<usize>> { Pin::new(&mut &*self).poll_write(cx, buf) } fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { Pin::new(&mut &*self).poll_flush(cx) } fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { Pin::new(&mut &*self).poll_close(cx) } } impl AsyncWrite for &File { fn poll_write( mut self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<io::Result<usize>> { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => { // Grab a reference to the inner representation of the file or return an error // if the file is closed. let inner = opt.as_mut().ok_or_else(|| io_error("file closed"))?; // Check if the operation has completed. if let Some(Operation::Write(res)) = inner.last_op.take() { let n = res?; // If more data was written than is available in the buffer, let's retry // the write operation. if n <= buf.len() { return Poll::Ready(Ok(n)); } } else { let mut inner = opt.take().unwrap(); // Set the length of the inner buffer to the length of the provided buffer. if inner.buf.len() < buf.len() { inner.buf.reserve(buf.len() - inner.buf.len()); } unsafe { inner.buf.set_len(buf.len()); } // Copy the data to write into the inner buffer. inner.buf[..buf.len()].copy_from_slice(buf); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.write(&mut inner.buf); inner.last_op = Some(Operation::Write(res)); State::Idle(Some(inner)) })); } } // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } } fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => { // Grab a reference to the inner representation of the file or return if the // file is closed. let inner = match opt.as_mut() { None => return Poll::Ready(Ok(())), Some(s) => s, }; // Check if the operation has completed. if let Some(Operation::Flush(res)) = inner.last_op.take() { return Poll::Ready(res); } else { let mut inner = opt.take().unwrap(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.flush(); inner.last_op = Some(Operation::Flush(res)); State::Idle(Some(inner)) })); } } // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } } fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => { // Grab a reference to the inner representation of the file or return if the // file is closed. let inner = match opt.take() { None => return Poll::Ready(Ok(())), Some(s) => s, }; // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { drop(inner); State::Idle(None) })); } // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } } } impl AsyncSeek for File { fn poll_seek( self: Pin<&mut Self>, cx: &mut Context<'_>, pos: SeekFrom, ) -> Poll<io::Result<u64>> { Pin::new(&mut &*self).poll_seek(cx, pos) } } impl AsyncSeek for &File { fn poll_seek( mut self: Pin<&mut Self>, cx: &mut Context<'_>, pos: SeekFrom, ) -> Poll<io::Result<u64>> { let state = &mut *self.mutex.lock().unwrap(); loop { match state { State::Idle(opt) => { // Grab a reference to the inner representation of the file or return an error // if the file is closed. let inner = opt.as_mut().ok_or_else(|| io_error("file closed"))?; // Check if the operation has completed. if let Some(Operation::Seek(res)) = inner.last_op.take() { return Poll::Ready(res); } else { let mut inner = opt.take().unwrap(); // Start the operation asynchronously. *state = State::Busy(blocking::spawn(async move { let res = inner.file.seek(pos); inner.last_op = Some(Operation::Seek(res)); State::Idle(Some(inner)) })); } } // Poll the asynchronous operation the file is currently blocked on. State::Busy(task) => *state = futures::ready!(Pin::new(task).poll(cx)), } } } } /// Creates a custom `io::Error` with an arbitrary error type. fn io_error(err: impl Into<Box<dyn std::error::Error + Send + Sync>>) -> io::Error { io::Error::new(io::ErrorKind::Other, err) } impl From<std::fs::File> for File { /// Converts a `std::fs::File` into its asynchronous equivalent. fn from(file: fs::File) -> File { #[cfg(unix)] let file = File { raw_fd: file.as_raw_fd(), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; #[cfg(windows)] let file = File { raw_handle: UnsafeShared(file.as_raw_handle()), mutex: Mutex::new(State::Idle(Some(Inner { file, buf: Vec::new(), last_op: None, }))), }; file } } cfg_if! { if #[cfg(feature = "docs")] { use crate::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd}; use crate::os::windows::io::{AsRawHandle, FromRawHandle, IntoRawHandle, RawHandle}; } else if #[cfg(unix)] { use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd}; } else if #[cfg(windows)] { use std::os::windows::io::{AsRawHandle, FromRawHandle, IntoRawHandle, RawHandle}; } } #[cfg_attr(feature = "docs", doc(cfg(unix)))] cfg_if! { if #[cfg(any(unix, feature = "docs"))] { impl AsRawFd for File { fn as_raw_fd(&self) -> RawFd { self.raw_fd } } impl FromRawFd for File { unsafe fn from_raw_fd(fd: RawFd) -> File { fs::File::from_raw_fd(fd).into() } } impl IntoRawFd for File { fn into_raw_fd(self) -> RawFd { self.raw_fd } } } } #[cfg_attr(feature = "docs", doc(cfg(windows)))] cfg_if! { if #[cfg(any(windows, feature = "docs"))] { impl AsRawHandle for File { fn as_raw_handle(&self) -> RawHandle { self.raw_handle.0 } } impl FromRawHandle for File { unsafe fn from_raw_handle(handle: RawHandle) -> File { fs::File::from_raw_handle(handle).into() } } impl IntoRawHandle for File { fn into_raw_handle(self) -> RawHandle { self.raw_handle.0 } } #[derive(Debug)] struct UnsafeShared<T>(T); unsafe impl<T> Send for UnsafeShared<T> {} unsafe impl<T> Sync for UnsafeShared<T> {} } }