| 1 | //! Traits, helpers, and type definitions for core I/O functionality. |
| 2 | //! |
|---|
| 3 | //! The `std::io` module contains a number of common things you'll need |
|---|
| 4 | //! when doing input and output. The most core part of this module is |
|---|
| 5 | //! the [`Read`] and [`Write`] traits, which provide the |
|---|
| 6 | //! most general interface for reading and writing input and output. |
|---|
| 7 | //! |
|---|
| 8 | //! ## Read and Write |
|---|
| 9 | //! |
|---|
| 10 | //! Because they are traits, [`Read`] and [`Write`] are implemented by a number |
|---|
| 11 | //! of other types, and you can implement them for your types too. As such, |
|---|
| 12 | //! you'll see a few different types of I/O throughout the documentation in |
|---|
| 13 | //! this module: [`File`]s, [`TcpStream`]s, and sometimes even [`Vec<T>`]s. For |
|---|
| 14 | //! example, [`Read`] adds a [`read`][`Read::read`] method, which we can use on |
|---|
| 15 | //! [`File`]s: |
|---|
| 16 | //! |
|---|
| 17 | //! ```no_run |
|---|
| 18 | //! use std::io; |
|---|
| 19 | //! use std::io::prelude::*; |
|---|
| 20 | //! use std::fs::File; |
|---|
| 21 | //! |
|---|
| 22 | //! fn main() -> io::Result<()> { |
|---|
| 23 | //! let mut f = File::open("foo.txt" )?; |
|---|
| 24 | //! let mut buffer = [0; 10]; |
|---|
| 25 | //! |
|---|
| 26 | //! // read up to 10 bytes |
|---|
| 27 | //! let n = f.read(&mut buffer)?; |
|---|
| 28 | //! |
|---|
| 29 | //! println!("The bytes: {:?}" , &buffer[..n]); |
|---|
| 30 | //! Ok(()) |
|---|
| 31 | //! } |
|---|
| 32 | //! ``` |
|---|
| 33 | //! |
|---|
| 34 | //! [`Read`] and [`Write`] are so important, implementors of the two traits have a |
|---|
| 35 | //! nickname: readers and writers. So you'll sometimes see 'a reader' instead |
|---|
| 36 | //! of 'a type that implements the [`Read`] trait'. Much easier! |
|---|
| 37 | //! |
|---|
| 38 | //! ## Seek and BufRead |
|---|
| 39 | //! |
|---|
| 40 | //! Beyond that, there are two important traits that are provided: [`Seek`] |
|---|
| 41 | //! and [`BufRead`]. Both of these build on top of a reader to control |
|---|
| 42 | //! how the reading happens. [`Seek`] lets you control where the next byte is |
|---|
| 43 | //! coming from: |
|---|
| 44 | //! |
|---|
| 45 | //! ```no_run |
|---|
| 46 | //! use std::io; |
|---|
| 47 | //! use std::io::prelude::*; |
|---|
| 48 | //! use std::io::SeekFrom; |
|---|
| 49 | //! use std::fs::File; |
|---|
| 50 | //! |
|---|
| 51 | //! fn main() -> io::Result<()> { |
|---|
| 52 | //! let mut f = File::open("foo.txt" )?; |
|---|
| 53 | //! let mut buffer = [0; 10]; |
|---|
| 54 | //! |
|---|
| 55 | //! // skip to the last 10 bytes of the file |
|---|
| 56 | //! f.seek(SeekFrom::End(-10))?; |
|---|
| 57 | //! |
|---|
| 58 | //! // read up to 10 bytes |
|---|
| 59 | //! let n = f.read(&mut buffer)?; |
|---|
| 60 | //! |
|---|
| 61 | //! println!("The bytes: {:?}" , &buffer[..n]); |
|---|
| 62 | //! Ok(()) |
|---|
| 63 | //! } |
|---|
| 64 | //! ``` |
|---|
| 65 | //! |
|---|
| 66 | //! [`BufRead`] uses an internal buffer to provide a number of other ways to read, but |
|---|
| 67 | //! to show it off, we'll need to talk about buffers in general. Keep reading! |
|---|
| 68 | //! |
|---|
| 69 | //! ## BufReader and BufWriter |
|---|
| 70 | //! |
|---|
| 71 | //! Byte-based interfaces are unwieldy and can be inefficient, as we'd need to be |
|---|
| 72 | //! making near-constant calls to the operating system. To help with this, |
|---|
| 73 | //! `std::io` comes with two structs, [`BufReader`] and [`BufWriter`], which wrap |
|---|
| 74 | //! readers and writers. The wrapper uses a buffer, reducing the number of |
|---|
| 75 | //! calls and providing nicer methods for accessing exactly what you want. |
|---|
| 76 | //! |
|---|
| 77 | //! For example, [`BufReader`] works with the [`BufRead`] trait to add extra |
|---|
| 78 | //! methods to any reader: |
|---|
| 79 | //! |
|---|
| 80 | //! ```no_run |
|---|
| 81 | //! use std::io; |
|---|
| 82 | //! use std::io::prelude::*; |
|---|
| 83 | //! use std::io::BufReader; |
|---|
| 84 | //! use std::fs::File; |
|---|
| 85 | //! |
|---|
| 86 | //! fn main() -> io::Result<()> { |
|---|
| 87 | //! let f = File::open("foo.txt" )?; |
|---|
| 88 | //! let mut reader = BufReader::new(f); |
|---|
| 89 | //! let mut buffer = String::new(); |
|---|
| 90 | //! |
|---|
| 91 | //! // read a line into buffer |
|---|
| 92 | //! reader.read_line(&mut buffer)?; |
|---|
| 93 | //! |
|---|
| 94 | //! println!("{buffer}" ); |
|---|
| 95 | //! Ok(()) |
|---|
| 96 | //! } |
|---|
| 97 | //! ``` |
|---|
| 98 | //! |
|---|
| 99 | //! [`BufWriter`] doesn't add any new ways of writing; it just buffers every call |
|---|
| 100 | //! to [`write`][`Write::write`]: |
|---|
| 101 | //! |
|---|
| 102 | //! ```no_run |
|---|
| 103 | //! use std::io; |
|---|
| 104 | //! use std::io::prelude::*; |
|---|
| 105 | //! use std::io::BufWriter; |
|---|
| 106 | //! use std::fs::File; |
|---|
| 107 | //! |
|---|
| 108 | //! fn main() -> io::Result<()> { |
|---|
| 109 | //! let f = File::create("foo.txt" )?; |
|---|
| 110 | //! { |
|---|
| 111 | //! let mut writer = BufWriter::new(f); |
|---|
| 112 | //! |
|---|
| 113 | //! // write a byte to the buffer |
|---|
| 114 | //! writer.write(&[42])?; |
|---|
| 115 | //! |
|---|
| 116 | //! } // the buffer is flushed once writer goes out of scope |
|---|
| 117 | //! |
|---|
| 118 | //! Ok(()) |
|---|
| 119 | //! } |
|---|
| 120 | //! ``` |
|---|
| 121 | //! |
|---|
| 122 | //! ## Standard input and output |
|---|
| 123 | //! |
|---|
| 124 | //! A very common source of input is standard input: |
|---|
| 125 | //! |
|---|
| 126 | //! ```no_run |
|---|
| 127 | //! use std::io; |
|---|
| 128 | //! |
|---|
| 129 | //! fn main() -> io::Result<()> { |
|---|
| 130 | //! let mut input = String::new(); |
|---|
| 131 | //! |
|---|
| 132 | //! io::stdin().read_line(&mut input)?; |
|---|
| 133 | //! |
|---|
| 134 | //! println!("You typed: {}" , input.trim()); |
|---|
| 135 | //! Ok(()) |
|---|
| 136 | //! } |
|---|
| 137 | //! ``` |
|---|
| 138 | //! |
|---|
| 139 | //! Note that you cannot use the [`?` operator] in functions that do not return |
|---|
| 140 | //! a [`Result<T, E>`][`Result`]. Instead, you can call [`.unwrap()`] |
|---|
| 141 | //! or `match` on the return value to catch any possible errors: |
|---|
| 142 | //! |
|---|
| 143 | //! ```no_run |
|---|
| 144 | //! use std::io; |
|---|
| 145 | //! |
|---|
| 146 | //! let mut input = String::new(); |
|---|
| 147 | //! |
|---|
| 148 | //! io::stdin().read_line(&mut input).unwrap(); |
|---|
| 149 | //! ``` |
|---|
| 150 | //! |
|---|
| 151 | //! And a very common source of output is standard output: |
|---|
| 152 | //! |
|---|
| 153 | //! ```no_run |
|---|
| 154 | //! use std::io; |
|---|
| 155 | //! use std::io::prelude::*; |
|---|
| 156 | //! |
|---|
| 157 | //! fn main() -> io::Result<()> { |
|---|
| 158 | //! io::stdout().write(&[42])?; |
|---|
| 159 | //! Ok(()) |
|---|
| 160 | //! } |
|---|
| 161 | //! ``` |
|---|
| 162 | //! |
|---|
| 163 | //! Of course, using [`io::stdout`] directly is less common than something like |
|---|
| 164 | //! [`println!`]. |
|---|
| 165 | //! |
|---|
| 166 | //! ## Iterator types |
|---|
| 167 | //! |
|---|
| 168 | //! A large number of the structures provided by `std::io` are for various |
|---|
| 169 | //! ways of iterating over I/O. For example, [`Lines`] is used to split over |
|---|
| 170 | //! lines: |
|---|
| 171 | //! |
|---|
| 172 | //! ```no_run |
|---|
| 173 | //! use std::io; |
|---|
| 174 | //! use std::io::prelude::*; |
|---|
| 175 | //! use std::io::BufReader; |
|---|
| 176 | //! use std::fs::File; |
|---|
| 177 | //! |
|---|
| 178 | //! fn main() -> io::Result<()> { |
|---|
| 179 | //! let f = File::open("foo.txt" )?; |
|---|
| 180 | //! let reader = BufReader::new(f); |
|---|
| 181 | //! |
|---|
| 182 | //! for line in reader.lines() { |
|---|
| 183 | //! println!("{}" , line?); |
|---|
| 184 | //! } |
|---|
| 185 | //! Ok(()) |
|---|
| 186 | //! } |
|---|
| 187 | //! ``` |
|---|
| 188 | //! |
|---|
| 189 | //! ## Functions |
|---|
| 190 | //! |
|---|
| 191 | //! There are a number of [functions][functions-list] that offer access to various |
|---|
| 192 | //! features. For example, we can use three of these functions to copy everything |
|---|
| 193 | //! from standard input to standard output: |
|---|
| 194 | //! |
|---|
| 195 | //! ```no_run |
|---|
| 196 | //! use std::io; |
|---|
| 197 | //! |
|---|
| 198 | //! fn main() -> io::Result<()> { |
|---|
| 199 | //! io::copy(&mut io::stdin(), &mut io::stdout())?; |
|---|
| 200 | //! Ok(()) |
|---|
| 201 | //! } |
|---|
| 202 | //! ``` |
|---|
| 203 | //! |
|---|
| 204 | //! [functions-list]: #functions-1 |
|---|
| 205 | //! |
|---|
| 206 | //! ## io::Result |
|---|
| 207 | //! |
|---|
| 208 | //! Last, but certainly not least, is [`io::Result`]. This type is used |
|---|
| 209 | //! as the return type of many `std::io` functions that can cause an error, and |
|---|
| 210 | //! can be returned from your own functions as well. Many of the examples in this |
|---|
| 211 | //! module use the [`?` operator]: |
|---|
| 212 | //! |
|---|
| 213 | //! ``` |
|---|
| 214 | //! use std::io; |
|---|
| 215 | //! |
|---|
| 216 | //! fn read_input() -> io::Result<()> { |
|---|
| 217 | //! let mut input = String::new(); |
|---|
| 218 | //! |
|---|
| 219 | //! io::stdin().read_line(&mut input)?; |
|---|
| 220 | //! |
|---|
| 221 | //! println!("You typed: {}" , input.trim()); |
|---|
| 222 | //! |
|---|
| 223 | //! Ok(()) |
|---|
| 224 | //! } |
|---|
| 225 | //! ``` |
|---|
| 226 | //! |
|---|
| 227 | //! The return type of `read_input()`, [`io::Result<()>`][`io::Result`], is a very |
|---|
| 228 | //! common type for functions which don't have a 'real' return value, but do want to |
|---|
| 229 | //! return errors if they happen. In this case, the only purpose of this function is |
|---|
| 230 | //! to read the line and print it, so we use `()`. |
|---|
| 231 | //! |
|---|
| 232 | //! ## Platform-specific behavior |
|---|
| 233 | //! |
|---|
| 234 | //! Many I/O functions throughout the standard library are documented to indicate |
|---|
| 235 | //! what various library or syscalls they are delegated to. This is done to help |
|---|
| 236 | //! applications both understand what's happening under the hood as well as investigate |
|---|
| 237 | //! any possibly unclear semantics. Note, however, that this is informative, not a binding |
|---|
| 238 | //! contract. The implementation of many of these functions are subject to change over |
|---|
| 239 | //! time and may call fewer or more syscalls/library functions. |
|---|
| 240 | //! |
|---|
| 241 | //! ## I/O Safety |
|---|
| 242 | //! |
|---|
| 243 | //! Rust follows an I/O safety discipline that is comparable to its memory safety discipline. This |
|---|
| 244 | //! means that file descriptors can be *exclusively owned*. (Here, "file descriptor" is meant to |
|---|
| 245 | //! subsume similar concepts that exist across a wide range of operating systems even if they might |
|---|
| 246 | //! use a different name, such as "handle".) An exclusively owned file descriptor is one that no |
|---|
| 247 | //! other code is allowed to access in any way, but the owner is allowed to access and even close |
|---|
| 248 | //! it any time. A type that owns its file descriptor should usually close it in its `drop` |
|---|
| 249 | //! function. Types like [`File`] own their file descriptor. Similarly, file descriptors |
|---|
| 250 | //! can be *borrowed*, granting the temporary right to perform operations on this file descriptor. |
|---|
| 251 | //! This indicates that the file descriptor will not be closed for the lifetime of the borrow, but |
|---|
| 252 | //! it does *not* imply any right to close this file descriptor, since it will likely be owned by |
|---|
| 253 | //! someone else. |
|---|
| 254 | //! |
|---|
| 255 | //! The platform-specific parts of the Rust standard library expose types that reflect these |
|---|
| 256 | //! concepts, see [`os::unix`] and [`os::windows`]. |
|---|
| 257 | //! |
|---|
| 258 | //! To uphold I/O safety, it is crucial that no code acts on file descriptors it does not own or |
|---|
| 259 | //! borrow, and no code closes file descriptors it does not own. In other words, a safe function |
|---|
| 260 | //! that takes a regular integer, treats it as a file descriptor, and acts on it, is *unsound*. |
|---|
| 261 | //! |
|---|
| 262 | //! Not upholding I/O safety and acting on a file descriptor without proof of ownership can lead to |
|---|
| 263 | //! misbehavior and even Undefined Behavior in code that relies on ownership of its file |
|---|
| 264 | //! descriptors: a closed file descriptor could be re-allocated, so the original owner of that file |
|---|
| 265 | //! descriptor is now working on the wrong file. Some code might even rely on fully encapsulating |
|---|
| 266 | //! its file descriptors with no operations being performed by any other part of the program. |
|---|
| 267 | //! |
|---|
| 268 | //! Note that exclusive ownership of a file descriptor does *not* imply exclusive ownership of the |
|---|
| 269 | //! underlying kernel object that the file descriptor references (also called "file description" on |
|---|
| 270 | //! some operating systems). File descriptors basically work like [`Arc`]: when you receive an owned |
|---|
| 271 | //! file descriptor, you cannot know whether there are any other file descriptors that reference the |
|---|
| 272 | //! same kernel object. However, when you create a new kernel object, you know that you are holding |
|---|
| 273 | //! the only reference to it. Just be careful not to lend it to anyone, since they can obtain a |
|---|
| 274 | //! clone and then you can no longer know what the reference count is! In that sense, [`OwnedFd`] is |
|---|
| 275 | //! like `Arc` and [`BorrowedFd<'a>`] is like `&'a Arc` (and similar for the Windows types). In |
|---|
| 276 | //! particular, given a `BorrowedFd<'a>`, you are not allowed to close the file descriptor -- just |
|---|
| 277 | //! like how, given a `&'a Arc`, you are not allowed to decrement the reference count and |
|---|
| 278 | //! potentially free the underlying object. There is no equivalent to `Box` for file descriptors in |
|---|
| 279 | //! the standard library (that would be a type that guarantees that the reference count is `1`), |
|---|
| 280 | //! however, it would be possible for a crate to define a type with those semantics. |
|---|
| 281 | //! |
|---|
| 282 | //! [`File`]: crate::fs::File |
|---|
| 283 | //! [`TcpStream`]: crate::net::TcpStream |
|---|
| 284 | //! [`io::stdout`]: stdout |
|---|
| 285 | //! [`io::Result`]: self::Result |
|---|
| 286 | //! [`?` operator]: ../../book/appendix-02-operators.html |
|---|
| 287 | //! [`Result`]: crate::result::Result |
|---|
| 288 | //! [`.unwrap()`]: crate::result::Result::unwrap |
|---|
| 289 | //! [`os::unix`]: ../os/unix/io/index.html |
|---|
| 290 | //! [`os::windows`]: ../os/windows/io/index.html |
|---|
| 291 | //! [`OwnedFd`]: ../os/fd/struct.OwnedFd.html |
|---|
| 292 | //! [`BorrowedFd<'a>`]: ../os/fd/struct.BorrowedFd.html |
|---|
| 293 | //! [`Arc`]: crate::sync::Arc |
|---|
| 294 | |
|---|
| 295 | #![stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 296 | |
|---|
| 297 | #[cfg (test)] |
|---|
| 298 | mod tests; |
|---|
| 299 | |
|---|
| 300 | use crate::cmp; |
|---|
| 301 | use crate::fmt; |
|---|
| 302 | use crate::mem::take; |
|---|
| 303 | use crate::ops::{Deref, DerefMut}; |
|---|
| 304 | use crate::slice; |
|---|
| 305 | use crate::str; |
|---|
| 306 | use crate::sys; |
|---|
| 307 | use crate::sys_common::memchr; |
|---|
| 308 | |
|---|
| 309 | #[stable (feature = "bufwriter_into_parts" , since = "1.56.0" )] |
|---|
| 310 | pub use self::buffered::WriterPanicked; |
|---|
| 311 | #[unstable (feature = "raw_os_error_ty" , issue = "107792" )] |
|---|
| 312 | pub use self::error::RawOsError; |
|---|
| 313 | pub(crate) use self::stdio::attempt_print_to_stderr; |
|---|
| 314 | #[unstable (feature = "internal_output_capture" , issue = "none" )] |
|---|
| 315 | #[doc (no_inline, hidden)] |
|---|
| 316 | pub use self::stdio::set_output_capture; |
|---|
| 317 | #[stable (feature = "is_terminal" , since = "1.70.0" )] |
|---|
| 318 | pub use self::stdio::IsTerminal; |
|---|
| 319 | #[unstable (feature = "print_internals" , issue = "none" )] |
|---|
| 320 | #[doc (hidden)] |
|---|
| 321 | pub use self::stdio::{_eprint, _print}; |
|---|
| 322 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 323 | pub use self::{ |
|---|
| 324 | buffered::{BufReader, BufWriter, IntoInnerError, LineWriter}, |
|---|
| 325 | copy::copy, |
|---|
| 326 | cursor::Cursor, |
|---|
| 327 | error::{Error, ErrorKind, Result}, |
|---|
| 328 | stdio::{stderr, stdin, stdout, Stderr, StderrLock, Stdin, StdinLock, Stdout, StdoutLock}, |
|---|
| 329 | util::{empty, repeat, sink, Empty, Repeat, Sink}, |
|---|
| 330 | }; |
|---|
| 331 | |
|---|
| 332 | #[unstable (feature = "read_buf" , issue = "78485" )] |
|---|
| 333 | pub use core::io::{BorrowedBuf, BorrowedCursor}; |
|---|
| 334 | pub(crate) use error::const_io_error; |
|---|
| 335 | |
|---|
| 336 | mod buffered; |
|---|
| 337 | pub(crate) mod copy; |
|---|
| 338 | mod cursor; |
|---|
| 339 | mod error; |
|---|
| 340 | mod impls; |
|---|
| 341 | pub mod prelude; |
|---|
| 342 | mod stdio; |
|---|
| 343 | mod util; |
|---|
| 344 | |
|---|
| 345 | const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE; |
|---|
| 346 | |
|---|
| 347 | pub(crate) use stdio::cleanup; |
|---|
| 348 | |
|---|
| 349 | struct Guard<'a> { |
|---|
| 350 | buf: &'a mut Vec<u8>, |
|---|
| 351 | len: usize, |
|---|
| 352 | } |
|---|
| 353 | |
|---|
| 354 | impl Drop for Guard<'_> { |
|---|
| 355 | fn drop(&mut self) { |
|---|
| 356 | unsafe { |
|---|
| 357 | self.buf.set_len(self.len); |
|---|
| 358 | } |
|---|
| 359 | } |
|---|
| 360 | } |
|---|
| 361 | |
|---|
| 362 | // Several `read_to_string` and `read_line` methods in the standard library will |
|---|
| 363 | // append data into a `String` buffer, but we need to be pretty careful when |
|---|
| 364 | // doing this. The implementation will just call `.as_mut_vec()` and then |
|---|
| 365 | // delegate to a byte-oriented reading method, but we must ensure that when |
|---|
| 366 | // returning we never leave `buf` in a state such that it contains invalid UTF-8 |
|---|
| 367 | // in its bounds. |
|---|
| 368 | // |
|---|
| 369 | // To this end, we use an RAII guard (to protect against panics) which updates |
|---|
| 370 | // the length of the string when it is dropped. This guard initially truncates |
|---|
| 371 | // the string to the prior length and only after we've validated that the |
|---|
| 372 | // new contents are valid UTF-8 do we allow it to set a longer length. |
|---|
| 373 | // |
|---|
| 374 | // The unsafety in this function is twofold: |
|---|
| 375 | // |
|---|
| 376 | // 1. We're looking at the raw bytes of `buf`, so we take on the burden of UTF-8 |
|---|
| 377 | // checks. |
|---|
| 378 | // 2. We're passing a raw buffer to the function `f`, and it is expected that |
|---|
| 379 | // the function only *appends* bytes to the buffer. We'll get undefined |
|---|
| 380 | // behavior if existing bytes are overwritten to have non-UTF-8 data. |
|---|
| 381 | pub(crate) unsafe fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize> |
|---|
| 382 | where |
|---|
| 383 | F: FnOnce(&mut Vec<u8>) -> Result<usize>, |
|---|
| 384 | { |
|---|
| 385 | let mut g: Guard<'_> = Guard { len: buf.len(), buf: buf.as_mut_vec() }; |
|---|
| 386 | let ret: Result = f(g.buf); |
|---|
| 387 | if str::from_utf8(&g.buf[g.len..]).is_err() { |
|---|
| 388 | ret.and_then(|_| { |
|---|
| 389 | Err(error::const_io_error!( |
|---|
| 390 | ErrorKind::InvalidData, |
|---|
| 391 | "stream did not contain valid UTF-8" |
|---|
| 392 | )) |
|---|
| 393 | }) |
|---|
| 394 | } else { |
|---|
| 395 | g.len = g.buf.len(); |
|---|
| 396 | ret |
|---|
| 397 | } |
|---|
| 398 | } |
|---|
| 399 | |
|---|
| 400 | // Here we must serve many masters with conflicting goals: |
|---|
| 401 | // |
|---|
| 402 | // - avoid allocating unless necessary |
|---|
| 403 | // - avoid overallocating if we know the exact size (#89165) |
|---|
| 404 | // - avoid passing large buffers to readers that always initialize the free capacity if they perform short reads (#23815, #23820) |
|---|
| 405 | // - pass large buffers to readers that do not initialize the spare capacity. this can amortize per-call overheads |
|---|
| 406 | // - and finally pass not-too-small and not-too-large buffers to Windows read APIs because they manage to suffer from both problems |
|---|
| 407 | // at the same time, i.e. small reads suffer from syscall overhead, all reads incur initialization cost |
|---|
| 408 | // proportional to buffer size (#110650) |
|---|
| 409 | // |
|---|
| 410 | pub(crate) fn default_read_to_end<R: Read + ?Sized>( |
|---|
| 411 | r: &mut R, |
|---|
| 412 | buf: &mut Vec<u8>, |
|---|
| 413 | size_hint: Option<usize>, |
|---|
| 414 | ) -> Result<usize> { |
|---|
| 415 | let start_len = buf.len(); |
|---|
| 416 | let start_cap = buf.capacity(); |
|---|
| 417 | // Optionally limit the maximum bytes read on each iteration. |
|---|
| 418 | // This adds an arbitrary fiddle factor to allow for more data than we expect. |
|---|
| 419 | let mut max_read_size = size_hint |
|---|
| 420 | .and_then(|s| s.checked_add(1024)?.checked_next_multiple_of(DEFAULT_BUF_SIZE)) |
|---|
| 421 | .unwrap_or(DEFAULT_BUF_SIZE); |
|---|
| 422 | |
|---|
| 423 | let mut initialized = 0; // Extra initialized bytes from previous loop iteration |
|---|
| 424 | |
|---|
| 425 | const PROBE_SIZE: usize = 32; |
|---|
| 426 | |
|---|
| 427 | fn small_probe_read<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> { |
|---|
| 428 | let mut probe = [0u8; PROBE_SIZE]; |
|---|
| 429 | |
|---|
| 430 | loop { |
|---|
| 431 | match r.read(&mut probe) { |
|---|
| 432 | Ok(n) => { |
|---|
| 433 | // there is no way to recover from allocation failure here |
|---|
| 434 | // because the data has already been read. |
|---|
| 435 | buf.extend_from_slice(&probe[..n]); |
|---|
| 436 | return Ok(n); |
|---|
| 437 | } |
|---|
| 438 | Err(ref e) if e.is_interrupted() => continue, |
|---|
| 439 | Err(e) => return Err(e), |
|---|
| 440 | } |
|---|
| 441 | } |
|---|
| 442 | } |
|---|
| 443 | |
|---|
| 444 | // avoid inflating empty/small vecs before we have determined that there's anything to read |
|---|
| 445 | if (size_hint.is_none() || size_hint == Some(0)) && buf.capacity() - buf.len() < PROBE_SIZE { |
|---|
| 446 | let read = small_probe_read(r, buf)?; |
|---|
| 447 | |
|---|
| 448 | if read == 0 { |
|---|
| 449 | return Ok(0); |
|---|
| 450 | } |
|---|
| 451 | } |
|---|
| 452 | |
|---|
| 453 | loop { |
|---|
| 454 | if buf.len() == buf.capacity() && buf.capacity() == start_cap { |
|---|
| 455 | // The buffer might be an exact fit. Let's read into a probe buffer |
|---|
| 456 | // and see if it returns `Ok(0)`. If so, we've avoided an |
|---|
| 457 | // unnecessary doubling of the capacity. But if not, append the |
|---|
| 458 | // probe buffer to the primary buffer and let its capacity grow. |
|---|
| 459 | let read = small_probe_read(r, buf)?; |
|---|
| 460 | |
|---|
| 461 | if read == 0 { |
|---|
| 462 | return Ok(buf.len() - start_len); |
|---|
| 463 | } |
|---|
| 464 | } |
|---|
| 465 | |
|---|
| 466 | if buf.len() == buf.capacity() { |
|---|
| 467 | // buf is full, need more space |
|---|
| 468 | buf.try_reserve(PROBE_SIZE).map_err(|_| ErrorKind::OutOfMemory)?; |
|---|
| 469 | } |
|---|
| 470 | |
|---|
| 471 | let mut spare = buf.spare_capacity_mut(); |
|---|
| 472 | let buf_len = cmp::min(spare.len(), max_read_size); |
|---|
| 473 | spare = &mut spare[..buf_len]; |
|---|
| 474 | let mut read_buf: BorrowedBuf<'_> = spare.into(); |
|---|
| 475 | |
|---|
| 476 | // SAFETY: These bytes were initialized but not filled in the previous loop |
|---|
| 477 | unsafe { |
|---|
| 478 | read_buf.set_init(initialized); |
|---|
| 479 | } |
|---|
| 480 | |
|---|
| 481 | let mut cursor = read_buf.unfilled(); |
|---|
| 482 | loop { |
|---|
| 483 | match r.read_buf(cursor.reborrow()) { |
|---|
| 484 | Ok(()) => break, |
|---|
| 485 | Err(e) if e.is_interrupted() => continue, |
|---|
| 486 | Err(e) => return Err(e), |
|---|
| 487 | } |
|---|
| 488 | } |
|---|
| 489 | |
|---|
| 490 | let unfilled_but_initialized = cursor.init_ref().len(); |
|---|
| 491 | let bytes_read = cursor.written(); |
|---|
| 492 | let was_fully_initialized = read_buf.init_len() == buf_len; |
|---|
| 493 | |
|---|
| 494 | if bytes_read == 0 { |
|---|
| 495 | return Ok(buf.len() - start_len); |
|---|
| 496 | } |
|---|
| 497 | |
|---|
| 498 | // store how much was initialized but not filled |
|---|
| 499 | initialized = unfilled_but_initialized; |
|---|
| 500 | |
|---|
| 501 | // SAFETY: BorrowedBuf's invariants mean this much memory is initialized. |
|---|
| 502 | unsafe { |
|---|
| 503 | let new_len = bytes_read + buf.len(); |
|---|
| 504 | buf.set_len(new_len); |
|---|
| 505 | } |
|---|
| 506 | |
|---|
| 507 | // Use heuristics to determine the max read size if no initial size hint was provided |
|---|
| 508 | if size_hint.is_none() { |
|---|
| 509 | // The reader is returning short reads but it doesn't call ensure_init(). |
|---|
| 510 | // In that case we no longer need to restrict read sizes to avoid |
|---|
| 511 | // initialization costs. |
|---|
| 512 | if !was_fully_initialized { |
|---|
| 513 | max_read_size = usize::MAX; |
|---|
| 514 | } |
|---|
| 515 | |
|---|
| 516 | // we have passed a larger buffer than previously and the |
|---|
| 517 | // reader still hasn't returned a short read |
|---|
| 518 | if buf_len >= max_read_size && bytes_read == buf_len { |
|---|
| 519 | max_read_size = max_read_size.saturating_mul(2); |
|---|
| 520 | } |
|---|
| 521 | } |
|---|
| 522 | } |
|---|
| 523 | } |
|---|
| 524 | |
|---|
| 525 | pub(crate) fn default_read_to_string<R: Read + ?Sized>( |
|---|
| 526 | r: &mut R, |
|---|
| 527 | buf: &mut String, |
|---|
| 528 | size_hint: Option<usize>, |
|---|
| 529 | ) -> Result<usize> { |
|---|
| 530 | // Note that we do *not* call `r.read_to_end()` here. We are passing |
|---|
| 531 | // `&mut Vec<u8>` (the raw contents of `buf`) into the `read_to_end` |
|---|
| 532 | // method to fill it up. An arbitrary implementation could overwrite the |
|---|
| 533 | // entire contents of the vector, not just append to it (which is what |
|---|
| 534 | // we are expecting). |
|---|
| 535 | // |
|---|
| 536 | // To prevent extraneously checking the UTF-8-ness of the entire buffer |
|---|
| 537 | // we pass it to our hardcoded `default_read_to_end` implementation which |
|---|
| 538 | // we know is guaranteed to only read data into the end of the buffer. |
|---|
| 539 | unsafe { append_to_string(buf, |b: &mut Vec| default_read_to_end(r, buf:b, size_hint)) } |
|---|
| 540 | } |
|---|
| 541 | |
|---|
| 542 | pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> |
|---|
| 543 | where |
|---|
| 544 | F: FnOnce(&mut [u8]) -> Result<usize>, |
|---|
| 545 | { |
|---|
| 546 | let buf: &mut [u8] = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b: &mut IoSliceMut<'_>| &mut **b); |
|---|
| 547 | read(buf) |
|---|
| 548 | } |
|---|
| 549 | |
|---|
| 550 | pub(crate) fn default_write_vectored<F>(write: F, bufs: &[IoSlice<'_>]) -> Result<usize> |
|---|
| 551 | where |
|---|
| 552 | F: FnOnce(&[u8]) -> Result<usize>, |
|---|
| 553 | { |
|---|
| 554 | let buf: &[u8] = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b: &IoSlice<'_>| &**b); |
|---|
| 555 | write(buf) |
|---|
| 556 | } |
|---|
| 557 | |
|---|
| 558 | pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [u8]) -> Result<()> { |
|---|
| 559 | while !buf.is_empty() { |
|---|
| 560 | match this.read(buf) { |
|---|
| 561 | Ok(0) => break, |
|---|
| 562 | Ok(n: usize) => { |
|---|
| 563 | buf = &mut buf[n..]; |
|---|
| 564 | } |
|---|
| 565 | Err(ref e: &Error) if e.is_interrupted() => {} |
|---|
| 566 | Err(e: Error) => return Err(e), |
|---|
| 567 | } |
|---|
| 568 | } |
|---|
| 569 | if !buf.is_empty() { |
|---|
| 570 | Err(error::const_io_error!(ErrorKind::UnexpectedEof, "failed to fill whole buffer" )) |
|---|
| 571 | } else { |
|---|
| 572 | Ok(()) |
|---|
| 573 | } |
|---|
| 574 | } |
|---|
| 575 | |
|---|
| 576 | pub(crate) fn default_read_buf<F>(read: F, mut cursor: BorrowedCursor<'_>) -> Result<()> |
|---|
| 577 | where |
|---|
| 578 | F: FnOnce(&mut [u8]) -> Result<usize>, |
|---|
| 579 | { |
|---|
| 580 | let n: usize = read(cursor.ensure_init().init_mut())?; |
|---|
| 581 | unsafe { |
|---|
| 582 | // SAFETY: we initialised using `ensure_init` so there is no uninit data to advance to. |
|---|
| 583 | cursor.advance(n); |
|---|
| 584 | } |
|---|
| 585 | Ok(()) |
|---|
| 586 | } |
|---|
| 587 | |
|---|
| 588 | /// The `Read` trait allows for reading bytes from a source. |
|---|
| 589 | /// |
|---|
| 590 | /// Implementors of the `Read` trait are called 'readers'. |
|---|
| 591 | /// |
|---|
| 592 | /// Readers are defined by one required method, [`read()`]. Each call to [`read()`] |
|---|
| 593 | /// will attempt to pull bytes from this source into a provided buffer. A |
|---|
| 594 | /// number of other methods are implemented in terms of [`read()`], giving |
|---|
| 595 | /// implementors a number of ways to read bytes while only needing to implement |
|---|
| 596 | /// a single method. |
|---|
| 597 | /// |
|---|
| 598 | /// Readers are intended to be composable with one another. Many implementors |
|---|
| 599 | /// throughout [`std::io`] take and provide types which implement the `Read` |
|---|
| 600 | /// trait. |
|---|
| 601 | /// |
|---|
| 602 | /// Please note that each call to [`read()`] may involve a system call, and |
|---|
| 603 | /// therefore, using something that implements [`BufRead`], such as |
|---|
| 604 | /// [`BufReader`], will be more efficient. |
|---|
| 605 | /// |
|---|
| 606 | /// Repeated calls to the reader use the same cursor, so for example |
|---|
| 607 | /// calling `read_to_end` twice on a [`File`] will only return the file's |
|---|
| 608 | /// contents once. It's recommended to first call `rewind()` in that case. |
|---|
| 609 | /// |
|---|
| 610 | /// # Examples |
|---|
| 611 | /// |
|---|
| 612 | /// [`File`]s implement `Read`: |
|---|
| 613 | /// |
|---|
| 614 | /// ```no_run |
|---|
| 615 | /// use std::io; |
|---|
| 616 | /// use std::io::prelude::*; |
|---|
| 617 | /// use std::fs::File; |
|---|
| 618 | /// |
|---|
| 619 | /// fn main() -> io::Result<()> { |
|---|
| 620 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 621 | /// let mut buffer = [0; 10]; |
|---|
| 622 | /// |
|---|
| 623 | /// // read up to 10 bytes |
|---|
| 624 | /// f.read(&mut buffer)?; |
|---|
| 625 | /// |
|---|
| 626 | /// let mut buffer = Vec::new(); |
|---|
| 627 | /// // read the whole file |
|---|
| 628 | /// f.read_to_end(&mut buffer)?; |
|---|
| 629 | /// |
|---|
| 630 | /// // read into a String, so that you don't need to do the conversion. |
|---|
| 631 | /// let mut buffer = String::new(); |
|---|
| 632 | /// f.read_to_string(&mut buffer)?; |
|---|
| 633 | /// |
|---|
| 634 | /// // and more! See the other methods for more details. |
|---|
| 635 | /// Ok(()) |
|---|
| 636 | /// } |
|---|
| 637 | /// ``` |
|---|
| 638 | /// |
|---|
| 639 | /// Read from [`&str`] because [`&[u8]`][prim@slice] implements `Read`: |
|---|
| 640 | /// |
|---|
| 641 | /// ```no_run |
|---|
| 642 | /// # use std::io; |
|---|
| 643 | /// use std::io::prelude::*; |
|---|
| 644 | /// |
|---|
| 645 | /// fn main() -> io::Result<()> { |
|---|
| 646 | /// let mut b = "This string will be read" .as_bytes(); |
|---|
| 647 | /// let mut buffer = [0; 10]; |
|---|
| 648 | /// |
|---|
| 649 | /// // read up to 10 bytes |
|---|
| 650 | /// b.read(&mut buffer)?; |
|---|
| 651 | /// |
|---|
| 652 | /// // etc... it works exactly as a File does! |
|---|
| 653 | /// Ok(()) |
|---|
| 654 | /// } |
|---|
| 655 | /// ``` |
|---|
| 656 | /// |
|---|
| 657 | /// [`read()`]: Read::read |
|---|
| 658 | /// [`&str`]: prim@str |
|---|
| 659 | /// [`std::io`]: self |
|---|
| 660 | /// [`File`]: crate::fs::File |
|---|
| 661 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 662 | #[doc (notable_trait)] |
|---|
| 663 | #[cfg_attr (not(test), rustc_diagnostic_item = "IoRead" )] |
|---|
| 664 | pub trait Read { |
|---|
| 665 | /// Pull some bytes from this source into the specified buffer, returning |
|---|
| 666 | /// how many bytes were read. |
|---|
| 667 | /// |
|---|
| 668 | /// This function does not provide any guarantees about whether it blocks |
|---|
| 669 | /// waiting for data, but if an object needs to block for a read and cannot, |
|---|
| 670 | /// it will typically signal this via an [`Err`] return value. |
|---|
| 671 | /// |
|---|
| 672 | /// If the return value of this method is [`Ok(n)`], then implementations must |
|---|
| 673 | /// guarantee that `0 <= n <= buf.len()`. A nonzero `n` value indicates |
|---|
| 674 | /// that the buffer `buf` has been filled in with `n` bytes of data from this |
|---|
| 675 | /// source. If `n` is `0`, then it can indicate one of two scenarios: |
|---|
| 676 | /// |
|---|
| 677 | /// 1. This reader has reached its "end of file" and will likely no longer |
|---|
| 678 | /// be able to produce bytes. Note that this does not mean that the |
|---|
| 679 | /// reader will *always* no longer be able to produce bytes. As an example, |
|---|
| 680 | /// on Linux, this method will call the `recv` syscall for a [`TcpStream`], |
|---|
| 681 | /// where returning zero indicates the connection was shut down correctly. While |
|---|
| 682 | /// for [`File`], it is possible to reach the end of file and get zero as result, |
|---|
| 683 | /// but if more data is appended to the file, future calls to `read` will return |
|---|
| 684 | /// more data. |
|---|
| 685 | /// 2. The buffer specified was 0 bytes in length. |
|---|
| 686 | /// |
|---|
| 687 | /// It is not an error if the returned value `n` is smaller than the buffer size, |
|---|
| 688 | /// even when the reader is not at the end of the stream yet. |
|---|
| 689 | /// This may happen for example because fewer bytes are actually available right now |
|---|
| 690 | /// (e. g. being close to end-of-file) or because read() was interrupted by a signal. |
|---|
| 691 | /// |
|---|
| 692 | /// As this trait is safe to implement, callers in unsafe code cannot rely on |
|---|
| 693 | /// `n <= buf.len()` for safety. |
|---|
| 694 | /// Extra care needs to be taken when `unsafe` functions are used to access the read bytes. |
|---|
| 695 | /// Callers have to ensure that no unchecked out-of-bounds accesses are possible even if |
|---|
| 696 | /// `n > buf.len()`. |
|---|
| 697 | /// |
|---|
| 698 | /// No guarantees are provided about the contents of `buf` when this |
|---|
| 699 | /// function is called, so implementations cannot rely on any property of the |
|---|
| 700 | /// contents of `buf` being true. It is recommended that *implementations* |
|---|
| 701 | /// only write data to `buf` instead of reading its contents. |
|---|
| 702 | /// |
|---|
| 703 | /// Correspondingly, however, *callers* of this method in unsafe code must not assume |
|---|
| 704 | /// any guarantees about how the implementation uses `buf`. The trait is safe to implement, |
|---|
| 705 | /// so it is possible that the code that's supposed to write to the buffer might also read |
|---|
| 706 | /// from it. It is your responsibility to make sure that `buf` is initialized |
|---|
| 707 | /// before calling `read`. Calling `read` with an uninitialized `buf` (of the kind one |
|---|
| 708 | /// obtains via [`MaybeUninit<T>`]) is not safe, and can lead to undefined behavior. |
|---|
| 709 | /// |
|---|
| 710 | /// [`MaybeUninit<T>`]: crate::mem::MaybeUninit |
|---|
| 711 | /// |
|---|
| 712 | /// # Errors |
|---|
| 713 | /// |
|---|
| 714 | /// If this function encounters any form of I/O or other error, an error |
|---|
| 715 | /// variant will be returned. If an error is returned then it must be |
|---|
| 716 | /// guaranteed that no bytes were read. |
|---|
| 717 | /// |
|---|
| 718 | /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the read |
|---|
| 719 | /// operation should be retried if there is nothing else to do. |
|---|
| 720 | /// |
|---|
| 721 | /// # Examples |
|---|
| 722 | /// |
|---|
| 723 | /// [`File`]s implement `Read`: |
|---|
| 724 | /// |
|---|
| 725 | /// [`Ok(n)`]: Ok |
|---|
| 726 | /// [`File`]: crate::fs::File |
|---|
| 727 | /// [`TcpStream`]: crate::net::TcpStream |
|---|
| 728 | /// |
|---|
| 729 | /// ```no_run |
|---|
| 730 | /// use std::io; |
|---|
| 731 | /// use std::io::prelude::*; |
|---|
| 732 | /// use std::fs::File; |
|---|
| 733 | /// |
|---|
| 734 | /// fn main() -> io::Result<()> { |
|---|
| 735 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 736 | /// let mut buffer = [0; 10]; |
|---|
| 737 | /// |
|---|
| 738 | /// // read up to 10 bytes |
|---|
| 739 | /// let n = f.read(&mut buffer[..])?; |
|---|
| 740 | /// |
|---|
| 741 | /// println!("The bytes: {:?}" , &buffer[..n]); |
|---|
| 742 | /// Ok(()) |
|---|
| 743 | /// } |
|---|
| 744 | /// ``` |
|---|
| 745 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 746 | fn read(&mut self, buf: &mut [u8]) -> Result<usize>; |
|---|
| 747 | |
|---|
| 748 | /// Like `read`, except that it reads into a slice of buffers. |
|---|
| 749 | /// |
|---|
| 750 | /// Data is copied to fill each buffer in order, with the final buffer |
|---|
| 751 | /// written to possibly being only partially filled. This method must |
|---|
| 752 | /// behave equivalently to a single call to `read` with concatenated |
|---|
| 753 | /// buffers. |
|---|
| 754 | /// |
|---|
| 755 | /// The default implementation calls `read` with either the first nonempty |
|---|
| 756 | /// buffer provided, or an empty one if none exists. |
|---|
| 757 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 758 | fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> { |
|---|
| 759 | default_read_vectored(|b| self.read(b), bufs) |
|---|
| 760 | } |
|---|
| 761 | |
|---|
| 762 | /// Determines if this `Read`er has an efficient `read_vectored` |
|---|
| 763 | /// implementation. |
|---|
| 764 | /// |
|---|
| 765 | /// If a `Read`er does not override the default `read_vectored` |
|---|
| 766 | /// implementation, code using it may want to avoid the method all together |
|---|
| 767 | /// and coalesce writes into a single buffer for higher performance. |
|---|
| 768 | /// |
|---|
| 769 | /// The default implementation returns `false`. |
|---|
| 770 | #[unstable (feature = "can_vector" , issue = "69941" )] |
|---|
| 771 | fn is_read_vectored(&self) -> bool { |
|---|
| 772 | false |
|---|
| 773 | } |
|---|
| 774 | |
|---|
| 775 | /// Read all bytes until EOF in this source, placing them into `buf`. |
|---|
| 776 | /// |
|---|
| 777 | /// All bytes read from this source will be appended to the specified buffer |
|---|
| 778 | /// `buf`. This function will continuously call [`read()`] to append more data to |
|---|
| 779 | /// `buf` until [`read()`] returns either [`Ok(0)`] or an error of |
|---|
| 780 | /// non-[`ErrorKind::Interrupted`] kind. |
|---|
| 781 | /// |
|---|
| 782 | /// If successful, this function will return the total number of bytes read. |
|---|
| 783 | /// |
|---|
| 784 | /// # Errors |
|---|
| 785 | /// |
|---|
| 786 | /// If this function encounters an error of the kind |
|---|
| 787 | /// [`ErrorKind::Interrupted`] then the error is ignored and the operation |
|---|
| 788 | /// will continue. |
|---|
| 789 | /// |
|---|
| 790 | /// If any other read error is encountered then this function immediately |
|---|
| 791 | /// returns. Any bytes which have already been read will be appended to |
|---|
| 792 | /// `buf`. |
|---|
| 793 | /// |
|---|
| 794 | /// # Examples |
|---|
| 795 | /// |
|---|
| 796 | /// [`File`]s implement `Read`: |
|---|
| 797 | /// |
|---|
| 798 | /// [`read()`]: Read::read |
|---|
| 799 | /// [`Ok(0)`]: Ok |
|---|
| 800 | /// [`File`]: crate::fs::File |
|---|
| 801 | /// |
|---|
| 802 | /// ```no_run |
|---|
| 803 | /// use std::io; |
|---|
| 804 | /// use std::io::prelude::*; |
|---|
| 805 | /// use std::fs::File; |
|---|
| 806 | /// |
|---|
| 807 | /// fn main() -> io::Result<()> { |
|---|
| 808 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 809 | /// let mut buffer = Vec::new(); |
|---|
| 810 | /// |
|---|
| 811 | /// // read the whole file |
|---|
| 812 | /// f.read_to_end(&mut buffer)?; |
|---|
| 813 | /// Ok(()) |
|---|
| 814 | /// } |
|---|
| 815 | /// ``` |
|---|
| 816 | /// |
|---|
| 817 | /// (See also the [`std::fs::read`] convenience function for reading from a |
|---|
| 818 | /// file.) |
|---|
| 819 | /// |
|---|
| 820 | /// [`std::fs::read`]: crate::fs::read |
|---|
| 821 | /// |
|---|
| 822 | /// ## Implementing `read_to_end` |
|---|
| 823 | /// |
|---|
| 824 | /// When implementing the `io::Read` trait, it is recommended to allocate |
|---|
| 825 | /// memory using [`Vec::try_reserve`]. However, this behavior is not guaranteed |
|---|
| 826 | /// by all implementations, and `read_to_end` may not handle out-of-memory |
|---|
| 827 | /// situations gracefully. |
|---|
| 828 | /// |
|---|
| 829 | /// ```no_run |
|---|
| 830 | /// # use std::io::{self, BufRead}; |
|---|
| 831 | /// # struct Example { example_datasource: io::Empty } impl Example { |
|---|
| 832 | /// # fn get_some_data_for_the_example(&self) -> &'static [u8] { &[] } |
|---|
| 833 | /// fn read_to_end(&mut self, dest_vec: &mut Vec<u8>) -> io::Result<usize> { |
|---|
| 834 | /// let initial_vec_len = dest_vec.len(); |
|---|
| 835 | /// loop { |
|---|
| 836 | /// let src_buf = self.example_datasource.fill_buf()?; |
|---|
| 837 | /// if src_buf.is_empty() { |
|---|
| 838 | /// break; |
|---|
| 839 | /// } |
|---|
| 840 | /// dest_vec.try_reserve(src_buf.len()).map_err(|_| io::ErrorKind::OutOfMemory)?; |
|---|
| 841 | /// dest_vec.extend_from_slice(src_buf); |
|---|
| 842 | /// |
|---|
| 843 | /// // Any irreversible side effects should happen after `try_reserve` succeeds, |
|---|
| 844 | /// // to avoid losing data on allocation error. |
|---|
| 845 | /// let read = src_buf.len(); |
|---|
| 846 | /// self.example_datasource.consume(read); |
|---|
| 847 | /// } |
|---|
| 848 | /// Ok(dest_vec.len() - initial_vec_len) |
|---|
| 849 | /// } |
|---|
| 850 | /// # } |
|---|
| 851 | /// ``` |
|---|
| 852 | /// |
|---|
| 853 | /// [`Vec::try_reserve`]: crate::vec::Vec::try_reserve |
|---|
| 854 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 855 | fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> { |
|---|
| 856 | default_read_to_end(self, buf, None) |
|---|
| 857 | } |
|---|
| 858 | |
|---|
| 859 | /// Read all bytes until EOF in this source, appending them to `buf`. |
|---|
| 860 | /// |
|---|
| 861 | /// If successful, this function returns the number of bytes which were read |
|---|
| 862 | /// and appended to `buf`. |
|---|
| 863 | /// |
|---|
| 864 | /// # Errors |
|---|
| 865 | /// |
|---|
| 866 | /// If the data in this stream is *not* valid UTF-8 then an error is |
|---|
| 867 | /// returned and `buf` is unchanged. |
|---|
| 868 | /// |
|---|
| 869 | /// See [`read_to_end`] for other error semantics. |
|---|
| 870 | /// |
|---|
| 871 | /// [`read_to_end`]: Read::read_to_end |
|---|
| 872 | /// |
|---|
| 873 | /// # Examples |
|---|
| 874 | /// |
|---|
| 875 | /// [`File`]s implement `Read`: |
|---|
| 876 | /// |
|---|
| 877 | /// [`File`]: crate::fs::File |
|---|
| 878 | /// |
|---|
| 879 | /// ```no_run |
|---|
| 880 | /// use std::io; |
|---|
| 881 | /// use std::io::prelude::*; |
|---|
| 882 | /// use std::fs::File; |
|---|
| 883 | /// |
|---|
| 884 | /// fn main() -> io::Result<()> { |
|---|
| 885 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 886 | /// let mut buffer = String::new(); |
|---|
| 887 | /// |
|---|
| 888 | /// f.read_to_string(&mut buffer)?; |
|---|
| 889 | /// Ok(()) |
|---|
| 890 | /// } |
|---|
| 891 | /// ``` |
|---|
| 892 | /// |
|---|
| 893 | /// (See also the [`std::fs::read_to_string`] convenience function for |
|---|
| 894 | /// reading from a file.) |
|---|
| 895 | /// |
|---|
| 896 | /// [`std::fs::read_to_string`]: crate::fs::read_to_string |
|---|
| 897 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 898 | fn read_to_string(&mut self, buf: &mut String) -> Result<usize> { |
|---|
| 899 | default_read_to_string(self, buf, None) |
|---|
| 900 | } |
|---|
| 901 | |
|---|
| 902 | /// Read the exact number of bytes required to fill `buf`. |
|---|
| 903 | /// |
|---|
| 904 | /// This function reads as many bytes as necessary to completely fill the |
|---|
| 905 | /// specified buffer `buf`. |
|---|
| 906 | /// |
|---|
| 907 | /// No guarantees are provided about the contents of `buf` when this |
|---|
| 908 | /// function is called, so implementations cannot rely on any property of the |
|---|
| 909 | /// contents of `buf` being true. It is recommended that implementations |
|---|
| 910 | /// only write data to `buf` instead of reading its contents. The |
|---|
| 911 | /// documentation on [`read`] has a more detailed explanation on this |
|---|
| 912 | /// subject. |
|---|
| 913 | /// |
|---|
| 914 | /// # Errors |
|---|
| 915 | /// |
|---|
| 916 | /// If this function encounters an error of the kind |
|---|
| 917 | /// [`ErrorKind::Interrupted`] then the error is ignored and the operation |
|---|
| 918 | /// will continue. |
|---|
| 919 | /// |
|---|
| 920 | /// If this function encounters an "end of file" before completely filling |
|---|
| 921 | /// the buffer, it returns an error of the kind [`ErrorKind::UnexpectedEof`]. |
|---|
| 922 | /// The contents of `buf` are unspecified in this case. |
|---|
| 923 | /// |
|---|
| 924 | /// If any other read error is encountered then this function immediately |
|---|
| 925 | /// returns. The contents of `buf` are unspecified in this case. |
|---|
| 926 | /// |
|---|
| 927 | /// If this function returns an error, it is unspecified how many bytes it |
|---|
| 928 | /// has read, but it will never read more than would be necessary to |
|---|
| 929 | /// completely fill the buffer. |
|---|
| 930 | /// |
|---|
| 931 | /// # Examples |
|---|
| 932 | /// |
|---|
| 933 | /// [`File`]s implement `Read`: |
|---|
| 934 | /// |
|---|
| 935 | /// [`read`]: Read::read |
|---|
| 936 | /// [`File`]: crate::fs::File |
|---|
| 937 | /// |
|---|
| 938 | /// ```no_run |
|---|
| 939 | /// use std::io; |
|---|
| 940 | /// use std::io::prelude::*; |
|---|
| 941 | /// use std::fs::File; |
|---|
| 942 | /// |
|---|
| 943 | /// fn main() -> io::Result<()> { |
|---|
| 944 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 945 | /// let mut buffer = [0; 10]; |
|---|
| 946 | /// |
|---|
| 947 | /// // read exactly 10 bytes |
|---|
| 948 | /// f.read_exact(&mut buffer)?; |
|---|
| 949 | /// Ok(()) |
|---|
| 950 | /// } |
|---|
| 951 | /// ``` |
|---|
| 952 | #[stable (feature = "read_exact" , since = "1.6.0" )] |
|---|
| 953 | fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> { |
|---|
| 954 | default_read_exact(self, buf) |
|---|
| 955 | } |
|---|
| 956 | |
|---|
| 957 | /// Pull some bytes from this source into the specified buffer. |
|---|
| 958 | /// |
|---|
| 959 | /// This is equivalent to the [`read`](Read::read) method, except that it is passed a [`BorrowedCursor`] rather than `[u8]` to allow use |
|---|
| 960 | /// with uninitialized buffers. The new data will be appended to any existing contents of `buf`. |
|---|
| 961 | /// |
|---|
| 962 | /// The default implementation delegates to `read`. |
|---|
| 963 | #[unstable (feature = "read_buf" , issue = "78485" )] |
|---|
| 964 | fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()> { |
|---|
| 965 | default_read_buf(|b| self.read(b), buf) |
|---|
| 966 | } |
|---|
| 967 | |
|---|
| 968 | /// Read the exact number of bytes required to fill `cursor`. |
|---|
| 969 | /// |
|---|
| 970 | /// This is similar to the [`read_exact`](Read::read_exact) method, except |
|---|
| 971 | /// that it is passed a [`BorrowedCursor`] rather than `[u8]` to allow use |
|---|
| 972 | /// with uninitialized buffers. |
|---|
| 973 | /// |
|---|
| 974 | /// # Errors |
|---|
| 975 | /// |
|---|
| 976 | /// If this function encounters an error of the kind [`ErrorKind::Interrupted`] |
|---|
| 977 | /// then the error is ignored and the operation will continue. |
|---|
| 978 | /// |
|---|
| 979 | /// If this function encounters an "end of file" before completely filling |
|---|
| 980 | /// the buffer, it returns an error of the kind [`ErrorKind::UnexpectedEof`]. |
|---|
| 981 | /// |
|---|
| 982 | /// If any other read error is encountered then this function immediately |
|---|
| 983 | /// returns. |
|---|
| 984 | /// |
|---|
| 985 | /// If this function returns an error, all bytes read will be appended to `cursor`. |
|---|
| 986 | #[unstable (feature = "read_buf" , issue = "78485" )] |
|---|
| 987 | fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> Result<()> { |
|---|
| 988 | while cursor.capacity() > 0 { |
|---|
| 989 | let prev_written = cursor.written(); |
|---|
| 990 | match self.read_buf(cursor.reborrow()) { |
|---|
| 991 | Ok(()) => {} |
|---|
| 992 | Err(e) if e.is_interrupted() => continue, |
|---|
| 993 | Err(e) => return Err(e), |
|---|
| 994 | } |
|---|
| 995 | |
|---|
| 996 | if cursor.written() == prev_written { |
|---|
| 997 | return Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill buffer" )); |
|---|
| 998 | } |
|---|
| 999 | } |
|---|
| 1000 | |
|---|
| 1001 | Ok(()) |
|---|
| 1002 | } |
|---|
| 1003 | |
|---|
| 1004 | /// Creates a "by reference" adaptor for this instance of `Read`. |
|---|
| 1005 | /// |
|---|
| 1006 | /// The returned adapter also implements `Read` and will simply borrow this |
|---|
| 1007 | /// current reader. |
|---|
| 1008 | /// |
|---|
| 1009 | /// # Examples |
|---|
| 1010 | /// |
|---|
| 1011 | /// [`File`]s implement `Read`: |
|---|
| 1012 | /// |
|---|
| 1013 | /// [`File`]: crate::fs::File |
|---|
| 1014 | /// |
|---|
| 1015 | /// ```no_run |
|---|
| 1016 | /// use std::io; |
|---|
| 1017 | /// use std::io::Read; |
|---|
| 1018 | /// use std::fs::File; |
|---|
| 1019 | /// |
|---|
| 1020 | /// fn main() -> io::Result<()> { |
|---|
| 1021 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 1022 | /// let mut buffer = Vec::new(); |
|---|
| 1023 | /// let mut other_buffer = Vec::new(); |
|---|
| 1024 | /// |
|---|
| 1025 | /// { |
|---|
| 1026 | /// let reference = f.by_ref(); |
|---|
| 1027 | /// |
|---|
| 1028 | /// // read at most 5 bytes |
|---|
| 1029 | /// reference.take(5).read_to_end(&mut buffer)?; |
|---|
| 1030 | /// |
|---|
| 1031 | /// } // drop our &mut reference so we can use f again |
|---|
| 1032 | /// |
|---|
| 1033 | /// // original file still usable, read the rest |
|---|
| 1034 | /// f.read_to_end(&mut other_buffer)?; |
|---|
| 1035 | /// Ok(()) |
|---|
| 1036 | /// } |
|---|
| 1037 | /// ``` |
|---|
| 1038 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1039 | fn by_ref(&mut self) -> &mut Self |
|---|
| 1040 | where |
|---|
| 1041 | Self: Sized, |
|---|
| 1042 | { |
|---|
| 1043 | self |
|---|
| 1044 | } |
|---|
| 1045 | |
|---|
| 1046 | /// Transforms this `Read` instance to an [`Iterator`] over its bytes. |
|---|
| 1047 | /// |
|---|
| 1048 | /// The returned type implements [`Iterator`] where the [`Item`] is |
|---|
| 1049 | /// <code>[Result]<[u8], [io::Error]></code>. |
|---|
| 1050 | /// The yielded item is [`Ok`] if a byte was successfully read and [`Err`] |
|---|
| 1051 | /// otherwise. EOF is mapped to returning [`None`] from this iterator. |
|---|
| 1052 | /// |
|---|
| 1053 | /// The default implementation calls `read` for each byte, |
|---|
| 1054 | /// which can be very inefficient for data that's not in memory, |
|---|
| 1055 | /// such as [`File`]. Consider using a [`BufReader`] in such cases. |
|---|
| 1056 | /// |
|---|
| 1057 | /// # Examples |
|---|
| 1058 | /// |
|---|
| 1059 | /// [`File`]s implement `Read`: |
|---|
| 1060 | /// |
|---|
| 1061 | /// [`Item`]: Iterator::Item |
|---|
| 1062 | /// [`File`]: crate::fs::File "fs::File" |
|---|
| 1063 | /// [Result]: crate::result::Result "Result" |
|---|
| 1064 | /// [io::Error]: self::Error "io::Error" |
|---|
| 1065 | /// |
|---|
| 1066 | /// ```no_run |
|---|
| 1067 | /// use std::io; |
|---|
| 1068 | /// use std::io::prelude::*; |
|---|
| 1069 | /// use std::io::BufReader; |
|---|
| 1070 | /// use std::fs::File; |
|---|
| 1071 | /// |
|---|
| 1072 | /// fn main() -> io::Result<()> { |
|---|
| 1073 | /// let f = BufReader::new(File::open("foo.txt" )?); |
|---|
| 1074 | /// |
|---|
| 1075 | /// for byte in f.bytes() { |
|---|
| 1076 | /// println!("{}" , byte.unwrap()); |
|---|
| 1077 | /// } |
|---|
| 1078 | /// Ok(()) |
|---|
| 1079 | /// } |
|---|
| 1080 | /// ``` |
|---|
| 1081 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1082 | fn bytes(self) -> Bytes<Self> |
|---|
| 1083 | where |
|---|
| 1084 | Self: Sized, |
|---|
| 1085 | { |
|---|
| 1086 | Bytes { inner: self } |
|---|
| 1087 | } |
|---|
| 1088 | |
|---|
| 1089 | /// Creates an adapter which will chain this stream with another. |
|---|
| 1090 | /// |
|---|
| 1091 | /// The returned `Read` instance will first read all bytes from this object |
|---|
| 1092 | /// until EOF is encountered. Afterwards the output is equivalent to the |
|---|
| 1093 | /// output of `next`. |
|---|
| 1094 | /// |
|---|
| 1095 | /// # Examples |
|---|
| 1096 | /// |
|---|
| 1097 | /// [`File`]s implement `Read`: |
|---|
| 1098 | /// |
|---|
| 1099 | /// [`File`]: crate::fs::File |
|---|
| 1100 | /// |
|---|
| 1101 | /// ```no_run |
|---|
| 1102 | /// use std::io; |
|---|
| 1103 | /// use std::io::prelude::*; |
|---|
| 1104 | /// use std::fs::File; |
|---|
| 1105 | /// |
|---|
| 1106 | /// fn main() -> io::Result<()> { |
|---|
| 1107 | /// let f1 = File::open("foo.txt" )?; |
|---|
| 1108 | /// let f2 = File::open("bar.txt" )?; |
|---|
| 1109 | /// |
|---|
| 1110 | /// let mut handle = f1.chain(f2); |
|---|
| 1111 | /// let mut buffer = String::new(); |
|---|
| 1112 | /// |
|---|
| 1113 | /// // read the value into a String. We could use any Read method here, |
|---|
| 1114 | /// // this is just one example. |
|---|
| 1115 | /// handle.read_to_string(&mut buffer)?; |
|---|
| 1116 | /// Ok(()) |
|---|
| 1117 | /// } |
|---|
| 1118 | /// ``` |
|---|
| 1119 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1120 | fn chain<R: Read>(self, next: R) -> Chain<Self, R> |
|---|
| 1121 | where |
|---|
| 1122 | Self: Sized, |
|---|
| 1123 | { |
|---|
| 1124 | Chain { first: self, second: next, done_first: false } |
|---|
| 1125 | } |
|---|
| 1126 | |
|---|
| 1127 | /// Creates an adapter which will read at most `limit` bytes from it. |
|---|
| 1128 | /// |
|---|
| 1129 | /// This function returns a new instance of `Read` which will read at most |
|---|
| 1130 | /// `limit` bytes, after which it will always return EOF ([`Ok(0)`]). Any |
|---|
| 1131 | /// read errors will not count towards the number of bytes read and future |
|---|
| 1132 | /// calls to [`read()`] may succeed. |
|---|
| 1133 | /// |
|---|
| 1134 | /// # Examples |
|---|
| 1135 | /// |
|---|
| 1136 | /// [`File`]s implement `Read`: |
|---|
| 1137 | /// |
|---|
| 1138 | /// [`File`]: crate::fs::File |
|---|
| 1139 | /// [`Ok(0)`]: Ok |
|---|
| 1140 | /// [`read()`]: Read::read |
|---|
| 1141 | /// |
|---|
| 1142 | /// ```no_run |
|---|
| 1143 | /// use std::io; |
|---|
| 1144 | /// use std::io::prelude::*; |
|---|
| 1145 | /// use std::fs::File; |
|---|
| 1146 | /// |
|---|
| 1147 | /// fn main() -> io::Result<()> { |
|---|
| 1148 | /// let f = File::open("foo.txt" )?; |
|---|
| 1149 | /// let mut buffer = [0; 5]; |
|---|
| 1150 | /// |
|---|
| 1151 | /// // read at most five bytes |
|---|
| 1152 | /// let mut handle = f.take(5); |
|---|
| 1153 | /// |
|---|
| 1154 | /// handle.read(&mut buffer)?; |
|---|
| 1155 | /// Ok(()) |
|---|
| 1156 | /// } |
|---|
| 1157 | /// ``` |
|---|
| 1158 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1159 | fn take(self, limit: u64) -> Take<Self> |
|---|
| 1160 | where |
|---|
| 1161 | Self: Sized, |
|---|
| 1162 | { |
|---|
| 1163 | Take { inner: self, limit } |
|---|
| 1164 | } |
|---|
| 1165 | } |
|---|
| 1166 | |
|---|
| 1167 | /// Read all bytes from a [reader][Read] into a new [`String`]. |
|---|
| 1168 | /// |
|---|
| 1169 | /// This is a convenience function for [`Read::read_to_string`]. Using this |
|---|
| 1170 | /// function avoids having to create a variable first and provides more type |
|---|
| 1171 | /// safety since you can only get the buffer out if there were no errors. (If you |
|---|
| 1172 | /// use [`Read::read_to_string`] you have to remember to check whether the read |
|---|
| 1173 | /// succeeded because otherwise your buffer will be empty or only partially full.) |
|---|
| 1174 | /// |
|---|
| 1175 | /// # Performance |
|---|
| 1176 | /// |
|---|
| 1177 | /// The downside of this function's increased ease of use and type safety is |
|---|
| 1178 | /// that it gives you less control over performance. For example, you can't |
|---|
| 1179 | /// pre-allocate memory like you can using [`String::with_capacity`] and |
|---|
| 1180 | /// [`Read::read_to_string`]. Also, you can't re-use the buffer if an error |
|---|
| 1181 | /// occurs while reading. |
|---|
| 1182 | /// |
|---|
| 1183 | /// In many cases, this function's performance will be adequate and the ease of use |
|---|
| 1184 | /// and type safety tradeoffs will be worth it. However, there are cases where you |
|---|
| 1185 | /// need more control over performance, and in those cases you should definitely use |
|---|
| 1186 | /// [`Read::read_to_string`] directly. |
|---|
| 1187 | /// |
|---|
| 1188 | /// Note that in some special cases, such as when reading files, this function will |
|---|
| 1189 | /// pre-allocate memory based on the size of the input it is reading. In those |
|---|
| 1190 | /// cases, the performance should be as good as if you had used |
|---|
| 1191 | /// [`Read::read_to_string`] with a manually pre-allocated buffer. |
|---|
| 1192 | /// |
|---|
| 1193 | /// # Errors |
|---|
| 1194 | /// |
|---|
| 1195 | /// This function forces you to handle errors because the output (the `String`) |
|---|
| 1196 | /// is wrapped in a [`Result`]. See [`Read::read_to_string`] for the errors |
|---|
| 1197 | /// that can occur. If any error occurs, you will get an [`Err`], so you |
|---|
| 1198 | /// don't have to worry about your buffer being empty or partially full. |
|---|
| 1199 | /// |
|---|
| 1200 | /// # Examples |
|---|
| 1201 | /// |
|---|
| 1202 | /// ```no_run |
|---|
| 1203 | /// # use std::io; |
|---|
| 1204 | /// fn main() -> io::Result<()> { |
|---|
| 1205 | /// let stdin = io::read_to_string(io::stdin())?; |
|---|
| 1206 | /// println!("Stdin was:" ); |
|---|
| 1207 | /// println!("{stdin}" ); |
|---|
| 1208 | /// Ok(()) |
|---|
| 1209 | /// } |
|---|
| 1210 | /// ``` |
|---|
| 1211 | #[stable (feature = "io_read_to_string" , since = "1.65.0" )] |
|---|
| 1212 | pub fn read_to_string<R: Read>(mut reader: R) -> Result<String> { |
|---|
| 1213 | let mut buf: String = String::new(); |
|---|
| 1214 | reader.read_to_string(&mut buf)?; |
|---|
| 1215 | Ok(buf) |
|---|
| 1216 | } |
|---|
| 1217 | |
|---|
| 1218 | /// A buffer type used with `Read::read_vectored`. |
|---|
| 1219 | /// |
|---|
| 1220 | /// It is semantically a wrapper around an `&mut [u8]`, but is guaranteed to be |
|---|
| 1221 | /// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on |
|---|
| 1222 | /// Windows. |
|---|
| 1223 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1224 | #[repr (transparent)] |
|---|
| 1225 | pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>); |
|---|
| 1226 | |
|---|
| 1227 | #[stable (feature = "iovec_send_sync" , since = "1.44.0" )] |
|---|
| 1228 | unsafe impl<'a> Send for IoSliceMut<'a> {} |
|---|
| 1229 | |
|---|
| 1230 | #[stable (feature = "iovec_send_sync" , since = "1.44.0" )] |
|---|
| 1231 | unsafe impl<'a> Sync for IoSliceMut<'a> {} |
|---|
| 1232 | |
|---|
| 1233 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1234 | impl<'a> fmt::Debug for IoSliceMut<'a> { |
|---|
| 1235 | fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { |
|---|
| 1236 | fmt::Debug::fmt(self.0.as_slice(), f:fmt) |
|---|
| 1237 | } |
|---|
| 1238 | } |
|---|
| 1239 | |
|---|
| 1240 | impl<'a> IoSliceMut<'a> { |
|---|
| 1241 | /// Creates a new `IoSliceMut` wrapping a byte slice. |
|---|
| 1242 | /// |
|---|
| 1243 | /// # Panics |
|---|
| 1244 | /// |
|---|
| 1245 | /// Panics on Windows if the slice is larger than 4GB. |
|---|
| 1246 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1247 | #[inline ] |
|---|
| 1248 | pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> { |
|---|
| 1249 | IoSliceMut(sys::io::IoSliceMut::new(buf)) |
|---|
| 1250 | } |
|---|
| 1251 | |
|---|
| 1252 | /// Advance the internal cursor of the slice. |
|---|
| 1253 | /// |
|---|
| 1254 | /// Also see [`IoSliceMut::advance_slices`] to advance the cursors of |
|---|
| 1255 | /// multiple buffers. |
|---|
| 1256 | /// |
|---|
| 1257 | /// # Panics |
|---|
| 1258 | /// |
|---|
| 1259 | /// Panics when trying to advance beyond the end of the slice. |
|---|
| 1260 | /// |
|---|
| 1261 | /// # Examples |
|---|
| 1262 | /// |
|---|
| 1263 | /// ``` |
|---|
| 1264 | /// #![feature(io_slice_advance)] |
|---|
| 1265 | /// |
|---|
| 1266 | /// use std::io::IoSliceMut; |
|---|
| 1267 | /// use std::ops::Deref; |
|---|
| 1268 | /// |
|---|
| 1269 | /// let mut data = [1; 8]; |
|---|
| 1270 | /// let mut buf = IoSliceMut::new(&mut data); |
|---|
| 1271 | /// |
|---|
| 1272 | /// // Mark 3 bytes as read. |
|---|
| 1273 | /// buf.advance(3); |
|---|
| 1274 | /// assert_eq!(buf.deref(), [1; 5].as_ref()); |
|---|
| 1275 | /// ``` |
|---|
| 1276 | #[unstable (feature = "io_slice_advance" , issue = "62726" )] |
|---|
| 1277 | #[inline ] |
|---|
| 1278 | pub fn advance(&mut self, n: usize) { |
|---|
| 1279 | self.0.advance(n) |
|---|
| 1280 | } |
|---|
| 1281 | |
|---|
| 1282 | /// Advance a slice of slices. |
|---|
| 1283 | /// |
|---|
| 1284 | /// Shrinks the slice to remove any `IoSliceMut`s that are fully advanced over. |
|---|
| 1285 | /// If the cursor ends up in the middle of an `IoSliceMut`, it is modified |
|---|
| 1286 | /// to start at that cursor. |
|---|
| 1287 | /// |
|---|
| 1288 | /// For example, if we have a slice of two 8-byte `IoSliceMut`s, and we advance by 10 bytes, |
|---|
| 1289 | /// the result will only include the second `IoSliceMut`, advanced by 2 bytes. |
|---|
| 1290 | /// |
|---|
| 1291 | /// # Panics |
|---|
| 1292 | /// |
|---|
| 1293 | /// Panics when trying to advance beyond the end of the slices. |
|---|
| 1294 | /// |
|---|
| 1295 | /// # Examples |
|---|
| 1296 | /// |
|---|
| 1297 | /// ``` |
|---|
| 1298 | /// #![feature(io_slice_advance)] |
|---|
| 1299 | /// |
|---|
| 1300 | /// use std::io::IoSliceMut; |
|---|
| 1301 | /// use std::ops::Deref; |
|---|
| 1302 | /// |
|---|
| 1303 | /// let mut buf1 = [1; 8]; |
|---|
| 1304 | /// let mut buf2 = [2; 16]; |
|---|
| 1305 | /// let mut buf3 = [3; 8]; |
|---|
| 1306 | /// let mut bufs = &mut [ |
|---|
| 1307 | /// IoSliceMut::new(&mut buf1), |
|---|
| 1308 | /// IoSliceMut::new(&mut buf2), |
|---|
| 1309 | /// IoSliceMut::new(&mut buf3), |
|---|
| 1310 | /// ][..]; |
|---|
| 1311 | /// |
|---|
| 1312 | /// // Mark 10 bytes as read. |
|---|
| 1313 | /// IoSliceMut::advance_slices(&mut bufs, 10); |
|---|
| 1314 | /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); |
|---|
| 1315 | /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); |
|---|
| 1316 | /// ``` |
|---|
| 1317 | #[unstable (feature = "io_slice_advance" , issue = "62726" )] |
|---|
| 1318 | #[inline ] |
|---|
| 1319 | pub fn advance_slices(bufs: &mut &mut [IoSliceMut<'a>], n: usize) { |
|---|
| 1320 | // Number of buffers to remove. |
|---|
| 1321 | let mut remove = 0; |
|---|
| 1322 | // Remaining length before reaching n. |
|---|
| 1323 | let mut left = n; |
|---|
| 1324 | for buf in bufs.iter() { |
|---|
| 1325 | if let Some(remainder) = left.checked_sub(buf.len()) { |
|---|
| 1326 | left = remainder; |
|---|
| 1327 | remove += 1; |
|---|
| 1328 | } else { |
|---|
| 1329 | break; |
|---|
| 1330 | } |
|---|
| 1331 | } |
|---|
| 1332 | |
|---|
| 1333 | *bufs = &mut take(bufs)[remove..]; |
|---|
| 1334 | if bufs.is_empty() { |
|---|
| 1335 | assert!(left == 0, "advancing io slices beyond their length" ); |
|---|
| 1336 | } else { |
|---|
| 1337 | bufs[0].advance(left); |
|---|
| 1338 | } |
|---|
| 1339 | } |
|---|
| 1340 | } |
|---|
| 1341 | |
|---|
| 1342 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1343 | impl<'a> Deref for IoSliceMut<'a> { |
|---|
| 1344 | type Target = [u8]; |
|---|
| 1345 | |
|---|
| 1346 | #[inline ] |
|---|
| 1347 | fn deref(&self) -> &[u8] { |
|---|
| 1348 | self.0.as_slice() |
|---|
| 1349 | } |
|---|
| 1350 | } |
|---|
| 1351 | |
|---|
| 1352 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1353 | impl<'a> DerefMut for IoSliceMut<'a> { |
|---|
| 1354 | #[inline ] |
|---|
| 1355 | fn deref_mut(&mut self) -> &mut [u8] { |
|---|
| 1356 | self.0.as_mut_slice() |
|---|
| 1357 | } |
|---|
| 1358 | } |
|---|
| 1359 | |
|---|
| 1360 | /// A buffer type used with `Write::write_vectored`. |
|---|
| 1361 | /// |
|---|
| 1362 | /// It is semantically a wrapper around a `&[u8]`, but is guaranteed to be |
|---|
| 1363 | /// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on |
|---|
| 1364 | /// Windows. |
|---|
| 1365 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1366 | #[derive (Copy, Clone)] |
|---|
| 1367 | #[repr (transparent)] |
|---|
| 1368 | pub struct IoSlice<'a>(sys::io::IoSlice<'a>); |
|---|
| 1369 | |
|---|
| 1370 | #[stable (feature = "iovec_send_sync" , since = "1.44.0" )] |
|---|
| 1371 | unsafe impl<'a> Send for IoSlice<'a> {} |
|---|
| 1372 | |
|---|
| 1373 | #[stable (feature = "iovec_send_sync" , since = "1.44.0" )] |
|---|
| 1374 | unsafe impl<'a> Sync for IoSlice<'a> {} |
|---|
| 1375 | |
|---|
| 1376 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1377 | impl<'a> fmt::Debug for IoSlice<'a> { |
|---|
| 1378 | fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { |
|---|
| 1379 | fmt::Debug::fmt(self.0.as_slice(), f:fmt) |
|---|
| 1380 | } |
|---|
| 1381 | } |
|---|
| 1382 | |
|---|
| 1383 | impl<'a> IoSlice<'a> { |
|---|
| 1384 | /// Creates a new `IoSlice` wrapping a byte slice. |
|---|
| 1385 | /// |
|---|
| 1386 | /// # Panics |
|---|
| 1387 | /// |
|---|
| 1388 | /// Panics on Windows if the slice is larger than 4GB. |
|---|
| 1389 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1390 | #[must_use ] |
|---|
| 1391 | #[inline ] |
|---|
| 1392 | pub fn new(buf: &'a [u8]) -> IoSlice<'a> { |
|---|
| 1393 | IoSlice(sys::io::IoSlice::new(buf)) |
|---|
| 1394 | } |
|---|
| 1395 | |
|---|
| 1396 | /// Advance the internal cursor of the slice. |
|---|
| 1397 | /// |
|---|
| 1398 | /// Also see [`IoSlice::advance_slices`] to advance the cursors of multiple |
|---|
| 1399 | /// buffers. |
|---|
| 1400 | /// |
|---|
| 1401 | /// # Panics |
|---|
| 1402 | /// |
|---|
| 1403 | /// Panics when trying to advance beyond the end of the slice. |
|---|
| 1404 | /// |
|---|
| 1405 | /// # Examples |
|---|
| 1406 | /// |
|---|
| 1407 | /// ``` |
|---|
| 1408 | /// #![feature(io_slice_advance)] |
|---|
| 1409 | /// |
|---|
| 1410 | /// use std::io::IoSlice; |
|---|
| 1411 | /// use std::ops::Deref; |
|---|
| 1412 | /// |
|---|
| 1413 | /// let data = [1; 8]; |
|---|
| 1414 | /// let mut buf = IoSlice::new(&data); |
|---|
| 1415 | /// |
|---|
| 1416 | /// // Mark 3 bytes as read. |
|---|
| 1417 | /// buf.advance(3); |
|---|
| 1418 | /// assert_eq!(buf.deref(), [1; 5].as_ref()); |
|---|
| 1419 | /// ``` |
|---|
| 1420 | #[unstable (feature = "io_slice_advance" , issue = "62726" )] |
|---|
| 1421 | #[inline ] |
|---|
| 1422 | pub fn advance(&mut self, n: usize) { |
|---|
| 1423 | self.0.advance(n) |
|---|
| 1424 | } |
|---|
| 1425 | |
|---|
| 1426 | /// Advance a slice of slices. |
|---|
| 1427 | /// |
|---|
| 1428 | /// Shrinks the slice to remove any `IoSlice`s that are fully advanced over. |
|---|
| 1429 | /// If the cursor ends up in the middle of an `IoSlice`, it is modified |
|---|
| 1430 | /// to start at that cursor. |
|---|
| 1431 | /// |
|---|
| 1432 | /// For example, if we have a slice of two 8-byte `IoSlice`s, and we advance by 10 bytes, |
|---|
| 1433 | /// the result will only include the second `IoSlice`, advanced by 2 bytes. |
|---|
| 1434 | /// |
|---|
| 1435 | /// # Panics |
|---|
| 1436 | /// |
|---|
| 1437 | /// Panics when trying to advance beyond the end of the slices. |
|---|
| 1438 | /// |
|---|
| 1439 | /// # Examples |
|---|
| 1440 | /// |
|---|
| 1441 | /// ``` |
|---|
| 1442 | /// #![feature(io_slice_advance)] |
|---|
| 1443 | /// |
|---|
| 1444 | /// use std::io::IoSlice; |
|---|
| 1445 | /// use std::ops::Deref; |
|---|
| 1446 | /// |
|---|
| 1447 | /// let buf1 = [1; 8]; |
|---|
| 1448 | /// let buf2 = [2; 16]; |
|---|
| 1449 | /// let buf3 = [3; 8]; |
|---|
| 1450 | /// let mut bufs = &mut [ |
|---|
| 1451 | /// IoSlice::new(&buf1), |
|---|
| 1452 | /// IoSlice::new(&buf2), |
|---|
| 1453 | /// IoSlice::new(&buf3), |
|---|
| 1454 | /// ][..]; |
|---|
| 1455 | /// |
|---|
| 1456 | /// // Mark 10 bytes as written. |
|---|
| 1457 | /// IoSlice::advance_slices(&mut bufs, 10); |
|---|
| 1458 | /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); |
|---|
| 1459 | /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); |
|---|
| 1460 | #[unstable (feature = "io_slice_advance" , issue = "62726" )] |
|---|
| 1461 | #[inline ] |
|---|
| 1462 | pub fn advance_slices(bufs: &mut &mut [IoSlice<'a>], n: usize) { |
|---|
| 1463 | // Number of buffers to remove. |
|---|
| 1464 | let mut remove = 0; |
|---|
| 1465 | // Remaining length before reaching n. This prevents overflow |
|---|
| 1466 | // that could happen if the length of slices in `bufs` were instead |
|---|
| 1467 | // accumulated. Those slice may be aliased and, if they are large |
|---|
| 1468 | // enough, their added length may overflow a `usize`. |
|---|
| 1469 | let mut left = n; |
|---|
| 1470 | for buf in bufs.iter() { |
|---|
| 1471 | if let Some(remainder) = left.checked_sub(buf.len()) { |
|---|
| 1472 | left = remainder; |
|---|
| 1473 | remove += 1; |
|---|
| 1474 | } else { |
|---|
| 1475 | break; |
|---|
| 1476 | } |
|---|
| 1477 | } |
|---|
| 1478 | |
|---|
| 1479 | *bufs = &mut take(bufs)[remove..]; |
|---|
| 1480 | if bufs.is_empty() { |
|---|
| 1481 | assert!(left == 0, "advancing io slices beyond their length" ); |
|---|
| 1482 | } else { |
|---|
| 1483 | bufs[0].advance(left); |
|---|
| 1484 | } |
|---|
| 1485 | } |
|---|
| 1486 | } |
|---|
| 1487 | |
|---|
| 1488 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1489 | impl<'a> Deref for IoSlice<'a> { |
|---|
| 1490 | type Target = [u8]; |
|---|
| 1491 | |
|---|
| 1492 | #[inline ] |
|---|
| 1493 | fn deref(&self) -> &[u8] { |
|---|
| 1494 | self.0.as_slice() |
|---|
| 1495 | } |
|---|
| 1496 | } |
|---|
| 1497 | |
|---|
| 1498 | /// A trait for objects which are byte-oriented sinks. |
|---|
| 1499 | /// |
|---|
| 1500 | /// Implementors of the `Write` trait are sometimes called 'writers'. |
|---|
| 1501 | /// |
|---|
| 1502 | /// Writers are defined by two required methods, [`write`] and [`flush`]: |
|---|
| 1503 | /// |
|---|
| 1504 | /// * The [`write`] method will attempt to write some data into the object, |
|---|
| 1505 | /// returning how many bytes were successfully written. |
|---|
| 1506 | /// |
|---|
| 1507 | /// * The [`flush`] method is useful for adapters and explicit buffers |
|---|
| 1508 | /// themselves for ensuring that all buffered data has been pushed out to the |
|---|
| 1509 | /// 'true sink'. |
|---|
| 1510 | /// |
|---|
| 1511 | /// Writers are intended to be composable with one another. Many implementors |
|---|
| 1512 | /// throughout [`std::io`] take and provide types which implement the `Write` |
|---|
| 1513 | /// trait. |
|---|
| 1514 | /// |
|---|
| 1515 | /// [`write`]: Write::write |
|---|
| 1516 | /// [`flush`]: Write::flush |
|---|
| 1517 | /// [`std::io`]: self |
|---|
| 1518 | /// |
|---|
| 1519 | /// # Examples |
|---|
| 1520 | /// |
|---|
| 1521 | /// ```no_run |
|---|
| 1522 | /// use std::io::prelude::*; |
|---|
| 1523 | /// use std::fs::File; |
|---|
| 1524 | /// |
|---|
| 1525 | /// fn main() -> std::io::Result<()> { |
|---|
| 1526 | /// let data = b"some bytes" ; |
|---|
| 1527 | /// |
|---|
| 1528 | /// let mut pos = 0; |
|---|
| 1529 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1530 | /// |
|---|
| 1531 | /// while pos < data.len() { |
|---|
| 1532 | /// let bytes_written = buffer.write(&data[pos..])?; |
|---|
| 1533 | /// pos += bytes_written; |
|---|
| 1534 | /// } |
|---|
| 1535 | /// Ok(()) |
|---|
| 1536 | /// } |
|---|
| 1537 | /// ``` |
|---|
| 1538 | /// |
|---|
| 1539 | /// The trait also provides convenience methods like [`write_all`], which calls |
|---|
| 1540 | /// `write` in a loop until its entire input has been written. |
|---|
| 1541 | /// |
|---|
| 1542 | /// [`write_all`]: Write::write_all |
|---|
| 1543 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1544 | #[doc (notable_trait)] |
|---|
| 1545 | #[cfg_attr (not(test), rustc_diagnostic_item = "IoWrite" )] |
|---|
| 1546 | pub trait Write { |
|---|
| 1547 | /// Write a buffer into this writer, returning how many bytes were written. |
|---|
| 1548 | /// |
|---|
| 1549 | /// This function will attempt to write the entire contents of `buf`, but |
|---|
| 1550 | /// the entire write might not succeed, or the write may also generate an |
|---|
| 1551 | /// error. Typically, a call to `write` represents one attempt to write to |
|---|
| 1552 | /// any wrapped object. |
|---|
| 1553 | /// |
|---|
| 1554 | /// Calls to `write` are not guaranteed to block waiting for data to be |
|---|
| 1555 | /// written, and a write which would otherwise block can be indicated through |
|---|
| 1556 | /// an [`Err`] variant. |
|---|
| 1557 | /// |
|---|
| 1558 | /// If this method consumed `n > 0` bytes of `buf` it must return [`Ok(n)`]. |
|---|
| 1559 | /// If the return value is `Ok(n)` then `n` must satisfy `n <= buf.len()`. |
|---|
| 1560 | /// A return value of `Ok(0)` typically means that the underlying object is |
|---|
| 1561 | /// no longer able to accept bytes and will likely not be able to in the |
|---|
| 1562 | /// future as well, or that the buffer provided is empty. |
|---|
| 1563 | /// |
|---|
| 1564 | /// # Errors |
|---|
| 1565 | /// |
|---|
| 1566 | /// Each call to `write` may generate an I/O error indicating that the |
|---|
| 1567 | /// operation could not be completed. If an error is returned then no bytes |
|---|
| 1568 | /// in the buffer were written to this writer. |
|---|
| 1569 | /// |
|---|
| 1570 | /// It is **not** considered an error if the entire buffer could not be |
|---|
| 1571 | /// written to this writer. |
|---|
| 1572 | /// |
|---|
| 1573 | /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the |
|---|
| 1574 | /// write operation should be retried if there is nothing else to do. |
|---|
| 1575 | /// |
|---|
| 1576 | /// # Examples |
|---|
| 1577 | /// |
|---|
| 1578 | /// ```no_run |
|---|
| 1579 | /// use std::io::prelude::*; |
|---|
| 1580 | /// use std::fs::File; |
|---|
| 1581 | /// |
|---|
| 1582 | /// fn main() -> std::io::Result<()> { |
|---|
| 1583 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1584 | /// |
|---|
| 1585 | /// // Writes some prefix of the byte string, not necessarily all of it. |
|---|
| 1586 | /// buffer.write(b"some bytes" )?; |
|---|
| 1587 | /// Ok(()) |
|---|
| 1588 | /// } |
|---|
| 1589 | /// ``` |
|---|
| 1590 | /// |
|---|
| 1591 | /// [`Ok(n)`]: Ok |
|---|
| 1592 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1593 | fn write(&mut self, buf: &[u8]) -> Result<usize>; |
|---|
| 1594 | |
|---|
| 1595 | /// Like [`write`], except that it writes from a slice of buffers. |
|---|
| 1596 | /// |
|---|
| 1597 | /// Data is copied from each buffer in order, with the final buffer |
|---|
| 1598 | /// read from possibly being only partially consumed. This method must |
|---|
| 1599 | /// behave as a call to [`write`] with the buffers concatenated would. |
|---|
| 1600 | /// |
|---|
| 1601 | /// The default implementation calls [`write`] with either the first nonempty |
|---|
| 1602 | /// buffer provided, or an empty one if none exists. |
|---|
| 1603 | /// |
|---|
| 1604 | /// # Examples |
|---|
| 1605 | /// |
|---|
| 1606 | /// ```no_run |
|---|
| 1607 | /// use std::io::IoSlice; |
|---|
| 1608 | /// use std::io::prelude::*; |
|---|
| 1609 | /// use std::fs::File; |
|---|
| 1610 | /// |
|---|
| 1611 | /// fn main() -> std::io::Result<()> { |
|---|
| 1612 | /// let data1 = [1; 8]; |
|---|
| 1613 | /// let data2 = [15; 8]; |
|---|
| 1614 | /// let io_slice1 = IoSlice::new(&data1); |
|---|
| 1615 | /// let io_slice2 = IoSlice::new(&data2); |
|---|
| 1616 | /// |
|---|
| 1617 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1618 | /// |
|---|
| 1619 | /// // Writes some prefix of the byte string, not necessarily all of it. |
|---|
| 1620 | /// buffer.write_vectored(&[io_slice1, io_slice2])?; |
|---|
| 1621 | /// Ok(()) |
|---|
| 1622 | /// } |
|---|
| 1623 | /// ``` |
|---|
| 1624 | /// |
|---|
| 1625 | /// [`write`]: Write::write |
|---|
| 1626 | #[stable (feature = "iovec" , since = "1.36.0" )] |
|---|
| 1627 | fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> { |
|---|
| 1628 | default_write_vectored(|b| self.write(b), bufs) |
|---|
| 1629 | } |
|---|
| 1630 | |
|---|
| 1631 | /// Determines if this `Write`r has an efficient [`write_vectored`] |
|---|
| 1632 | /// implementation. |
|---|
| 1633 | /// |
|---|
| 1634 | /// If a `Write`r does not override the default [`write_vectored`] |
|---|
| 1635 | /// implementation, code using it may want to avoid the method all together |
|---|
| 1636 | /// and coalesce writes into a single buffer for higher performance. |
|---|
| 1637 | /// |
|---|
| 1638 | /// The default implementation returns `false`. |
|---|
| 1639 | /// |
|---|
| 1640 | /// [`write_vectored`]: Write::write_vectored |
|---|
| 1641 | #[unstable (feature = "can_vector" , issue = "69941" )] |
|---|
| 1642 | fn is_write_vectored(&self) -> bool { |
|---|
| 1643 | false |
|---|
| 1644 | } |
|---|
| 1645 | |
|---|
| 1646 | /// Flush this output stream, ensuring that all intermediately buffered |
|---|
| 1647 | /// contents reach their destination. |
|---|
| 1648 | /// |
|---|
| 1649 | /// # Errors |
|---|
| 1650 | /// |
|---|
| 1651 | /// It is considered an error if not all bytes could be written due to |
|---|
| 1652 | /// I/O errors or EOF being reached. |
|---|
| 1653 | /// |
|---|
| 1654 | /// # Examples |
|---|
| 1655 | /// |
|---|
| 1656 | /// ```no_run |
|---|
| 1657 | /// use std::io::prelude::*; |
|---|
| 1658 | /// use std::io::BufWriter; |
|---|
| 1659 | /// use std::fs::File; |
|---|
| 1660 | /// |
|---|
| 1661 | /// fn main() -> std::io::Result<()> { |
|---|
| 1662 | /// let mut buffer = BufWriter::new(File::create("foo.txt" )?); |
|---|
| 1663 | /// |
|---|
| 1664 | /// buffer.write_all(b"some bytes" )?; |
|---|
| 1665 | /// buffer.flush()?; |
|---|
| 1666 | /// Ok(()) |
|---|
| 1667 | /// } |
|---|
| 1668 | /// ``` |
|---|
| 1669 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1670 | fn flush(&mut self) -> Result<()>; |
|---|
| 1671 | |
|---|
| 1672 | /// Attempts to write an entire buffer into this writer. |
|---|
| 1673 | /// |
|---|
| 1674 | /// This method will continuously call [`write`] until there is no more data |
|---|
| 1675 | /// to be written or an error of non-[`ErrorKind::Interrupted`] kind is |
|---|
| 1676 | /// returned. This method will not return until the entire buffer has been |
|---|
| 1677 | /// successfully written or such an error occurs. The first error that is |
|---|
| 1678 | /// not of [`ErrorKind::Interrupted`] kind generated from this method will be |
|---|
| 1679 | /// returned. |
|---|
| 1680 | /// |
|---|
| 1681 | /// If the buffer contains no data, this will never call [`write`]. |
|---|
| 1682 | /// |
|---|
| 1683 | /// # Errors |
|---|
| 1684 | /// |
|---|
| 1685 | /// This function will return the first error of |
|---|
| 1686 | /// non-[`ErrorKind::Interrupted`] kind that [`write`] returns. |
|---|
| 1687 | /// |
|---|
| 1688 | /// [`write`]: Write::write |
|---|
| 1689 | /// |
|---|
| 1690 | /// # Examples |
|---|
| 1691 | /// |
|---|
| 1692 | /// ```no_run |
|---|
| 1693 | /// use std::io::prelude::*; |
|---|
| 1694 | /// use std::fs::File; |
|---|
| 1695 | /// |
|---|
| 1696 | /// fn main() -> std::io::Result<()> { |
|---|
| 1697 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1698 | /// |
|---|
| 1699 | /// buffer.write_all(b"some bytes" )?; |
|---|
| 1700 | /// Ok(()) |
|---|
| 1701 | /// } |
|---|
| 1702 | /// ``` |
|---|
| 1703 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1704 | fn write_all(&mut self, mut buf: &[u8]) -> Result<()> { |
|---|
| 1705 | while !buf.is_empty() { |
|---|
| 1706 | match self.write(buf) { |
|---|
| 1707 | Ok(0) => { |
|---|
| 1708 | return Err(error::const_io_error!( |
|---|
| 1709 | ErrorKind::WriteZero, |
|---|
| 1710 | "failed to write whole buffer" , |
|---|
| 1711 | )); |
|---|
| 1712 | } |
|---|
| 1713 | Ok(n) => buf = &buf[n..], |
|---|
| 1714 | Err(ref e) if e.is_interrupted() => {} |
|---|
| 1715 | Err(e) => return Err(e), |
|---|
| 1716 | } |
|---|
| 1717 | } |
|---|
| 1718 | Ok(()) |
|---|
| 1719 | } |
|---|
| 1720 | |
|---|
| 1721 | /// Attempts to write multiple buffers into this writer. |
|---|
| 1722 | /// |
|---|
| 1723 | /// This method will continuously call [`write_vectored`] until there is no |
|---|
| 1724 | /// more data to be written or an error of non-[`ErrorKind::Interrupted`] |
|---|
| 1725 | /// kind is returned. This method will not return until all buffers have |
|---|
| 1726 | /// been successfully written or such an error occurs. The first error that |
|---|
| 1727 | /// is not of [`ErrorKind::Interrupted`] kind generated from this method |
|---|
| 1728 | /// will be returned. |
|---|
| 1729 | /// |
|---|
| 1730 | /// If the buffer contains no data, this will never call [`write_vectored`]. |
|---|
| 1731 | /// |
|---|
| 1732 | /// # Notes |
|---|
| 1733 | /// |
|---|
| 1734 | /// Unlike [`write_vectored`], this takes a *mutable* reference to |
|---|
| 1735 | /// a slice of [`IoSlice`]s, not an immutable one. That's because we need to |
|---|
| 1736 | /// modify the slice to keep track of the bytes already written. |
|---|
| 1737 | /// |
|---|
| 1738 | /// Once this function returns, the contents of `bufs` are unspecified, as |
|---|
| 1739 | /// this depends on how many calls to [`write_vectored`] were necessary. It is |
|---|
| 1740 | /// best to understand this function as taking ownership of `bufs` and to |
|---|
| 1741 | /// not use `bufs` afterwards. The underlying buffers, to which the |
|---|
| 1742 | /// [`IoSlice`]s point (but not the [`IoSlice`]s themselves), are unchanged and |
|---|
| 1743 | /// can be reused. |
|---|
| 1744 | /// |
|---|
| 1745 | /// [`write_vectored`]: Write::write_vectored |
|---|
| 1746 | /// |
|---|
| 1747 | /// # Examples |
|---|
| 1748 | /// |
|---|
| 1749 | /// ``` |
|---|
| 1750 | /// #![feature(write_all_vectored)] |
|---|
| 1751 | /// # fn main() -> std::io::Result<()> { |
|---|
| 1752 | /// |
|---|
| 1753 | /// use std::io::{Write, IoSlice}; |
|---|
| 1754 | /// |
|---|
| 1755 | /// let mut writer = Vec::new(); |
|---|
| 1756 | /// let bufs = &mut [ |
|---|
| 1757 | /// IoSlice::new(&[1]), |
|---|
| 1758 | /// IoSlice::new(&[2, 3]), |
|---|
| 1759 | /// IoSlice::new(&[4, 5, 6]), |
|---|
| 1760 | /// ]; |
|---|
| 1761 | /// |
|---|
| 1762 | /// writer.write_all_vectored(bufs)?; |
|---|
| 1763 | /// // Note: the contents of `bufs` is now undefined, see the Notes section. |
|---|
| 1764 | /// |
|---|
| 1765 | /// assert_eq!(writer, &[1, 2, 3, 4, 5, 6]); |
|---|
| 1766 | /// # Ok(()) } |
|---|
| 1767 | /// ``` |
|---|
| 1768 | #[unstable (feature = "write_all_vectored" , issue = "70436" )] |
|---|
| 1769 | fn write_all_vectored(&mut self, mut bufs: &mut [IoSlice<'_>]) -> Result<()> { |
|---|
| 1770 | // Guarantee that bufs is empty if it contains no data, |
|---|
| 1771 | // to avoid calling write_vectored if there is no data to be written. |
|---|
| 1772 | IoSlice::advance_slices(&mut bufs, 0); |
|---|
| 1773 | while !bufs.is_empty() { |
|---|
| 1774 | match self.write_vectored(bufs) { |
|---|
| 1775 | Ok(0) => { |
|---|
| 1776 | return Err(error::const_io_error!( |
|---|
| 1777 | ErrorKind::WriteZero, |
|---|
| 1778 | "failed to write whole buffer" , |
|---|
| 1779 | )); |
|---|
| 1780 | } |
|---|
| 1781 | Ok(n) => IoSlice::advance_slices(&mut bufs, n), |
|---|
| 1782 | Err(ref e) if e.is_interrupted() => {} |
|---|
| 1783 | Err(e) => return Err(e), |
|---|
| 1784 | } |
|---|
| 1785 | } |
|---|
| 1786 | Ok(()) |
|---|
| 1787 | } |
|---|
| 1788 | |
|---|
| 1789 | /// Writes a formatted string into this writer, returning any error |
|---|
| 1790 | /// encountered. |
|---|
| 1791 | /// |
|---|
| 1792 | /// This method is primarily used to interface with the |
|---|
| 1793 | /// [`format_args!()`] macro, and it is rare that this should |
|---|
| 1794 | /// explicitly be called. The [`write!()`] macro should be favored to |
|---|
| 1795 | /// invoke this method instead. |
|---|
| 1796 | /// |
|---|
| 1797 | /// This function internally uses the [`write_all`] method on |
|---|
| 1798 | /// this trait and hence will continuously write data so long as no errors |
|---|
| 1799 | /// are received. This also means that partial writes are not indicated in |
|---|
| 1800 | /// this signature. |
|---|
| 1801 | /// |
|---|
| 1802 | /// [`write_all`]: Write::write_all |
|---|
| 1803 | /// |
|---|
| 1804 | /// # Errors |
|---|
| 1805 | /// |
|---|
| 1806 | /// This function will return any I/O error reported while formatting. |
|---|
| 1807 | /// |
|---|
| 1808 | /// # Examples |
|---|
| 1809 | /// |
|---|
| 1810 | /// ```no_run |
|---|
| 1811 | /// use std::io::prelude::*; |
|---|
| 1812 | /// use std::fs::File; |
|---|
| 1813 | /// |
|---|
| 1814 | /// fn main() -> std::io::Result<()> { |
|---|
| 1815 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1816 | /// |
|---|
| 1817 | /// // this call |
|---|
| 1818 | /// write!(buffer, "{:.*}" , 2, 1.234567)?; |
|---|
| 1819 | /// // turns into this: |
|---|
| 1820 | /// buffer.write_fmt(format_args!("{:.*}" , 2, 1.234567))?; |
|---|
| 1821 | /// Ok(()) |
|---|
| 1822 | /// } |
|---|
| 1823 | /// ``` |
|---|
| 1824 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1825 | fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> Result<()> { |
|---|
| 1826 | // Create a shim which translates a Write to a fmt::Write and saves |
|---|
| 1827 | // off I/O errors. instead of discarding them |
|---|
| 1828 | struct Adapter<'a, T: ?Sized + 'a> { |
|---|
| 1829 | inner: &'a mut T, |
|---|
| 1830 | error: Result<()>, |
|---|
| 1831 | } |
|---|
| 1832 | |
|---|
| 1833 | impl<T: Write + ?Sized> fmt::Write for Adapter<'_, T> { |
|---|
| 1834 | fn write_str(&mut self, s: &str) -> fmt::Result { |
|---|
| 1835 | match self.inner.write_all(s.as_bytes()) { |
|---|
| 1836 | Ok(()) => Ok(()), |
|---|
| 1837 | Err(e) => { |
|---|
| 1838 | self.error = Err(e); |
|---|
| 1839 | Err(fmt::Error) |
|---|
| 1840 | } |
|---|
| 1841 | } |
|---|
| 1842 | } |
|---|
| 1843 | } |
|---|
| 1844 | |
|---|
| 1845 | let mut output = Adapter { inner: self, error: Ok(()) }; |
|---|
| 1846 | match fmt::write(&mut output, fmt) { |
|---|
| 1847 | Ok(()) => Ok(()), |
|---|
| 1848 | Err(..) => { |
|---|
| 1849 | // check if the error came from the underlying `Write` or not |
|---|
| 1850 | if output.error.is_err() { |
|---|
| 1851 | output.error |
|---|
| 1852 | } else { |
|---|
| 1853 | Err(error::const_io_error!(ErrorKind::Uncategorized, "formatter error" )) |
|---|
| 1854 | } |
|---|
| 1855 | } |
|---|
| 1856 | } |
|---|
| 1857 | } |
|---|
| 1858 | |
|---|
| 1859 | /// Creates a "by reference" adapter for this instance of `Write`. |
|---|
| 1860 | /// |
|---|
| 1861 | /// The returned adapter also implements `Write` and will simply borrow this |
|---|
| 1862 | /// current writer. |
|---|
| 1863 | /// |
|---|
| 1864 | /// # Examples |
|---|
| 1865 | /// |
|---|
| 1866 | /// ```no_run |
|---|
| 1867 | /// use std::io::Write; |
|---|
| 1868 | /// use std::fs::File; |
|---|
| 1869 | /// |
|---|
| 1870 | /// fn main() -> std::io::Result<()> { |
|---|
| 1871 | /// let mut buffer = File::create("foo.txt" )?; |
|---|
| 1872 | /// |
|---|
| 1873 | /// let reference = buffer.by_ref(); |
|---|
| 1874 | /// |
|---|
| 1875 | /// // we can use reference just like our original buffer |
|---|
| 1876 | /// reference.write_all(b"some bytes" )?; |
|---|
| 1877 | /// Ok(()) |
|---|
| 1878 | /// } |
|---|
| 1879 | /// ``` |
|---|
| 1880 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1881 | fn by_ref(&mut self) -> &mut Self |
|---|
| 1882 | where |
|---|
| 1883 | Self: Sized, |
|---|
| 1884 | { |
|---|
| 1885 | self |
|---|
| 1886 | } |
|---|
| 1887 | } |
|---|
| 1888 | |
|---|
| 1889 | /// The `Seek` trait provides a cursor which can be moved within a stream of |
|---|
| 1890 | /// bytes. |
|---|
| 1891 | /// |
|---|
| 1892 | /// The stream typically has a fixed size, allowing seeking relative to either |
|---|
| 1893 | /// end or the current offset. |
|---|
| 1894 | /// |
|---|
| 1895 | /// # Examples |
|---|
| 1896 | /// |
|---|
| 1897 | /// [`File`]s implement `Seek`: |
|---|
| 1898 | /// |
|---|
| 1899 | /// [`File`]: crate::fs::File |
|---|
| 1900 | /// |
|---|
| 1901 | /// ```no_run |
|---|
| 1902 | /// use std::io; |
|---|
| 1903 | /// use std::io::prelude::*; |
|---|
| 1904 | /// use std::fs::File; |
|---|
| 1905 | /// use std::io::SeekFrom; |
|---|
| 1906 | /// |
|---|
| 1907 | /// fn main() -> io::Result<()> { |
|---|
| 1908 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 1909 | /// |
|---|
| 1910 | /// // move the cursor 42 bytes from the start of the file |
|---|
| 1911 | /// f.seek(SeekFrom::Start(42))?; |
|---|
| 1912 | /// Ok(()) |
|---|
| 1913 | /// } |
|---|
| 1914 | /// ``` |
|---|
| 1915 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1916 | #[cfg_attr (not(test), rustc_diagnostic_item = "IoSeek" )] |
|---|
| 1917 | pub trait Seek { |
|---|
| 1918 | /// Seek to an offset, in bytes, in a stream. |
|---|
| 1919 | /// |
|---|
| 1920 | /// A seek beyond the end of a stream is allowed, but behavior is defined |
|---|
| 1921 | /// by the implementation. |
|---|
| 1922 | /// |
|---|
| 1923 | /// If the seek operation completed successfully, |
|---|
| 1924 | /// this method returns the new position from the start of the stream. |
|---|
| 1925 | /// That position can be used later with [`SeekFrom::Start`]. |
|---|
| 1926 | /// |
|---|
| 1927 | /// # Errors |
|---|
| 1928 | /// |
|---|
| 1929 | /// Seeking can fail, for example because it might involve flushing a buffer. |
|---|
| 1930 | /// |
|---|
| 1931 | /// Seeking to a negative offset is considered an error. |
|---|
| 1932 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 1933 | fn seek(&mut self, pos: SeekFrom) -> Result<u64>; |
|---|
| 1934 | |
|---|
| 1935 | /// Rewind to the beginning of a stream. |
|---|
| 1936 | /// |
|---|
| 1937 | /// This is a convenience method, equivalent to `seek(SeekFrom::Start(0))`. |
|---|
| 1938 | /// |
|---|
| 1939 | /// # Errors |
|---|
| 1940 | /// |
|---|
| 1941 | /// Rewinding can fail, for example because it might involve flushing a buffer. |
|---|
| 1942 | /// |
|---|
| 1943 | /// # Example |
|---|
| 1944 | /// |
|---|
| 1945 | /// ```no_run |
|---|
| 1946 | /// use std::io::{Read, Seek, Write}; |
|---|
| 1947 | /// use std::fs::OpenOptions; |
|---|
| 1948 | /// |
|---|
| 1949 | /// let mut f = OpenOptions::new() |
|---|
| 1950 | /// .write(true) |
|---|
| 1951 | /// .read(true) |
|---|
| 1952 | /// .create(true) |
|---|
| 1953 | /// .open("foo.txt" ).unwrap(); |
|---|
| 1954 | /// |
|---|
| 1955 | /// let hello = "Hello! \n" ; |
|---|
| 1956 | /// write!(f, "{hello}" ).unwrap(); |
|---|
| 1957 | /// f.rewind().unwrap(); |
|---|
| 1958 | /// |
|---|
| 1959 | /// let mut buf = String::new(); |
|---|
| 1960 | /// f.read_to_string(&mut buf).unwrap(); |
|---|
| 1961 | /// assert_eq!(&buf, hello); |
|---|
| 1962 | /// ``` |
|---|
| 1963 | #[stable (feature = "seek_rewind" , since = "1.55.0" )] |
|---|
| 1964 | fn rewind(&mut self) -> Result<()> { |
|---|
| 1965 | self.seek(SeekFrom::Start(0))?; |
|---|
| 1966 | Ok(()) |
|---|
| 1967 | } |
|---|
| 1968 | |
|---|
| 1969 | /// Returns the length of this stream (in bytes). |
|---|
| 1970 | /// |
|---|
| 1971 | /// This method is implemented using up to three seek operations. If this |
|---|
| 1972 | /// method returns successfully, the seek position is unchanged (i.e. the |
|---|
| 1973 | /// position before calling this method is the same as afterwards). |
|---|
| 1974 | /// However, if this method returns an error, the seek position is |
|---|
| 1975 | /// unspecified. |
|---|
| 1976 | /// |
|---|
| 1977 | /// If you need to obtain the length of *many* streams and you don't care |
|---|
| 1978 | /// about the seek position afterwards, you can reduce the number of seek |
|---|
| 1979 | /// operations by simply calling `seek(SeekFrom::End(0))` and using its |
|---|
| 1980 | /// return value (it is also the stream length). |
|---|
| 1981 | /// |
|---|
| 1982 | /// Note that length of a stream can change over time (for example, when |
|---|
| 1983 | /// data is appended to a file). So calling this method multiple times does |
|---|
| 1984 | /// not necessarily return the same length each time. |
|---|
| 1985 | /// |
|---|
| 1986 | /// # Example |
|---|
| 1987 | /// |
|---|
| 1988 | /// ```no_run |
|---|
| 1989 | /// #![feature(seek_stream_len)] |
|---|
| 1990 | /// use std::{ |
|---|
| 1991 | /// io::{self, Seek}, |
|---|
| 1992 | /// fs::File, |
|---|
| 1993 | /// }; |
|---|
| 1994 | /// |
|---|
| 1995 | /// fn main() -> io::Result<()> { |
|---|
| 1996 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 1997 | /// |
|---|
| 1998 | /// let len = f.stream_len()?; |
|---|
| 1999 | /// println!("The file is currently {len} bytes long" ); |
|---|
| 2000 | /// Ok(()) |
|---|
| 2001 | /// } |
|---|
| 2002 | /// ``` |
|---|
| 2003 | #[unstable (feature = "seek_stream_len" , issue = "59359" )] |
|---|
| 2004 | fn stream_len(&mut self) -> Result<u64> { |
|---|
| 2005 | let old_pos = self.stream_position()?; |
|---|
| 2006 | let len = self.seek(SeekFrom::End(0))?; |
|---|
| 2007 | |
|---|
| 2008 | // Avoid seeking a third time when we were already at the end of the |
|---|
| 2009 | // stream. The branch is usually way cheaper than a seek operation. |
|---|
| 2010 | if old_pos != len { |
|---|
| 2011 | self.seek(SeekFrom::Start(old_pos))?; |
|---|
| 2012 | } |
|---|
| 2013 | |
|---|
| 2014 | Ok(len) |
|---|
| 2015 | } |
|---|
| 2016 | |
|---|
| 2017 | /// Returns the current seek position from the start of the stream. |
|---|
| 2018 | /// |
|---|
| 2019 | /// This is equivalent to `self.seek(SeekFrom::Current(0))`. |
|---|
| 2020 | /// |
|---|
| 2021 | /// # Example |
|---|
| 2022 | /// |
|---|
| 2023 | /// ```no_run |
|---|
| 2024 | /// use std::{ |
|---|
| 2025 | /// io::{self, BufRead, BufReader, Seek}, |
|---|
| 2026 | /// fs::File, |
|---|
| 2027 | /// }; |
|---|
| 2028 | /// |
|---|
| 2029 | /// fn main() -> io::Result<()> { |
|---|
| 2030 | /// let mut f = BufReader::new(File::open("foo.txt" )?); |
|---|
| 2031 | /// |
|---|
| 2032 | /// let before = f.stream_position()?; |
|---|
| 2033 | /// f.read_line(&mut String::new())?; |
|---|
| 2034 | /// let after = f.stream_position()?; |
|---|
| 2035 | /// |
|---|
| 2036 | /// println!("The first line was {} bytes long" , after - before); |
|---|
| 2037 | /// Ok(()) |
|---|
| 2038 | /// } |
|---|
| 2039 | /// ``` |
|---|
| 2040 | #[stable (feature = "seek_convenience" , since = "1.51.0" )] |
|---|
| 2041 | fn stream_position(&mut self) -> Result<u64> { |
|---|
| 2042 | self.seek(SeekFrom::Current(0)) |
|---|
| 2043 | } |
|---|
| 2044 | |
|---|
| 2045 | /// Seeks relative to the current position. |
|---|
| 2046 | /// |
|---|
| 2047 | /// This is equivalent to `self.seek(SeekFrom::Current(offset))` but |
|---|
| 2048 | /// doesn't return the new position which can allow some implementations |
|---|
| 2049 | /// such as [`BufReader`] to perform more efficient seeks. |
|---|
| 2050 | /// |
|---|
| 2051 | /// # Example |
|---|
| 2052 | /// |
|---|
| 2053 | /// ```no_run |
|---|
| 2054 | /// #![feature(seek_seek_relative)] |
|---|
| 2055 | /// use std::{ |
|---|
| 2056 | /// io::{self, Seek}, |
|---|
| 2057 | /// fs::File, |
|---|
| 2058 | /// }; |
|---|
| 2059 | /// |
|---|
| 2060 | /// fn main() -> io::Result<()> { |
|---|
| 2061 | /// let mut f = File::open("foo.txt" )?; |
|---|
| 2062 | /// f.seek_relative(10)?; |
|---|
| 2063 | /// assert_eq!(f.stream_position()?, 10); |
|---|
| 2064 | /// Ok(()) |
|---|
| 2065 | /// } |
|---|
| 2066 | /// ``` |
|---|
| 2067 | /// |
|---|
| 2068 | /// [`BufReader`]: crate::io::BufReader |
|---|
| 2069 | #[unstable (feature = "seek_seek_relative" , issue = "117374" )] |
|---|
| 2070 | fn seek_relative(&mut self, offset: i64) -> Result<()> { |
|---|
| 2071 | self.seek(SeekFrom::Current(offset))?; |
|---|
| 2072 | Ok(()) |
|---|
| 2073 | } |
|---|
| 2074 | } |
|---|
| 2075 | |
|---|
| 2076 | /// Enumeration of possible methods to seek within an I/O object. |
|---|
| 2077 | /// |
|---|
| 2078 | /// It is used by the [`Seek`] trait. |
|---|
| 2079 | #[derive (Copy, PartialEq, Eq, Clone, Debug)] |
|---|
| 2080 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2081 | pub enum SeekFrom { |
|---|
| 2082 | /// Sets the offset to the provided number of bytes. |
|---|
| 2083 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2084 | Start(#[stable (feature = "rust1" , since = "1.0.0" )] u64), |
|---|
| 2085 | |
|---|
| 2086 | /// Sets the offset to the size of this object plus the specified number of |
|---|
| 2087 | /// bytes. |
|---|
| 2088 | /// |
|---|
| 2089 | /// It is possible to seek beyond the end of an object, but it's an error to |
|---|
| 2090 | /// seek before byte 0. |
|---|
| 2091 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2092 | End(#[stable (feature = "rust1" , since = "1.0.0" )] i64), |
|---|
| 2093 | |
|---|
| 2094 | /// Sets the offset to the current position plus the specified number of |
|---|
| 2095 | /// bytes. |
|---|
| 2096 | /// |
|---|
| 2097 | /// It is possible to seek beyond the end of an object, but it's an error to |
|---|
| 2098 | /// seek before byte 0. |
|---|
| 2099 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2100 | Current(#[stable (feature = "rust1" , since = "1.0.0" )] i64), |
|---|
| 2101 | } |
|---|
| 2102 | |
|---|
| 2103 | fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>) -> Result<usize> { |
|---|
| 2104 | let mut read = 0; |
|---|
| 2105 | loop { |
|---|
| 2106 | let (done, used) = { |
|---|
| 2107 | let available = match r.fill_buf() { |
|---|
| 2108 | Ok(n) => n, |
|---|
| 2109 | Err(ref e) if e.is_interrupted() => continue, |
|---|
| 2110 | Err(e) => return Err(e), |
|---|
| 2111 | }; |
|---|
| 2112 | match memchr::memchr(delim, available) { |
|---|
| 2113 | Some(i) => { |
|---|
| 2114 | buf.extend_from_slice(&available[..=i]); |
|---|
| 2115 | (true, i + 1) |
|---|
| 2116 | } |
|---|
| 2117 | None => { |
|---|
| 2118 | buf.extend_from_slice(available); |
|---|
| 2119 | (false, available.len()) |
|---|
| 2120 | } |
|---|
| 2121 | } |
|---|
| 2122 | }; |
|---|
| 2123 | r.consume(used); |
|---|
| 2124 | read += used; |
|---|
| 2125 | if done || used == 0 { |
|---|
| 2126 | return Ok(read); |
|---|
| 2127 | } |
|---|
| 2128 | } |
|---|
| 2129 | } |
|---|
| 2130 | |
|---|
| 2131 | fn skip_until<R: BufRead + ?Sized>(r: &mut R, delim: u8) -> Result<usize> { |
|---|
| 2132 | let mut read: usize = 0; |
|---|
| 2133 | loop { |
|---|
| 2134 | let (done: bool, used: usize) = { |
|---|
| 2135 | let available: &[u8] = match r.fill_buf() { |
|---|
| 2136 | Ok(n: &[u8]) => n, |
|---|
| 2137 | Err(ref e: &Error) if e.kind() == ErrorKind::Interrupted => continue, |
|---|
| 2138 | Err(e: Error) => return Err(e), |
|---|
| 2139 | }; |
|---|
| 2140 | match memchr::memchr(needle:delim, haystack:available) { |
|---|
| 2141 | Some(i: usize) => (true, i + 1), |
|---|
| 2142 | None => (false, available.len()), |
|---|
| 2143 | } |
|---|
| 2144 | }; |
|---|
| 2145 | r.consume(amt:used); |
|---|
| 2146 | read += used; |
|---|
| 2147 | if done || used == 0 { |
|---|
| 2148 | return Ok(read); |
|---|
| 2149 | } |
|---|
| 2150 | } |
|---|
| 2151 | } |
|---|
| 2152 | |
|---|
| 2153 | /// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it |
|---|
| 2154 | /// to perform extra ways of reading. |
|---|
| 2155 | /// |
|---|
| 2156 | /// For example, reading line-by-line is inefficient without using a buffer, so |
|---|
| 2157 | /// if you want to read by line, you'll need `BufRead`, which includes a |
|---|
| 2158 | /// [`read_line`] method as well as a [`lines`] iterator. |
|---|
| 2159 | /// |
|---|
| 2160 | /// # Examples |
|---|
| 2161 | /// |
|---|
| 2162 | /// A locked standard input implements `BufRead`: |
|---|
| 2163 | /// |
|---|
| 2164 | /// ```no_run |
|---|
| 2165 | /// use std::io; |
|---|
| 2166 | /// use std::io::prelude::*; |
|---|
| 2167 | /// |
|---|
| 2168 | /// let stdin = io::stdin(); |
|---|
| 2169 | /// for line in stdin.lock().lines() { |
|---|
| 2170 | /// println!("{}" , line.unwrap()); |
|---|
| 2171 | /// } |
|---|
| 2172 | /// ``` |
|---|
| 2173 | /// |
|---|
| 2174 | /// If you have something that implements [`Read`], you can use the [`BufReader` |
|---|
| 2175 | /// type][`BufReader`] to turn it into a `BufRead`. |
|---|
| 2176 | /// |
|---|
| 2177 | /// For example, [`File`] implements [`Read`], but not `BufRead`. |
|---|
| 2178 | /// [`BufReader`] to the rescue! |
|---|
| 2179 | /// |
|---|
| 2180 | /// [`File`]: crate::fs::File |
|---|
| 2181 | /// [`read_line`]: BufRead::read_line |
|---|
| 2182 | /// [`lines`]: BufRead::lines |
|---|
| 2183 | /// |
|---|
| 2184 | /// ```no_run |
|---|
| 2185 | /// use std::io::{self, BufReader}; |
|---|
| 2186 | /// use std::io::prelude::*; |
|---|
| 2187 | /// use std::fs::File; |
|---|
| 2188 | /// |
|---|
| 2189 | /// fn main() -> io::Result<()> { |
|---|
| 2190 | /// let f = File::open("foo.txt" )?; |
|---|
| 2191 | /// let f = BufReader::new(f); |
|---|
| 2192 | /// |
|---|
| 2193 | /// for line in f.lines() { |
|---|
| 2194 | /// println!("{}" , line.unwrap()); |
|---|
| 2195 | /// } |
|---|
| 2196 | /// |
|---|
| 2197 | /// Ok(()) |
|---|
| 2198 | /// } |
|---|
| 2199 | /// ``` |
|---|
| 2200 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2201 | pub trait BufRead: Read { |
|---|
| 2202 | /// Returns the contents of the internal buffer, filling it with more data |
|---|
| 2203 | /// from the inner reader if it is empty. |
|---|
| 2204 | /// |
|---|
| 2205 | /// This function is a lower-level call. It needs to be paired with the |
|---|
| 2206 | /// [`consume`] method to function properly. When calling this |
|---|
| 2207 | /// method, none of the contents will be "read" in the sense that later |
|---|
| 2208 | /// calling `read` may return the same contents. As such, [`consume`] must |
|---|
| 2209 | /// be called with the number of bytes that are consumed from this buffer to |
|---|
| 2210 | /// ensure that the bytes are never returned twice. |
|---|
| 2211 | /// |
|---|
| 2212 | /// [`consume`]: BufRead::consume |
|---|
| 2213 | /// |
|---|
| 2214 | /// An empty buffer returned indicates that the stream has reached EOF. |
|---|
| 2215 | /// |
|---|
| 2216 | /// # Errors |
|---|
| 2217 | /// |
|---|
| 2218 | /// This function will return an I/O error if the underlying reader was |
|---|
| 2219 | /// read, but returned an error. |
|---|
| 2220 | /// |
|---|
| 2221 | /// # Examples |
|---|
| 2222 | /// |
|---|
| 2223 | /// A locked standard input implements `BufRead`: |
|---|
| 2224 | /// |
|---|
| 2225 | /// ```no_run |
|---|
| 2226 | /// use std::io; |
|---|
| 2227 | /// use std::io::prelude::*; |
|---|
| 2228 | /// |
|---|
| 2229 | /// let stdin = io::stdin(); |
|---|
| 2230 | /// let mut stdin = stdin.lock(); |
|---|
| 2231 | /// |
|---|
| 2232 | /// let buffer = stdin.fill_buf().unwrap(); |
|---|
| 2233 | /// |
|---|
| 2234 | /// // work with buffer |
|---|
| 2235 | /// println!("{buffer:?}" ); |
|---|
| 2236 | /// |
|---|
| 2237 | /// // ensure the bytes we worked with aren't returned again later |
|---|
| 2238 | /// let length = buffer.len(); |
|---|
| 2239 | /// stdin.consume(length); |
|---|
| 2240 | /// ``` |
|---|
| 2241 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2242 | fn fill_buf(&mut self) -> Result<&[u8]>; |
|---|
| 2243 | |
|---|
| 2244 | /// Tells this buffer that `amt` bytes have been consumed from the buffer, |
|---|
| 2245 | /// so they should no longer be returned in calls to `read`. |
|---|
| 2246 | /// |
|---|
| 2247 | /// This function is a lower-level call. It needs to be paired with the |
|---|
| 2248 | /// [`fill_buf`] method to function properly. This function does |
|---|
| 2249 | /// not perform any I/O, it simply informs this object that some amount of |
|---|
| 2250 | /// its buffer, returned from [`fill_buf`], has been consumed and should |
|---|
| 2251 | /// no longer be returned. As such, this function may do odd things if |
|---|
| 2252 | /// [`fill_buf`] isn't called before calling it. |
|---|
| 2253 | /// |
|---|
| 2254 | /// The `amt` must be `<=` the number of bytes in the buffer returned by |
|---|
| 2255 | /// [`fill_buf`]. |
|---|
| 2256 | /// |
|---|
| 2257 | /// # Examples |
|---|
| 2258 | /// |
|---|
| 2259 | /// Since `consume()` is meant to be used with [`fill_buf`], |
|---|
| 2260 | /// that method's example includes an example of `consume()`. |
|---|
| 2261 | /// |
|---|
| 2262 | /// [`fill_buf`]: BufRead::fill_buf |
|---|
| 2263 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2264 | fn consume(&mut self, amt: usize); |
|---|
| 2265 | |
|---|
| 2266 | /// Check if the underlying `Read` has any data left to be read. |
|---|
| 2267 | /// |
|---|
| 2268 | /// This function may fill the buffer to check for data, |
|---|
| 2269 | /// so this functions returns `Result<bool>`, not `bool`. |
|---|
| 2270 | /// |
|---|
| 2271 | /// Default implementation calls `fill_buf` and checks that |
|---|
| 2272 | /// returned slice is empty (which means that there is no data left, |
|---|
| 2273 | /// since EOF is reached). |
|---|
| 2274 | /// |
|---|
| 2275 | /// Examples |
|---|
| 2276 | /// |
|---|
| 2277 | /// ``` |
|---|
| 2278 | /// #![feature(buf_read_has_data_left)] |
|---|
| 2279 | /// use std::io; |
|---|
| 2280 | /// use std::io::prelude::*; |
|---|
| 2281 | /// |
|---|
| 2282 | /// let stdin = io::stdin(); |
|---|
| 2283 | /// let mut stdin = stdin.lock(); |
|---|
| 2284 | /// |
|---|
| 2285 | /// while stdin.has_data_left().unwrap() { |
|---|
| 2286 | /// let mut line = String::new(); |
|---|
| 2287 | /// stdin.read_line(&mut line).unwrap(); |
|---|
| 2288 | /// // work with line |
|---|
| 2289 | /// println!("{line:?}" ); |
|---|
| 2290 | /// } |
|---|
| 2291 | /// ``` |
|---|
| 2292 | #[unstable (feature = "buf_read_has_data_left" , reason = "recently added" , issue = "86423" )] |
|---|
| 2293 | fn has_data_left(&mut self) -> Result<bool> { |
|---|
| 2294 | self.fill_buf().map(|b| !b.is_empty()) |
|---|
| 2295 | } |
|---|
| 2296 | |
|---|
| 2297 | /// Read all bytes into `buf` until the delimiter `byte` or EOF is reached. |
|---|
| 2298 | /// |
|---|
| 2299 | /// This function will read bytes from the underlying stream until the |
|---|
| 2300 | /// delimiter or EOF is found. Once found, all bytes up to, and including, |
|---|
| 2301 | /// the delimiter (if found) will be appended to `buf`. |
|---|
| 2302 | /// |
|---|
| 2303 | /// If successful, this function will return the total number of bytes read. |
|---|
| 2304 | /// |
|---|
| 2305 | /// This function is blocking and should be used carefully: it is possible for |
|---|
| 2306 | /// an attacker to continuously send bytes without ever sending the delimiter |
|---|
| 2307 | /// or EOF. |
|---|
| 2308 | /// |
|---|
| 2309 | /// # Errors |
|---|
| 2310 | /// |
|---|
| 2311 | /// This function will ignore all instances of [`ErrorKind::Interrupted`] and |
|---|
| 2312 | /// will otherwise return any errors returned by [`fill_buf`]. |
|---|
| 2313 | /// |
|---|
| 2314 | /// If an I/O error is encountered then all bytes read so far will be |
|---|
| 2315 | /// present in `buf` and its length will have been adjusted appropriately. |
|---|
| 2316 | /// |
|---|
| 2317 | /// [`fill_buf`]: BufRead::fill_buf |
|---|
| 2318 | /// |
|---|
| 2319 | /// # Examples |
|---|
| 2320 | /// |
|---|
| 2321 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
|---|
| 2322 | /// this example, we use [`Cursor`] to read all the bytes in a byte slice |
|---|
| 2323 | /// in hyphen delimited segments: |
|---|
| 2324 | /// |
|---|
| 2325 | /// ``` |
|---|
| 2326 | /// use std::io::{self, BufRead}; |
|---|
| 2327 | /// |
|---|
| 2328 | /// let mut cursor = io::Cursor::new(b"lorem-ipsum" ); |
|---|
| 2329 | /// let mut buf = vec![]; |
|---|
| 2330 | /// |
|---|
| 2331 | /// // cursor is at 'l' |
|---|
| 2332 | /// let num_bytes = cursor.read_until(b'-' , &mut buf) |
|---|
| 2333 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2334 | /// assert_eq!(num_bytes, 6); |
|---|
| 2335 | /// assert_eq!(buf, b"lorem-" ); |
|---|
| 2336 | /// buf.clear(); |
|---|
| 2337 | /// |
|---|
| 2338 | /// // cursor is at 'i' |
|---|
| 2339 | /// let num_bytes = cursor.read_until(b'-' , &mut buf) |
|---|
| 2340 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2341 | /// assert_eq!(num_bytes, 5); |
|---|
| 2342 | /// assert_eq!(buf, b"ipsum" ); |
|---|
| 2343 | /// buf.clear(); |
|---|
| 2344 | /// |
|---|
| 2345 | /// // cursor is at EOF |
|---|
| 2346 | /// let num_bytes = cursor.read_until(b'-' , &mut buf) |
|---|
| 2347 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2348 | /// assert_eq!(num_bytes, 0); |
|---|
| 2349 | /// assert_eq!(buf, b"" ); |
|---|
| 2350 | /// ``` |
|---|
| 2351 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2352 | fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> { |
|---|
| 2353 | read_until(self, byte, buf) |
|---|
| 2354 | } |
|---|
| 2355 | |
|---|
| 2356 | /// Skip all bytes until the delimiter `byte` or EOF is reached. |
|---|
| 2357 | /// |
|---|
| 2358 | /// This function will read (and discard) bytes from the underlying stream until the |
|---|
| 2359 | /// delimiter or EOF is found. |
|---|
| 2360 | /// |
|---|
| 2361 | /// If successful, this function will return the total number of bytes read, |
|---|
| 2362 | /// including the delimiter byte. |
|---|
| 2363 | /// |
|---|
| 2364 | /// This is useful for efficiently skipping data such as NUL-terminated strings |
|---|
| 2365 | /// in binary file formats without buffering. |
|---|
| 2366 | /// |
|---|
| 2367 | /// This function is blocking and should be used carefully: it is possible for |
|---|
| 2368 | /// an attacker to continuously send bytes without ever sending the delimiter |
|---|
| 2369 | /// or EOF. |
|---|
| 2370 | /// |
|---|
| 2371 | /// # Errors |
|---|
| 2372 | /// |
|---|
| 2373 | /// This function will ignore all instances of [`ErrorKind::Interrupted`] and |
|---|
| 2374 | /// will otherwise return any errors returned by [`fill_buf`]. |
|---|
| 2375 | /// |
|---|
| 2376 | /// If an I/O error is encountered then all bytes read so far will be |
|---|
| 2377 | /// present in `buf` and its length will have been adjusted appropriately. |
|---|
| 2378 | /// |
|---|
| 2379 | /// [`fill_buf`]: BufRead::fill_buf |
|---|
| 2380 | /// |
|---|
| 2381 | /// # Examples |
|---|
| 2382 | /// |
|---|
| 2383 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
|---|
| 2384 | /// this example, we use [`Cursor`] to read some NUL-terminated information |
|---|
| 2385 | /// about Ferris from a binary string, skipping the fun fact: |
|---|
| 2386 | /// |
|---|
| 2387 | /// ``` |
|---|
| 2388 | /// #![feature(bufread_skip_until)] |
|---|
| 2389 | /// |
|---|
| 2390 | /// use std::io::{self, BufRead}; |
|---|
| 2391 | /// |
|---|
| 2392 | /// let mut cursor = io::Cursor::new(b"Ferris \0Likes long walks on the beach \0Crustacean \0" ); |
|---|
| 2393 | /// |
|---|
| 2394 | /// // read name |
|---|
| 2395 | /// let mut name = Vec::new(); |
|---|
| 2396 | /// let num_bytes = cursor.read_until(b' \0' , &mut name) |
|---|
| 2397 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2398 | /// assert_eq!(num_bytes, 7); |
|---|
| 2399 | /// assert_eq!(name, b"Ferris \0" ); |
|---|
| 2400 | /// |
|---|
| 2401 | /// // skip fun fact |
|---|
| 2402 | /// let num_bytes = cursor.skip_until(b' \0' ) |
|---|
| 2403 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2404 | /// assert_eq!(num_bytes, 30); |
|---|
| 2405 | /// |
|---|
| 2406 | /// // read animal type |
|---|
| 2407 | /// let mut animal = Vec::new(); |
|---|
| 2408 | /// let num_bytes = cursor.read_until(b' \0' , &mut animal) |
|---|
| 2409 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2410 | /// assert_eq!(num_bytes, 11); |
|---|
| 2411 | /// assert_eq!(animal, b"Crustacean \0" ); |
|---|
| 2412 | /// ``` |
|---|
| 2413 | #[unstable (feature = "bufread_skip_until" , issue = "111735" )] |
|---|
| 2414 | fn skip_until(&mut self, byte: u8) -> Result<usize> { |
|---|
| 2415 | skip_until(self, byte) |
|---|
| 2416 | } |
|---|
| 2417 | |
|---|
| 2418 | /// Read all bytes until a newline (the `0xA` byte) is reached, and append |
|---|
| 2419 | /// them to the provided `String` buffer. |
|---|
| 2420 | /// |
|---|
| 2421 | /// Previous content of the buffer will be preserved. To avoid appending to |
|---|
| 2422 | /// the buffer, you need to [`clear`] it first. |
|---|
| 2423 | /// |
|---|
| 2424 | /// This function will read bytes from the underlying stream until the |
|---|
| 2425 | /// newline delimiter (the `0xA` byte) or EOF is found. Once found, all bytes |
|---|
| 2426 | /// up to, and including, the delimiter (if found) will be appended to |
|---|
| 2427 | /// `buf`. |
|---|
| 2428 | /// |
|---|
| 2429 | /// If successful, this function will return the total number of bytes read. |
|---|
| 2430 | /// |
|---|
| 2431 | /// If this function returns [`Ok(0)`], the stream has reached EOF. |
|---|
| 2432 | /// |
|---|
| 2433 | /// This function is blocking and should be used carefully: it is possible for |
|---|
| 2434 | /// an attacker to continuously send bytes without ever sending a newline |
|---|
| 2435 | /// or EOF. You can use [`take`] to limit the maximum number of bytes read. |
|---|
| 2436 | /// |
|---|
| 2437 | /// [`Ok(0)`]: Ok |
|---|
| 2438 | /// [`clear`]: String::clear |
|---|
| 2439 | /// [`take`]: crate::io::Read::take |
|---|
| 2440 | /// |
|---|
| 2441 | /// # Errors |
|---|
| 2442 | /// |
|---|
| 2443 | /// This function has the same error semantics as [`read_until`] and will |
|---|
| 2444 | /// also return an error if the read bytes are not valid UTF-8. If an I/O |
|---|
| 2445 | /// error is encountered then `buf` may contain some bytes already read in |
|---|
| 2446 | /// the event that all data read so far was valid UTF-8. |
|---|
| 2447 | /// |
|---|
| 2448 | /// [`read_until`]: BufRead::read_until |
|---|
| 2449 | /// |
|---|
| 2450 | /// # Examples |
|---|
| 2451 | /// |
|---|
| 2452 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
|---|
| 2453 | /// this example, we use [`Cursor`] to read all the lines in a byte slice: |
|---|
| 2454 | /// |
|---|
| 2455 | /// ``` |
|---|
| 2456 | /// use std::io::{self, BufRead}; |
|---|
| 2457 | /// |
|---|
| 2458 | /// let mut cursor = io::Cursor::new(b"foo \nbar" ); |
|---|
| 2459 | /// let mut buf = String::new(); |
|---|
| 2460 | /// |
|---|
| 2461 | /// // cursor is at 'f' |
|---|
| 2462 | /// let num_bytes = cursor.read_line(&mut buf) |
|---|
| 2463 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2464 | /// assert_eq!(num_bytes, 4); |
|---|
| 2465 | /// assert_eq!(buf, "foo \n" ); |
|---|
| 2466 | /// buf.clear(); |
|---|
| 2467 | /// |
|---|
| 2468 | /// // cursor is at 'b' |
|---|
| 2469 | /// let num_bytes = cursor.read_line(&mut buf) |
|---|
| 2470 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2471 | /// assert_eq!(num_bytes, 3); |
|---|
| 2472 | /// assert_eq!(buf, "bar" ); |
|---|
| 2473 | /// buf.clear(); |
|---|
| 2474 | /// |
|---|
| 2475 | /// // cursor is at EOF |
|---|
| 2476 | /// let num_bytes = cursor.read_line(&mut buf) |
|---|
| 2477 | /// .expect("reading from cursor won't fail" ); |
|---|
| 2478 | /// assert_eq!(num_bytes, 0); |
|---|
| 2479 | /// assert_eq!(buf, "" ); |
|---|
| 2480 | /// ``` |
|---|
| 2481 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2482 | fn read_line(&mut self, buf: &mut String) -> Result<usize> { |
|---|
| 2483 | // Note that we are not calling the `.read_until` method here, but |
|---|
| 2484 | // rather our hardcoded implementation. For more details as to why, see |
|---|
| 2485 | // the comments in `read_to_end`. |
|---|
| 2486 | unsafe { append_to_string(buf, |b| read_until(self, b' \n' , b)) } |
|---|
| 2487 | } |
|---|
| 2488 | |
|---|
| 2489 | /// Returns an iterator over the contents of this reader split on the byte |
|---|
| 2490 | /// `byte`. |
|---|
| 2491 | /// |
|---|
| 2492 | /// The iterator returned from this function will return instances of |
|---|
| 2493 | /// <code>[io::Result]<[Vec]\<u8>></code>. Each vector returned will *not* have |
|---|
| 2494 | /// the delimiter byte at the end. |
|---|
| 2495 | /// |
|---|
| 2496 | /// This function will yield errors whenever [`read_until`] would have |
|---|
| 2497 | /// also yielded an error. |
|---|
| 2498 | /// |
|---|
| 2499 | /// [io::Result]: self::Result "io::Result" |
|---|
| 2500 | /// [`read_until`]: BufRead::read_until |
|---|
| 2501 | /// |
|---|
| 2502 | /// # Examples |
|---|
| 2503 | /// |
|---|
| 2504 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
|---|
| 2505 | /// this example, we use [`Cursor`] to iterate over all hyphen delimited |
|---|
| 2506 | /// segments in a byte slice |
|---|
| 2507 | /// |
|---|
| 2508 | /// ``` |
|---|
| 2509 | /// use std::io::{self, BufRead}; |
|---|
| 2510 | /// |
|---|
| 2511 | /// let cursor = io::Cursor::new(b"lorem-ipsum-dolor" ); |
|---|
| 2512 | /// |
|---|
| 2513 | /// let mut split_iter = cursor.split(b'-' ).map(|l| l.unwrap()); |
|---|
| 2514 | /// assert_eq!(split_iter.next(), Some(b"lorem" .to_vec())); |
|---|
| 2515 | /// assert_eq!(split_iter.next(), Some(b"ipsum" .to_vec())); |
|---|
| 2516 | /// assert_eq!(split_iter.next(), Some(b"dolor" .to_vec())); |
|---|
| 2517 | /// assert_eq!(split_iter.next(), None); |
|---|
| 2518 | /// ``` |
|---|
| 2519 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2520 | fn split(self, byte: u8) -> Split<Self> |
|---|
| 2521 | where |
|---|
| 2522 | Self: Sized, |
|---|
| 2523 | { |
|---|
| 2524 | Split { buf: self, delim: byte } |
|---|
| 2525 | } |
|---|
| 2526 | |
|---|
| 2527 | /// Returns an iterator over the lines of this reader. |
|---|
| 2528 | /// |
|---|
| 2529 | /// The iterator returned from this function will yield instances of |
|---|
| 2530 | /// <code>[io::Result]<[String]></code>. Each string returned will *not* have a newline |
|---|
| 2531 | /// byte (the `0xA` byte) or `CRLF` (`0xD`, `0xA` bytes) at the end. |
|---|
| 2532 | /// |
|---|
| 2533 | /// [io::Result]: self::Result "io::Result" |
|---|
| 2534 | /// |
|---|
| 2535 | /// # Examples |
|---|
| 2536 | /// |
|---|
| 2537 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
|---|
| 2538 | /// this example, we use [`Cursor`] to iterate over all the lines in a byte |
|---|
| 2539 | /// slice. |
|---|
| 2540 | /// |
|---|
| 2541 | /// ``` |
|---|
| 2542 | /// use std::io::{self, BufRead}; |
|---|
| 2543 | /// |
|---|
| 2544 | /// let cursor = io::Cursor::new(b"lorem \nipsum \r\ndolor" ); |
|---|
| 2545 | /// |
|---|
| 2546 | /// let mut lines_iter = cursor.lines().map(|l| l.unwrap()); |
|---|
| 2547 | /// assert_eq!(lines_iter.next(), Some(String::from("lorem" ))); |
|---|
| 2548 | /// assert_eq!(lines_iter.next(), Some(String::from("ipsum" ))); |
|---|
| 2549 | /// assert_eq!(lines_iter.next(), Some(String::from("dolor" ))); |
|---|
| 2550 | /// assert_eq!(lines_iter.next(), None); |
|---|
| 2551 | /// ``` |
|---|
| 2552 | /// |
|---|
| 2553 | /// # Errors |
|---|
| 2554 | /// |
|---|
| 2555 | /// Each line of the iterator has the same error semantics as [`BufRead::read_line`]. |
|---|
| 2556 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2557 | fn lines(self) -> Lines<Self> |
|---|
| 2558 | where |
|---|
| 2559 | Self: Sized, |
|---|
| 2560 | { |
|---|
| 2561 | Lines { buf: self } |
|---|
| 2562 | } |
|---|
| 2563 | } |
|---|
| 2564 | |
|---|
| 2565 | /// Adapter to chain together two readers. |
|---|
| 2566 | /// |
|---|
| 2567 | /// This struct is generally created by calling [`chain`] on a reader. |
|---|
| 2568 | /// Please see the documentation of [`chain`] for more details. |
|---|
| 2569 | /// |
|---|
| 2570 | /// [`chain`]: Read::chain |
|---|
| 2571 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2572 | #[derive (Debug)] |
|---|
| 2573 | pub struct Chain<T, U> { |
|---|
| 2574 | first: T, |
|---|
| 2575 | second: U, |
|---|
| 2576 | done_first: bool, |
|---|
| 2577 | } |
|---|
| 2578 | |
|---|
| 2579 | impl<T, U> Chain<T, U> { |
|---|
| 2580 | /// Consumes the `Chain`, returning the wrapped readers. |
|---|
| 2581 | /// |
|---|
| 2582 | /// # Examples |
|---|
| 2583 | /// |
|---|
| 2584 | /// ```no_run |
|---|
| 2585 | /// use std::io; |
|---|
| 2586 | /// use std::io::prelude::*; |
|---|
| 2587 | /// use std::fs::File; |
|---|
| 2588 | /// |
|---|
| 2589 | /// fn main() -> io::Result<()> { |
|---|
| 2590 | /// let mut foo_file = File::open("foo.txt" )?; |
|---|
| 2591 | /// let mut bar_file = File::open("bar.txt" )?; |
|---|
| 2592 | /// |
|---|
| 2593 | /// let chain = foo_file.chain(bar_file); |
|---|
| 2594 | /// let (foo_file, bar_file) = chain.into_inner(); |
|---|
| 2595 | /// Ok(()) |
|---|
| 2596 | /// } |
|---|
| 2597 | /// ``` |
|---|
| 2598 | #[stable (feature = "more_io_inner_methods" , since = "1.20.0" )] |
|---|
| 2599 | pub fn into_inner(self) -> (T, U) { |
|---|
| 2600 | (self.first, self.second) |
|---|
| 2601 | } |
|---|
| 2602 | |
|---|
| 2603 | /// Gets references to the underlying readers in this `Chain`. |
|---|
| 2604 | /// |
|---|
| 2605 | /// # Examples |
|---|
| 2606 | /// |
|---|
| 2607 | /// ```no_run |
|---|
| 2608 | /// use std::io; |
|---|
| 2609 | /// use std::io::prelude::*; |
|---|
| 2610 | /// use std::fs::File; |
|---|
| 2611 | /// |
|---|
| 2612 | /// fn main() -> io::Result<()> { |
|---|
| 2613 | /// let mut foo_file = File::open("foo.txt" )?; |
|---|
| 2614 | /// let mut bar_file = File::open("bar.txt" )?; |
|---|
| 2615 | /// |
|---|
| 2616 | /// let chain = foo_file.chain(bar_file); |
|---|
| 2617 | /// let (foo_file, bar_file) = chain.get_ref(); |
|---|
| 2618 | /// Ok(()) |
|---|
| 2619 | /// } |
|---|
| 2620 | /// ``` |
|---|
| 2621 | #[stable (feature = "more_io_inner_methods" , since = "1.20.0" )] |
|---|
| 2622 | pub fn get_ref(&self) -> (&T, &U) { |
|---|
| 2623 | (&self.first, &self.second) |
|---|
| 2624 | } |
|---|
| 2625 | |
|---|
| 2626 | /// Gets mutable references to the underlying readers in this `Chain`. |
|---|
| 2627 | /// |
|---|
| 2628 | /// Care should be taken to avoid modifying the internal I/O state of the |
|---|
| 2629 | /// underlying readers as doing so may corrupt the internal state of this |
|---|
| 2630 | /// `Chain`. |
|---|
| 2631 | /// |
|---|
| 2632 | /// # Examples |
|---|
| 2633 | /// |
|---|
| 2634 | /// ```no_run |
|---|
| 2635 | /// use std::io; |
|---|
| 2636 | /// use std::io::prelude::*; |
|---|
| 2637 | /// use std::fs::File; |
|---|
| 2638 | /// |
|---|
| 2639 | /// fn main() -> io::Result<()> { |
|---|
| 2640 | /// let mut foo_file = File::open("foo.txt" )?; |
|---|
| 2641 | /// let mut bar_file = File::open("bar.txt" )?; |
|---|
| 2642 | /// |
|---|
| 2643 | /// let mut chain = foo_file.chain(bar_file); |
|---|
| 2644 | /// let (foo_file, bar_file) = chain.get_mut(); |
|---|
| 2645 | /// Ok(()) |
|---|
| 2646 | /// } |
|---|
| 2647 | /// ``` |
|---|
| 2648 | #[stable (feature = "more_io_inner_methods" , since = "1.20.0" )] |
|---|
| 2649 | pub fn get_mut(&mut self) -> (&mut T, &mut U) { |
|---|
| 2650 | (&mut self.first, &mut self.second) |
|---|
| 2651 | } |
|---|
| 2652 | } |
|---|
| 2653 | |
|---|
| 2654 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2655 | impl<T: Read, U: Read> Read for Chain<T, U> { |
|---|
| 2656 | fn read(&mut self, buf: &mut [u8]) -> Result<usize> { |
|---|
| 2657 | if !self.done_first { |
|---|
| 2658 | match self.first.read(buf)? { |
|---|
| 2659 | 0 if !buf.is_empty() => self.done_first = true, |
|---|
| 2660 | n: usize => return Ok(n), |
|---|
| 2661 | } |
|---|
| 2662 | } |
|---|
| 2663 | self.second.read(buf) |
|---|
| 2664 | } |
|---|
| 2665 | |
|---|
| 2666 | fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> { |
|---|
| 2667 | if !self.done_first { |
|---|
| 2668 | match self.first.read_vectored(bufs)? { |
|---|
| 2669 | 0 if bufs.iter().any(|b: &IoSliceMut<'_>| !b.is_empty()) => self.done_first = true, |
|---|
| 2670 | n: usize => return Ok(n), |
|---|
| 2671 | } |
|---|
| 2672 | } |
|---|
| 2673 | self.second.read_vectored(bufs) |
|---|
| 2674 | } |
|---|
| 2675 | } |
|---|
| 2676 | |
|---|
| 2677 | #[stable (feature = "chain_bufread" , since = "1.9.0" )] |
|---|
| 2678 | impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> { |
|---|
| 2679 | fn fill_buf(&mut self) -> Result<&[u8]> { |
|---|
| 2680 | if !self.done_first { |
|---|
| 2681 | match self.first.fill_buf()? { |
|---|
| 2682 | buf: &[u8] if buf.is_empty() => { |
|---|
| 2683 | self.done_first = true; |
|---|
| 2684 | } |
|---|
| 2685 | buf: &[u8] => return Ok(buf), |
|---|
| 2686 | } |
|---|
| 2687 | } |
|---|
| 2688 | self.second.fill_buf() |
|---|
| 2689 | } |
|---|
| 2690 | |
|---|
| 2691 | fn consume(&mut self, amt: usize) { |
|---|
| 2692 | if !self.done_first { self.first.consume(amt) } else { self.second.consume(amt) } |
|---|
| 2693 | } |
|---|
| 2694 | } |
|---|
| 2695 | |
|---|
| 2696 | impl<T, U> SizeHint for Chain<T, U> { |
|---|
| 2697 | #[inline ] |
|---|
| 2698 | fn lower_bound(&self) -> usize { |
|---|
| 2699 | SizeHint::lower_bound(&self.first) + SizeHint::lower_bound(&self.second) |
|---|
| 2700 | } |
|---|
| 2701 | |
|---|
| 2702 | #[inline ] |
|---|
| 2703 | fn upper_bound(&self) -> Option<usize> { |
|---|
| 2704 | match (SizeHint::upper_bound(&self.first), SizeHint::upper_bound(&self.second)) { |
|---|
| 2705 | (Some(first: usize), Some(second: usize)) => first.checked_add(second), |
|---|
| 2706 | _ => None, |
|---|
| 2707 | } |
|---|
| 2708 | } |
|---|
| 2709 | } |
|---|
| 2710 | |
|---|
| 2711 | /// Reader adapter which limits the bytes read from an underlying reader. |
|---|
| 2712 | /// |
|---|
| 2713 | /// This struct is generally created by calling [`take`] on a reader. |
|---|
| 2714 | /// Please see the documentation of [`take`] for more details. |
|---|
| 2715 | /// |
|---|
| 2716 | /// [`take`]: Read::take |
|---|
| 2717 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2718 | #[derive (Debug)] |
|---|
| 2719 | pub struct Take<T> { |
|---|
| 2720 | inner: T, |
|---|
| 2721 | limit: u64, |
|---|
| 2722 | } |
|---|
| 2723 | |
|---|
| 2724 | impl<T> Take<T> { |
|---|
| 2725 | /// Returns the number of bytes that can be read before this instance will |
|---|
| 2726 | /// return EOF. |
|---|
| 2727 | /// |
|---|
| 2728 | /// # Note |
|---|
| 2729 | /// |
|---|
| 2730 | /// This instance may reach `EOF` after reading fewer bytes than indicated by |
|---|
| 2731 | /// this method if the underlying [`Read`] instance reaches EOF. |
|---|
| 2732 | /// |
|---|
| 2733 | /// # Examples |
|---|
| 2734 | /// |
|---|
| 2735 | /// ```no_run |
|---|
| 2736 | /// use std::io; |
|---|
| 2737 | /// use std::io::prelude::*; |
|---|
| 2738 | /// use std::fs::File; |
|---|
| 2739 | /// |
|---|
| 2740 | /// fn main() -> io::Result<()> { |
|---|
| 2741 | /// let f = File::open("foo.txt" )?; |
|---|
| 2742 | /// |
|---|
| 2743 | /// // read at most five bytes |
|---|
| 2744 | /// let handle = f.take(5); |
|---|
| 2745 | /// |
|---|
| 2746 | /// println!("limit: {}" , handle.limit()); |
|---|
| 2747 | /// Ok(()) |
|---|
| 2748 | /// } |
|---|
| 2749 | /// ``` |
|---|
| 2750 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2751 | pub fn limit(&self) -> u64 { |
|---|
| 2752 | self.limit |
|---|
| 2753 | } |
|---|
| 2754 | |
|---|
| 2755 | /// Sets the number of bytes that can be read before this instance will |
|---|
| 2756 | /// return EOF. This is the same as constructing a new `Take` instance, so |
|---|
| 2757 | /// the amount of bytes read and the previous limit value don't matter when |
|---|
| 2758 | /// calling this method. |
|---|
| 2759 | /// |
|---|
| 2760 | /// # Examples |
|---|
| 2761 | /// |
|---|
| 2762 | /// ```no_run |
|---|
| 2763 | /// use std::io; |
|---|
| 2764 | /// use std::io::prelude::*; |
|---|
| 2765 | /// use std::fs::File; |
|---|
| 2766 | /// |
|---|
| 2767 | /// fn main() -> io::Result<()> { |
|---|
| 2768 | /// let f = File::open("foo.txt" )?; |
|---|
| 2769 | /// |
|---|
| 2770 | /// // read at most five bytes |
|---|
| 2771 | /// let mut handle = f.take(5); |
|---|
| 2772 | /// handle.set_limit(10); |
|---|
| 2773 | /// |
|---|
| 2774 | /// assert_eq!(handle.limit(), 10); |
|---|
| 2775 | /// Ok(()) |
|---|
| 2776 | /// } |
|---|
| 2777 | /// ``` |
|---|
| 2778 | #[stable (feature = "take_set_limit" , since = "1.27.0" )] |
|---|
| 2779 | pub fn set_limit(&mut self, limit: u64) { |
|---|
| 2780 | self.limit = limit; |
|---|
| 2781 | } |
|---|
| 2782 | |
|---|
| 2783 | /// Consumes the `Take`, returning the wrapped reader. |
|---|
| 2784 | /// |
|---|
| 2785 | /// # Examples |
|---|
| 2786 | /// |
|---|
| 2787 | /// ```no_run |
|---|
| 2788 | /// use std::io; |
|---|
| 2789 | /// use std::io::prelude::*; |
|---|
| 2790 | /// use std::fs::File; |
|---|
| 2791 | /// |
|---|
| 2792 | /// fn main() -> io::Result<()> { |
|---|
| 2793 | /// let mut file = File::open("foo.txt" )?; |
|---|
| 2794 | /// |
|---|
| 2795 | /// let mut buffer = [0; 5]; |
|---|
| 2796 | /// let mut handle = file.take(5); |
|---|
| 2797 | /// handle.read(&mut buffer)?; |
|---|
| 2798 | /// |
|---|
| 2799 | /// let file = handle.into_inner(); |
|---|
| 2800 | /// Ok(()) |
|---|
| 2801 | /// } |
|---|
| 2802 | /// ``` |
|---|
| 2803 | #[stable (feature = "io_take_into_inner" , since = "1.15.0" )] |
|---|
| 2804 | pub fn into_inner(self) -> T { |
|---|
| 2805 | self.inner |
|---|
| 2806 | } |
|---|
| 2807 | |
|---|
| 2808 | /// Gets a reference to the underlying reader. |
|---|
| 2809 | /// |
|---|
| 2810 | /// # Examples |
|---|
| 2811 | /// |
|---|
| 2812 | /// ```no_run |
|---|
| 2813 | /// use std::io; |
|---|
| 2814 | /// use std::io::prelude::*; |
|---|
| 2815 | /// use std::fs::File; |
|---|
| 2816 | /// |
|---|
| 2817 | /// fn main() -> io::Result<()> { |
|---|
| 2818 | /// let mut file = File::open("foo.txt" )?; |
|---|
| 2819 | /// |
|---|
| 2820 | /// let mut buffer = [0; 5]; |
|---|
| 2821 | /// let mut handle = file.take(5); |
|---|
| 2822 | /// handle.read(&mut buffer)?; |
|---|
| 2823 | /// |
|---|
| 2824 | /// let file = handle.get_ref(); |
|---|
| 2825 | /// Ok(()) |
|---|
| 2826 | /// } |
|---|
| 2827 | /// ``` |
|---|
| 2828 | #[stable (feature = "more_io_inner_methods" , since = "1.20.0" )] |
|---|
| 2829 | pub fn get_ref(&self) -> &T { |
|---|
| 2830 | &self.inner |
|---|
| 2831 | } |
|---|
| 2832 | |
|---|
| 2833 | /// Gets a mutable reference to the underlying reader. |
|---|
| 2834 | /// |
|---|
| 2835 | /// Care should be taken to avoid modifying the internal I/O state of the |
|---|
| 2836 | /// underlying reader as doing so may corrupt the internal limit of this |
|---|
| 2837 | /// `Take`. |
|---|
| 2838 | /// |
|---|
| 2839 | /// # Examples |
|---|
| 2840 | /// |
|---|
| 2841 | /// ```no_run |
|---|
| 2842 | /// use std::io; |
|---|
| 2843 | /// use std::io::prelude::*; |
|---|
| 2844 | /// use std::fs::File; |
|---|
| 2845 | /// |
|---|
| 2846 | /// fn main() -> io::Result<()> { |
|---|
| 2847 | /// let mut file = File::open("foo.txt" )?; |
|---|
| 2848 | /// |
|---|
| 2849 | /// let mut buffer = [0; 5]; |
|---|
| 2850 | /// let mut handle = file.take(5); |
|---|
| 2851 | /// handle.read(&mut buffer)?; |
|---|
| 2852 | /// |
|---|
| 2853 | /// let file = handle.get_mut(); |
|---|
| 2854 | /// Ok(()) |
|---|
| 2855 | /// } |
|---|
| 2856 | /// ``` |
|---|
| 2857 | #[stable (feature = "more_io_inner_methods" , since = "1.20.0" )] |
|---|
| 2858 | pub fn get_mut(&mut self) -> &mut T { |
|---|
| 2859 | &mut self.inner |
|---|
| 2860 | } |
|---|
| 2861 | } |
|---|
| 2862 | |
|---|
| 2863 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2864 | impl<T: Read> Read for Take<T> { |
|---|
| 2865 | fn read(&mut self, buf: &mut [u8]) -> Result<usize> { |
|---|
| 2866 | // Don't call into inner reader at all at EOF because it may still block |
|---|
| 2867 | if self.limit == 0 { |
|---|
| 2868 | return Ok(0); |
|---|
| 2869 | } |
|---|
| 2870 | |
|---|
| 2871 | let max = cmp::min(buf.len() as u64, self.limit) as usize; |
|---|
| 2872 | let n = self.inner.read(&mut buf[..max])?; |
|---|
| 2873 | assert!(n as u64 <= self.limit, "number of read bytes exceeds limit" ); |
|---|
| 2874 | self.limit -= n as u64; |
|---|
| 2875 | Ok(n) |
|---|
| 2876 | } |
|---|
| 2877 | |
|---|
| 2878 | fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> Result<()> { |
|---|
| 2879 | // Don't call into inner reader at all at EOF because it may still block |
|---|
| 2880 | if self.limit == 0 { |
|---|
| 2881 | return Ok(()); |
|---|
| 2882 | } |
|---|
| 2883 | |
|---|
| 2884 | if self.limit <= buf.capacity() as u64 { |
|---|
| 2885 | // if we just use an as cast to convert, limit may wrap around on a 32 bit target |
|---|
| 2886 | let limit = cmp::min(self.limit, usize::MAX as u64) as usize; |
|---|
| 2887 | |
|---|
| 2888 | let extra_init = cmp::min(limit as usize, buf.init_ref().len()); |
|---|
| 2889 | |
|---|
| 2890 | // SAFETY: no uninit data is written to ibuf |
|---|
| 2891 | let ibuf = unsafe { &mut buf.as_mut()[..limit] }; |
|---|
| 2892 | |
|---|
| 2893 | let mut sliced_buf: BorrowedBuf<'_> = ibuf.into(); |
|---|
| 2894 | |
|---|
| 2895 | // SAFETY: extra_init bytes of ibuf are known to be initialized |
|---|
| 2896 | unsafe { |
|---|
| 2897 | sliced_buf.set_init(extra_init); |
|---|
| 2898 | } |
|---|
| 2899 | |
|---|
| 2900 | let mut cursor = sliced_buf.unfilled(); |
|---|
| 2901 | self.inner.read_buf(cursor.reborrow())?; |
|---|
| 2902 | |
|---|
| 2903 | let new_init = cursor.init_ref().len(); |
|---|
| 2904 | let filled = sliced_buf.len(); |
|---|
| 2905 | |
|---|
| 2906 | // cursor / sliced_buf / ibuf must drop here |
|---|
| 2907 | |
|---|
| 2908 | unsafe { |
|---|
| 2909 | // SAFETY: filled bytes have been filled and therefore initialized |
|---|
| 2910 | buf.advance(filled); |
|---|
| 2911 | // SAFETY: new_init bytes of buf's unfilled buffer have been initialized |
|---|
| 2912 | buf.set_init(new_init); |
|---|
| 2913 | } |
|---|
| 2914 | |
|---|
| 2915 | self.limit -= filled as u64; |
|---|
| 2916 | } else { |
|---|
| 2917 | let written = buf.written(); |
|---|
| 2918 | self.inner.read_buf(buf.reborrow())?; |
|---|
| 2919 | self.limit -= (buf.written() - written) as u64; |
|---|
| 2920 | } |
|---|
| 2921 | |
|---|
| 2922 | Ok(()) |
|---|
| 2923 | } |
|---|
| 2924 | } |
|---|
| 2925 | |
|---|
| 2926 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2927 | impl<T: BufRead> BufRead for Take<T> { |
|---|
| 2928 | fn fill_buf(&mut self) -> Result<&[u8]> { |
|---|
| 2929 | // Don't call into inner reader at all at EOF because it may still block |
|---|
| 2930 | if self.limit == 0 { |
|---|
| 2931 | return Ok(&[]); |
|---|
| 2932 | } |
|---|
| 2933 | |
|---|
| 2934 | let buf: &[u8] = self.inner.fill_buf()?; |
|---|
| 2935 | let cap: usize = cmp::min(v1:buf.len() as u64, self.limit) as usize; |
|---|
| 2936 | Ok(&buf[..cap]) |
|---|
| 2937 | } |
|---|
| 2938 | |
|---|
| 2939 | fn consume(&mut self, amt: usize) { |
|---|
| 2940 | // Don't let callers reset the limit by passing an overlarge value |
|---|
| 2941 | let amt: usize = cmp::min(v1:amt as u64, self.limit) as usize; |
|---|
| 2942 | self.limit -= amt as u64; |
|---|
| 2943 | self.inner.consume(amt); |
|---|
| 2944 | } |
|---|
| 2945 | } |
|---|
| 2946 | |
|---|
| 2947 | impl<T> SizeHint for Take<T> { |
|---|
| 2948 | #[inline ] |
|---|
| 2949 | fn lower_bound(&self) -> usize { |
|---|
| 2950 | cmp::min(v1:SizeHint::lower_bound(&self.inner) as u64, self.limit) as usize |
|---|
| 2951 | } |
|---|
| 2952 | |
|---|
| 2953 | #[inline ] |
|---|
| 2954 | fn upper_bound(&self) -> Option<usize> { |
|---|
| 2955 | match SizeHint::upper_bound(&self.inner) { |
|---|
| 2956 | Some(upper_bound: usize) => Some(cmp::min(v1:upper_bound as u64, self.limit) as usize), |
|---|
| 2957 | None => self.limit.try_into().ok(), |
|---|
| 2958 | } |
|---|
| 2959 | } |
|---|
| 2960 | } |
|---|
| 2961 | |
|---|
| 2962 | /// An iterator over `u8` values of a reader. |
|---|
| 2963 | /// |
|---|
| 2964 | /// This struct is generally created by calling [`bytes`] on a reader. |
|---|
| 2965 | /// Please see the documentation of [`bytes`] for more details. |
|---|
| 2966 | /// |
|---|
| 2967 | /// [`bytes`]: Read::bytes |
|---|
| 2968 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2969 | #[derive (Debug)] |
|---|
| 2970 | pub struct Bytes<R> { |
|---|
| 2971 | inner: R, |
|---|
| 2972 | } |
|---|
| 2973 | |
|---|
| 2974 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 2975 | impl<R: Read> Iterator for Bytes<R> { |
|---|
| 2976 | type Item = Result<u8>; |
|---|
| 2977 | |
|---|
| 2978 | // Not `#[inline]`. This function gets inlined even without it, but having |
|---|
| 2979 | // the inline annotation can result in worse code generation. See #116785. |
|---|
| 2980 | fn next(&mut self) -> Option<Result<u8>> { |
|---|
| 2981 | SpecReadByte::spec_read_byte(&mut self.inner) |
|---|
| 2982 | } |
|---|
| 2983 | |
|---|
| 2984 | #[inline ] |
|---|
| 2985 | fn size_hint(&self) -> (usize, Option<usize>) { |
|---|
| 2986 | SizeHint::size_hint(&self.inner) |
|---|
| 2987 | } |
|---|
| 2988 | } |
|---|
| 2989 | |
|---|
| 2990 | /// For the specialization of `Bytes::next`. |
|---|
| 2991 | trait SpecReadByte { |
|---|
| 2992 | fn spec_read_byte(&mut self) -> Option<Result<u8>>; |
|---|
| 2993 | } |
|---|
| 2994 | |
|---|
| 2995 | impl<R> SpecReadByte for R |
|---|
| 2996 | where |
|---|
| 2997 | Self: Read, |
|---|
| 2998 | { |
|---|
| 2999 | #[inline ] |
|---|
| 3000 | default fn spec_read_byte(&mut self) -> Option<Result<u8>> { |
|---|
| 3001 | inlined_slow_read_byte(self) |
|---|
| 3002 | } |
|---|
| 3003 | } |
|---|
| 3004 | |
|---|
| 3005 | /// Read a single byte in a slow, generic way. This is used by the default |
|---|
| 3006 | /// `spec_read_byte`. |
|---|
| 3007 | #[inline ] |
|---|
| 3008 | fn inlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> { |
|---|
| 3009 | let mut byte: u8 = 0; |
|---|
| 3010 | loop { |
|---|
| 3011 | return match reader.read(buf:slice::from_mut(&mut byte)) { |
|---|
| 3012 | Ok(0) => None, |
|---|
| 3013 | Ok(..) => Some(Ok(byte)), |
|---|
| 3014 | Err(ref e: &Error) if e.is_interrupted() => continue, |
|---|
| 3015 | Err(e: Error) => Some(Err(e)), |
|---|
| 3016 | }; |
|---|
| 3017 | } |
|---|
| 3018 | } |
|---|
| 3019 | |
|---|
| 3020 | // Used by `BufReader::spec_read_byte`, for which the `inline(ever)` is |
|---|
| 3021 | // important. |
|---|
| 3022 | #[inline (never)] |
|---|
| 3023 | fn uninlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> { |
|---|
| 3024 | inlined_slow_read_byte(reader) |
|---|
| 3025 | } |
|---|
| 3026 | |
|---|
| 3027 | trait SizeHint { |
|---|
| 3028 | fn lower_bound(&self) -> usize; |
|---|
| 3029 | |
|---|
| 3030 | fn upper_bound(&self) -> Option<usize>; |
|---|
| 3031 | |
|---|
| 3032 | fn size_hint(&self) -> (usize, Option<usize>) { |
|---|
| 3033 | (self.lower_bound(), self.upper_bound()) |
|---|
| 3034 | } |
|---|
| 3035 | } |
|---|
| 3036 | |
|---|
| 3037 | impl<T: ?Sized> SizeHint for T { |
|---|
| 3038 | #[inline ] |
|---|
| 3039 | default fn lower_bound(&self) -> usize { |
|---|
| 3040 | 0 |
|---|
| 3041 | } |
|---|
| 3042 | |
|---|
| 3043 | #[inline ] |
|---|
| 3044 | default fn upper_bound(&self) -> Option<usize> { |
|---|
| 3045 | None |
|---|
| 3046 | } |
|---|
| 3047 | } |
|---|
| 3048 | |
|---|
| 3049 | impl<T> SizeHint for &mut T { |
|---|
| 3050 | #[inline ] |
|---|
| 3051 | fn lower_bound(&self) -> usize { |
|---|
| 3052 | SizeHint::lower_bound(*self) |
|---|
| 3053 | } |
|---|
| 3054 | |
|---|
| 3055 | #[inline ] |
|---|
| 3056 | fn upper_bound(&self) -> Option<usize> { |
|---|
| 3057 | SizeHint::upper_bound(*self) |
|---|
| 3058 | } |
|---|
| 3059 | } |
|---|
| 3060 | |
|---|
| 3061 | impl<T> SizeHint for Box<T> { |
|---|
| 3062 | #[inline ] |
|---|
| 3063 | fn lower_bound(&self) -> usize { |
|---|
| 3064 | SizeHint::lower_bound(&**self) |
|---|
| 3065 | } |
|---|
| 3066 | |
|---|
| 3067 | #[inline ] |
|---|
| 3068 | fn upper_bound(&self) -> Option<usize> { |
|---|
| 3069 | SizeHint::upper_bound(&**self) |
|---|
| 3070 | } |
|---|
| 3071 | } |
|---|
| 3072 | |
|---|
| 3073 | impl SizeHint for &[u8] { |
|---|
| 3074 | #[inline ] |
|---|
| 3075 | fn lower_bound(&self) -> usize { |
|---|
| 3076 | self.len() |
|---|
| 3077 | } |
|---|
| 3078 | |
|---|
| 3079 | #[inline ] |
|---|
| 3080 | fn upper_bound(&self) -> Option<usize> { |
|---|
| 3081 | Some(self.len()) |
|---|
| 3082 | } |
|---|
| 3083 | } |
|---|
| 3084 | |
|---|
| 3085 | /// An iterator over the contents of an instance of `BufRead` split on a |
|---|
| 3086 | /// particular byte. |
|---|
| 3087 | /// |
|---|
| 3088 | /// This struct is generally created by calling [`split`] on a `BufRead`. |
|---|
| 3089 | /// Please see the documentation of [`split`] for more details. |
|---|
| 3090 | /// |
|---|
| 3091 | /// [`split`]: BufRead::split |
|---|
| 3092 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 3093 | #[derive (Debug)] |
|---|
| 3094 | pub struct Split<B> { |
|---|
| 3095 | buf: B, |
|---|
| 3096 | delim: u8, |
|---|
| 3097 | } |
|---|
| 3098 | |
|---|
| 3099 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 3100 | impl<B: BufRead> Iterator for Split<B> { |
|---|
| 3101 | type Item = Result<Vec<u8>>; |
|---|
| 3102 | |
|---|
| 3103 | fn next(&mut self) -> Option<Result<Vec<u8>>> { |
|---|
| 3104 | let mut buf: Vec = Vec::new(); |
|---|
| 3105 | match self.buf.read_until(self.delim, &mut buf) { |
|---|
| 3106 | Ok(0) => None, |
|---|
| 3107 | Ok(_n: usize) => { |
|---|
| 3108 | if buf[buf.len() - 1] == self.delim { |
|---|
| 3109 | buf.pop(); |
|---|
| 3110 | } |
|---|
| 3111 | Some(Ok(buf)) |
|---|
| 3112 | } |
|---|
| 3113 | Err(e: Error) => Some(Err(e)), |
|---|
| 3114 | } |
|---|
| 3115 | } |
|---|
| 3116 | } |
|---|
| 3117 | |
|---|
| 3118 | /// An iterator over the lines of an instance of `BufRead`. |
|---|
| 3119 | /// |
|---|
| 3120 | /// This struct is generally created by calling [`lines`] on a `BufRead`. |
|---|
| 3121 | /// Please see the documentation of [`lines`] for more details. |
|---|
| 3122 | /// |
|---|
| 3123 | /// [`lines`]: BufRead::lines |
|---|
| 3124 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 3125 | #[derive (Debug)] |
|---|
| 3126 | #[cfg_attr (not(test), rustc_diagnostic_item = "IoLines" )] |
|---|
| 3127 | pub struct Lines<B> { |
|---|
| 3128 | buf: B, |
|---|
| 3129 | } |
|---|
| 3130 | |
|---|
| 3131 | #[stable (feature = "rust1" , since = "1.0.0" )] |
|---|
| 3132 | impl<B: BufRead> Iterator for Lines<B> { |
|---|
| 3133 | type Item = Result<String>; |
|---|
| 3134 | |
|---|
| 3135 | fn next(&mut self) -> Option<Result<String>> { |
|---|
| 3136 | let mut buf: String = String::new(); |
|---|
| 3137 | match self.buf.read_line(&mut buf) { |
|---|
| 3138 | Ok(0) => None, |
|---|
| 3139 | Ok(_n: usize) => { |
|---|
| 3140 | if buf.ends_with(' \n' ) { |
|---|
| 3141 | buf.pop(); |
|---|
| 3142 | if buf.ends_with(' \r' ) { |
|---|
| 3143 | buf.pop(); |
|---|
| 3144 | } |
|---|
| 3145 | } |
|---|
| 3146 | Some(Ok(buf)) |
|---|
| 3147 | } |
|---|
| 3148 | Err(e: Error) => Some(Err(e)), |
|---|
| 3149 | } |
|---|
| 3150 | } |
|---|
| 3151 | } |
|---|
| 3152 | |
|---|
