mod.rs - source
Description: Source of the Rust file `library/std/src/io/buffered/mod.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Buffering wrappers for I/O traits

    mod bufreader;
    mod bufwriter;
    mod linewriter;
    mod linewritershim;

    #[cfg(test)]
    mod tests;

    use crate::error;
    use crate::fmt;
    use crate::io::Error;

    pub use bufreader::BufReader;
    pub use bufwriter::BufWriter;
    pub use linewriter::LineWriter;
    use linewritershim::LineWriterShim;

    /// An error returned by [`BufWriter::into_inner`] which combines an error that
    /// happened while writing out the buffer, and the buffered writer object
    /// which may be used to recover from the condition.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use std::io::BufWriter;
    /// use std::net::TcpStream;
    ///
    /// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
    ///
    /// // do stuff with the stream
    ///
    /// // we want to get our `TcpStream` back, so let's try:
    ///
    /// let stream = match stream.into_inner() {
    ///     Ok(s) => s,
    ///     Err(e) => {
    ///         // Here, e is an IntoInnerError
    ///         panic!("An error occurred");
    ///     }
    /// };
    /// ```
    #[derive(Debug)]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct IntoInnerError<W>(W, Error);

    impl<W> IntoInnerError<W> {
        /// Construct a new IntoInnerError
        fn new(writer: W, error: Error) -> Self {
            Self(writer, error)
        }

        /// Helper to construct a new IntoInnerError; intended to help with
        /// adapters that wrap other adapters
        fn new_wrapped<W2>(self, f: impl FnOnce(W) -> W2) -> IntoInnerError<W2> {
            let Self(writer, error) = self;
            IntoInnerError::new(f(writer), error)
        }

        /// Returns the error which caused the call to [`BufWriter::into_inner()`]
        /// to fail.
        ///
        /// This error was returned when attempting to write the internal buffer.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io::BufWriter;
        /// use std::net::TcpStream;
        ///
        /// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
        ///
        /// // do stuff with the stream
        ///
        /// // we want to get our `TcpStream` back, so let's try:
        ///
        /// let stream = match stream.into_inner() {
        ///     Ok(s) => s,
        ///     Err(e) => {
        ///         // Here, e is an IntoInnerError, let's log the inner error.
        ///         //
        ///         // We'll just 'log' to stdout for this example.
        ///         println!("{}", e.error());
        ///
        ///         panic!("An unexpected error occurred.");
        ///     }
        /// };
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn error(&self) -> &Error {
            &self.1
        }

        /// Returns the buffered writer instance which generated the error.
        ///
        /// The returned object can be used for error recovery, such as
        /// re-inspecting the buffer.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io::BufWriter;
        /// use std::net::TcpStream;
        ///
        /// let mut stream = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
        ///
        /// // do stuff with the stream
        ///
        /// // we want to get our `TcpStream` back, so let's try:
        ///
        /// let stream = match stream.into_inner() {
        ///     Ok(s) => s,
        ///     Err(e) => {
        ///         // Here, e is an IntoInnerError, let's re-examine the buffer:
        ///         let buffer = e.into_inner();
        ///
        ///         // do stuff to try to recover
        ///
        ///         // afterwards, let's just return the stream
        ///         buffer.into_inner().unwrap()
        ///     }
        /// };
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn into_inner(self) -> W {
            self.0
        }

        /// Consumes the [`IntoInnerError`] and returns the error which caused the call to
        /// [`BufWriter::into_inner()`] to fail.  Unlike `error`, this can be used to
        /// obtain ownership of the underlying error.
        ///
        /// # Example
        /// ```
        /// #![feature(io_into_inner_error_parts)]
        /// use std::io::{BufWriter, ErrorKind, Write};
        ///
        /// let mut not_enough_space = [0u8; 10];
        /// let mut stream = BufWriter::new(not_enough_space.as_mut());
        /// write!(stream, "this cannot be actually written").unwrap();
        /// let into_inner_err = stream.into_inner().expect_err("now we discover it's too small");
        /// let err = into_inner_err.into_error();
        /// assert_eq!(err.kind(), ErrorKind::WriteZero);
        /// ```
        #[unstable(feature = "io_into_inner_error_parts", issue = "79704")]
        pub fn into_error(self) -> Error {
            self.1
        }

        /// Consumes the [`IntoInnerError`] and returns the error which caused the call to
        /// [`BufWriter::into_inner()`] to fail, and the underlying writer.
        ///
        /// This can be used to simply obtain ownership of the underlying error; it can also be used for
        /// advanced error recovery.
        ///
        /// # Example
        /// ```
        /// #![feature(io_into_inner_error_parts)]
        /// use std::io::{BufWriter, ErrorKind, Write};
        ///
        /// let mut not_enough_space = [0u8; 10];
        /// let mut stream = BufWriter::new(not_enough_space.as_mut());
        /// write!(stream, "this cannot be actually written").unwrap();
        /// let into_inner_err = stream.into_inner().expect_err("now we discover it's too small");
        /// let (err, recovered_writer) = into_inner_err.into_parts();
        /// assert_eq!(err.kind(), ErrorKind::WriteZero);
        /// assert_eq!(recovered_writer.buffer(), b"t be actually written");
        /// ```
        #[unstable(feature = "io_into_inner_error_parts", issue = "79704")]
        pub fn into_parts(self) -> (Error, W) {
            (self.1, self.0)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<W> From<IntoInnerError<W>> for Error {
        fn from(iie: IntoInnerError<W>) -> Error {
            iie.1
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> {
        #[allow(deprecated, deprecated_in_future)]
        fn description(&self) -> &str {
            error::Error::description(self.error())
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<W> fmt::Display for IntoInnerError<W> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            self.error().fmt(f)
        }
    }