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Diffstat (limited to 'src/libstd/io/mod.rs')
| -rw-r--r-- | src/libstd/io/mod.rs | 2993 |
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diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs deleted file mode 100644 index 9eb54c2cc00..00000000000 --- a/src/libstd/io/mod.rs +++ /dev/null @@ -1,2993 +0,0 @@ -//! 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<T>`]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<T, E>`][`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 -//! [`Vec<T>`]: crate::vec::Vec -//! [`io::stdout`]: stdout -//! [`io::Result`]: crate::io::Result -//! [`?` operator]: ../../book/appendix-02-operators.html -//! [`Result`]: crate::result::Result -//! [`.unwrap()`]: crate::result::Result::unwrap - -#![stable(feature = "rust1", since = "1.0.0")] - -use crate::cmp; -use crate::fmt; -use crate::memchr; -use crate::ops::{Deref, DerefMut}; -use crate::ptr; -use crate::slice; -use crate::str; -use crate::sys; - -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::buffered::IntoInnerError; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::buffered::{BufReader, BufWriter, LineWriter}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::cursor::Cursor; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::error::{Error, ErrorKind, Result}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::stdio::{stderr, stdin, stdout, Stderr, Stdin, Stdout}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::stdio::{StderrLock, StdinLock, StdoutLock}; -#[unstable(feature = "print_internals", issue = "none")] -pub use self::stdio::{_eprint, _print}; -#[unstable(feature = "libstd_io_internals", issue = "42788")] -#[doc(no_inline, hidden)] -pub use self::stdio::{set_panic, set_print}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::util::{copy, empty, repeat, sink, Empty, Repeat, Sink}; - -mod buffered; -mod cursor; -mod error; -mod impls; -mod lazy; -pub mod prelude; -mod stdio; -mod util; - -const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE; - -struct Guard<'a> { - buf: &'a mut Vec<u8>, - len: usize, -} - -impl Drop for Guard<'_> { - fn drop(&mut self) { - unsafe { - self.buf.set_len(self.len); - } - } -} - -// A few methods below (read_to_string, read_line) 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. -fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize> -where - F: FnOnce(&mut Vec<u8>) -> Result<usize>, -{ - unsafe { - 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::new(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. -// -// Because we're extending the buffer with uninitialized data for trusted -// readers, we need to make sure to truncate that if any of this panics. -fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> { - read_to_end_with_reservation(r, buf, |_| 32) -} - -fn read_to_end_with_reservation<R, F>( - r: &mut R, - buf: &mut Vec<u8>, - mut reservation_size: F, -) -> Result<usize> -where - R: Read + ?Sized, - F: FnMut(&R) -> usize, -{ - let start_len = buf.len(); - let mut g = Guard { len: buf.len(), buf }; - let ret; - loop { - if g.len == g.buf.len() { - unsafe { - // FIXME(danielhenrymantilla): #42788 - // - // - This creates a (mut) reference to a slice of - // _uninitialized_ integers, which is **undefined behavior** - // - // - Only the standard library gets to soundly "ignore" this, - // based on its privileged knowledge of unstable rustc - // internals; - g.buf.reserve(reservation_size(r)); - let capacity = g.buf.capacity(); - g.buf.set_len(capacity); - r.initializer().initialize(&mut g.buf[g.len..]); - } - } - - match r.read(&mut g.buf[g.len..]) { - Ok(0) => { - ret = Ok(g.len - start_len); - break; - } - Ok(n) => g.len += n, - Err(ref e) if e.kind() == ErrorKind::Interrupted => {} - Err(e) => { - ret = Err(e); - break; - } - } - } - - ret -} - -pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> -where - F: FnOnce(&mut [u8]) -> Result<usize>, -{ - let buf = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b| &mut **b); - read(buf) -} - -pub(crate) fn default_write_vectored<F>(write: F, bufs: &[IoSlice<'_>]) -> Result<usize> -where - F: FnOnce(&[u8]) -> Result<usize>, -{ - let buf = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b| &**b); - write(buf) -} - -/// 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]`][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`]: str -/// [`std::io`]: self -/// [`File`]: crate::fs::File -/// [slice]: ../../std/primitive.slice.html -#[stable(feature = "rust1", since = "1.0.0")] -#[doc(spotlight)] -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 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. - /// - /// 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. - /// - /// 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`. 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<T>`]) is not safe, and can lead to undefined behavior. - /// - /// [`MaybeUninit<T>`]: 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 - /// - /// ```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<usize>; - - /// 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<usize> { - 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 - } - - /// Determines if this `Read`er can work with buffers of uninitialized - /// memory. - /// - /// The default implementation returns an initializer which will zero - /// buffers. - /// - /// If a `Read`er guarantees that it can work properly with uninitialized - /// memory, it should call [`Initializer::nop()`]. See the documentation for - /// [`Initializer`] for details. - /// - /// The behavior of this method must be independent of the state of the - /// `Read`er - the method only takes `&self` so that it can be used through - /// trait objects. - /// - /// # Safety - /// - /// This method is unsafe because a `Read`er could otherwise return a - /// non-zeroing `Initializer` from another `Read` type without an `unsafe` - /// block. - #[unstable(feature = "read_initializer", issue = "42788")] - #[inline] - unsafe fn initializer(&self) -> Initializer { - Initializer::zeroing() - } - - /// 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<u8>) -> Result<usize> { - 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`][readtoend] for other error semantics. - /// - /// [readtoend]: Self::read_to_end - /// - /// # Examples - /// - /// [`File`][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<usize> { - // Note that we do *not* call `.read_to_end()` here. We are passing - // `&mut Vec<u8>` (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 `read_to_end` implementation which we - // know is guaranteed to only read data into the end of the buffer. - append_to_string(buf, |b| read_to_end(self, b)) - } - - /// 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, mut buf: &mut [u8]) -> Result<()> { - while !buf.is_empty() { - match self.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::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer")) - } else { - Ok(()) - } - } - - /// Creates a "by reference" adaptor for this instance of `Read`. - /// - /// The returned adaptor also implements `Read` and will simply borrow this - /// current reader. - /// - /// # Examples - /// - /// [`File`][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`][file]s implement `Read`: - /// - /// [file]: crate::fs::File - /// [`Iterator`]: crate::iter::Iterator - /// [`Result`]: crate::result::Result - /// [`io::Error`]: self::Error - /// - /// ```no_run - /// use std::io; - /// use std::io::prelude::*; - /// use std::fs::File; - /// - /// fn main() -> io::Result<()> { - /// let mut 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<Self> - where - Self: Sized, - { - Bytes { inner: self } - } - - /// Creates an adaptor 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`][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 f1 = File::open("foo.txt")?; - /// let mut 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<R: Read>(self, next: R) -> Chain<Self, R> - where - Self: Sized, - { - Chain { first: self, second: next, done_first: false } - } - - /// Creates an adaptor 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 mut 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<Self> - where - Self: Sized, - { - Take { inner: self, limit } - } -} - -/// 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. - /// - /// # Notes - /// - /// Elements in the slice may be modified if the cursor is not advanced to - /// the end of the slice. For example if we have a slice of buffers with 2 - /// `IoSliceMut`s, both of length 8, and we advance the cursor by 10 bytes - /// the first `IoSliceMut` will be untouched however the second will be - /// modified to remove the first 2 bytes (10 - 8). - /// - /// # 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. - /// bufs = IoSliceMut::advance(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<'b>(bufs: &'b mut [IoSliceMut<'a>], n: usize) -> &'b mut [IoSliceMut<'a>] { - // 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; - } - } - - let bufs = &mut bufs[remove..]; - if !bufs.is_empty() { - bufs[0].0.advance(n - accumulated_len) - } - bufs - } -} - -#[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 an `&[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")] - #[inline] - pub fn new(buf: &'a [u8]) -> IoSlice<'a> { - IoSlice(sys::io::IoSlice::new(buf)) - } - - /// Advance the internal cursor of the slice. - /// - /// # Notes - /// - /// Elements in the slice may be modified if the cursor is not advanced to - /// the end of the slice. For example if we have a slice of buffers with 2 - /// `IoSlice`s, both of length 8, and we advance the cursor by 10 bytes the - /// first `IoSlice` will be untouched however the second will be modified to - /// remove the first 2 bytes (10 - 8). - /// - /// # 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. - /// bufs = IoSlice::advance(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<'b>(bufs: &'b mut [IoSlice<'a>], n: usize) -> &'b mut [IoSlice<'a>] { - // 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; - } - } - - let bufs = &mut bufs[remove..]; - if !bufs.is_empty() { - bufs[0].0.advance(n - accumulated_len) - } - bufs - } -} - -#[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 type used to conditionally initialize buffers passed to `Read` methods. -#[unstable(feature = "read_initializer", issue = "42788")] -#[derive(Debug)] -pub struct Initializer(bool); - -impl Initializer { - /// Returns a new `Initializer` which will zero out buffers. - #[unstable(feature = "read_initializer", issue = "42788")] - #[inline] - pub fn zeroing() -> Initializer { - Initializer(true) - } - - /// Returns a new `Initializer` which will not zero out buffers. - /// - /// # Safety - /// - /// This may only be called by `Read`ers which guarantee that they will not - /// read from buffers passed to `Read` methods, and that the return value of - /// the method accurately reflects the number of bytes that have been - /// written to the head of the buffer. - #[unstable(feature = "read_initializer", issue = "42788")] - #[inline] - pub unsafe fn nop() -> Initializer { - Initializer(false) - } - - /// Indicates if a buffer should be initialized. - #[unstable(feature = "read_initializer", issue = "42788")] - #[inline] - pub fn should_initialize(&self) -> bool { - self.0 - } - - /// Initializes a buffer if necessary. - #[unstable(feature = "read_initializer", issue = "42788")] - #[inline] - pub fn initialize(&self, buf: &mut [u8]) { - if self.should_initialize() { - unsafe { ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len()) } - } - } -} - -/// 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 adaptors 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`]: Self::write -/// [`flush`]: Self::flush -/// [`std::io`]: index.html -/// -/// # 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`]: Self::write_all -#[stable(feature = "rust1", since = "1.0.0")] -#[doc(spotlight)] -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 may 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(()) - /// } - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - fn write(&mut self, buf: &[u8]) -> Result<usize>; - - /// 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. - #[stable(feature = "iovec", since = "1.36.0")] - fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> { - default_write_vectored(|b| self.write(b), bufs) - } - - /// Determines if this `Write`er has an efficient `write_vectored` - /// implementation. - /// - /// If a `Write`er 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`. - #[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`]: Self::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::new(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`]. - /// - /// [`write_vectored`]: Self::write_vectored - /// - /// # Notes - /// - /// - /// Unlike `io::Write::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. - /// - /// # 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. - bufs = IoSlice::advance(bufs, 0); - while !bufs.is_empty() { - match self.write_vectored(bufs) { - Ok(0) => { - return Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer")); - } - Ok(n) => bufs = IoSlice::advance(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, but 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`][writeall] 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. - /// - /// [writeall]: Self::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 Adaptor<'a, T: ?Sized + 'a> { - inner: &'a mut T, - error: Result<()>, - } - - impl<T: Write + ?Sized> fmt::Write for Adaptor<'_, 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 = Adaptor { 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::new(ErrorKind::Other, "formatter error")) - } - } - } - } - - /// Creates a "by reference" adaptor for this instance of `Write`. - /// - /// The returned adaptor 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`][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 to a negative offset is considered an error. - /// - /// [`SeekFrom::Start`]: enum.SeekFrom.html#variant.Start - #[stable(feature = "rust1", since = "1.0.0")] - fn seek(&mut self, pos: SeekFrom) -> Result<u64>; - - /// 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_convenience)] - /// 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 {} bytes long", len); - /// Ok(()) - /// } - /// ``` - #[unstable(feature = "seek_convenience", issue = "59359")] - fn stream_len(&mut self) -> Result<u64> { - 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 - /// #![feature(seek_convenience)] - /// 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(()) - /// } - /// ``` - #[unstable(feature = "seek_convenience", issue = "59359")] - fn stream_position(&mut self) -> Result<u64> { - self.seek(SeekFrom::Current(0)) - } -} - -/// Enumeration of possible methods to seek within an I/O object. -/// -/// It is used by the [`Seek`] trait. -/// -/// [`Seek`]: trait.Seek.html -#[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: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>) -> Result<usize> { - 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! -/// -/// [`BufReader`]: struct.BufReader.html -/// [`File`]: crate::fs::File -/// [`read_line`]: Self::read_line -/// [`lines`]: Self::lines -/// [`Read`]: trait.Read.html -/// -/// ```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`]: Self::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`]: Self::fill_buf - #[stable(feature = "rust1", since = "1.0.0")] - fn consume(&mut self, amt: usize); - - /// 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`]: Self::fill_buf - /// [`ErrorKind::Interrupted`]: enum.ErrorKind.html#variant.Interrupted - /// - /// # 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: - /// - /// [`Cursor`]: struct.Cursor.html - /// - /// ``` - /// 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<u8>) -> Result<usize> { - read_until(self, byte, buf) - } - - /// Read all bytes until a newline (the 0xA byte) is reached, and append - /// them to the provided buffer. - /// - /// 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. - /// - /// # 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`]: Self::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: - /// - /// [`Cursor`]: struct.Cursor.html - /// - /// ``` - /// 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<usize> { - // 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`. - 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<u8>`]`>`. 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 - /// [`Vec<u8>`]: crate::vec::Vec - /// [`read_until`]: Self::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 - /// - /// [`Cursor`]: struct.Cursor.html - /// - /// ``` - /// 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<Self> - 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 - /// - /// # 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`]. - /// - /// [`BufRead::read_line`]: trait.BufRead.html#method.read_line - #[stable(feature = "rust1", since = "1.0.0")] - fn lines(self) -> Lines<Self> - where - Self: Sized, - { - Lines { buf: self } - } -} - -/// Adaptor 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`]: trait.Read.html#method.chain -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Chain<T, U> { - first: T, - second: U, - done_first: bool, -} - -impl<T, U> Chain<T, U> { - /// 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 = "std_debug", since = "1.16.0")] -impl<T: fmt::Debug, U: fmt::Debug> fmt::Debug for Chain<T, U> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Chain").field("t", &self.first).field("u", &self.second).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Read, U: Read> Read for Chain<T, U> { - fn read(&mut self, buf: &mut [u8]) -> Result<usize> { - 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<usize> { - 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) - } - - unsafe fn initializer(&self) -> Initializer { - let initializer = self.first.initializer(); - if initializer.should_initialize() { initializer } else { self.second.initializer() } - } -} - -#[stable(feature = "chain_bufread", since = "1.9.0")] -impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> { - 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) } - } -} - -/// Reader adaptor 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`]: trait.Read.html#method.take -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Debug)] -pub struct Take<T> { - inner: T, - limit: u64, -} - -impl<T> Take<T> { - /// 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<T: Read> Read for Take<T> { - fn read(&mut self, buf: &mut [u8]) -> Result<usize> { - // 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])?; - self.limit -= n as u64; - Ok(n) - } - - unsafe fn initializer(&self) -> Initializer { - self.inner.initializer() - } - - fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> { - // Pass in a reservation_size closure that respects the current value - // of limit for each read. If we hit the read limit, this prevents the - // final zero-byte read from allocating again. - read_to_end_with_reservation(self, buf, |self_| cmp::min(self_.limit, 32) as usize) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: BufRead> BufRead for Take<T> { - 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); - } -} - -/// 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`]: trait.Read.html#method.bytes -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Debug)] -pub struct Bytes<R> { - inner: R, -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<R: Read> Iterator for Bytes<R> { - type Item = Result<u8>; - - fn next(&mut self) -> Option<Result<u8>> { - 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)), - }; - } - } -} - -/// 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`]: trait.BufRead.html#method.split -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Debug)] -pub struct Split<B> { - buf: B, - delim: u8, -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: BufRead> Iterator for Split<B> { - type Item = Result<Vec<u8>>; - - fn next(&mut self) -> Option<Result<Vec<u8>>> { - 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`]: trait.BufRead.html#method.lines -#[stable(feature = "rust1", since = "1.0.0")] -#[derive(Debug)] -pub struct Lines<B> { - buf: B, -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: BufRead> Iterator for Lines<B> { - type Item = Result<String>; - - fn next(&mut self) -> Option<Result<String>> { - 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)), - } - } -} - -#[cfg(test)] -mod tests { - use super::{repeat, Cursor, SeekFrom}; - use crate::cmp::{self, min}; - use crate::io::prelude::*; - use crate::io::{self, IoSlice, IoSliceMut}; - use crate::ops::Deref; - - #[test] - #[cfg_attr(target_os = "emscripten", ignore)] - fn read_until() { - let mut buf = Cursor::new(&b"12"[..]); - let mut v = Vec::new(); - assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 2); - assert_eq!(v, b"12"); - - let mut buf = Cursor::new(&b"1233"[..]); - let mut v = Vec::new(); - assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 3); - assert_eq!(v, b"123"); - v.truncate(0); - assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 1); - assert_eq!(v, b"3"); - v.truncate(0); - assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 0); - assert_eq!(v, []); - } - - #[test] - fn split() { - let buf = Cursor::new(&b"12"[..]); - let mut s = buf.split(b'3'); - assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']); - assert!(s.next().is_none()); - - let buf = Cursor::new(&b"1233"[..]); - let mut s = buf.split(b'3'); - assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']); - assert_eq!(s.next().unwrap().unwrap(), vec![]); - assert!(s.next().is_none()); - } - - #[test] - fn read_line() { - let mut buf = Cursor::new(&b"12"[..]); - let mut v = String::new(); - assert_eq!(buf.read_line(&mut v).unwrap(), 2); - assert_eq!(v, "12"); - - let mut buf = Cursor::new(&b"12\n\n"[..]); - let mut v = String::new(); - assert_eq!(buf.read_line(&mut v).unwrap(), 3); - assert_eq!(v, "12\n"); - v.truncate(0); - assert_eq!(buf.read_line(&mut v).unwrap(), 1); - assert_eq!(v, "\n"); - v.truncate(0); - assert_eq!(buf.read_line(&mut v).unwrap(), 0); - assert_eq!(v, ""); - } - - #[test] - fn lines() { - let buf = Cursor::new(&b"12\r"[..]); - let mut s = buf.lines(); - assert_eq!(s.next().unwrap().unwrap(), "12\r".to_string()); - assert!(s.next().is_none()); - - let buf = Cursor::new(&b"12\r\n\n"[..]); - let mut s = buf.lines(); - assert_eq!(s.next().unwrap().unwrap(), "12".to_string()); - assert_eq!(s.next().unwrap().unwrap(), "".to_string()); - assert!(s.next().is_none()); - } - - #[test] - fn read_to_end() { - let mut c = Cursor::new(&b""[..]); - let mut v = Vec::new(); - assert_eq!(c.read_to_end(&mut v).unwrap(), 0); - assert_eq!(v, []); - - let mut c = Cursor::new(&b"1"[..]); - let mut v = Vec::new(); - assert_eq!(c.read_to_end(&mut v).unwrap(), 1); - assert_eq!(v, b"1"); - - let cap = 1024 * 1024; - let data = (0..cap).map(|i| (i / 3) as u8).collect::<Vec<_>>(); - let mut v = Vec::new(); - let (a, b) = data.split_at(data.len() / 2); - assert_eq!(Cursor::new(a).read_to_end(&mut v).unwrap(), a.len()); - assert_eq!(Cursor::new(b).read_to_end(&mut v).unwrap(), b.len()); - assert_eq!(v, data); - } - - #[test] - fn read_to_string() { - let mut c = Cursor::new(&b""[..]); - let mut v = String::new(); - assert_eq!(c.read_to_string(&mut v).unwrap(), 0); - assert_eq!(v, ""); - - let mut c = Cursor::new(&b"1"[..]); - let mut v = String::new(); - assert_eq!(c.read_to_string(&mut v).unwrap(), 1); - assert_eq!(v, "1"); - - let mut c = Cursor::new(&b"\xff"[..]); - let mut v = String::new(); - assert!(c.read_to_string(&mut v).is_err()); - } - - #[test] - fn read_exact() { - let mut buf = [0; 4]; - - let mut c = Cursor::new(&b""[..]); - assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof); - - let mut c = Cursor::new(&b"123"[..]).chain(Cursor::new(&b"456789"[..])); - c.read_exact(&mut buf).unwrap(); - assert_eq!(&buf, b"1234"); - c.read_exact(&mut buf).unwrap(); - assert_eq!(&buf, b"5678"); - assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof); - } - - #[test] - fn read_exact_slice() { - let mut buf = [0; 4]; - - let mut c = &b""[..]; - assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof); - - let mut c = &b"123"[..]; - assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(), io::ErrorKind::UnexpectedEof); - // make sure the optimized (early returning) method is being used - assert_eq!(&buf, &[0; 4]); - - let mut c = &b"1234"[..]; - c.read_exact(&mut buf).unwrap(); - assert_eq!(&buf, b"1234"); - - let mut c = &b"56789"[..]; - c.read_exact(&mut buf).unwrap(); - assert_eq!(&buf, b"5678"); - assert_eq!(c, b"9"); - } - - #[test] - fn take_eof() { - struct R; - - impl Read for R { - fn read(&mut self, _: &mut [u8]) -> io::Result<usize> { - Err(io::Error::new(io::ErrorKind::Other, "")) - } - } - impl BufRead for R { - fn fill_buf(&mut self) -> io::Result<&[u8]> { - Err(io::Error::new(io::ErrorKind::Other, "")) - } - fn consume(&mut self, _amt: usize) {} - } - - let mut buf = [0; 1]; - assert_eq!(0, R.take(0).read(&mut buf).unwrap()); - assert_eq!(b"", R.take(0).fill_buf().unwrap()); - } - - fn cmp_bufread<Br1: BufRead, Br2: BufRead>(mut br1: Br1, mut br2: Br2, exp: &[u8]) { - let mut cat = Vec::new(); - loop { - let consume = { - let buf1 = br1.fill_buf().unwrap(); - let buf2 = br2.fill_buf().unwrap(); - let minlen = if buf1.len() < buf2.len() { buf1.len() } else { buf2.len() }; - assert_eq!(buf1[..minlen], buf2[..minlen]); - cat.extend_from_slice(&buf1[..minlen]); - minlen - }; - if consume == 0 { - break; - } - br1.consume(consume); - br2.consume(consume); - } - assert_eq!(br1.fill_buf().unwrap().len(), 0); - assert_eq!(br2.fill_buf().unwrap().len(), 0); - assert_eq!(&cat[..], &exp[..]) - } - - #[test] - fn chain_bufread() { - let testdata = b"ABCDEFGHIJKL"; - let chain1 = - (&testdata[..3]).chain(&testdata[3..6]).chain(&testdata[6..9]).chain(&testdata[9..]); - let chain2 = (&testdata[..4]).chain(&testdata[4..8]).chain(&testdata[8..]); - cmp_bufread(chain1, chain2, &testdata[..]); - } - - #[test] - fn chain_zero_length_read_is_not_eof() { - let a = b"A"; - let b = b"B"; - let mut s = String::new(); - let mut chain = (&a[..]).chain(&b[..]); - chain.read(&mut []).unwrap(); - chain.read_to_string(&mut s).unwrap(); - assert_eq!("AB", s); - } - - #[bench] - #[cfg_attr(target_os = "emscripten", ignore)] - fn bench_read_to_end(b: &mut test::Bencher) { - b.iter(|| { - let mut lr = repeat(1).take(10000000); - let mut vec = Vec::with_capacity(1024); - super::read_to_end(&mut lr, &mut vec) - }); - } - - #[test] - fn seek_len() -> io::Result<()> { - let mut c = Cursor::new(vec![0; 15]); - assert_eq!(c.stream_len()?, 15); - - c.seek(SeekFrom::End(0))?; - let old_pos = c.stream_position()?; - assert_eq!(c.stream_len()?, 15); - assert_eq!(c.stream_position()?, old_pos); - - c.seek(SeekFrom::Start(7))?; - c.seek(SeekFrom::Current(2))?; - let old_pos = c.stream_position()?; - assert_eq!(c.stream_len()?, 15); - assert_eq!(c.stream_position()?, old_pos); - - Ok(()) - } - - #[test] - fn seek_position() -> io::Result<()> { - // All `asserts` are duplicated here to make sure the method does not - // change anything about the seek state. - let mut c = Cursor::new(vec![0; 15]); - assert_eq!(c.stream_position()?, 0); - assert_eq!(c.stream_position()?, 0); - - c.seek(SeekFrom::End(0))?; - assert_eq!(c.stream_position()?, 15); - assert_eq!(c.stream_position()?, 15); - - c.seek(SeekFrom::Start(7))?; - c.seek(SeekFrom::Current(2))?; - assert_eq!(c.stream_position()?, 9); - assert_eq!(c.stream_position()?, 9); - - c.seek(SeekFrom::End(-3))?; - c.seek(SeekFrom::Current(1))?; - c.seek(SeekFrom::Current(-5))?; - assert_eq!(c.stream_position()?, 8); - assert_eq!(c.stream_position()?, 8); - - Ok(()) - } - - // A simple example reader which uses the default implementation of - // read_to_end. - struct ExampleSliceReader<'a> { - slice: &'a [u8], - } - - impl<'a> Read for ExampleSliceReader<'a> { - fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { - let len = cmp::min(self.slice.len(), buf.len()); - buf[..len].copy_from_slice(&self.slice[..len]); - self.slice = &self.slice[len..]; - Ok(len) - } - } - - #[test] - fn test_read_to_end_capacity() -> io::Result<()> { - let input = &b"foo"[..]; - - // read_to_end() generally needs to over-allocate, both for efficiency - // and so that it can distinguish EOF. Assert that this is the case - // with this simple ExampleSliceReader struct, which uses the default - // implementation of read_to_end. Even though vec1 is allocated with - // exactly enough capacity for the read, read_to_end will allocate more - // space here. - let mut vec1 = Vec::with_capacity(input.len()); - ExampleSliceReader { slice: input }.read_to_end(&mut vec1)?; - assert_eq!(vec1.len(), input.len()); - assert!(vec1.capacity() > input.len(), "allocated more"); - - // However, std::io::Take includes an implementation of read_to_end - // that will not allocate when the limit has already been reached. In - // this case, vec2 never grows. - let mut vec2 = Vec::with_capacity(input.len()); - ExampleSliceReader { slice: input }.take(input.len() as u64).read_to_end(&mut vec2)?; - assert_eq!(vec2.len(), input.len()); - assert_eq!(vec2.capacity(), input.len(), "did not allocate more"); - - Ok(()) - } - - #[test] - fn io_slice_mut_advance() { - 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), - ][..]; - - // Only in a single buffer.. - bufs = IoSliceMut::advance(bufs, 1); - assert_eq!(bufs[0].deref(), [1; 7].as_ref()); - assert_eq!(bufs[1].deref(), [2; 16].as_ref()); - assert_eq!(bufs[2].deref(), [3; 8].as_ref()); - - // Removing a buffer, leaving others as is. - bufs = IoSliceMut::advance(bufs, 7); - assert_eq!(bufs[0].deref(), [2; 16].as_ref()); - assert_eq!(bufs[1].deref(), [3; 8].as_ref()); - - // Removing a buffer and removing from the next buffer. - bufs = IoSliceMut::advance(bufs, 18); - assert_eq!(bufs[0].deref(), [3; 6].as_ref()); - } - - #[test] - fn io_slice_mut_advance_empty_slice() { - let empty_bufs = &mut [][..]; - // Shouldn't panic. - IoSliceMut::advance(empty_bufs, 1); - } - - #[test] - fn io_slice_mut_advance_beyond_total_length() { - let mut buf1 = [1; 8]; - let mut bufs = &mut [IoSliceMut::new(&mut buf1)][..]; - - // Going beyond the total length should be ok. - bufs = IoSliceMut::advance(bufs, 9); - assert!(bufs.is_empty()); - } - - #[test] - fn io_slice_advance() { - 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)][..]; - - // Only in a single buffer.. - bufs = IoSlice::advance(bufs, 1); - assert_eq!(bufs[0].deref(), [1; 7].as_ref()); - assert_eq!(bufs[1].deref(), [2; 16].as_ref()); - assert_eq!(bufs[2].deref(), [3; 8].as_ref()); - - // Removing a buffer, leaving others as is. - bufs = IoSlice::advance(bufs, 7); - assert_eq!(bufs[0].deref(), [2; 16].as_ref()); - assert_eq!(bufs[1].deref(), [3; 8].as_ref()); - - // Removing a buffer and removing from the next buffer. - bufs = IoSlice::advance(bufs, 18); - assert_eq!(bufs[0].deref(), [3; 6].as_ref()); - } - - #[test] - fn io_slice_advance_empty_slice() { - let empty_bufs = &mut [][..]; - // Shouldn't panic. - IoSlice::advance(empty_bufs, 1); - } - - #[test] - fn io_slice_advance_beyond_total_length() { - let buf1 = [1; 8]; - let mut bufs = &mut [IoSlice::new(&buf1)][..]; - - // Going beyond the total length should be ok. - bufs = IoSlice::advance(bufs, 9); - assert!(bufs.is_empty()); - } - - /// Create a new writer that reads from at most `n_bufs` and reads - /// `per_call` bytes (in total) per call to write. - fn test_writer(n_bufs: usize, per_call: usize) -> TestWriter { - TestWriter { n_bufs, per_call, written: Vec::new() } - } - - struct TestWriter { - n_bufs: usize, - per_call: usize, - written: Vec<u8>, - } - - impl Write for TestWriter { - fn write(&mut self, buf: &[u8]) -> io::Result<usize> { - self.write_vectored(&[IoSlice::new(buf)]) - } - - fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> { - let mut left = self.per_call; - let mut written = 0; - for buf in bufs.iter().take(self.n_bufs) { - let n = min(left, buf.len()); - self.written.extend_from_slice(&buf[0..n]); - left -= n; - written += n; - } - Ok(written) - } - - fn flush(&mut self) -> io::Result<()> { - Ok(()) - } - } - - #[test] - fn test_writer_read_from_one_buf() { - let mut writer = test_writer(1, 2); - - assert_eq!(writer.write(&[]).unwrap(), 0); - assert_eq!(writer.write_vectored(&[]).unwrap(), 0); - - // Read at most 2 bytes. - assert_eq!(writer.write(&[1, 1, 1]).unwrap(), 2); - let bufs = &[IoSlice::new(&[2, 2, 2])]; - assert_eq!(writer.write_vectored(bufs).unwrap(), 2); - - // Only read from first buf. - let bufs = &[IoSlice::new(&[3]), IoSlice::new(&[4, 4])]; - assert_eq!(writer.write_vectored(bufs).unwrap(), 1); - - assert_eq!(writer.written, &[1, 1, 2, 2, 3]); - } - - #[test] - fn test_writer_read_from_multiple_bufs() { - let mut writer = test_writer(3, 3); - - // Read at most 3 bytes from two buffers. - let bufs = &[IoSlice::new(&[1]), IoSlice::new(&[2, 2, 2])]; - assert_eq!(writer.write_vectored(bufs).unwrap(), 3); - - // Read at most 3 bytes from three buffers. - let bufs = &[IoSlice::new(&[3]), IoSlice::new(&[4]), IoSlice::new(&[5, 5])]; - assert_eq!(writer.write_vectored(bufs).unwrap(), 3); - - assert_eq!(writer.written, &[1, 2, 2, 3, 4, 5]); - } - - #[test] - fn test_write_all_vectored() { - #[rustfmt::skip] // Becomes unreadable otherwise. - let tests: Vec<(_, &'static [u8])> = vec![ - (vec![], &[]), - (vec![IoSlice::new(&[]), IoSlice::new(&[])], &[]), - (vec![IoSlice::new(&[1])], &[1]), - (vec![IoSlice::new(&[1, 2])], &[1, 2]), - (vec![IoSlice::new(&[1, 2, 3])], &[1, 2, 3]), - (vec![IoSlice::new(&[1, 2, 3, 4])], &[1, 2, 3, 4]), - (vec![IoSlice::new(&[1, 2, 3, 4, 5])], &[1, 2, 3, 4, 5]), - (vec![IoSlice::new(&[1]), IoSlice::new(&[2])], &[1, 2]), - (vec![IoSlice::new(&[1]), IoSlice::new(&[2, 2])], &[1, 2, 2]), - (vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2])], &[1, 1, 2, 2]), - (vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 2, 2, 2]), - (vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 2, 2, 2]), - (vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2])], &[1, 1, 1, 2, 2, 2]), - (vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2, 2])], &[1, 1, 1, 2, 2, 2, 2]), - (vec![IoSlice::new(&[1, 1, 1, 1]), IoSlice::new(&[2, 2, 2, 2])], &[1, 1, 1, 1, 2, 2, 2, 2]), - (vec![IoSlice::new(&[1]), IoSlice::new(&[2]), IoSlice::new(&[3])], &[1, 2, 3]), - (vec![IoSlice::new(&[1, 1]), IoSlice::new(&[2, 2]), IoSlice::new(&[3, 3])], &[1, 1, 2, 2, 3, 3]), - (vec![IoSlice::new(&[1]), IoSlice::new(&[2, 2]), IoSlice::new(&[3, 3, 3])], &[1, 2, 2, 3, 3, 3]), - (vec![IoSlice::new(&[1, 1, 1]), IoSlice::new(&[2, 2, 2]), IoSlice::new(&[3, 3, 3])], &[1, 1, 1, 2, 2, 2, 3, 3, 3]), - ]; - - let writer_configs = &[(1, 1), (1, 2), (1, 3), (2, 2), (2, 3), (3, 3)]; - - for (n_bufs, per_call) in writer_configs.iter().copied() { - for (mut input, wanted) in tests.clone().into_iter() { - let mut writer = test_writer(n_bufs, per_call); - assert!(writer.write_all_vectored(&mut *input).is_ok()); - assert_eq!(&*writer.written, &*wanted); - } - } - } -} |