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mod read; mod read_exact; mod read_to_end; mod read_to_string; mod read_vectored; use read::ReadFuture; use read_exact::ReadExactFuture; use read_to_end::{read_to_end_internal, ReadToEndFuture}; use read_to_string::ReadToStringFuture; use read_vectored::ReadVectoredFuture; use std::io; use std::mem; use cfg_if::cfg_if; use futures_io::AsyncRead; cfg_if! { if #[cfg(feature = "docs")] { #[doc(hidden)] pub struct ImplFuture<'a, T>(std::marker::PhantomData<&'a T>); macro_rules! ret { ($a:lifetime, $f:tt, $o:ty) => (ImplFuture<$a, $o>); } } else { macro_rules! ret { ($a:lifetime, $f:tt, $o:ty) => ($f<$a, Self>); } } } /// Allows reading from a byte stream. /// /// This trait is an async version of [`std::io::Read`]. /// /// While it is currently not possible to implement this trait directly, it gets implemented /// automatically for all types that implement [`futures::io::AsyncRead`]. /// /// [`std::io::Read`]: https://doc.rust-lang.org/std/io/trait.Read.html /// [`futures::io::AsyncRead`]: /// https://docs.rs/futures-preview/0.3.0-alpha.17/futures/io/trait.AsyncRead.html pub trait Read { /// Reads some bytes from the byte stream. /// /// Returns the number of bytes read from the start of the buffer. /// /// If the return value is `Ok(n)`, then it must be guaranteed that `0 <= n <= buf.len()`. A /// nonzero `n` value indicates that the buffer has been filled in with `n` bytes of data. If /// `n` is `0`, then it can indicate one of two scenarios: /// /// 1. This reader has reached its "end of file" and will likely no longer be able to produce /// bytes. Note that this does not mean that the reader will always no longer be able to /// produce bytes. /// 2. The buffer specified was 0 bytes in length. /// /// # Examples /// /// ```no_run /// # 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 buf = vec![0; 1024]; /// let n = file.read(&mut buf).await?; /// # /// # Ok(()) }) } /// ``` fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> ret!('a, ReadFuture, io::Result<usize>) where Self: Unpin; /// Like [`read`], except that it reads into a slice of buffers. /// /// Data is copied to fill each buffer in order, with the final buffer written to possibly /// being only partially filled. This method must behave as a single call to [`read`] with the /// buffers concatenated would. /// /// The default implementation calls [`read`] with either the first nonempty buffer provided, /// or an empty one if none exists. /// /// [`read`]: #tymethod.read fn read_vectored<'a>( &'a mut self, bufs: &'a mut [io::IoSliceMut<'a>], ) -> ret!('a, ReadVectoredFuture, io::Result<usize>) where Self: Unpin, { ReadVectoredFuture { reader: self, bufs } } /// Reads all bytes from the byte stream. /// /// All bytes read from this stream will be appended to the specified buffer `buf`. This /// function will continuously call [`read`] to append more data to `buf` until [`read`] /// returns either `Ok(0)` or an error. /// /// If successful, this function will return the total number of bytes read. /// /// [`read`]: #tymethod.read /// /// # Examples /// /// ```no_run /// # 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 buf = Vec::new(); /// file.read_to_end(&mut buf).await?; /// # /// # Ok(()) }) } /// ``` fn read_to_end<'a>( &'a mut self, buf: &'a mut Vec<u8>, ) -> ret!('a, ReadToEndFuture, io::Result<usize>) where Self: Unpin, { let start_len = buf.len(); ReadToEndFuture { reader: self, buf, start_len, } } /// Reads all bytes from the byte stream and appends them into a string. /// /// If successful, this function will return the number of bytes read. /// /// If the data in this stream is not valid UTF-8 then an error will be returned and `buf` will /// be left unmodified. /// /// # Examples /// /// ```no_run /// # 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 buf = String::new(); /// file.read_to_string(&mut buf).await?; /// # /// # Ok(()) }) } /// ``` fn read_to_string<'a>( &'a mut self, buf: &'a mut String, ) -> ret!('a, ReadToStringFuture, io::Result<usize>) where Self: Unpin, { let start_len = buf.len(); ReadToStringFuture { reader: self, bytes: unsafe { mem::replace(buf.as_mut_vec(), Vec::new()) }, buf, start_len, } } /// Reads the exact number of bytes required to fill `buf`. /// /// This function reads as many bytes as necessary to completely fill the specified buffer /// `buf`. /// /// No guarantees are provided about the contents of `buf` when this function is called, /// implementations cannot rely on any property of the contents of `buf` being true. It is /// recommended that implementations only write data to `buf` instead of reading its contents. /// /// If this function encounters an "end of file" before completely filling the buffer, it /// returns an error of the kind [`ErrorKind::UnexpectedEof`]. The contents of `buf` are /// unspecified in this case. /// /// If any other read error is encountered then this function immediately returns. The contents /// of `buf` are unspecified in this case. /// /// If this function returns an error, it is unspecified how many bytes it has read, but it /// will never read more than would be necessary to completely fill the buffer. /// /// [`ErrorKind::UnexpectedEof`]: enum.ErrorKind.html#variant.UnexpectedEof /// /// # Examples /// /// ```no_run /// # 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 buf = vec![0; 10]; /// file.read_exact(&mut buf).await?; /// # /// # Ok(()) }) } /// ``` fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ret!('a, ReadExactFuture, io::Result<()>) where Self: Unpin, { ReadExactFuture { reader: self, buf } } } impl<T: AsyncRead + Unpin + ?Sized> Read for T { fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> ret!('a, ReadFuture, io::Result<usize>) { ReadFuture { reader: self, buf } } }