| //! 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. |
| //! |
| //! [`Read`]: trait.Read.html |
| //! [`Write`]: trait.Write.html |
| //! [`Seek`]: trait.Seek.html |
| //! [`BufRead`]: trait.BufRead.html |
| //! [`File`]: ../fs/struct.File.html |
| //! [`TcpStream`]: ../net/struct.TcpStream.html |
| //! [`Vec<T>`]: ../vec/struct.Vec.html |
| //! [`BufReader`]: struct.BufReader.html |
| //! [`BufWriter`]: struct.BufWriter.html |
| //! [`Write::write`]: trait.Write.html#tymethod.write |
| //! [`io::stdout`]: fn.stdout.html |
| //! [`println!`]: ../macro.println.html |
| //! [`Lines`]: struct.Lines.html |
| //! [`io::Result`]: type.Result.html |
| //! [`?` operator]: ../../book/appendix-02-operators.html |
| //! [`Read::read`]: trait.Read.html#tymethod.read |
| //! [`Result`]: ../result/enum.Result.html |
| //! [`.unwrap()`]: ../result/enum.Result.html#method.unwrap |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use crate::cmp; |
| use crate::fmt; |
| use crate::slice; |
| use crate::str; |
| use crate::memchr; |
| use crate::ops::{Deref, DerefMut}; |
| use crate::ptr; |
| use crate::sys; |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::buffered::{BufReader, BufWriter, LineWriter}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::buffered::IntoInnerError; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::cursor::Cursor; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::error::{Result, Error, ErrorKind}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::util::{copy, sink, Sink, empty, Empty, repeat, Repeat}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::stdio::{stdin, stdout, stderr, Stdin, Stdout, Stderr}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::stdio::{StdoutLock, StderrLock, StdinLock}; |
| #[unstable(feature = "print_internals", issue = "0")] |
| pub use self::stdio::{_print, _eprint}; |
| #[unstable(feature = "libstd_io_internals", issue = "42788")] |
| #[doc(no_inline, hidden)] |
| pub use self::stdio::{set_panic, set_print}; |
| |
| pub mod prelude; |
| mod buffered; |
| mod cursor; |
| mod error; |
| mod impls; |
| mod lazy; |
| mod util; |
| mod stdio; |
| |
| 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: 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()`]: trait.Read.html#tymethod.read |
| /// [`std::io`]: ../../std/io/index.html |
| /// [`File`]: ../fs/struct.File.html |
| /// [`BufRead`]: trait.BufRead.html |
| /// [`BufReader`]: struct.BufReader.html |
| /// [`&str`]: ../../std/primitive.str.html |
| /// [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 but 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. |
| /// |
| /// 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>`]: ../mem/union.MaybeUninit.html |
| /// |
| /// # 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`: |
| /// |
| /// [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| /// [`Ok(n)`]: ../../std/result/enum.Result.html#variant.Ok |
| /// [`ErrorKind::Interrupted`]: ../../std/io/enum.ErrorKind.html#variant.Interrupted |
| /// [`File`]: ../fs/struct.File.html |
| /// |
| /// ```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 |
| /// as a single call to `read` with the buffers concatenated would. |
| /// |
| /// The default implementation calls `read` with either the first nonempty |
| /// buffer provided, or an empty one if none exists. |
| #[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 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. |
| /// |
| /// [`Initializer::nop()`]: ../../std/io/struct.Initializer.html#method.nop |
| /// [`Initializer`]: ../../std/io/struct.Initializer.html |
| #[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()`]: trait.Read.html#tymethod.read |
| /// [`Ok(0)`]: ../../std/result/enum.Result.html#variant.Ok |
| /// [`ErrorKind::Interrupted`]: ../../std/io/enum.ErrorKind.html#variant.Interrupted |
| /// [`File`]: ../fs/struct.File.html |
| /// |
| /// ```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`]: ../fs/fn.read.html |
| #[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]: #method.read_to_end |
| /// |
| /// # Examples |
| /// |
| /// [`File`][file]s implement `Read`: |
| /// |
| /// [file]: ../fs/struct.File.html |
| /// |
| /// ```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`]: ../fs/fn.read_to_string.html |
| #[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. |
| /// |
| /// # 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`: |
| /// |
| /// [`File`]: ../fs/struct.File.html |
| /// [`ErrorKind::Interrupted`]: ../../std/io/enum.ErrorKind.html#variant.Interrupted |
| /// [`ErrorKind::UnexpectedEof`]: ../../std/io/enum.ErrorKind.html#variant.UnexpectedEof |
| /// |
| /// ```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]: ../fs/struct.File.html |
| /// |
| /// ```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]: ../fs/struct.File.html |
| /// [`Iterator`]: ../../std/iter/trait.Iterator.html |
| /// [`Result`]: ../../std/result/enum.Result.html |
| /// [`io::Error`]: ../../std/io/struct.Error.html |
| /// [`u8`]: ../../std/primitive.u8.html |
| /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok |
| /// [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| /// [`None`]: ../../std/option/enum.Option.html#variant.None |
| /// |
| /// ```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]: ../fs/struct.File.html |
| /// |
| /// ```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`]: ../fs/struct.File.html |
| /// [`Ok(0)`]: ../../std/result/enum.Result.html#variant.Ok |
| /// [`read()`]: trait.Read.html#tymethod.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: 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", 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::mem; |
| /// 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(mem::replace(&mut bufs, &mut []), 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")] |
| #[repr(transparent)] |
| pub struct IoSlice<'a>(sys::io::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::mem; |
| /// use std::ops::Deref; |
| /// |
| /// let mut buf1 = [1; 8]; |
| /// let mut buf2 = [2; 16]; |
| /// let mut buf3 = [3; 8]; |
| /// let mut bufs = &mut [ |
| /// IoSlice::new(&mut buf1), |
| /// IoSlice::new(&mut buf2), |
| /// IoSlice::new(&mut buf3), |
| /// ][..]; |
| /// |
| /// // Mark 10 bytes as written. |
| /// bufs = IoSlice::advance(mem::replace(&mut bufs, &mut []), 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`]: #tymethod.write |
| /// [`flush`]: #tymethod.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`]: #method.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. |
| /// |
| /// [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| /// [`Ok(n)`]: ../../std/result/enum.Result.html#variant.Ok |
| /// [`ErrorKind::Interrupted`]: ../../std/io/enum.ErrorKind.html#variant.Interrupted |
| /// |
| /// # 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) |
| } |
| |
| /// 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. |
| /// |
| /// # Errors |
| /// |
| /// This function will return the first error of |
| /// non-[`ErrorKind::Interrupted`] kind that [`write`] returns. |
| /// |
| /// [`ErrorKind::Interrupted`]: ../../std/io/enum.ErrorKind.html#variant.Interrupted |
| /// [`write`]: #tymethod.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(()) |
| } |
| |
| /// Writes a formatted string into this writer, returning any error |
| /// encountered. |
| /// |
| /// This method is primarily used to interface with the |
| /// [`format_args!`][formatargs] macro, but it is rare that this should |
| /// explicitly be called. The [`write!`][write] macro should be favored to |
| /// invoke this method instead. |
| /// |
| /// [formatargs]: ../macro.format_args.html |
| /// [write]: ../macro.write.html |
| /// |
| /// 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]: #method.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]: ../fs/struct.File.html |
| /// |
| /// ```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`]: ../fs/struct.File.html |
| /// [`read_line`]: #method.read_line |
| /// [`lines`]: #method.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`]: #tymethod.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`]: #tymethod.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. |
| /// |
| /// # 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`]: #tymethod.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. |
| /// |
| /// # 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`]: #method.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`]: type.Result.html |
| /// [`Vec<u8>`]: ../vec/struct.Vec.html |
| /// [`read_until`]: #method.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`]: type.Result.html |
| /// [`String`]: ../string/struct.String.html |
| /// |
| /// # 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. |
| /// |
| /// [`Cursor`]: struct.Cursor.html |
| /// |
| /// ``` |
| /// 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. |
| /// |
| /// [`Read`]: ../../std/io/trait.Read.html |
| /// |
| /// # 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 crate::cmp; |
| use crate::io::prelude::*; |
| use super::{Cursor, SeekFrom, repeat}; |
| use crate::io::{self, IoSlice, IoSliceMut}; |
| use crate::mem; |
| 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(mem::replace(&mut bufs, &mut []), 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(mem::replace(&mut bufs, &mut []), 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(mem::replace(&mut bufs, &mut []), 18); |
| assert_eq!(bufs[0].deref(), [3; 6].as_ref()); |
| } |
| |
| #[test] |
| fn io_slice_mut_advance_empty_slice() { |
| let mut empty_bufs = &mut [][..]; |
| // Shouldn't panic. |
| IoSliceMut::advance(&mut 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(mem::replace(&mut bufs, &mut []), 9); |
| assert!(bufs.is_empty()); |
| } |
| |
| #[test] |
| fn io_slice_advance() { |
| let mut buf1 = [1; 8]; |
| let mut buf2 = [2; 16]; |
| let mut buf3 = [3; 8]; |
| let mut bufs = |
| &mut [IoSlice::new(&mut buf1), IoSlice::new(&mut buf2), IoSlice::new(&mut buf3)][..]; |
| |
| // Only in a single buffer.. |
| bufs = IoSlice::advance(mem::replace(&mut bufs, &mut []), 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(mem::replace(&mut bufs, &mut []), 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(mem::replace(&mut bufs, &mut []), 18); |
| assert_eq!(bufs[0].deref(), [3; 6].as_ref()); |
| } |
| |
| #[test] |
| fn io_slice_advance_empty_slice() { |
| let mut empty_bufs = &mut [][..]; |
| // Shouldn't panic. |
| IoSlice::advance(&mut empty_bufs, 1); |
| } |
| |
| #[test] |
| fn io_slice_advance_beyond_total_length() { |
| let mut buf1 = [1; 8]; |
| let mut bufs = &mut [IoSlice::new(&mut buf1)][..]; |
| |
| // Going beyond the total length should be ok. |
| bufs = IoSlice::advance(mem::replace(&mut bufs, &mut []), 9); |
| assert!(bufs.is_empty()); |
| } |
| } |