From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- library/std/src/io/mod.rs | 2827 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 2827 insertions(+) create mode 100644 library/std/src/io/mod.rs (limited to 'library/std/src/io/mod.rs') diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs new file mode 100644 index 000000000..96addbd1a --- /dev/null +++ b/library/std/src/io/mod.rs @@ -0,0 +1,2827 @@ +//! Traits, helpers, and type definitions for core I/O functionality. +//! +//! The `std::io` module contains a number of common things you'll need +//! when doing input and output. The most core part of this module is +//! the [`Read`] and [`Write`] traits, which provide the +//! most general interface for reading and writing input and output. +//! +//! # Read and Write +//! +//! Because they are traits, [`Read`] and [`Write`] are implemented by a number +//! of other types, and you can implement them for your types too. As such, +//! you'll see a few different types of I/O throughout the documentation in +//! this module: [`File`]s, [`TcpStream`]s, and sometimes even [`Vec`]s. For +//! example, [`Read`] adds a [`read`][`Read::read`] method, which we can use on +//! [`File`]s: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! use std::fs::File; +//! +//! fn main() -> io::Result<()> { +//! let mut f = File::open("foo.txt")?; +//! let mut buffer = [0; 10]; +//! +//! // read up to 10 bytes +//! let n = f.read(&mut buffer)?; +//! +//! println!("The bytes: {:?}", &buffer[..n]); +//! Ok(()) +//! } +//! ``` +//! +//! [`Read`] and [`Write`] are so important, implementors of the two traits have a +//! nickname: readers and writers. So you'll sometimes see 'a reader' instead +//! of 'a type that implements the [`Read`] trait'. Much easier! +//! +//! ## Seek and BufRead +//! +//! Beyond that, there are two important traits that are provided: [`Seek`] +//! and [`BufRead`]. Both of these build on top of a reader to control +//! how the reading happens. [`Seek`] lets you control where the next byte is +//! coming from: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! use std::io::SeekFrom; +//! use std::fs::File; +//! +//! fn main() -> io::Result<()> { +//! let mut f = File::open("foo.txt")?; +//! let mut buffer = [0; 10]; +//! +//! // skip to the last 10 bytes of the file +//! f.seek(SeekFrom::End(-10))?; +//! +//! // read up to 10 bytes +//! let n = f.read(&mut buffer)?; +//! +//! println!("The bytes: {:?}", &buffer[..n]); +//! Ok(()) +//! } +//! ``` +//! +//! [`BufRead`] uses an internal buffer to provide a number of other ways to read, but +//! to show it off, we'll need to talk about buffers in general. Keep reading! +//! +//! ## BufReader and BufWriter +//! +//! Byte-based interfaces are unwieldy and can be inefficient, as we'd need to be +//! making near-constant calls to the operating system. To help with this, +//! `std::io` comes with two structs, [`BufReader`] and [`BufWriter`], which wrap +//! readers and writers. The wrapper uses a buffer, reducing the number of +//! calls and providing nicer methods for accessing exactly what you want. +//! +//! For example, [`BufReader`] works with the [`BufRead`] trait to add extra +//! methods to any reader: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! use std::io::BufReader; +//! use std::fs::File; +//! +//! fn main() -> io::Result<()> { +//! let f = File::open("foo.txt")?; +//! let mut reader = BufReader::new(f); +//! let mut buffer = String::new(); +//! +//! // read a line into buffer +//! reader.read_line(&mut buffer)?; +//! +//! println!("{buffer}"); +//! Ok(()) +//! } +//! ``` +//! +//! [`BufWriter`] doesn't add any new ways of writing; it just buffers every call +//! to [`write`][`Write::write`]: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! use std::io::BufWriter; +//! use std::fs::File; +//! +//! fn main() -> io::Result<()> { +//! let f = File::create("foo.txt")?; +//! { +//! let mut writer = BufWriter::new(f); +//! +//! // write a byte to the buffer +//! writer.write(&[42])?; +//! +//! } // the buffer is flushed once writer goes out of scope +//! +//! Ok(()) +//! } +//! ``` +//! +//! ## Standard input and output +//! +//! A very common source of input is standard input: +//! +//! ```no_run +//! use std::io; +//! +//! fn main() -> io::Result<()> { +//! let mut input = String::new(); +//! +//! io::stdin().read_line(&mut input)?; +//! +//! println!("You typed: {}", input.trim()); +//! Ok(()) +//! } +//! ``` +//! +//! Note that you cannot use the [`?` operator] in functions that do not return +//! a [`Result`][`Result`]. Instead, you can call [`.unwrap()`] +//! or `match` on the return value to catch any possible errors: +//! +//! ```no_run +//! use std::io; +//! +//! let mut input = String::new(); +//! +//! io::stdin().read_line(&mut input).unwrap(); +//! ``` +//! +//! And a very common source of output is standard output: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! +//! fn main() -> io::Result<()> { +//! io::stdout().write(&[42])?; +//! Ok(()) +//! } +//! ``` +//! +//! Of course, using [`io::stdout`] directly is less common than something like +//! [`println!`]. +//! +//! ## Iterator types +//! +//! A large number of the structures provided by `std::io` are for various +//! ways of iterating over I/O. For example, [`Lines`] is used to split over +//! lines: +//! +//! ```no_run +//! use std::io; +//! use std::io::prelude::*; +//! use std::io::BufReader; +//! use std::fs::File; +//! +//! fn main() -> io::Result<()> { +//! let f = File::open("foo.txt")?; +//! let reader = BufReader::new(f); +//! +//! for line in reader.lines() { +//! println!("{}", line?); +//! } +//! Ok(()) +//! } +//! ``` +//! +//! ## Functions +//! +//! There are a number of [functions][functions-list] that offer access to various +//! features. For example, we can use three of these functions to copy everything +//! from standard input to standard output: +//! +//! ```no_run +//! use std::io; +//! +//! fn main() -> io::Result<()> { +//! io::copy(&mut io::stdin(), &mut io::stdout())?; +//! Ok(()) +//! } +//! ``` +//! +//! [functions-list]: #functions-1 +//! +//! ## io::Result +//! +//! Last, but certainly not least, is [`io::Result`]. This type is used +//! as the return type of many `std::io` functions that can cause an error, and +//! can be returned from your own functions as well. Many of the examples in this +//! module use the [`?` operator]: +//! +//! ``` +//! use std::io; +//! +//! fn read_input() -> io::Result<()> { +//! let mut input = String::new(); +//! +//! io::stdin().read_line(&mut input)?; +//! +//! println!("You typed: {}", input.trim()); +//! +//! Ok(()) +//! } +//! ``` +//! +//! The return type of `read_input()`, [`io::Result<()>`][`io::Result`], is a very +//! common type for functions which don't have a 'real' return value, but do want to +//! return errors if they happen. In this case, the only purpose of this function is +//! to read the line and print it, so we use `()`. +//! +//! ## Platform-specific behavior +//! +//! Many I/O functions throughout the standard library are documented to indicate +//! what various library or syscalls they are delegated to. This is done to help +//! applications both understand what's happening under the hood as well as investigate +//! any possibly unclear semantics. Note, however, that this is informative, not a binding +//! contract. The implementation of many of these functions are subject to change over +//! time and may call fewer or more syscalls/library functions. +//! +//! [`File`]: crate::fs::File +//! [`TcpStream`]: crate::net::TcpStream +//! [`io::stdout`]: stdout +//! [`io::Result`]: self::Result +//! [`?` operator]: ../../book/appendix-02-operators.html +//! [`Result`]: crate::result::Result +//! [`.unwrap()`]: crate::result::Result::unwrap + +#![stable(feature = "rust1", since = "1.0.0")] + +#[cfg(test)] +mod tests; + +use crate::cmp; +use crate::fmt; +use crate::mem::replace; +use crate::ops::{Deref, DerefMut}; +use crate::slice; +use crate::str; +use crate::sys; +use crate::sys_common::memchr; + +#[stable(feature = "bufwriter_into_parts", since = "1.56.0")] +pub use self::buffered::WriterPanicked; +#[unstable(feature = "internal_output_capture", issue = "none")] +#[doc(no_inline, hidden)] +pub use self::stdio::set_output_capture; +#[unstable(feature = "print_internals", issue = "none")] +pub use self::stdio::{_eprint, _print}; +#[stable(feature = "rust1", since = "1.0.0")] +pub use self::{ + buffered::{BufReader, BufWriter, IntoInnerError, LineWriter}, + copy::copy, + cursor::Cursor, + error::{Error, ErrorKind, Result}, + stdio::{stderr, stdin, stdout, Stderr, StderrLock, Stdin, StdinLock, Stdout, StdoutLock}, + util::{empty, repeat, sink, Empty, Repeat, Sink}, +}; + +#[unstable(feature = "read_buf", issue = "78485")] +pub use self::readbuf::ReadBuf; +pub(crate) use error::const_io_error; + +mod buffered; +pub(crate) mod copy; +mod cursor; +mod error; +mod impls; +pub mod prelude; +mod readbuf; +mod stdio; +mod util; + +const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE; + +pub(crate) use stdio::cleanup; + +struct Guard<'a> { + buf: &'a mut Vec, + len: usize, +} + +impl Drop for Guard<'_> { + fn drop(&mut self) { + unsafe { + self.buf.set_len(self.len); + } + } +} + +// Several `read_to_string` and `read_line` methods in the standard library will +// append data into a `String` buffer, but we need to be pretty careful when +// doing this. The implementation will just call `.as_mut_vec()` and then +// delegate to a byte-oriented reading method, but we must ensure that when +// returning we never leave `buf` in a state such that it contains invalid UTF-8 +// in its bounds. +// +// To this end, we use an RAII guard (to protect against panics) which updates +// the length of the string when it is dropped. This guard initially truncates +// the string to the prior length and only after we've validated that the +// new contents are valid UTF-8 do we allow it to set a longer length. +// +// The unsafety in this function is twofold: +// +// 1. We're looking at the raw bytes of `buf`, so we take on the burden of UTF-8 +// checks. +// 2. We're passing a raw buffer to the function `f`, and it is expected that +// the function only *appends* bytes to the buffer. We'll get undefined +// behavior if existing bytes are overwritten to have non-UTF-8 data. +pub(crate) unsafe fn append_to_string(buf: &mut String, f: F) -> Result +where + F: FnOnce(&mut Vec) -> Result, +{ + let mut g = Guard { len: buf.len(), buf: buf.as_mut_vec() }; + let ret = f(g.buf); + if str::from_utf8(&g.buf[g.len..]).is_err() { + ret.and_then(|_| { + Err(error::const_io_error!( + ErrorKind::InvalidData, + "stream did not contain valid UTF-8" + )) + }) + } else { + g.len = g.buf.len(); + ret + } +} + +// This uses an adaptive system to extend the vector when it fills. We want to +// avoid paying to allocate and zero a huge chunk of memory if the reader only +// has 4 bytes while still making large reads if the reader does have a ton +// of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every +// time is 4,500 times (!) slower than a default reservation size of 32 if the +// reader has a very small amount of data to return. +pub(crate) fn default_read_to_end(r: &mut R, buf: &mut Vec) -> Result { + let start_len = buf.len(); + let start_cap = buf.capacity(); + + let mut initialized = 0; // Extra initialized bytes from previous loop iteration + loop { + if buf.len() == buf.capacity() { + buf.reserve(32); // buf is full, need more space + } + + let mut read_buf = ReadBuf::uninit(buf.spare_capacity_mut()); + + // SAFETY: These bytes were initialized but not filled in the previous loop + unsafe { + read_buf.assume_init(initialized); + } + + match r.read_buf(&mut read_buf) { + Ok(()) => {} + Err(e) if e.kind() == ErrorKind::Interrupted => continue, + Err(e) => return Err(e), + } + + if read_buf.filled_len() == 0 { + return Ok(buf.len() - start_len); + } + + // store how much was initialized but not filled + initialized = read_buf.initialized_len() - read_buf.filled_len(); + let new_len = read_buf.filled_len() + buf.len(); + + // SAFETY: ReadBuf's invariants mean this much memory is init + unsafe { + buf.set_len(new_len); + } + + if buf.len() == buf.capacity() && buf.capacity() == start_cap { + // The buffer might be an exact fit. Let's read into a probe buffer + // and see if it returns `Ok(0)`. If so, we've avoided an + // unnecessary doubling of the capacity. But if not, append the + // probe buffer to the primary buffer and let its capacity grow. + let mut probe = [0u8; 32]; + + loop { + match r.read(&mut probe) { + Ok(0) => return Ok(buf.len() - start_len), + Ok(n) => { + buf.extend_from_slice(&probe[..n]); + break; + } + Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, + Err(e) => return Err(e), + } + } + } + } +} + +pub(crate) fn default_read_to_string( + r: &mut R, + buf: &mut String, +) -> Result { + // Note that we do *not* call `r.read_to_end()` here. We are passing + // `&mut Vec` (the raw contents of `buf`) into the `read_to_end` + // method to fill it up. An arbitrary implementation could overwrite the + // entire contents of the vector, not just append to it (which is what + // we are expecting). + // + // To prevent extraneously checking the UTF-8-ness of the entire buffer + // we pass it to our hardcoded `default_read_to_end` implementation which + // we know is guaranteed to only read data into the end of the buffer. + unsafe { append_to_string(buf, |b| default_read_to_end(r, b)) } +} + +pub(crate) fn default_read_vectored(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result +where + F: FnOnce(&mut [u8]) -> Result, +{ + let buf = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b| &mut **b); + read(buf) +} + +pub(crate) fn default_write_vectored(write: F, bufs: &[IoSlice<'_>]) -> Result +where + F: FnOnce(&[u8]) -> Result, +{ + let buf = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b| &**b); + write(buf) +} + +pub(crate) fn default_read_exact(this: &mut R, mut buf: &mut [u8]) -> Result<()> { + while !buf.is_empty() { + match this.read(buf) { + Ok(0) => break, + Ok(n) => { + let tmp = buf; + buf = &mut tmp[n..]; + } + Err(ref e) if e.kind() == ErrorKind::Interrupted => {} + Err(e) => return Err(e), + } + } + if !buf.is_empty() { + Err(error::const_io_error!(ErrorKind::UnexpectedEof, "failed to fill whole buffer")) + } else { + Ok(()) + } +} + +pub(crate) fn default_read_buf(read: F, buf: &mut ReadBuf<'_>) -> Result<()> +where + F: FnOnce(&mut [u8]) -> Result, +{ + let n = read(buf.initialize_unfilled())?; + buf.add_filled(n); + Ok(()) +} + +/// The `Read` trait allows for reading bytes from a source. +/// +/// Implementors of the `Read` trait are called 'readers'. +/// +/// Readers are defined by one required method, [`read()`]. Each call to [`read()`] +/// will attempt to pull bytes from this source into a provided buffer. A +/// number of other methods are implemented in terms of [`read()`], giving +/// implementors a number of ways to read bytes while only needing to implement +/// a single method. +/// +/// Readers are intended to be composable with one another. Many implementors +/// throughout [`std::io`] take and provide types which implement the `Read` +/// trait. +/// +/// Please note that each call to [`read()`] may involve a system call, and +/// therefore, using something that implements [`BufRead`], such as +/// [`BufReader`], will be more efficient. +/// +/// # Examples +/// +/// [`File`]s implement `Read`: +/// +/// ```no_run +/// use std::io; +/// use std::io::prelude::*; +/// use std::fs::File; +/// +/// fn main() -> io::Result<()> { +/// let mut f = File::open("foo.txt")?; +/// let mut buffer = [0; 10]; +/// +/// // read up to 10 bytes +/// f.read(&mut buffer)?; +/// +/// let mut buffer = Vec::new(); +/// // read the whole file +/// f.read_to_end(&mut buffer)?; +/// +/// // read into a String, so that you don't need to do the conversion. +/// let mut buffer = String::new(); +/// f.read_to_string(&mut buffer)?; +/// +/// // and more! See the other methods for more details. +/// Ok(()) +/// } +/// ``` +/// +/// Read from [`&str`] because [`&[u8]`][prim@slice] implements `Read`: +/// +/// ```no_run +/// # use std::io; +/// use std::io::prelude::*; +/// +/// fn main() -> io::Result<()> { +/// let mut b = "This string will be read".as_bytes(); +/// let mut buffer = [0; 10]; +/// +/// // read up to 10 bytes +/// b.read(&mut buffer)?; +/// +/// // etc... it works exactly as a File does! +/// Ok(()) +/// } +/// ``` +/// +/// [`read()`]: Read::read +/// [`&str`]: prim@str +/// [`std::io`]: self +/// [`File`]: crate::fs::File +#[stable(feature = "rust1", since = "1.0.0")] +#[doc(notable_trait)] +#[cfg_attr(not(test), rustc_diagnostic_item = "IoRead")] +pub trait Read { + /// Pull some bytes from this source into the specified buffer, returning + /// how many bytes were read. + /// + /// This function does not provide any guarantees about whether it blocks + /// waiting for data, but if an object needs to block for a read and cannot, + /// it will typically signal this via an [`Err`] return value. + /// + /// If the return value of this method is [`Ok(n)`], then implementations must + /// guarantee 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. As an example, + /// on Linux, this method will call the `recv` syscall for a [`TcpStream`], + /// where returning zero indicates the connection was shut down correctly. While + /// for [`File`], it is possible to reach the end of file and get zero as result, + /// but if more data is appended to the file, future calls to `read` will return + /// more data. + /// 2. The buffer specified was 0 bytes in length. + /// + /// It is not an error if the returned value `n` is smaller than the buffer size, + /// even when the reader is not at the end of the stream yet. + /// This may happen for example because fewer bytes are actually available right now + /// (e. g. being close to end-of-file) or because read() was interrupted by a signal. + /// + /// As this trait is safe to implement, callers cannot rely on `n <= buf.len()` for safety. + /// Extra care needs to be taken when `unsafe` functions are used to access the read bytes. + /// Callers have to ensure that no unchecked out-of-bounds accesses are possible even if + /// `n > buf.len()`. + /// + /// 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 must not assume any guarantees + /// about how the implementation uses `buf`. The trait is safe to implement, + /// so 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`. Calling `read` with an uninitialized `buf` (of the kind one + /// obtains via [`MaybeUninit`]) is not safe, and can lead to undefined behavior. + /// + /// [`MaybeUninit`]: crate::mem::MaybeUninit + /// + /// # 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. + /// + /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the read + /// operation should be retried if there is nothing else to do. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`Ok(n)`]: Ok + /// [`File`]: crate::fs::File + /// [`TcpStream`]: crate::net::TcpStream + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// let mut buffer = [0; 10]; + /// + /// // read up to 10 bytes + /// let n = f.read(&mut buffer[..])?; + /// + /// println!("The bytes: {:?}", &buffer[..n]); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn read(&mut self, buf: &mut [u8]) -> Result; + + /// 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 equivalently to a single call to `read` with concatenated + /// buffers. + /// + /// The default implementation calls `read` with either the first nonempty + /// buffer provided, or an empty one if none exists. + #[stable(feature = "iovec", since = "1.36.0")] + fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result { + default_read_vectored(|b| self.read(b), bufs) + } + + /// Determines if this `Read`er has an efficient `read_vectored` + /// implementation. + /// + /// If a `Read`er does not override the default `read_vectored` + /// implementation, code using it may want to avoid the method all together + /// and coalesce writes into a single buffer for higher performance. + /// + /// The default implementation returns `false`. + #[unstable(feature = "can_vector", issue = "69941")] + fn is_read_vectored(&self) -> bool { + false + } + + /// Read all bytes until EOF in this source, placing them into `buf`. + /// + /// 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()`] returns either [`Ok(0)`] or an error of + /// non-[`ErrorKind::Interrupted`] kind. + /// + /// If successful, this function will return the total number of bytes read. + /// + /// # Errors + /// + /// If this function encounters an error of the kind + /// [`ErrorKind::Interrupted`] then the error is ignored and the operation + /// will continue. + /// + /// If any other read error is encountered then this function immediately + /// returns. Any bytes which have already been read will be appended to + /// `buf`. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`read()`]: Read::read + /// [`Ok(0)`]: Ok + /// [`File`]: crate::fs::File + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// let mut buffer = Vec::new(); + /// + /// // read the whole file + /// f.read_to_end(&mut buffer)?; + /// Ok(()) + /// } + /// ``` + /// + /// (See also the [`std::fs::read`] convenience function for reading from a + /// file.) + /// + /// [`std::fs::read`]: crate::fs::read + #[stable(feature = "rust1", since = "1.0.0")] + fn read_to_end(&mut self, buf: &mut Vec) -> Result { + default_read_to_end(self, buf) + } + + /// Read all bytes until EOF in this source, appending them to `buf`. + /// + /// If successful, this function returns the number of bytes which were read + /// and appended to `buf`. + /// + /// # 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`] for other error semantics. + /// + /// [`read_to_end`]: Read::read_to_end + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`File`]: crate::fs::File + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// let mut buffer = String::new(); + /// + /// f.read_to_string(&mut buffer)?; + /// Ok(()) + /// } + /// ``` + /// + /// (See also the [`std::fs::read_to_string`] convenience function for + /// reading from a file.) + /// + /// [`std::fs::read_to_string`]: crate::fs::read_to_string + #[stable(feature = "rust1", since = "1.0.0")] + fn read_to_string(&mut self, buf: &mut String) -> Result { + default_read_to_string(self, buf) + } + + /// Read 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. The + /// documentation on [`read`] has a more detailed explanation on this + /// subject. + /// + /// # Errors + /// + /// If this function encounters an error of the kind + /// [`ErrorKind::Interrupted`] then the error is ignored and the operation + /// will continue. + /// + /// 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. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`read`]: Read::read + /// [`File`]: crate::fs::File + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// let mut buffer = [0; 10]; + /// + /// // read exactly 10 bytes + /// f.read_exact(&mut buffer)?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "read_exact", since = "1.6.0")] + fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> { + default_read_exact(self, buf) + } + + /// Pull some bytes from this source into the specified buffer. + /// + /// This is equivalent to the [`read`](Read::read) method, except that it is passed a [`ReadBuf`] rather than `[u8]` to allow use + /// with uninitialized buffers. The new data will be appended to any existing contents of `buf`. + /// + /// The default implementation delegates to `read`. + #[unstable(feature = "read_buf", issue = "78485")] + fn read_buf(&mut self, buf: &mut ReadBuf<'_>) -> Result<()> { + default_read_buf(|b| self.read(b), buf) + } + + /// Read the exact number of bytes required to fill `buf`. + /// + /// This is equivalent to the [`read_exact`](Read::read_exact) method, except that it is passed a [`ReadBuf`] rather than `[u8]` to + /// allow use with uninitialized buffers. + #[unstable(feature = "read_buf", issue = "78485")] + fn read_buf_exact(&mut self, buf: &mut ReadBuf<'_>) -> Result<()> { + while buf.remaining() > 0 { + let prev_filled = buf.filled().len(); + match self.read_buf(buf) { + Ok(()) => {} + Err(e) if e.kind() == ErrorKind::Interrupted => continue, + Err(e) => return Err(e), + } + + if buf.filled().len() == prev_filled { + return Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill buffer")); + } + } + + Ok(()) + } + + /// Creates a "by reference" adaptor for this instance of `Read`. + /// + /// The returned adapter also implements `Read` and will simply borrow this + /// current reader. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`File`]: crate::fs::File + /// + /// ```no_run + /// use std::io; + /// use std::io::Read; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// let mut buffer = Vec::new(); + /// let mut other_buffer = Vec::new(); + /// + /// { + /// let reference = f.by_ref(); + /// + /// // read at most 5 bytes + /// reference.take(5).read_to_end(&mut buffer)?; + /// + /// } // drop our &mut reference so we can use f again + /// + /// // original file still usable, read the rest + /// f.read_to_end(&mut other_buffer)?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn by_ref(&mut self) -> &mut Self + where + Self: Sized, + { + self + } + + /// Transforms this `Read` instance to an [`Iterator`] over its bytes. + /// + /// The returned type implements [`Iterator`] where the [`Item`] is + /// [Result]<[u8], [io::Error]>. + /// The yielded item is [`Ok`] if a byte was successfully read and [`Err`] + /// otherwise. EOF is mapped to returning [`None`] from this iterator. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`Item`]: Iterator::Item + /// [`File`]: crate::fs::File "fs::File" + /// [Result]: crate::result::Result "Result" + /// [io::Error]: self::Error "io::Error" + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let f = File::open("foo.txt")?; + /// + /// for byte in f.bytes() { + /// println!("{}", byte.unwrap()); + /// } + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn bytes(self) -> Bytes + where + Self: Sized, + { + Bytes { inner: self } + } + + /// Creates an adapter which will chain this stream with another. + /// + /// The returned `Read` 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`]s implement `Read`: + /// + /// [`File`]: crate::fs::File + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let f1 = File::open("foo.txt")?; + /// let f2 = File::open("bar.txt")?; + /// + /// let mut handle = f1.chain(f2); + /// let mut buffer = String::new(); + /// + /// // read the value into a String. We could use any Read method here, + /// // this is just one example. + /// handle.read_to_string(&mut buffer)?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn chain(self, next: R) -> Chain + where + Self: Sized, + { + Chain { first: self, second: next, done_first: false } + } + + /// Creates an adapter which will read at most `limit` bytes from it. + /// + /// This function returns a new instance of `Read` 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()`] may succeed. + /// + /// # Examples + /// + /// [`File`]s implement `Read`: + /// + /// [`File`]: crate::fs::File + /// [`Ok(0)`]: Ok + /// [`read()`]: Read::read + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let f = File::open("foo.txt")?; + /// let mut buffer = [0; 5]; + /// + /// // read at most five bytes + /// let mut handle = f.take(5); + /// + /// handle.read(&mut buffer)?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn take(self, limit: u64) -> Take + where + Self: Sized, + { + Take { inner: self, limit } + } +} + +/// Read all bytes from a [reader][Read] into a new [`String`]. +/// +/// This is a convenience function for [`Read::read_to_string`]. Using this +/// function avoids having to create a variable first and provides more type +/// safety since you can only get the buffer out if there were no errors. (If you +/// use [`Read::read_to_string`] you have to remember to check whether the read +/// succeeded because otherwise your buffer will be empty or only partially full.) +/// +/// # Performance +/// +/// The downside of this function's increased ease of use and type safety is +/// that it gives you less control over performance. For example, you can't +/// pre-allocate memory like you can using [`String::with_capacity`] and +/// [`Read::read_to_string`]. Also, you can't re-use the buffer if an error +/// occurs while reading. +/// +/// In many cases, this function's performance will be adequate and the ease of use +/// and type safety tradeoffs will be worth it. However, there are cases where you +/// need more control over performance, and in those cases you should definitely use +/// [`Read::read_to_string`] directly. +/// +/// Note that in some special cases, such as when reading files, this function will +/// pre-allocate memory based on the size of the input it is reading. In those +/// cases, the performance should be as good as if you had used +/// [`Read::read_to_string`] with a manually pre-allocated buffer. +/// +/// # Errors +/// +/// This function forces you to handle errors because the output (the `String`) +/// is wrapped in a [`Result`]. See [`Read::read_to_string`] for the errors +/// that can occur. If any error occurs, you will get an [`Err`], so you +/// don't have to worry about your buffer being empty or partially full. +/// +/// # Examples +/// +/// ```no_run +/// #![feature(io_read_to_string)] +/// +/// # use std::io; +/// fn main() -> io::Result<()> { +/// let stdin = io::read_to_string(io::stdin())?; +/// println!("Stdin was:"); +/// println!("{stdin}"); +/// Ok(()) +/// } +/// ``` +#[unstable(feature = "io_read_to_string", issue = "80218")] +pub fn read_to_string(mut reader: R) -> Result { + let mut buf = String::new(); + reader.read_to_string(&mut buf)?; + Ok(buf) +} + +/// A buffer type used with `Read::read_vectored`. +/// +/// It is semantically a wrapper around an `&mut [u8]`, but is guaranteed to be +/// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on +/// Windows. +#[stable(feature = "iovec", since = "1.36.0")] +#[repr(transparent)] +pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>); + +#[stable(feature = "iovec-send-sync", since = "1.44.0")] +unsafe impl<'a> Send for IoSliceMut<'a> {} + +#[stable(feature = "iovec-send-sync", since = "1.44.0")] +unsafe impl<'a> Sync for IoSliceMut<'a> {} + +#[stable(feature = "iovec", since = "1.36.0")] +impl<'a> fmt::Debug for IoSliceMut<'a> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Debug::fmt(self.0.as_slice(), fmt) + } +} + +impl<'a> IoSliceMut<'a> { + /// Creates a new `IoSliceMut` wrapping a byte slice. + /// + /// # Panics + /// + /// Panics on Windows if the slice is larger than 4GB. + #[stable(feature = "iovec", since = "1.36.0")] + #[inline] + pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> { + IoSliceMut(sys::io::IoSliceMut::new(buf)) + } + + /// Advance the internal cursor of the slice. + /// + /// Also see [`IoSliceMut::advance_slices`] to advance the cursors of + /// multiple buffers. + /// + /// # Panics + /// + /// Panics when trying to advance beyond the end of the slice. + /// + /// # Examples + /// + /// ``` + /// #![feature(io_slice_advance)] + /// + /// use std::io::IoSliceMut; + /// use std::ops::Deref; + /// + /// let mut data = [1; 8]; + /// let mut buf = IoSliceMut::new(&mut data); + /// + /// // Mark 3 bytes as read. + /// buf.advance(3); + /// assert_eq!(buf.deref(), [1; 5].as_ref()); + /// ``` + #[unstable(feature = "io_slice_advance", issue = "62726")] + #[inline] + pub fn advance(&mut self, n: usize) { + self.0.advance(n) + } + + /// Advance a slice of slices. + /// + /// Shrinks the slice to remove any `IoSliceMut`s that are fully advanced over. + /// If the cursor ends up in the middle of an `IoSliceMut`, it is modified + /// to start at that cursor. + /// + /// For example, if we have a slice of two 8-byte `IoSliceMut`s, and we advance by 10 bytes, + /// the result will only include the second `IoSliceMut`, advanced by 2 bytes. + /// + /// # Panics + /// + /// Panics when trying to advance beyond the end of the slices. + /// + /// # Examples + /// + /// ``` + /// #![feature(io_slice_advance)] + /// + /// use std::io::IoSliceMut; + /// use std::ops::Deref; + /// + /// let mut buf1 = [1; 8]; + /// let mut buf2 = [2; 16]; + /// let mut buf3 = [3; 8]; + /// let mut bufs = &mut [ + /// IoSliceMut::new(&mut buf1), + /// IoSliceMut::new(&mut buf2), + /// IoSliceMut::new(&mut buf3), + /// ][..]; + /// + /// // Mark 10 bytes as read. + /// IoSliceMut::advance_slices(&mut bufs, 10); + /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); + /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); + /// ``` + #[unstable(feature = "io_slice_advance", issue = "62726")] + #[inline] + pub fn advance_slices(bufs: &mut &mut [IoSliceMut<'a>], n: usize) { + // Number of buffers to remove. + let mut remove = 0; + // Total length of all the to be removed buffers. + let mut accumulated_len = 0; + for buf in bufs.iter() { + if accumulated_len + buf.len() > n { + break; + } else { + accumulated_len += buf.len(); + remove += 1; + } + } + + *bufs = &mut replace(bufs, &mut [])[remove..]; + if bufs.is_empty() { + assert!(n == accumulated_len, "advancing io slices beyond their length"); + } else { + bufs[0].advance(n - accumulated_len) + } + } +} + +#[stable(feature = "iovec", since = "1.36.0")] +impl<'a> Deref for IoSliceMut<'a> { + type Target = [u8]; + + #[inline] + fn deref(&self) -> &[u8] { + self.0.as_slice() + } +} + +#[stable(feature = "iovec", since = "1.36.0")] +impl<'a> DerefMut for IoSliceMut<'a> { + #[inline] + fn deref_mut(&mut self) -> &mut [u8] { + self.0.as_mut_slice() + } +} + +/// A buffer type used with `Write::write_vectored`. +/// +/// It is semantically a wrapper around a `&[u8]`, but is guaranteed to be +/// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on +/// Windows. +#[stable(feature = "iovec", since = "1.36.0")] +#[derive(Copy, Clone)] +#[repr(transparent)] +pub struct IoSlice<'a>(sys::io::IoSlice<'a>); + +#[stable(feature = "iovec-send-sync", since = "1.44.0")] +unsafe impl<'a> Send for IoSlice<'a> {} + +#[stable(feature = "iovec-send-sync", since = "1.44.0")] +unsafe impl<'a> Sync for IoSlice<'a> {} + +#[stable(feature = "iovec", since = "1.36.0")] +impl<'a> fmt::Debug for IoSlice<'a> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Debug::fmt(self.0.as_slice(), fmt) + } +} + +impl<'a> IoSlice<'a> { + /// Creates a new `IoSlice` wrapping a byte slice. + /// + /// # Panics + /// + /// Panics on Windows if the slice is larger than 4GB. + #[stable(feature = "iovec", since = "1.36.0")] + #[must_use] + #[inline] + pub fn new(buf: &'a [u8]) -> IoSlice<'a> { + IoSlice(sys::io::IoSlice::new(buf)) + } + + /// Advance the internal cursor of the slice. + /// + /// Also see [`IoSlice::advance_slices`] to advance the cursors of multiple + /// buffers. + /// + /// # Panics + /// + /// Panics when trying to advance beyond the end of the slice. + /// + /// # Examples + /// + /// ``` + /// #![feature(io_slice_advance)] + /// + /// use std::io::IoSlice; + /// use std::ops::Deref; + /// + /// let data = [1; 8]; + /// let mut buf = IoSlice::new(&data); + /// + /// // Mark 3 bytes as read. + /// buf.advance(3); + /// assert_eq!(buf.deref(), [1; 5].as_ref()); + /// ``` + #[unstable(feature = "io_slice_advance", issue = "62726")] + #[inline] + pub fn advance(&mut self, n: usize) { + self.0.advance(n) + } + + /// Advance a slice of slices. + /// + /// Shrinks the slice to remove any `IoSlice`s that are fully advanced over. + /// If the cursor ends up in the middle of an `IoSlice`, it is modified + /// to start at that cursor. + /// + /// For example, if we have a slice of two 8-byte `IoSlice`s, and we advance by 10 bytes, + /// the result will only include the second `IoSlice`, advanced by 2 bytes. + /// + /// # Panics + /// + /// Panics when trying to advance beyond the end of the slices. + /// + /// # Examples + /// + /// ``` + /// #![feature(io_slice_advance)] + /// + /// use std::io::IoSlice; + /// use std::ops::Deref; + /// + /// let buf1 = [1; 8]; + /// let buf2 = [2; 16]; + /// let buf3 = [3; 8]; + /// let mut bufs = &mut [ + /// IoSlice::new(&buf1), + /// IoSlice::new(&buf2), + /// IoSlice::new(&buf3), + /// ][..]; + /// + /// // Mark 10 bytes as written. + /// IoSlice::advance_slices(&mut bufs, 10); + /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); + /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); + #[unstable(feature = "io_slice_advance", issue = "62726")] + #[inline] + pub fn advance_slices(bufs: &mut &mut [IoSlice<'a>], n: usize) { + // Number of buffers to remove. + let mut remove = 0; + // Total length of all the to be removed buffers. + let mut accumulated_len = 0; + for buf in bufs.iter() { + if accumulated_len + buf.len() > n { + break; + } else { + accumulated_len += buf.len(); + remove += 1; + } + } + + *bufs = &mut replace(bufs, &mut [])[remove..]; + if bufs.is_empty() { + assert!(n == accumulated_len, "advancing io slices beyond their length"); + } else { + bufs[0].advance(n - accumulated_len) + } + } +} + +#[stable(feature = "iovec", since = "1.36.0")] +impl<'a> Deref for IoSlice<'a> { + type Target = [u8]; + + #[inline] + fn deref(&self) -> &[u8] { + self.0.as_slice() + } +} + +/// A trait for objects which are byte-oriented sinks. +/// +/// Implementors of the `Write` trait are sometimes called 'writers'. +/// +/// Writers are defined by two required methods, [`write`] and [`flush`]: +/// +/// * The [`write`] method will attempt to write some data into the object, +/// returning how many bytes were successfully written. +/// +/// * The [`flush`] method is useful for adapters and explicit buffers +/// themselves for ensuring that all buffered data has been pushed out to the +/// 'true sink'. +/// +/// Writers are intended to be composable with one another. Many implementors +/// throughout [`std::io`] take and provide types which implement the `Write` +/// trait. +/// +/// [`write`]: Write::write +/// [`flush`]: Write::flush +/// [`std::io`]: self +/// +/// # Examples +/// +/// ```no_run +/// use std::io::prelude::*; +/// use std::fs::File; +/// +/// fn main() -> std::io::Result<()> { +/// let data = b"some bytes"; +/// +/// let mut pos = 0; +/// let mut buffer = File::create("foo.txt")?; +/// +/// while pos < data.len() { +/// let bytes_written = buffer.write(&data[pos..])?; +/// pos += bytes_written; +/// } +/// Ok(()) +/// } +/// ``` +/// +/// The trait also provides convenience methods like [`write_all`], which calls +/// `write` in a loop until its entire input has been written. +/// +/// [`write_all`]: Write::write_all +#[stable(feature = "rust1", since = "1.0.0")] +#[doc(notable_trait)] +#[cfg_attr(not(test), rustc_diagnostic_item = "IoWrite")] +pub trait Write { + /// Write a buffer into this writer, returning how many bytes were written. + /// + /// This function will attempt to write the entire contents of `buf`, but + /// the entire write might not succeed, or the write may also generate an + /// error. A call to `write` represents *at most one* attempt to write to + /// any wrapped object. + /// + /// Calls to `write` are not guaranteed to block waiting for data to be + /// written, and a write which would otherwise block can be indicated through + /// an [`Err`] variant. + /// + /// If the return value is [`Ok(n)`] then it must be guaranteed that + /// `n <= buf.len()`. A return value of `0` typically means that the + /// underlying object is no longer able to accept bytes and will likely not + /// be able to in the future as well, or that the buffer provided is empty. + /// + /// # Errors + /// + /// Each call to `write` may generate an I/O error indicating that the + /// operation could not be completed. If an error is returned then no bytes + /// in the buffer were written to this writer. + /// + /// It is **not** considered an error if the entire buffer could not be + /// written to this writer. + /// + /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the + /// write operation should be retried if there is nothing else to do. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let mut buffer = File::create("foo.txt")?; + /// + /// // Writes some prefix of the byte string, not necessarily all of it. + /// buffer.write(b"some bytes")?; + /// Ok(()) + /// } + /// ``` + /// + /// [`Ok(n)`]: Ok + #[stable(feature = "rust1", since = "1.0.0")] + fn write(&mut self, buf: &[u8]) -> Result; + + /// Like [`write`], except that it writes from a slice of buffers. + /// + /// Data is copied from each buffer in order, with the final buffer + /// read from possibly being only partially consumed. This method must + /// behave as a call to [`write`] with the buffers concatenated would. + /// + /// The default implementation calls [`write`] with either the first nonempty + /// buffer provided, or an empty one if none exists. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::IoSlice; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let data1 = [1; 8]; + /// let data2 = [15; 8]; + /// let io_slice1 = IoSlice::new(&data1); + /// let io_slice2 = IoSlice::new(&data2); + /// + /// let mut buffer = File::create("foo.txt")?; + /// + /// // Writes some prefix of the byte string, not necessarily all of it. + /// buffer.write_vectored(&[io_slice1, io_slice2])?; + /// Ok(()) + /// } + /// ``` + /// + /// [`write`]: Write::write + #[stable(feature = "iovec", since = "1.36.0")] + fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result { + default_write_vectored(|b| self.write(b), bufs) + } + + /// Determines if this `Write`r has an efficient [`write_vectored`] + /// implementation. + /// + /// If a `Write`r does not override the default [`write_vectored`] + /// implementation, code using it may want to avoid the method all together + /// and coalesce writes into a single buffer for higher performance. + /// + /// The default implementation returns `false`. + /// + /// [`write_vectored`]: Write::write_vectored + #[unstable(feature = "can_vector", issue = "69941")] + fn is_write_vectored(&self) -> bool { + false + } + + /// Flush this output stream, ensuring that all intermediately buffered + /// contents reach their destination. + /// + /// # Errors + /// + /// It is considered an error if not all bytes could be written due to + /// I/O errors or EOF being reached. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::prelude::*; + /// use std::io::BufWriter; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let mut buffer = BufWriter::new(File::create("foo.txt")?); + /// + /// buffer.write_all(b"some bytes")?; + /// buffer.flush()?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn flush(&mut self) -> Result<()>; + + /// Attempts to write an entire buffer into this writer. + /// + /// This method will continuously call [`write`] until there is no more data + /// to be written or an error of non-[`ErrorKind::Interrupted`] kind is + /// returned. This method will not return until the entire buffer has been + /// successfully written or such an error occurs. The first error that is + /// not of [`ErrorKind::Interrupted`] kind generated from this method will be + /// returned. + /// + /// If the buffer contains no data, this will never call [`write`]. + /// + /// # Errors + /// + /// This function will return the first error of + /// non-[`ErrorKind::Interrupted`] kind that [`write`] returns. + /// + /// [`write`]: Write::write + /// + /// # Examples + /// + /// ```no_run + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let mut buffer = File::create("foo.txt")?; + /// + /// buffer.write_all(b"some bytes")?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn write_all(&mut self, mut buf: &[u8]) -> Result<()> { + while !buf.is_empty() { + match self.write(buf) { + Ok(0) => { + return Err(error::const_io_error!( + ErrorKind::WriteZero, + "failed to write whole buffer", + )); + } + Ok(n) => buf = &buf[n..], + Err(ref e) if e.kind() == ErrorKind::Interrupted => {} + Err(e) => return Err(e), + } + } + Ok(()) + } + + /// Attempts to write multiple buffers into this writer. + /// + /// This method will continuously call [`write_vectored`] until there is no + /// more data to be written or an error of non-[`ErrorKind::Interrupted`] + /// kind is returned. This method will not return until all buffers have + /// been successfully written or such an error occurs. The first error that + /// is not of [`ErrorKind::Interrupted`] kind generated from this method + /// will be returned. + /// + /// If the buffer contains no data, this will never call [`write_vectored`]. + /// + /// # Notes + /// + /// Unlike [`write_vectored`], this takes a *mutable* reference to + /// a slice of [`IoSlice`]s, not an immutable one. That's because we need to + /// modify the slice to keep track of the bytes already written. + /// + /// Once this function returns, the contents of `bufs` are unspecified, as + /// this depends on how many calls to [`write_vectored`] were necessary. It is + /// best to understand this function as taking ownership of `bufs` and to + /// not use `bufs` afterwards. The underlying buffers, to which the + /// [`IoSlice`]s point (but not the [`IoSlice`]s themselves), are unchanged and + /// can be reused. + /// + /// [`write_vectored`]: Write::write_vectored + /// + /// # Examples + /// + /// ``` + /// #![feature(write_all_vectored)] + /// # fn main() -> std::io::Result<()> { + /// + /// use std::io::{Write, IoSlice}; + /// + /// let mut writer = Vec::new(); + /// let bufs = &mut [ + /// IoSlice::new(&[1]), + /// IoSlice::new(&[2, 3]), + /// IoSlice::new(&[4, 5, 6]), + /// ]; + /// + /// writer.write_all_vectored(bufs)?; + /// // Note: the contents of `bufs` is now undefined, see the Notes section. + /// + /// assert_eq!(writer, &[1, 2, 3, 4, 5, 6]); + /// # Ok(()) } + /// ``` + #[unstable(feature = "write_all_vectored", issue = "70436")] + fn write_all_vectored(&mut self, mut bufs: &mut [IoSlice<'_>]) -> Result<()> { + // Guarantee that bufs is empty if it contains no data, + // to avoid calling write_vectored if there is no data to be written. + IoSlice::advance_slices(&mut bufs, 0); + while !bufs.is_empty() { + match self.write_vectored(bufs) { + Ok(0) => { + return Err(error::const_io_error!( + ErrorKind::WriteZero, + "failed to write whole buffer", + )); + } + Ok(n) => IoSlice::advance_slices(&mut bufs, n), + Err(ref e) if e.kind() == ErrorKind::Interrupted => {} + Err(e) => return Err(e), + } + } + Ok(()) + } + + /// Writes a formatted string into this writer, returning any error + /// encountered. + /// + /// This method is primarily used to interface with the + /// [`format_args!()`] macro, and it is rare that this should + /// explicitly be called. The [`write!()`] macro should be favored to + /// invoke this method instead. + /// + /// This function internally uses the [`write_all`] method on + /// this trait and hence will continuously write data so long as no errors + /// are received. This also means that partial writes are not indicated in + /// this signature. + /// + /// [`write_all`]: Write::write_all + /// + /// # Errors + /// + /// This function will return any I/O error reported while formatting. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let mut buffer = File::create("foo.txt")?; + /// + /// // this call + /// write!(buffer, "{:.*}", 2, 1.234567)?; + /// // turns into this: + /// buffer.write_fmt(format_args!("{:.*}", 2, 1.234567))?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> Result<()> { + // Create a shim which translates a Write to a fmt::Write and saves + // off I/O errors. instead of discarding them + struct Adapter<'a, T: ?Sized + 'a> { + inner: &'a mut T, + error: Result<()>, + } + + impl fmt::Write for Adapter<'_, T> { + fn write_str(&mut self, s: &str) -> fmt::Result { + match self.inner.write_all(s.as_bytes()) { + Ok(()) => Ok(()), + Err(e) => { + self.error = Err(e); + Err(fmt::Error) + } + } + } + } + + let mut output = Adapter { inner: self, error: Ok(()) }; + match fmt::write(&mut output, fmt) { + Ok(()) => Ok(()), + Err(..) => { + // check if the error came from the underlying `Write` or not + if output.error.is_err() { + output.error + } else { + Err(error::const_io_error!(ErrorKind::Uncategorized, "formatter error")) + } + } + } + } + + /// Creates a "by reference" adapter for this instance of `Write`. + /// + /// The returned adapter also implements `Write` and will simply borrow this + /// current writer. + /// + /// # Examples + /// + /// ```no_run + /// use std::io::Write; + /// use std::fs::File; + /// + /// fn main() -> std::io::Result<()> { + /// let mut buffer = File::create("foo.txt")?; + /// + /// let reference = buffer.by_ref(); + /// + /// // we can use reference just like our original buffer + /// reference.write_all(b"some bytes")?; + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn by_ref(&mut self) -> &mut Self + where + Self: Sized, + { + self + } +} + +/// The `Seek` trait provides a cursor which can be moved within a stream of +/// bytes. +/// +/// The stream typically has a fixed size, allowing seeking relative to either +/// end or the current offset. +/// +/// # Examples +/// +/// [`File`]s implement `Seek`: +/// +/// [`File`]: crate::fs::File +/// +/// ```no_run +/// use std::io; +/// use std::io::prelude::*; +/// use std::fs::File; +/// use std::io::SeekFrom; +/// +/// fn main() -> io::Result<()> { +/// let mut f = File::open("foo.txt")?; +/// +/// // move the cursor 42 bytes from the start of the file +/// f.seek(SeekFrom::Start(42))?; +/// Ok(()) +/// } +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +pub trait Seek { + /// Seek to an offset, in bytes, in a stream. + /// + /// A seek beyond the end of a stream is allowed, but behavior is defined + /// by the implementation. + /// + /// If the seek operation completed successfully, + /// this method returns the new position from the start of the stream. + /// That position can be used later with [`SeekFrom::Start`]. + /// + /// # Errors + /// + /// Seeking can fail, for example because it might involve flushing a buffer. + /// + /// Seeking to a negative offset is considered an error. + #[stable(feature = "rust1", since = "1.0.0")] + fn seek(&mut self, pos: SeekFrom) -> Result; + + /// Rewind to the beginning of a stream. + /// + /// This is a convenience method, equivalent to `seek(SeekFrom::Start(0))`. + /// + /// # Errors + /// + /// Rewinding can fail, for example because it might involve flushing a buffer. + /// + /// # Example + /// + /// ```no_run + /// use std::io::{Read, Seek, Write}; + /// use std::fs::OpenOptions; + /// + /// let mut f = OpenOptions::new() + /// .write(true) + /// .read(true) + /// .create(true) + /// .open("foo.txt").unwrap(); + /// + /// let hello = "Hello!\n"; + /// write!(f, "{hello}").unwrap(); + /// f.rewind().unwrap(); + /// + /// let mut buf = String::new(); + /// f.read_to_string(&mut buf).unwrap(); + /// assert_eq!(&buf, hello); + /// ``` + #[stable(feature = "seek_rewind", since = "1.55.0")] + fn rewind(&mut self) -> Result<()> { + self.seek(SeekFrom::Start(0))?; + Ok(()) + } + + /// Returns the length of this stream (in bytes). + /// + /// This method is implemented using up to three seek operations. If this + /// method returns successfully, the seek position is unchanged (i.e. the + /// position before calling this method is the same as afterwards). + /// However, if this method returns an error, the seek position is + /// unspecified. + /// + /// If you need to obtain the length of *many* streams and you don't care + /// about the seek position afterwards, you can reduce the number of seek + /// operations by simply calling `seek(SeekFrom::End(0))` and using its + /// return value (it is also the stream length). + /// + /// Note that length of a stream can change over time (for example, when + /// data is appended to a file). So calling this method multiple times does + /// not necessarily return the same length each time. + /// + /// # Example + /// + /// ```no_run + /// #![feature(seek_stream_len)] + /// use std::{ + /// io::{self, Seek}, + /// fs::File, + /// }; + /// + /// fn main() -> io::Result<()> { + /// let mut f = File::open("foo.txt")?; + /// + /// let len = f.stream_len()?; + /// println!("The file is currently {len} bytes long"); + /// Ok(()) + /// } + /// ``` + #[unstable(feature = "seek_stream_len", issue = "59359")] + fn stream_len(&mut self) -> Result { + let old_pos = self.stream_position()?; + let len = self.seek(SeekFrom::End(0))?; + + // Avoid seeking a third time when we were already at the end of the + // stream. The branch is usually way cheaper than a seek operation. + if old_pos != len { + self.seek(SeekFrom::Start(old_pos))?; + } + + Ok(len) + } + + /// Returns the current seek position from the start of the stream. + /// + /// This is equivalent to `self.seek(SeekFrom::Current(0))`. + /// + /// # Example + /// + /// ```no_run + /// use std::{ + /// io::{self, BufRead, BufReader, Seek}, + /// fs::File, + /// }; + /// + /// fn main() -> io::Result<()> { + /// let mut f = BufReader::new(File::open("foo.txt")?); + /// + /// let before = f.stream_position()?; + /// f.read_line(&mut String::new())?; + /// let after = f.stream_position()?; + /// + /// println!("The first line was {} bytes long", after - before); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "seek_convenience", since = "1.51.0")] + fn stream_position(&mut self) -> Result { + self.seek(SeekFrom::Current(0)) + } +} + +/// Enumeration of possible methods to seek within an I/O object. +/// +/// It is used by the [`Seek`] trait. +#[derive(Copy, PartialEq, Eq, Clone, Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub enum SeekFrom { + /// Sets the offset to the provided number of bytes. + #[stable(feature = "rust1", since = "1.0.0")] + Start(#[stable(feature = "rust1", since = "1.0.0")] u64), + + /// Sets the offset to the size of this object plus the specified number of + /// bytes. + /// + /// It is possible to seek beyond the end of an object, but it's an error to + /// seek before byte 0. + #[stable(feature = "rust1", since = "1.0.0")] + End(#[stable(feature = "rust1", since = "1.0.0")] i64), + + /// Sets the offset to the current position plus the specified number of + /// bytes. + /// + /// It is possible to seek beyond the end of an object, but it's an error to + /// seek before byte 0. + #[stable(feature = "rust1", since = "1.0.0")] + Current(#[stable(feature = "rust1", since = "1.0.0")] i64), +} + +fn read_until(r: &mut R, delim: u8, buf: &mut Vec) -> Result { + let mut read = 0; + loop { + let (done, used) = { + let available = match r.fill_buf() { + Ok(n) => n, + Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, + Err(e) => return Err(e), + }; + match memchr::memchr(delim, available) { + Some(i) => { + buf.extend_from_slice(&available[..=i]); + (true, i + 1) + } + None => { + buf.extend_from_slice(available); + (false, available.len()) + } + } + }; + r.consume(used); + read += used; + if done || used == 0 { + return Ok(read); + } + } +} + +/// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it +/// to perform extra ways of reading. +/// +/// For example, reading line-by-line is inefficient without using a buffer, so +/// if you want to read by line, you'll need `BufRead`, which includes a +/// [`read_line`] method as well as a [`lines`] iterator. +/// +/// # Examples +/// +/// A locked standard input implements `BufRead`: +/// +/// ```no_run +/// use std::io; +/// use std::io::prelude::*; +/// +/// let stdin = io::stdin(); +/// for line in stdin.lock().lines() { +/// println!("{}", line.unwrap()); +/// } +/// ``` +/// +/// If you have something that implements [`Read`], you can use the [`BufReader` +/// type][`BufReader`] to turn it into a `BufRead`. +/// +/// For example, [`File`] implements [`Read`], but not `BufRead`. +/// [`BufReader`] to the rescue! +/// +/// [`File`]: crate::fs::File +/// [`read_line`]: BufRead::read_line +/// [`lines`]: BufRead::lines +/// +/// ```no_run +/// use std::io::{self, BufReader}; +/// use std::io::prelude::*; +/// use std::fs::File; +/// +/// fn main() -> io::Result<()> { +/// let f = File::open("foo.txt")?; +/// let f = BufReader::new(f); +/// +/// for line in f.lines() { +/// println!("{}", line.unwrap()); +/// } +/// +/// Ok(()) +/// } +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +pub trait BufRead: Read { + /// Returns the contents of the internal buffer, filling it with more data + /// from the inner reader if it is empty. + /// + /// This function is a lower-level call. It needs to be paired with the + /// [`consume`] method to function properly. When calling this + /// method, none of the contents will be "read" in the sense that later + /// calling `read` may return the same contents. As such, [`consume`] must + /// be called with the number of bytes that are consumed from this buffer to + /// ensure that the bytes are never returned twice. + /// + /// [`consume`]: BufRead::consume + /// + /// An empty buffer returned indicates that the stream has reached EOF. + /// + /// # Errors + /// + /// This function will return an I/O error if the underlying reader was + /// read, but returned an error. + /// + /// # Examples + /// + /// A locked standard input implements `BufRead`: + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// let mut stdin = stdin.lock(); + /// + /// let buffer = stdin.fill_buf().unwrap(); + /// + /// // work with buffer + /// println!("{buffer:?}"); + /// + /// // ensure the bytes we worked with aren't returned again later + /// let length = buffer.len(); + /// stdin.consume(length); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn fill_buf(&mut self) -> Result<&[u8]>; + + /// Tells this buffer that `amt` bytes have been consumed from the buffer, + /// so they should no longer be returned in calls to `read`. + /// + /// This function is a lower-level call. It needs to be paired with the + /// [`fill_buf`] method to function properly. This function does + /// not perform any I/O, it simply informs this object that some amount of + /// its buffer, returned from [`fill_buf`], has been consumed and should + /// no longer be returned. As such, this function may do odd things if + /// [`fill_buf`] isn't called before calling it. + /// + /// The `amt` must be `<=` the number of bytes in the buffer returned by + /// [`fill_buf`]. + /// + /// # Examples + /// + /// Since `consume()` is meant to be used with [`fill_buf`], + /// that method's example includes an example of `consume()`. + /// + /// [`fill_buf`]: BufRead::fill_buf + #[stable(feature = "rust1", since = "1.0.0")] + fn consume(&mut self, amt: usize); + + /// Check if the underlying `Read` has any data left to be read. + /// + /// This function may fill the buffer to check for data, + /// so this functions returns `Result`, not `bool`. + /// + /// Default implementation calls `fill_buf` and checks that + /// returned slice is empty (which means that there is no data left, + /// since EOF is reached). + /// + /// Examples + /// + /// ``` + /// #![feature(buf_read_has_data_left)] + /// use std::io; + /// use std::io::prelude::*; + /// + /// let stdin = io::stdin(); + /// let mut stdin = stdin.lock(); + /// + /// while stdin.has_data_left().unwrap() { + /// let mut line = String::new(); + /// stdin.read_line(&mut line).unwrap(); + /// // work with line + /// println!("{line:?}"); + /// } + /// ``` + #[unstable(feature = "buf_read_has_data_left", reason = "recently added", issue = "86423")] + fn has_data_left(&mut self) -> Result { + self.fill_buf().map(|b| !b.is_empty()) + } + + /// Read all bytes into `buf` until the delimiter `byte` or EOF is reached. + /// + /// This function will read bytes from the underlying stream until the + /// delimiter or EOF is found. Once found, all bytes up to, and including, + /// the delimiter (if found) will be appended to `buf`. + /// + /// If successful, this function will return the total number of bytes read. + /// + /// This function is blocking and should be used carefully: it is possible for + /// an attacker to continuously send bytes without ever sending the delimiter + /// or EOF. + /// + /// # Errors + /// + /// This function will ignore all instances of [`ErrorKind::Interrupted`] and + /// will otherwise return any errors returned by [`fill_buf`]. + /// + /// If an I/O error is encountered then all bytes read so far will be + /// present in `buf` and its length will have been adjusted appropriately. + /// + /// [`fill_buf`]: BufRead::fill_buf + /// + /// # Examples + /// + /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In + /// this example, we use [`Cursor`] to read all the bytes in a byte slice + /// in hyphen delimited segments: + /// + /// ``` + /// use std::io::{self, BufRead}; + /// + /// let mut cursor = io::Cursor::new(b"lorem-ipsum"); + /// let mut buf = vec![]; + /// + /// // cursor is at 'l' + /// let num_bytes = cursor.read_until(b'-', &mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 6); + /// assert_eq!(buf, b"lorem-"); + /// buf.clear(); + /// + /// // cursor is at 'i' + /// let num_bytes = cursor.read_until(b'-', &mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 5); + /// assert_eq!(buf, b"ipsum"); + /// buf.clear(); + /// + /// // cursor is at EOF + /// let num_bytes = cursor.read_until(b'-', &mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 0); + /// assert_eq!(buf, b""); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn read_until(&mut self, byte: u8, buf: &mut Vec) -> Result { + read_until(self, byte, buf) + } + + /// Read all bytes until a newline (the `0xA` byte) is reached, and append + /// them to the provided buffer. You do not need to clear the buffer before + /// appending. + /// + /// This function will read bytes from the underlying stream until the + /// newline delimiter (the `0xA` byte) or EOF is found. Once found, all bytes + /// up to, and including, the delimiter (if found) will be appended to + /// `buf`. + /// + /// If successful, this function will return the total number of bytes read. + /// + /// If this function returns [`Ok(0)`], the stream has reached EOF. + /// + /// This function is blocking and should be used carefully: it is possible for + /// an attacker to continuously send bytes without ever sending a newline + /// or EOF. + /// + /// [`Ok(0)`]: Ok + /// + /// # Errors + /// + /// This function has the same error semantics as [`read_until`] and will + /// also return an error if the read bytes are not valid UTF-8. If an I/O + /// error is encountered then `buf` may contain some bytes already read in + /// the event that all data read so far was valid UTF-8. + /// + /// [`read_until`]: BufRead::read_until + /// + /// # Examples + /// + /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In + /// this example, we use [`Cursor`] to read all the lines in a byte slice: + /// + /// ``` + /// use std::io::{self, BufRead}; + /// + /// let mut cursor = io::Cursor::new(b"foo\nbar"); + /// let mut buf = String::new(); + /// + /// // cursor is at 'f' + /// let num_bytes = cursor.read_line(&mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 4); + /// assert_eq!(buf, "foo\n"); + /// buf.clear(); + /// + /// // cursor is at 'b' + /// let num_bytes = cursor.read_line(&mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 3); + /// assert_eq!(buf, "bar"); + /// buf.clear(); + /// + /// // cursor is at EOF + /// let num_bytes = cursor.read_line(&mut buf) + /// .expect("reading from cursor won't fail"); + /// assert_eq!(num_bytes, 0); + /// assert_eq!(buf, ""); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn read_line(&mut self, buf: &mut String) -> Result { + // Note that we are not calling the `.read_until` method here, but + // rather our hardcoded implementation. For more details as to why, see + // the comments in `read_to_end`. + unsafe { append_to_string(buf, |b| read_until(self, b'\n', b)) } + } + + /// Returns an iterator over the contents of this reader split on the byte + /// `byte`. + /// + /// The iterator returned from this function will return instances of + /// [io::Result]<[Vec]\>. Each vector returned will *not* have + /// the delimiter byte at the end. + /// + /// This function will yield errors whenever [`read_until`] would have + /// also yielded an error. + /// + /// [io::Result]: self::Result "io::Result" + /// [`read_until`]: BufRead::read_until + /// + /// # Examples + /// + /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In + /// this example, we use [`Cursor`] to iterate over all hyphen delimited + /// segments in a byte slice + /// + /// ``` + /// use std::io::{self, BufRead}; + /// + /// let cursor = io::Cursor::new(b"lorem-ipsum-dolor"); + /// + /// let mut split_iter = cursor.split(b'-').map(|l| l.unwrap()); + /// assert_eq!(split_iter.next(), Some(b"lorem".to_vec())); + /// assert_eq!(split_iter.next(), Some(b"ipsum".to_vec())); + /// assert_eq!(split_iter.next(), Some(b"dolor".to_vec())); + /// assert_eq!(split_iter.next(), None); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn split(self, byte: u8) -> Split + where + Self: Sized, + { + Split { buf: self, delim: byte } + } + + /// Returns an iterator over the lines of this reader. + /// + /// The iterator returned from this function will yield instances of + /// [io::Result]<[String]>. Each string returned will *not* have a newline + /// byte (the `0xA` byte) or `CRLF` (`0xD`, `0xA` bytes) at the end. + /// + /// [io::Result]: self::Result "io::Result" + /// + /// # Examples + /// + /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In + /// this example, we use [`Cursor`] to iterate over all the lines in a byte + /// slice. + /// + /// ``` + /// use std::io::{self, BufRead}; + /// + /// let cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor"); + /// + /// let mut lines_iter = cursor.lines().map(|l| l.unwrap()); + /// assert_eq!(lines_iter.next(), Some(String::from("lorem"))); + /// assert_eq!(lines_iter.next(), Some(String::from("ipsum"))); + /// assert_eq!(lines_iter.next(), Some(String::from("dolor"))); + /// assert_eq!(lines_iter.next(), None); + /// ``` + /// + /// # Errors + /// + /// Each line of the iterator has the same error semantics as [`BufRead::read_line`]. + #[stable(feature = "rust1", since = "1.0.0")] + fn lines(self) -> Lines + where + Self: Sized, + { + Lines { buf: self } + } +} + +/// Adapter to chain together two readers. +/// +/// This struct is generally created by calling [`chain`] on a reader. +/// Please see the documentation of [`chain`] for more details. +/// +/// [`chain`]: Read::chain +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Debug)] +pub struct Chain { + first: T, + second: U, + done_first: bool, +} + +impl Chain { + /// Consumes the `Chain`, returning the wrapped readers. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut foo_file = File::open("foo.txt")?; + /// let mut bar_file = File::open("bar.txt")?; + /// + /// let chain = foo_file.chain(bar_file); + /// let (foo_file, bar_file) = chain.into_inner(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "more_io_inner_methods", since = "1.20.0")] + pub fn into_inner(self) -> (T, U) { + (self.first, self.second) + } + + /// Gets references to the underlying readers in this `Chain`. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut foo_file = File::open("foo.txt")?; + /// let mut bar_file = File::open("bar.txt")?; + /// + /// let chain = foo_file.chain(bar_file); + /// let (foo_file, bar_file) = chain.get_ref(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "more_io_inner_methods", since = "1.20.0")] + pub fn get_ref(&self) -> (&T, &U) { + (&self.first, &self.second) + } + + /// Gets mutable references to the underlying readers in this `Chain`. + /// + /// Care should be taken to avoid modifying the internal I/O state of the + /// underlying readers as doing so may corrupt the internal state of this + /// `Chain`. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut foo_file = File::open("foo.txt")?; + /// let mut bar_file = File::open("bar.txt")?; + /// + /// let mut chain = foo_file.chain(bar_file); + /// let (foo_file, bar_file) = chain.get_mut(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "more_io_inner_methods", since = "1.20.0")] + pub fn get_mut(&mut self) -> (&mut T, &mut U) { + (&mut self.first, &mut self.second) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Read for Chain { + fn read(&mut self, buf: &mut [u8]) -> Result { + if !self.done_first { + match self.first.read(buf)? { + 0 if !buf.is_empty() => self.done_first = true, + n => return Ok(n), + } + } + self.second.read(buf) + } + + fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result { + if !self.done_first { + match self.first.read_vectored(bufs)? { + 0 if bufs.iter().any(|b| !b.is_empty()) => self.done_first = true, + n => return Ok(n), + } + } + self.second.read_vectored(bufs) + } +} + +#[stable(feature = "chain_bufread", since = "1.9.0")] +impl BufRead for Chain { + fn fill_buf(&mut self) -> Result<&[u8]> { + if !self.done_first { + match self.first.fill_buf()? { + buf if buf.is_empty() => { + self.done_first = true; + } + buf => return Ok(buf), + } + } + self.second.fill_buf() + } + + fn consume(&mut self, amt: usize) { + if !self.done_first { self.first.consume(amt) } else { self.second.consume(amt) } + } +} + +impl SizeHint for Chain { + #[inline] + fn lower_bound(&self) -> usize { + SizeHint::lower_bound(&self.first) + SizeHint::lower_bound(&self.second) + } + + #[inline] + fn upper_bound(&self) -> Option { + match (SizeHint::upper_bound(&self.first), SizeHint::upper_bound(&self.second)) { + (Some(first), Some(second)) => first.checked_add(second), + _ => None, + } + } +} + +/// Reader adapter which limits the bytes read from an underlying reader. +/// +/// This struct is generally created by calling [`take`] on a reader. +/// Please see the documentation of [`take`] for more details. +/// +/// [`take`]: Read::take +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Debug)] +pub struct Take { + inner: T, + limit: u64, +} + +impl Take { + /// Returns the number of bytes that can be read before this instance will + /// return EOF. + /// + /// # Note + /// + /// This instance may reach `EOF` after reading fewer bytes than indicated by + /// this method if the underlying [`Read`] instance reaches EOF. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let f = File::open("foo.txt")?; + /// + /// // read at most five bytes + /// let handle = f.take(5); + /// + /// println!("limit: {}", handle.limit()); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn limit(&self) -> u64 { + self.limit + } + + /// Sets the number of bytes that can be read before this instance will + /// return EOF. This is the same as constructing a new `Take` instance, so + /// the amount of bytes read and the previous limit value don't matter when + /// calling this method. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let f = File::open("foo.txt")?; + /// + /// // read at most five bytes + /// let mut handle = f.take(5); + /// handle.set_limit(10); + /// + /// assert_eq!(handle.limit(), 10); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "take_set_limit", since = "1.27.0")] + pub fn set_limit(&mut self, limit: u64) { + self.limit = limit; + } + + /// Consumes the `Take`, returning the wrapped reader. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut file = File::open("foo.txt")?; + /// + /// let mut buffer = [0; 5]; + /// let mut handle = file.take(5); + /// handle.read(&mut buffer)?; + /// + /// let file = handle.into_inner(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "io_take_into_inner", since = "1.15.0")] + pub fn into_inner(self) -> T { + self.inner + } + + /// Gets a reference to the underlying reader. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut file = File::open("foo.txt")?; + /// + /// let mut buffer = [0; 5]; + /// let mut handle = file.take(5); + /// handle.read(&mut buffer)?; + /// + /// let file = handle.get_ref(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "more_io_inner_methods", since = "1.20.0")] + pub fn get_ref(&self) -> &T { + &self.inner + } + + /// Gets a mutable reference to the underlying reader. + /// + /// Care should be taken to avoid modifying the internal I/O state of the + /// underlying reader as doing so may corrupt the internal limit of this + /// `Take`. + /// + /// # Examples + /// + /// ```no_run + /// use std::io; + /// use std::io::prelude::*; + /// use std::fs::File; + /// + /// fn main() -> io::Result<()> { + /// let mut file = File::open("foo.txt")?; + /// + /// let mut buffer = [0; 5]; + /// let mut handle = file.take(5); + /// handle.read(&mut buffer)?; + /// + /// let file = handle.get_mut(); + /// Ok(()) + /// } + /// ``` + #[stable(feature = "more_io_inner_methods", since = "1.20.0")] + pub fn get_mut(&mut self) -> &mut T { + &mut self.inner + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Read for Take { + fn read(&mut self, buf: &mut [u8]) -> Result { + // Don't call into inner reader at all at EOF because it may still block + if self.limit == 0 { + return Ok(0); + } + + let max = cmp::min(buf.len() as u64, self.limit) as usize; + let n = self.inner.read(&mut buf[..max])?; + assert!(n as u64 <= self.limit, "number of read bytes exceeds limit"); + self.limit -= n as u64; + Ok(n) + } + + fn read_buf(&mut self, buf: &mut ReadBuf<'_>) -> Result<()> { + // Don't call into inner reader at all at EOF because it may still block + if self.limit == 0 { + return Ok(()); + } + + let prev_filled = buf.filled_len(); + + if self.limit <= buf.remaining() as u64 { + // if we just use an as cast to convert, limit may wrap around on a 32 bit target + let limit = cmp::min(self.limit, usize::MAX as u64) as usize; + + let extra_init = cmp::min(limit as usize, buf.initialized_len() - buf.filled_len()); + + // SAFETY: no uninit data is written to ibuf + let ibuf = unsafe { &mut buf.unfilled_mut()[..limit] }; + + let mut sliced_buf = ReadBuf::uninit(ibuf); + + // SAFETY: extra_init bytes of ibuf are known to be initialized + unsafe { + sliced_buf.assume_init(extra_init); + } + + self.inner.read_buf(&mut sliced_buf)?; + + let new_init = sliced_buf.initialized_len(); + let filled = sliced_buf.filled_len(); + + // sliced_buf / ibuf must drop here + + // SAFETY: new_init bytes of buf's unfilled buffer have been initialized + unsafe { + buf.assume_init(new_init); + } + + buf.add_filled(filled); + + self.limit -= filled as u64; + } else { + self.inner.read_buf(buf)?; + + //inner may unfill + self.limit -= buf.filled_len().saturating_sub(prev_filled) as u64; + } + + Ok(()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl BufRead for Take { + fn fill_buf(&mut self) -> Result<&[u8]> { + // Don't call into inner reader at all at EOF because it may still block + if self.limit == 0 { + return Ok(&[]); + } + + let buf = self.inner.fill_buf()?; + let cap = cmp::min(buf.len() as u64, self.limit) as usize; + Ok(&buf[..cap]) + } + + fn consume(&mut self, amt: usize) { + // Don't let callers reset the limit by passing an overlarge value + let amt = cmp::min(amt as u64, self.limit) as usize; + self.limit -= amt as u64; + self.inner.consume(amt); + } +} + +impl SizeHint for Take { + #[inline] + fn lower_bound(&self) -> usize { + cmp::min(SizeHint::lower_bound(&self.inner) as u64, self.limit) as usize + } + + #[inline] + fn upper_bound(&self) -> Option { + match SizeHint::upper_bound(&self.inner) { + Some(upper_bound) => Some(cmp::min(upper_bound as u64, self.limit) as usize), + None => self.limit.try_into().ok(), + } + } +} + +/// An iterator over `u8` values of a reader. +/// +/// This struct is generally created by calling [`bytes`] on a reader. +/// Please see the documentation of [`bytes`] for more details. +/// +/// [`bytes`]: Read::bytes +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Debug)] +pub struct Bytes { + inner: R, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Bytes { + type Item = Result; + + fn next(&mut self) -> Option> { + let mut byte = 0; + loop { + return match self.inner.read(slice::from_mut(&mut byte)) { + Ok(0) => None, + Ok(..) => Some(Ok(byte)), + Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, + Err(e) => Some(Err(e)), + }; + } + } + + fn size_hint(&self) -> (usize, Option) { + SizeHint::size_hint(&self.inner) + } +} + +trait SizeHint { + fn lower_bound(&self) -> usize; + + fn upper_bound(&self) -> Option; + + fn size_hint(&self) -> (usize, Option) { + (self.lower_bound(), self.upper_bound()) + } +} + +impl SizeHint for T { + #[inline] + default fn lower_bound(&self) -> usize { + 0 + } + + #[inline] + default fn upper_bound(&self) -> Option { + None + } +} + +impl SizeHint for &mut T { + #[inline] + fn lower_bound(&self) -> usize { + SizeHint::lower_bound(*self) + } + + #[inline] + fn upper_bound(&self) -> Option { + SizeHint::upper_bound(*self) + } +} + +impl SizeHint for Box { + #[inline] + fn lower_bound(&self) -> usize { + SizeHint::lower_bound(&**self) + } + + #[inline] + fn upper_bound(&self) -> Option { + SizeHint::upper_bound(&**self) + } +} + +impl SizeHint for &[u8] { + #[inline] + fn lower_bound(&self) -> usize { + self.len() + } + + #[inline] + fn upper_bound(&self) -> Option { + Some(self.len()) + } +} + +/// An iterator over the contents of an instance of `BufRead` split on a +/// particular byte. +/// +/// This struct is generally created by calling [`split`] on a `BufRead`. +/// Please see the documentation of [`split`] for more details. +/// +/// [`split`]: BufRead::split +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Debug)] +pub struct Split { + buf: B, + delim: u8, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Split { + type Item = Result>; + + fn next(&mut self) -> Option>> { + let mut buf = Vec::new(); + match self.buf.read_until(self.delim, &mut buf) { + Ok(0) => None, + Ok(_n) => { + if buf[buf.len() - 1] == self.delim { + buf.pop(); + } + Some(Ok(buf)) + } + Err(e) => Some(Err(e)), + } + } +} + +/// An iterator over the lines of an instance of `BufRead`. +/// +/// This struct is generally created by calling [`lines`] on a `BufRead`. +/// Please see the documentation of [`lines`] for more details. +/// +/// [`lines`]: BufRead::lines +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Debug)] +pub struct Lines { + buf: B, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for Lines { + type Item = Result; + + fn next(&mut self) -> Option> { + let mut buf = String::new(); + match self.buf.read_line(&mut buf) { + Ok(0) => None, + Ok(_n) => { + if buf.ends_with('\n') { + buf.pop(); + if buf.ends_with('\r') { + buf.pop(); + } + } + Some(Ok(buf)) + } + Err(e) => Some(Err(e)), + } + } +} -- cgit v1.2.3