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use crate::io::util::chain::{chain, Chain}; use crate::io::util::read::{read, Read}; use crate::io::util::read_exact::{read_exact, ReadExact}; use crate::io::util::read_to_end::{read_to_end, ReadToEnd}; use crate::io::util::read_to_string::{read_to_string, ReadToString}; use crate::io::util::take::{take, Take}; use crate::io::AsyncRead; cfg_io_util! { /// Read bytes from a source. /// /// Implemented as an extention trait, adding utility methods to all /// [`AsyncRead`] types. Callers will tend to import this trait instead of /// [`AsyncRead`]. /// /// As a convenience, this trait may be imported using the [`prelude`]: /// /// ```no_run /// use tokio::fs::File; /// use tokio::prelude::*; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let mut f = File::open("foo.txt").await?; /// let mut buffer = [0; 10]; /// /// // The `read` method is defined by this trait. /// let n = f.read(&mut buffer[..]).await?; /// /// Ok(()) /// } /// ``` /// /// See [module][crate::io] documentation for more details. /// /// [`AsyncRead`]: AsyncRead /// [`prelude`]: crate::prelude pub trait AsyncReadExt: AsyncRead { /// Create a new `AsyncRead` instance that chains this stream with /// `next`. /// /// The returned `AsyncRead` instance will first read all bytes from this object /// until EOF is encountered. Afterwards the output is equivalent to the /// output of `next`. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `AsyncRead`: /// /// ```no_run /// use tokio::fs::File; /// use tokio::io::{self, AsyncReadExt}; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let f1 = File::open("foo.txt").await?; /// let f2 = File::open("bar.txt").await?; /// /// let mut handle = f1.chain(f2); /// let mut buffer = String::new(); /// /// // read the value into a String. We could use any AsyncRead /// // method here, this is just one example. /// handle.read_to_string(&mut buffer).await?; /// Ok(()) /// } /// ``` fn chain<R>(self, next: R) -> Chain<Self, R> where Self: Sized, R: AsyncRead, { chain(self, next) } /// Pull some bytes from this source into the specified buffer, /// returning how many bytes were read. /// /// Equivalent to: /// /// ```ignore /// async fn read(&mut self, buf: &mut [u8]) -> io::Result<usize>; /// ``` /// /// This function does not provide any guarantees about whether it /// completes immediately or asynchronously /// /// If the return value of this method is `Ok(n)`, then it must be /// guaranteed that `0 <= n <= buf.len()`. A nonzero `n` value indicates /// that the buffer `buf` has been filled in with `n` bytes of data from /// this source. 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. /// /// 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. /// /// Correspondingly, however, *callers* of this method may not assume /// any guarantees about how the implementation uses `buf`. It is /// possible that the code that's supposed to write to the buffer might /// also read from it. It is your responsibility to make sure that `buf` /// is initialized before calling `read`. /// /// # Errors /// /// If this function encounters any form of I/O or other error, an error /// variant will be returned. If an error is returned then it must be /// guaranteed that no bytes were read. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `Read`: /// /// ```no_run /// use tokio::fs::File; /// use tokio::io::{self, AsyncReadExt}; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let mut f = File::open("foo.txt").await?; /// let mut buffer = [0; 10]; /// /// // read up to 10 bytes /// let n = f.read(&mut buffer[..]).await?; /// /// println!("The bytes: {:?}", &buffer[..n]); /// Ok(()) /// } /// ``` fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self> where Self: Unpin, { read(self, buf) } /// Read the exact number of bytes required to fill `buf`. /// /// Equivalent to: /// /// ```ignore /// async fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<usize>; /// ``` /// /// 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. /// /// # Errors /// /// If the operation 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 the operation /// immediately returns. The contents of `buf` are unspecified in this /// case. /// /// If this operation 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. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `Read`: /// /// ```no_run /// use tokio::fs::File; /// use tokio::io::{self, AsyncReadExt}; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let mut f = File::open("foo.txt").await?; /// let mut buffer = [0; 10]; /// /// // read exactly 10 bytes /// f.read_exact(&mut buffer).await?; /// Ok(()) /// } /// ``` /// /// [`ErrorKind::UnexpectedEof`]: std::io::ErrorKind::UnexpectedEof fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExact<'a, Self> where Self: Unpin, { read_exact(self, buf) } /// Read all bytes until EOF in this source, placing them into `buf`. /// /// Equivalent to: /// /// ```ignore /// async fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize>; /// ``` /// /// All bytes read from this source will be appended to the specified /// buffer `buf`. This function will continuously call [`read()`] to /// append more data to `buf` until [`read()`][read] returns `Ok(0)`. /// /// If successful, the total number of bytes read is returned. /// /// # Errors /// /// If a read error is encountered then the `read_to_end` operation /// immediately completes. Any bytes which have already been read will /// be appended to `buf`. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `Read`: /// /// ```no_run /// use tokio::io::{self, AsyncReadExt}; /// use tokio::fs::File; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let mut f = File::open("foo.txt").await?; /// let mut buffer = Vec::new(); /// /// // read the whole file /// f.read_to_end(&mut buffer).await?; /// Ok(()) /// } /// ``` /// /// (See also the [`tokio::fs::read`] convenience function for reading from a /// file.) /// /// [`tokio::fs::read`]: crate::fs::read::read fn read_to_end<'a>(&'a mut self, buf: &'a mut Vec<u8>) -> ReadToEnd<'a, Self> where Self: Unpin, { read_to_end(self, buf) } /// Read all bytes until EOF in this source, appending them to `buf`. /// /// Equivalent to: /// /// ```ignore /// async fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize>; /// ``` /// /// If successful, the number of bytes which were read and appended to /// `buf` is returned. /// /// # Errors /// /// If the data in this stream is *not* valid UTF-8 then an error is /// returned and `buf` is unchanged. /// /// See [`read_to_end`][AsyncReadExt::read_to_end] for other error semantics. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `Read`: /// /// ```no_run /// use tokio::io::{self, AsyncReadExt}; /// use tokio::fs::File; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let mut f = File::open("foo.txt").await?; /// let mut buffer = String::new(); /// /// f.read_to_string(&mut buffer).await?; /// Ok(()) /// } /// ``` /// /// (See also the [`crate::fs::read_to_string`] convenience function for /// reading from a file.) /// /// [`crate::fs::read_to_string`]: crate::fs::read_to_string::read_to_string fn read_to_string<'a>(&'a mut self, dst: &'a mut String) -> ReadToString<'a, Self> where Self: Unpin, { read_to_string(self, dst) } /// Creates an adaptor which reads at most `limit` bytes from it. /// /// This function returns a new instance of `AsyncRead` which will read /// at most `limit` bytes, after which it will always return EOF /// (`Ok(0)`). Any read errors will not count towards the number of /// bytes read and future calls to [`read()`][read] may succeed. /// /// # Examples /// /// [`File`][crate::fs::File]s implement `Read`: /// /// ```no_run /// use tokio::io::{self, AsyncReadExt}; /// use tokio::fs::File; /// /// #[tokio::main] /// async fn main() -> io::Result<()> { /// let f = File::open("foo.txt").await?; /// let mut buffer = [0; 5]; /// /// // read at most five bytes /// let mut handle = f.take(5); /// /// handle.read(&mut buffer).await?; /// Ok(()) /// } /// ``` fn take(self, limit: u64) -> Take<Self> where Self: Sized, { take(self, limit) } } } impl<R: AsyncRead + ?Sized> AsyncReadExt for R {}