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85aaf69f | 1 | //! Traits, helpers, and type definitions for core I/O functionality. |
c1a9b12d SL |
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 | |
c30ab7b3 | 5 | //! the [`Read`] and [`Write`] traits, which provide the |
c1a9b12d SL |
6 | //! most general interface for reading and writing input and output. |
7 | //! | |
c1a9b12d SL |
8 | //! # Read and Write |
9 | //! | |
c30ab7b3 | 10 | //! Because they are traits, [`Read`] and [`Write`] are implemented by a number |
b039eaaf SL |
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 | |
c30ab7b3 | 13 | //! this module: [`File`]s, [`TcpStream`]s, and sometimes even [`Vec<T>`]s. For |
cc61c64b | 14 | //! example, [`Read`] adds a [`read`][`Read::read`] method, which we can use on |
3b2f2976 | 15 | //! [`File`]s: |
c1a9b12d | 16 | //! |
0531ce1d | 17 | //! ```no_run |
c1a9b12d SL |
18 | //! use std::io; |
19 | //! use std::io::prelude::*; | |
20 | //! use std::fs::File; | |
21 | //! | |
0531ce1d XL |
22 | //! fn main() -> io::Result<()> { |
23 | //! let mut f = File::open("foo.txt")?; | |
24 | //! let mut buffer = [0; 10]; | |
c1a9b12d | 25 | //! |
0531ce1d | 26 | //! // read up to 10 bytes |
532ac7d7 | 27 | //! let n = f.read(&mut buffer)?; |
c1a9b12d | 28 | //! |
532ac7d7 | 29 | //! println!("The bytes: {:?}", &buffer[..n]); |
0531ce1d XL |
30 | //! Ok(()) |
31 | //! } | |
c1a9b12d SL |
32 | //! ``` |
33 | //! | |
c30ab7b3 | 34 | //! [`Read`] and [`Write`] are so important, implementors of the two traits have a |
c1a9b12d | 35 | //! nickname: readers and writers. So you'll sometimes see 'a reader' instead |
c30ab7b3 | 36 | //! of 'a type that implements the [`Read`] trait'. Much easier! |
c1a9b12d SL |
37 | //! |
38 | //! ## Seek and BufRead | |
39 | //! | |
c30ab7b3 SL |
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 | |
c1a9b12d SL |
43 | //! coming from: |
44 | //! | |
0531ce1d | 45 | //! ```no_run |
c1a9b12d SL |
46 | //! use std::io; |
47 | //! use std::io::prelude::*; | |
48 | //! use std::io::SeekFrom; | |
49 | //! use std::fs::File; | |
50 | //! | |
0531ce1d XL |
51 | //! fn main() -> io::Result<()> { |
52 | //! let mut f = File::open("foo.txt")?; | |
53 | //! let mut buffer = [0; 10]; | |
c1a9b12d | 54 | //! |
0531ce1d XL |
55 | //! // skip to the last 10 bytes of the file |
56 | //! f.seek(SeekFrom::End(-10))?; | |
c1a9b12d | 57 | //! |
0531ce1d | 58 | //! // read up to 10 bytes |
532ac7d7 | 59 | //! let n = f.read(&mut buffer)?; |
c1a9b12d | 60 | //! |
532ac7d7 | 61 | //! println!("The bytes: {:?}", &buffer[..n]); |
0531ce1d XL |
62 | //! Ok(()) |
63 | //! } | |
c1a9b12d SL |
64 | //! ``` |
65 | //! | |
c30ab7b3 | 66 | //! [`BufRead`] uses an internal buffer to provide a number of other ways to read, but |
c1a9b12d SL |
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, | |
c30ab7b3 | 73 | //! `std::io` comes with two structs, [`BufReader`] and [`BufWriter`], which wrap |
c1a9b12d SL |
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 | //! | |
c30ab7b3 | 77 | //! For example, [`BufReader`] works with the [`BufRead`] trait to add extra |
c1a9b12d SL |
78 | //! methods to any reader: |
79 | //! | |
0531ce1d | 80 | //! ```no_run |
c1a9b12d SL |
81 | //! use std::io; |
82 | //! use std::io::prelude::*; | |
83 | //! use std::io::BufReader; | |
84 | //! use std::fs::File; | |
85 | //! | |
0531ce1d XL |
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(); | |
c1a9b12d | 90 | //! |
0531ce1d XL |
91 | //! // read a line into buffer |
92 | //! reader.read_line(&mut buffer)?; | |
c1a9b12d | 93 | //! |
0531ce1d XL |
94 | //! println!("{}", buffer); |
95 | //! Ok(()) | |
96 | //! } | |
c1a9b12d SL |
97 | //! ``` |
98 | //! | |
c30ab7b3 | 99 | //! [`BufWriter`] doesn't add any new ways of writing; it just buffers every call |
cc61c64b | 100 | //! to [`write`][`Write::write`]: |
c1a9b12d | 101 | //! |
0531ce1d | 102 | //! ```no_run |
c1a9b12d SL |
103 | //! use std::io; |
104 | //! use std::io::prelude::*; | |
105 | //! use std::io::BufWriter; | |
106 | //! use std::fs::File; | |
107 | //! | |
0531ce1d XL |
108 | //! fn main() -> io::Result<()> { |
109 | //! let f = File::create("foo.txt")?; | |
110 | //! { | |
111 | //! let mut writer = BufWriter::new(f); | |
c1a9b12d | 112 | //! |
0531ce1d XL |
113 | //! // write a byte to the buffer |
114 | //! writer.write(&[42])?; | |
c1a9b12d | 115 | //! |
0531ce1d | 116 | //! } // the buffer is flushed once writer goes out of scope |
c1a9b12d | 117 | //! |
0531ce1d XL |
118 | //! Ok(()) |
119 | //! } | |
c1a9b12d SL |
120 | //! ``` |
121 | //! | |
c1a9b12d SL |
122 | //! ## Standard input and output |
123 | //! | |
124 | //! A very common source of input is standard input: | |
125 | //! | |
0531ce1d | 126 | //! ```no_run |
c1a9b12d SL |
127 | //! use std::io; |
128 | //! | |
0531ce1d XL |
129 | //! fn main() -> io::Result<()> { |
130 | //! let mut input = String::new(); | |
c1a9b12d | 131 | //! |
0531ce1d | 132 | //! io::stdin().read_line(&mut input)?; |
c1a9b12d | 133 | //! |
0531ce1d XL |
134 | //! println!("You typed: {}", input.trim()); |
135 | //! Ok(()) | |
136 | //! } | |
c1a9b12d SL |
137 | //! ``` |
138 | //! | |
3b2f2976 | 139 | //! Note that you cannot use the [`?` operator] in functions that do not return |
94b46f34 | 140 | //! a [`Result<T, E>`][`Result`]. Instead, you can call [`.unwrap()`] |
3b2f2976 | 141 | //! or `match` on the return value to catch any possible errors: |
cc61c64b | 142 | //! |
0531ce1d | 143 | //! ```no_run |
cc61c64b XL |
144 | //! use std::io; |
145 | //! | |
146 | //! let mut input = String::new(); | |
147 | //! | |
148 | //! io::stdin().read_line(&mut input).unwrap(); | |
149 | //! ``` | |
150 | //! | |
c1a9b12d SL |
151 | //! And a very common source of output is standard output: |
152 | //! | |
0531ce1d | 153 | //! ```no_run |
c1a9b12d SL |
154 | //! use std::io; |
155 | //! use std::io::prelude::*; | |
156 | //! | |
0531ce1d XL |
157 | //! fn main() -> io::Result<()> { |
158 | //! io::stdout().write(&[42])?; | |
159 | //! Ok(()) | |
160 | //! } | |
c1a9b12d SL |
161 | //! ``` |
162 | //! | |
cc61c64b | 163 | //! Of course, using [`io::stdout`] directly is less common than something like |
c30ab7b3 | 164 | //! [`println!`]. |
c1a9b12d SL |
165 | //! |
166 | //! ## Iterator types | |
167 | //! | |
168 | //! A large number of the structures provided by `std::io` are for various | |
c30ab7b3 | 169 | //! ways of iterating over I/O. For example, [`Lines`] is used to split over |
c1a9b12d SL |
170 | //! lines: |
171 | //! | |
0531ce1d | 172 | //! ```no_run |
c1a9b12d SL |
173 | //! use std::io; |
174 | //! use std::io::prelude::*; | |
175 | //! use std::io::BufReader; | |
176 | //! use std::fs::File; | |
177 | //! | |
0531ce1d XL |
178 | //! fn main() -> io::Result<()> { |
179 | //! let f = File::open("foo.txt")?; | |
180 | //! let reader = BufReader::new(f); | |
c1a9b12d | 181 | //! |
0531ce1d XL |
182 | //! for line in reader.lines() { |
183 | //! println!("{}", line?); | |
184 | //! } | |
185 | //! Ok(()) | |
c1a9b12d | 186 | //! } |
c1a9b12d SL |
187 | //! ``` |
188 | //! | |
189 | //! ## Functions | |
190 | //! | |
a7813a04 | 191 | //! There are a number of [functions][functions-list] that offer access to various |
c1a9b12d SL |
192 | //! features. For example, we can use three of these functions to copy everything |
193 | //! from standard input to standard output: | |
194 | //! | |
0531ce1d | 195 | //! ```no_run |
c1a9b12d SL |
196 | //! use std::io; |
197 | //! | |
0531ce1d XL |
198 | //! fn main() -> io::Result<()> { |
199 | //! io::copy(&mut io::stdin(), &mut io::stdout())?; | |
200 | //! Ok(()) | |
201 | //! } | |
c1a9b12d SL |
202 | //! ``` |
203 | //! | |
a7813a04 | 204 | //! [functions-list]: #functions-1 |
c1a9b12d SL |
205 | //! |
206 | //! ## io::Result | |
207 | //! | |
c30ab7b3 | 208 | //! Last, but certainly not least, is [`io::Result`]. This type is used |
c1a9b12d SL |
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 | |
32a655c1 | 211 | //! module use the [`?` operator]: |
c1a9b12d SL |
212 | //! |
213 | //! ``` | |
214 | //! use std::io; | |
215 | //! | |
216 | //! fn read_input() -> io::Result<()> { | |
217 | //! let mut input = String::new(); | |
218 | //! | |
32a655c1 | 219 | //! io::stdin().read_line(&mut input)?; |
c1a9b12d SL |
220 | //! |
221 | //! println!("You typed: {}", input.trim()); | |
222 | //! | |
223 | //! Ok(()) | |
224 | //! } | |
225 | //! ``` | |
226 | //! | |
c30ab7b3 SL |
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 | |
b039eaaf | 230 | //! to read the line and print it, so we use `()`. |
c1a9b12d | 231 | //! |
9cc50fc6 SL |
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. | |
c30ab7b3 | 240 | //! |
3dfed10e XL |
241 | //! [`File`]: crate::fs::File |
242 | //! [`TcpStream`]: crate::net::TcpStream | |
3dfed10e XL |
243 | //! [`io::stdout`]: stdout |
244 | //! [`io::Result`]: self::Result | |
0731742a | 245 | //! [`?` operator]: ../../book/appendix-02-operators.html |
3dfed10e XL |
246 | //! [`Result`]: crate::result::Result |
247 | //! [`.unwrap()`]: crate::result::Result::unwrap | |
1a4d82fc | 248 | |
c34b1796 | 249 | #![stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 250 | |
1b1a35ee XL |
251 | #[cfg(test)] |
252 | mod tests; | |
253 | ||
532ac7d7 XL |
254 | use crate::cmp; |
255 | use crate::fmt; | |
532ac7d7 XL |
256 | use crate::memchr; |
257 | use crate::ops::{Deref, DerefMut}; | |
258 | use crate::ptr; | |
60c5eb7d XL |
259 | use crate::slice; |
260 | use crate::str; | |
532ac7d7 | 261 | use crate::sys; |
1a4d82fc | 262 | |
92a42be0 | 263 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 264 | pub use self::buffered::IntoInnerError; |
92a42be0 | 265 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d | 266 | pub use self::buffered::{BufReader, BufWriter, LineWriter}; |
92a42be0 | 267 | #[stable(feature = "rust1", since = "1.0.0")] |
fc512014 XL |
268 | pub use self::copy::copy; |
269 | #[stable(feature = "rust1", since = "1.0.0")] | |
60c5eb7d | 270 | pub use self::cursor::Cursor; |
92a42be0 | 271 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d | 272 | pub use self::error::{Error, ErrorKind, Result}; |
fc512014 XL |
273 | #[unstable(feature = "internal_output_capture", issue = "none")] |
274 | #[doc(no_inline, hidden)] | |
275 | pub use self::stdio::set_output_capture; | |
92a42be0 | 276 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d | 277 | pub use self::stdio::{stderr, stdin, stdout, Stderr, Stdin, Stdout}; |
92a42be0 | 278 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d | 279 | pub use self::stdio::{StderrLock, StdinLock, StdoutLock}; |
dfeec247 | 280 | #[unstable(feature = "print_internals", issue = "none")] |
60c5eb7d | 281 | pub use self::stdio::{_eprint, _print}; |
60c5eb7d | 282 | #[stable(feature = "rust1", since = "1.0.0")] |
fc512014 | 283 | pub use self::util::{empty, repeat, sink, Empty, Repeat, Sink}; |
29967ef6 | 284 | |
1a4d82fc | 285 | mod buffered; |
fc512014 | 286 | pub(crate) mod copy; |
85aaf69f SL |
287 | mod cursor; |
288 | mod error; | |
289 | mod impls; | |
60c5eb7d | 290 | pub mod prelude; |
c34b1796 | 291 | mod stdio; |
60c5eb7d | 292 | mod util; |
1a4d82fc | 293 | |
532ac7d7 | 294 | const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE; |
1a4d82fc | 295 | |
60c5eb7d XL |
296 | struct Guard<'a> { |
297 | buf: &'a mut Vec<u8>, | |
298 | len: usize, | |
299 | } | |
041b39d2 | 300 | |
9fa01778 | 301 | impl Drop for Guard<'_> { |
041b39d2 | 302 | fn drop(&mut self) { |
60c5eb7d XL |
303 | unsafe { |
304 | self.buf.set_len(self.len); | |
305 | } | |
041b39d2 XL |
306 | } |
307 | } | |
308 | ||
85aaf69f SL |
309 | // A few methods below (read_to_string, read_line) will append data into a |
310 | // `String` buffer, but we need to be pretty careful when doing this. The | |
311 | // implementation will just call `.as_mut_vec()` and then delegate to a | |
312 | // byte-oriented reading method, but we must ensure that when returning we never | |
313 | // leave `buf` in a state such that it contains invalid UTF-8 in its bounds. | |
314 | // | |
315 | // To this end, we use an RAII guard (to protect against panics) which updates | |
316 | // the length of the string when it is dropped. This guard initially truncates | |
317 | // the string to the prior length and only after we've validated that the | |
318 | // new contents are valid UTF-8 do we allow it to set a longer length. | |
319 | // | |
320 | // The unsafety in this function is twofold: | |
321 | // | |
322 | // 1. We're looking at the raw bytes of `buf`, so we take on the burden of UTF-8 | |
323 | // checks. | |
324 | // 2. We're passing a raw buffer to the function `f`, and it is expected that | |
325 | // the function only *appends* bytes to the buffer. We'll get undefined | |
326 | // behavior if existing bytes are overwritten to have non-UTF-8 data. | |
c34b1796 | 327 | fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize> |
60c5eb7d XL |
328 | where |
329 | F: FnOnce(&mut Vec<u8>) -> Result<usize>, | |
85aaf69f | 330 | { |
85aaf69f | 331 | unsafe { |
041b39d2 XL |
332 | let mut g = Guard { len: buf.len(), buf: buf.as_mut_vec() }; |
333 | let ret = f(g.buf); | |
334 | if str::from_utf8(&g.buf[g.len..]).is_err() { | |
c34b1796 | 335 | ret.and_then(|_| { |
60c5eb7d | 336 | Err(Error::new(ErrorKind::InvalidData, "stream did not contain valid UTF-8")) |
85aaf69f SL |
337 | }) |
338 | } else { | |
041b39d2 | 339 | g.len = g.buf.len(); |
85aaf69f SL |
340 | ret |
341 | } | |
1a4d82fc JJ |
342 | } |
343 | } | |
344 | ||
c34b1796 AL |
345 | // This uses an adaptive system to extend the vector when it fills. We want to |
346 | // avoid paying to allocate and zero a huge chunk of memory if the reader only | |
347 | // has 4 bytes while still making large reads if the reader does have a ton | |
348 | // of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every | |
b7449926 XL |
349 | // time is 4,500 times (!) slower than a default reservation size of 32 if the |
350 | // reader has a very small amount of data to return. | |
041b39d2 XL |
351 | // |
352 | // Because we're extending the buffer with uninitialized data for trusted | |
353 | // readers, we need to make sure to truncate that if any of this panics. | |
c34b1796 | 354 | fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> { |
e1599b0c | 355 | read_to_end_with_reservation(r, buf, |_| 32) |
b7449926 XL |
356 | } |
357 | ||
e1599b0c XL |
358 | fn read_to_end_with_reservation<R, F>( |
359 | r: &mut R, | |
360 | buf: &mut Vec<u8>, | |
361 | mut reservation_size: F, | |
362 | ) -> Result<usize> | |
363 | where | |
364 | R: Read + ?Sized, | |
365 | F: FnMut(&R) -> usize, | |
b7449926 | 366 | { |
c34b1796 | 367 | let start_len = buf.len(); |
74b04a01 | 368 | let mut g = Guard { len: buf.len(), buf }; |
85aaf69f | 369 | loop { |
041b39d2 | 370 | if g.len == g.buf.len() { |
041b39d2 | 371 | unsafe { |
e1599b0c XL |
372 | // FIXME(danielhenrymantilla): #42788 |
373 | // | |
374 | // - This creates a (mut) reference to a slice of | |
375 | // _uninitialized_ integers, which is **undefined behavior** | |
376 | // | |
377 | // - Only the standard library gets to soundly "ignore" this, | |
378 | // based on its privileged knowledge of unstable rustc | |
379 | // internals; | |
380 | g.buf.reserve(reservation_size(r)); | |
ff7c6d11 XL |
381 | let capacity = g.buf.capacity(); |
382 | g.buf.set_len(capacity); | |
041b39d2 XL |
383 | r.initializer().initialize(&mut g.buf[g.len..]); |
384 | } | |
85aaf69f | 385 | } |
c34b1796 | 386 | |
fc512014 XL |
387 | let buf = &mut g.buf[g.len..]; |
388 | match r.read(buf) { | |
389 | Ok(0) => return Ok(g.len - start_len), | |
390 | Ok(n) => { | |
391 | // We can't allow bogus values from read. If it is too large, the returned vec could have its length | |
392 | // set past its capacity, or if it overflows the vec could be shortened which could create an invalid | |
393 | // string if this is called via read_to_string. | |
394 | assert!(n <= buf.len()); | |
395 | g.len += n; | |
c34b1796 | 396 | } |
85aaf69f | 397 | Err(ref e) if e.kind() == ErrorKind::Interrupted => {} |
fc512014 | 398 | Err(e) => return Err(e), |
85aaf69f | 399 | } |
1a4d82fc JJ |
400 | } |
401 | } | |
402 | ||
48663c56 | 403 | pub(crate) fn default_read_vectored<F>(read: F, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> |
532ac7d7 | 404 | where |
60c5eb7d | 405 | F: FnOnce(&mut [u8]) -> Result<usize>, |
532ac7d7 | 406 | { |
60c5eb7d | 407 | let buf = bufs.iter_mut().find(|b| !b.is_empty()).map_or(&mut [][..], |b| &mut **b); |
532ac7d7 XL |
408 | read(buf) |
409 | } | |
410 | ||
48663c56 | 411 | pub(crate) fn default_write_vectored<F>(write: F, bufs: &[IoSlice<'_>]) -> Result<usize> |
532ac7d7 | 412 | where |
60c5eb7d | 413 | F: FnOnce(&[u8]) -> Result<usize>, |
532ac7d7 | 414 | { |
60c5eb7d | 415 | let buf = bufs.iter().find(|b| !b.is_empty()).map_or(&[][..], |b| &**b); |
532ac7d7 XL |
416 | write(buf) |
417 | } | |
418 | ||
5869c6ff XL |
419 | pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [u8]) -> Result<()> { |
420 | while !buf.is_empty() { | |
421 | match this.read(buf) { | |
422 | Ok(0) => break, | |
423 | Ok(n) => { | |
424 | let tmp = buf; | |
425 | buf = &mut tmp[n..]; | |
426 | } | |
427 | Err(ref e) if e.kind() == ErrorKind::Interrupted => {} | |
428 | Err(e) => return Err(e), | |
429 | } | |
430 | } | |
431 | if !buf.is_empty() { | |
432 | Err(Error::new(ErrorKind::UnexpectedEof, "failed to fill whole buffer")) | |
433 | } else { | |
434 | Ok(()) | |
435 | } | |
436 | } | |
437 | ||
c1a9b12d | 438 | /// The `Read` trait allows for reading bytes from a source. |
85aaf69f | 439 | /// |
041b39d2 | 440 | /// Implementors of the `Read` trait are called 'readers'. |
1a4d82fc | 441 | /// |
3b2f2976 | 442 | /// Readers are defined by one required method, [`read()`]. Each call to [`read()`] |
c1a9b12d | 443 | /// will attempt to pull bytes from this source into a provided buffer. A |
3b2f2976 | 444 | /// number of other methods are implemented in terms of [`read()`], giving |
c1a9b12d SL |
445 | /// implementors a number of ways to read bytes while only needing to implement |
446 | /// a single method. | |
447 | /// | |
448 | /// Readers are intended to be composable with one another. Many implementors | |
3b2f2976 | 449 | /// throughout [`std::io`] take and provide types which implement the `Read` |
c1a9b12d SL |
450 | /// trait. |
451 | /// | |
3b2f2976 XL |
452 | /// Please note that each call to [`read()`] may involve a system call, and |
453 | /// therefore, using something that implements [`BufRead`], such as | |
454 | /// [`BufReader`], will be more efficient. | |
b039eaaf | 455 | /// |
c1a9b12d SL |
456 | /// # Examples |
457 | /// | |
3b2f2976 | 458 | /// [`File`]s implement `Read`: |
c1a9b12d | 459 | /// |
0531ce1d XL |
460 | /// ```no_run |
461 | /// use std::io; | |
c1a9b12d SL |
462 | /// use std::io::prelude::*; |
463 | /// use std::fs::File; | |
464 | /// | |
0531ce1d XL |
465 | /// fn main() -> io::Result<()> { |
466 | /// let mut f = File::open("foo.txt")?; | |
467 | /// let mut buffer = [0; 10]; | |
c1a9b12d | 468 | /// |
0531ce1d XL |
469 | /// // read up to 10 bytes |
470 | /// f.read(&mut buffer)?; | |
c1a9b12d | 471 | /// |
a1dfa0c6 | 472 | /// let mut buffer = Vec::new(); |
0531ce1d XL |
473 | /// // read the whole file |
474 | /// f.read_to_end(&mut buffer)?; | |
c1a9b12d | 475 | /// |
0531ce1d XL |
476 | /// // read into a String, so that you don't need to do the conversion. |
477 | /// let mut buffer = String::new(); | |
478 | /// f.read_to_string(&mut buffer)?; | |
c1a9b12d | 479 | /// |
0531ce1d XL |
480 | /// // and more! See the other methods for more details. |
481 | /// Ok(()) | |
482 | /// } | |
c1a9b12d | 483 | /// ``` |
ff7c6d11 | 484 | /// |
6a06907d | 485 | /// Read from [`&str`] because [`&[u8]`][prim@slice] implements `Read`: |
ff7c6d11 | 486 | /// |
0531ce1d | 487 | /// ```no_run |
ff7c6d11 XL |
488 | /// # use std::io; |
489 | /// use std::io::prelude::*; | |
490 | /// | |
0531ce1d XL |
491 | /// fn main() -> io::Result<()> { |
492 | /// let mut b = "This string will be read".as_bytes(); | |
493 | /// let mut buffer = [0; 10]; | |
ff7c6d11 | 494 | /// |
0531ce1d XL |
495 | /// // read up to 10 bytes |
496 | /// b.read(&mut buffer)?; | |
ff7c6d11 | 497 | /// |
0531ce1d XL |
498 | /// // etc... it works exactly as a File does! |
499 | /// Ok(()) | |
500 | /// } | |
ff7c6d11 XL |
501 | /// ``` |
502 | /// | |
3dfed10e XL |
503 | /// [`read()`]: Read::read |
504 | /// [`&str`]: prim@str | |
505 | /// [`std::io`]: self | |
506 | /// [`File`]: crate::fs::File | |
c34b1796 | 507 | #[stable(feature = "rust1", since = "1.0.0")] |
3dfed10e | 508 | #[doc(spotlight)] |
85aaf69f SL |
509 | pub trait Read { |
510 | /// Pull some bytes from this source into the specified buffer, returning | |
511 | /// how many bytes were read. | |
512 | /// | |
513 | /// This function does not provide any guarantees about whether it blocks | |
ba9703b0 | 514 | /// waiting for data, but if an object needs to block for a read and cannot, |
3b2f2976 | 515 | /// it will typically signal this via an [`Err`] return value. |
85aaf69f | 516 | /// |
6a06907d XL |
517 | /// If the return value of this method is [`Ok(n)`], then implementations must |
518 | /// guarantee that `0 <= n <= buf.len()`. A nonzero `n` value indicates | |
9346a6ac | 519 | /// that the buffer `buf` has been filled in with `n` bytes of data from this |
85aaf69f SL |
520 | /// source. If `n` is `0`, then it can indicate one of two scenarios: |
521 | /// | |
522 | /// 1. This reader has reached its "end of file" and will likely no longer | |
523 | /// be able to produce bytes. Note that this does not mean that the | |
524 | /// reader will *always* no longer be able to produce bytes. | |
525 | /// 2. The buffer specified was 0 bytes in length. | |
526 | /// | |
f9f354fc XL |
527 | /// It is not an error if the returned value `n` is smaller than the buffer size, |
528 | /// even when the reader is not at the end of the stream yet. | |
529 | /// This may happen for example because fewer bytes are actually available right now | |
530 | /// (e. g. being close to end-of-file) or because read() was interrupted by a signal. | |
531 | /// | |
6a06907d XL |
532 | /// As this trait is safe to implement, callers cannot rely on `n <= buf.len()` for safety. |
533 | /// Extra care needs to be taken when `unsafe` functions are used to access the read bytes. | |
534 | /// Callers have to ensure that no unchecked out-of-bounds accesses are possible even if | |
535 | /// `n > buf.len()`. | |
536 | /// | |
85aaf69f SL |
537 | /// No guarantees are provided about the contents of `buf` when this |
538 | /// function is called, implementations cannot rely on any property of the | |
dc9dc135 | 539 | /// contents of `buf` being true. It is recommended that *implementations* |
85aaf69f | 540 | /// only write data to `buf` instead of reading its contents. |
1a4d82fc | 541 | /// |
dc9dc135 XL |
542 | /// Correspondingly, however, *callers* of this method may not assume any guarantees |
543 | /// about how the implementation uses `buf`. The trait is safe to implement, | |
416331ca XL |
544 | /// so it is possible that the code that's supposed to write to the buffer might also read |
545 | /// from it. It is your responsibility to make sure that `buf` is initialized | |
dc9dc135 XL |
546 | /// before calling `read`. Calling `read` with an uninitialized `buf` (of the kind one |
547 | /// obtains via [`MaybeUninit<T>`]) is not safe, and can lead to undefined behavior. | |
548 | /// | |
3dfed10e | 549 | /// [`MaybeUninit<T>`]: crate::mem::MaybeUninit |
dc9dc135 | 550 | /// |
85aaf69f | 551 | /// # Errors |
1a4d82fc | 552 | /// |
85aaf69f SL |
553 | /// If this function encounters any form of I/O or other error, an error |
554 | /// variant will be returned. If an error is returned then it must be | |
555 | /// guaranteed that no bytes were read. | |
c1a9b12d | 556 | /// |
3b2f2976 | 557 | /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the read |
7cac9316 XL |
558 | /// operation should be retried if there is nothing else to do. |
559 | /// | |
c1a9b12d SL |
560 | /// # Examples |
561 | /// | |
3b2f2976 | 562 | /// [`File`]s implement `Read`: |
c1a9b12d | 563 | /// |
3dfed10e XL |
564 | /// [`Ok(n)`]: Ok |
565 | /// [`File`]: crate::fs::File | |
c1a9b12d | 566 | /// |
0531ce1d | 567 | /// ```no_run |
c1a9b12d SL |
568 | /// use std::io; |
569 | /// use std::io::prelude::*; | |
570 | /// use std::fs::File; | |
571 | /// | |
0531ce1d XL |
572 | /// fn main() -> io::Result<()> { |
573 | /// let mut f = File::open("foo.txt")?; | |
574 | /// let mut buffer = [0; 10]; | |
c1a9b12d | 575 | /// |
0531ce1d | 576 | /// // read up to 10 bytes |
532ac7d7 XL |
577 | /// let n = f.read(&mut buffer[..])?; |
578 | /// | |
579 | /// println!("The bytes: {:?}", &buffer[..n]); | |
0531ce1d XL |
580 | /// Ok(()) |
581 | /// } | |
c1a9b12d | 582 | /// ``` |
c34b1796 | 583 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 584 | fn read(&mut self, buf: &mut [u8]) -> Result<usize>; |
1a4d82fc | 585 | |
9fa01778 XL |
586 | /// Like `read`, except that it reads into a slice of buffers. |
587 | /// | |
588 | /// Data is copied to fill each buffer in order, with the final buffer | |
f9f354fc XL |
589 | /// written to possibly being only partially filled. This method must |
590 | /// behave equivalently to a single call to `read` with concatenated | |
591 | /// buffers. | |
9fa01778 | 592 | /// |
532ac7d7 XL |
593 | /// The default implementation calls `read` with either the first nonempty |
594 | /// buffer provided, or an empty one if none exists. | |
48663c56 XL |
595 | #[stable(feature = "iovec", since = "1.36.0")] |
596 | fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> { | |
532ac7d7 | 597 | default_read_vectored(|b| self.read(b), bufs) |
9fa01778 XL |
598 | } |
599 | ||
f9f354fc XL |
600 | /// Determines if this `Read`er has an efficient `read_vectored` |
601 | /// implementation. | |
602 | /// | |
603 | /// If a `Read`er does not override the default `read_vectored` | |
604 | /// implementation, code using it may want to avoid the method all together | |
605 | /// and coalesce writes into a single buffer for higher performance. | |
606 | /// | |
607 | /// The default implementation returns `false`. | |
608 | #[unstable(feature = "can_vector", issue = "69941")] | |
609 | fn is_read_vectored(&self) -> bool { | |
610 | false | |
611 | } | |
612 | ||
041b39d2 XL |
613 | /// Determines if this `Read`er can work with buffers of uninitialized |
614 | /// memory. | |
615 | /// | |
616 | /// The default implementation returns an initializer which will zero | |
617 | /// buffers. | |
618 | /// | |
619 | /// If a `Read`er guarantees that it can work properly with uninitialized | |
3b2f2976 XL |
620 | /// memory, it should call [`Initializer::nop()`]. See the documentation for |
621 | /// [`Initializer`] for details. | |
041b39d2 XL |
622 | /// |
623 | /// The behavior of this method must be independent of the state of the | |
624 | /// `Read`er - the method only takes `&self` so that it can be used through | |
625 | /// trait objects. | |
626 | /// | |
3b2f2976 | 627 | /// # Safety |
041b39d2 XL |
628 | /// |
629 | /// This method is unsafe because a `Read`er could otherwise return a | |
630 | /// non-zeroing `Initializer` from another `Read` type without an `unsafe` | |
631 | /// block. | |
632 | #[unstable(feature = "read_initializer", issue = "42788")] | |
633 | #[inline] | |
634 | unsafe fn initializer(&self) -> Initializer { | |
635 | Initializer::zeroing() | |
636 | } | |
637 | ||
85aaf69f | 638 | /// Read all bytes until EOF in this source, placing them into `buf`. |
1a4d82fc | 639 | /// |
85aaf69f | 640 | /// All bytes read from this source will be appended to the specified buffer |
3b2f2976 XL |
641 | /// `buf`. This function will continuously call [`read()`] to append more data to |
642 | /// `buf` until [`read()`] returns either [`Ok(0)`] or an error of | |
643 | /// non-[`ErrorKind::Interrupted`] kind. | |
1a4d82fc | 644 | /// |
9346a6ac | 645 | /// If successful, this function will return the total number of bytes read. |
1a4d82fc | 646 | /// |
85aaf69f | 647 | /// # Errors |
1a4d82fc | 648 | /// |
85aaf69f | 649 | /// If this function encounters an error of the kind |
3b2f2976 | 650 | /// [`ErrorKind::Interrupted`] then the error is ignored and the operation |
85aaf69f | 651 | /// will continue. |
1a4d82fc | 652 | /// |
85aaf69f SL |
653 | /// If any other read error is encountered then this function immediately |
654 | /// returns. Any bytes which have already been read will be appended to | |
655 | /// `buf`. | |
c1a9b12d SL |
656 | /// |
657 | /// # Examples | |
658 | /// | |
3b2f2976 | 659 | /// [`File`]s implement `Read`: |
c1a9b12d | 660 | /// |
3dfed10e XL |
661 | /// [`read()`]: Read::read |
662 | /// [`Ok(0)`]: Ok | |
663 | /// [`File`]: crate::fs::File | |
c1a9b12d | 664 | /// |
0531ce1d | 665 | /// ```no_run |
c1a9b12d SL |
666 | /// use std::io; |
667 | /// use std::io::prelude::*; | |
668 | /// use std::fs::File; | |
669 | /// | |
0531ce1d XL |
670 | /// fn main() -> io::Result<()> { |
671 | /// let mut f = File::open("foo.txt")?; | |
672 | /// let mut buffer = Vec::new(); | |
c1a9b12d | 673 | /// |
0531ce1d XL |
674 | /// // read the whole file |
675 | /// f.read_to_end(&mut buffer)?; | |
676 | /// Ok(()) | |
677 | /// } | |
c1a9b12d | 678 | /// ``` |
83c7162d XL |
679 | /// |
680 | /// (See also the [`std::fs::read`] convenience function for reading from a | |
681 | /// file.) | |
682 | /// | |
3dfed10e | 683 | /// [`std::fs::read`]: crate::fs::read |
c34b1796 AL |
684 | #[stable(feature = "rust1", since = "1.0.0")] |
685 | fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> { | |
85aaf69f | 686 | read_to_end(self, buf) |
1a4d82fc JJ |
687 | } |
688 | ||
2c00a5a8 | 689 | /// Read all bytes until EOF in this source, appending them to `buf`. |
1a4d82fc | 690 | /// |
c34b1796 AL |
691 | /// If successful, this function returns the number of bytes which were read |
692 | /// and appended to `buf`. | |
693 | /// | |
85aaf69f | 694 | /// # Errors |
1a4d82fc | 695 | /// |
85aaf69f SL |
696 | /// If the data in this stream is *not* valid UTF-8 then an error is |
697 | /// returned and `buf` is unchanged. | |
1a4d82fc | 698 | /// |
3dfed10e | 699 | /// See [`read_to_end`] for other error semantics. |
c1a9b12d | 700 | /// |
3dfed10e | 701 | /// [`read_to_end`]: Read::read_to_end |
c1a9b12d SL |
702 | /// |
703 | /// # Examples | |
704 | /// | |
3dfed10e | 705 | /// [`File`]s implement `Read`: |
c1a9b12d | 706 | /// |
3dfed10e | 707 | /// [`File`]: crate::fs::File |
c1a9b12d | 708 | /// |
0531ce1d | 709 | /// ```no_run |
c1a9b12d SL |
710 | /// use std::io; |
711 | /// use std::io::prelude::*; | |
712 | /// use std::fs::File; | |
713 | /// | |
0531ce1d XL |
714 | /// fn main() -> io::Result<()> { |
715 | /// let mut f = File::open("foo.txt")?; | |
716 | /// let mut buffer = String::new(); | |
c1a9b12d | 717 | /// |
0531ce1d XL |
718 | /// f.read_to_string(&mut buffer)?; |
719 | /// Ok(()) | |
720 | /// } | |
c1a9b12d | 721 | /// ``` |
83c7162d XL |
722 | /// |
723 | /// (See also the [`std::fs::read_to_string`] convenience function for | |
724 | /// reading from a file.) | |
725 | /// | |
3dfed10e | 726 | /// [`std::fs::read_to_string`]: crate::fs::read_to_string |
c34b1796 AL |
727 | #[stable(feature = "rust1", since = "1.0.0")] |
728 | fn read_to_string(&mut self, buf: &mut String) -> Result<usize> { | |
85aaf69f SL |
729 | // Note that we do *not* call `.read_to_end()` here. We are passing |
730 | // `&mut Vec<u8>` (the raw contents of `buf`) into the `read_to_end` | |
731 | // method to fill it up. An arbitrary implementation could overwrite the | |
732 | // entire contents of the vector, not just append to it (which is what | |
733 | // we are expecting). | |
734 | // | |
735 | // To prevent extraneously checking the UTF-8-ness of the entire buffer | |
736 | // we pass it to our hardcoded `read_to_end` implementation which we | |
737 | // know is guaranteed to only read data into the end of the buffer. | |
738 | append_to_string(buf, |b| read_to_end(self, b)) | |
1a4d82fc JJ |
739 | } |
740 | ||
e9174d1e SL |
741 | /// Read the exact number of bytes required to fill `buf`. |
742 | /// | |
743 | /// This function reads as many bytes as necessary to completely fill the | |
744 | /// specified buffer `buf`. | |
745 | /// | |
746 | /// No guarantees are provided about the contents of `buf` when this | |
747 | /// function is called, implementations cannot rely on any property of the | |
748 | /// contents of `buf` being true. It is recommended that implementations | |
3dfed10e XL |
749 | /// only write data to `buf` instead of reading its contents. The |
750 | /// documentation on [`read`] has a more detailed explanation on this | |
751 | /// subject. | |
e9174d1e SL |
752 | /// |
753 | /// # Errors | |
754 | /// | |
755 | /// If this function encounters an error of the kind | |
3b2f2976 | 756 | /// [`ErrorKind::Interrupted`] then the error is ignored and the operation |
e9174d1e SL |
757 | /// will continue. |
758 | /// | |
759 | /// If this function encounters an "end of file" before completely filling | |
3b2f2976 | 760 | /// the buffer, it returns an error of the kind [`ErrorKind::UnexpectedEof`]. |
e9174d1e SL |
761 | /// The contents of `buf` are unspecified in this case. |
762 | /// | |
763 | /// If any other read error is encountered then this function immediately | |
764 | /// returns. The contents of `buf` are unspecified in this case. | |
765 | /// | |
766 | /// If this function returns an error, it is unspecified how many bytes it | |
767 | /// has read, but it will never read more than would be necessary to | |
768 | /// completely fill the buffer. | |
769 | /// | |
770 | /// # Examples | |
771 | /// | |
3b2f2976 | 772 | /// [`File`]s implement `Read`: |
e9174d1e | 773 | /// |
3dfed10e XL |
774 | /// [`read`]: Read::read |
775 | /// [`File`]: crate::fs::File | |
e9174d1e | 776 | /// |
0531ce1d | 777 | /// ```no_run |
e9174d1e SL |
778 | /// use std::io; |
779 | /// use std::io::prelude::*; | |
780 | /// use std::fs::File; | |
781 | /// | |
0531ce1d XL |
782 | /// fn main() -> io::Result<()> { |
783 | /// let mut f = File::open("foo.txt")?; | |
784 | /// let mut buffer = [0; 10]; | |
e9174d1e | 785 | /// |
0531ce1d XL |
786 | /// // read exactly 10 bytes |
787 | /// f.read_exact(&mut buffer)?; | |
788 | /// Ok(()) | |
789 | /// } | |
e9174d1e | 790 | /// ``` |
92a42be0 | 791 | #[stable(feature = "read_exact", since = "1.6.0")] |
5869c6ff XL |
792 | fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> { |
793 | default_read_exact(self, buf) | |
e9174d1e SL |
794 | } |
795 | ||
9346a6ac | 796 | /// Creates a "by reference" adaptor for this instance of `Read`. |
1a4d82fc | 797 | /// |
85aaf69f SL |
798 | /// The returned adaptor also implements `Read` and will simply borrow this |
799 | /// current reader. | |
c1a9b12d SL |
800 | /// |
801 | /// # Examples | |
802 | /// | |
3dfed10e | 803 | /// [`File`]s implement `Read`: |
c1a9b12d | 804 | /// |
3dfed10e | 805 | /// [`File`]: crate::fs::File |
c1a9b12d | 806 | /// |
0531ce1d | 807 | /// ```no_run |
c1a9b12d SL |
808 | /// use std::io; |
809 | /// use std::io::Read; | |
810 | /// use std::fs::File; | |
811 | /// | |
0531ce1d XL |
812 | /// fn main() -> io::Result<()> { |
813 | /// let mut f = File::open("foo.txt")?; | |
814 | /// let mut buffer = Vec::new(); | |
815 | /// let mut other_buffer = Vec::new(); | |
c1a9b12d | 816 | /// |
0531ce1d XL |
817 | /// { |
818 | /// let reference = f.by_ref(); | |
c1a9b12d | 819 | /// |
0531ce1d XL |
820 | /// // read at most 5 bytes |
821 | /// reference.take(5).read_to_end(&mut buffer)?; | |
c1a9b12d | 822 | /// |
0531ce1d | 823 | /// } // drop our &mut reference so we can use f again |
c1a9b12d | 824 | /// |
0531ce1d XL |
825 | /// // original file still usable, read the rest |
826 | /// f.read_to_end(&mut other_buffer)?; | |
827 | /// Ok(()) | |
828 | /// } | |
c1a9b12d | 829 | /// ``` |
c34b1796 | 830 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
831 | fn by_ref(&mut self) -> &mut Self |
832 | where | |
833 | Self: Sized, | |
834 | { | |
835 | self | |
836 | } | |
1a4d82fc | 837 | |
3b2f2976 | 838 | /// Transforms this `Read` instance to an [`Iterator`] over its bytes. |
1a4d82fc | 839 | /// |
abe05a73 XL |
840 | /// The returned type implements [`Iterator`] where the `Item` is |
841 | /// [`Result`]`<`[`u8`]`, `[`io::Error`]`>`. | |
842 | /// The yielded item is [`Ok`] if a byte was successfully read and [`Err`] | |
843 | /// otherwise. EOF is mapped to returning [`None`] from this iterator. | |
c1a9b12d SL |
844 | /// |
845 | /// # Examples | |
846 | /// | |
3dfed10e | 847 | /// [`File`]s implement `Read`: |
c1a9b12d | 848 | /// |
3dfed10e XL |
849 | /// [`File`]: crate::fs::File |
850 | /// [`Result`]: crate::result::Result | |
851 | /// [`io::Error`]: self::Error | |
c1a9b12d | 852 | /// |
0531ce1d | 853 | /// ```no_run |
c1a9b12d SL |
854 | /// use std::io; |
855 | /// use std::io::prelude::*; | |
856 | /// use std::fs::File; | |
857 | /// | |
0531ce1d XL |
858 | /// fn main() -> io::Result<()> { |
859 | /// let mut f = File::open("foo.txt")?; | |
c1a9b12d | 860 | /// |
0531ce1d XL |
861 | /// for byte in f.bytes() { |
862 | /// println!("{}", byte.unwrap()); | |
863 | /// } | |
864 | /// Ok(()) | |
c1a9b12d | 865 | /// } |
c1a9b12d | 866 | /// ``` |
c34b1796 | 867 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
868 | fn bytes(self) -> Bytes<Self> |
869 | where | |
870 | Self: Sized, | |
871 | { | |
85aaf69f | 872 | Bytes { inner: self } |
1a4d82fc JJ |
873 | } |
874 | ||
9346a6ac | 875 | /// Creates an adaptor which will chain this stream with another. |
1a4d82fc | 876 | /// |
85aaf69f SL |
877 | /// The returned `Read` instance will first read all bytes from this object |
878 | /// until EOF is encountered. Afterwards the output is equivalent to the | |
879 | /// output of `next`. | |
c1a9b12d SL |
880 | /// |
881 | /// # Examples | |
882 | /// | |
3dfed10e | 883 | /// [`File`]s implement `Read`: |
c1a9b12d | 884 | /// |
3dfed10e | 885 | /// [`File`]: crate::fs::File |
c1a9b12d | 886 | /// |
0531ce1d | 887 | /// ```no_run |
c1a9b12d SL |
888 | /// use std::io; |
889 | /// use std::io::prelude::*; | |
890 | /// use std::fs::File; | |
891 | /// | |
0531ce1d XL |
892 | /// fn main() -> io::Result<()> { |
893 | /// let mut f1 = File::open("foo.txt")?; | |
894 | /// let mut f2 = File::open("bar.txt")?; | |
c1a9b12d | 895 | /// |
0531ce1d XL |
896 | /// let mut handle = f1.chain(f2); |
897 | /// let mut buffer = String::new(); | |
c1a9b12d | 898 | /// |
0531ce1d XL |
899 | /// // read the value into a String. We could use any Read method here, |
900 | /// // this is just one example. | |
901 | /// handle.read_to_string(&mut buffer)?; | |
902 | /// Ok(()) | |
903 | /// } | |
c1a9b12d | 904 | /// ``` |
c34b1796 | 905 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
906 | fn chain<R: Read>(self, next: R) -> Chain<Self, R> |
907 | where | |
908 | Self: Sized, | |
909 | { | |
85aaf69f | 910 | Chain { first: self, second: next, done_first: false } |
1a4d82fc JJ |
911 | } |
912 | ||
9346a6ac | 913 | /// Creates an adaptor which will read at most `limit` bytes from it. |
1a4d82fc | 914 | /// |
85aaf69f | 915 | /// This function returns a new instance of `Read` which will read at most |
3b2f2976 | 916 | /// `limit` bytes, after which it will always return EOF ([`Ok(0)`]). Any |
85aaf69f | 917 | /// read errors will not count towards the number of bytes read and future |
3b2f2976 | 918 | /// calls to [`read()`] may succeed. |
c1a9b12d SL |
919 | /// |
920 | /// # Examples | |
921 | /// | |
3b2f2976 | 922 | /// [`File`]s implement `Read`: |
c1a9b12d | 923 | /// |
3dfed10e XL |
924 | /// [`File`]: crate::fs::File |
925 | /// [`Ok(0)`]: Ok | |
926 | /// [`read()`]: Read::read | |
c1a9b12d | 927 | /// |
0531ce1d | 928 | /// ```no_run |
c1a9b12d SL |
929 | /// use std::io; |
930 | /// use std::io::prelude::*; | |
931 | /// use std::fs::File; | |
932 | /// | |
0531ce1d XL |
933 | /// fn main() -> io::Result<()> { |
934 | /// let mut f = File::open("foo.txt")?; | |
935 | /// let mut buffer = [0; 5]; | |
c1a9b12d | 936 | /// |
0531ce1d XL |
937 | /// // read at most five bytes |
938 | /// let mut handle = f.take(5); | |
c1a9b12d | 939 | /// |
0531ce1d XL |
940 | /// handle.read(&mut buffer)?; |
941 | /// Ok(()) | |
942 | /// } | |
c1a9b12d | 943 | /// ``` |
c34b1796 | 944 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
945 | fn take(self, limit: u64) -> Take<Self> |
946 | where | |
947 | Self: Sized, | |
948 | { | |
74b04a01 | 949 | Take { inner: self, limit } |
1a4d82fc | 950 | } |
85aaf69f | 951 | } |
1a4d82fc | 952 | |
5869c6ff XL |
953 | /// Read all bytes from a [reader][Read] into a new [`String`]. |
954 | /// | |
955 | /// This is a convenience function for [`Read::read_to_string`]. Using this | |
956 | /// function avoids having to create a variable first and provides more type | |
957 | /// safety since you can only get the buffer out if there were no errors. (If you | |
958 | /// use [`Read::read_to_string`] you have to remember to check whether the read | |
959 | /// succeeded because otherwise your buffer will be empty or only partially full.) | |
960 | /// | |
961 | /// # Performance | |
962 | /// | |
963 | /// The downside of this function's increased ease of use and type safety is | |
964 | /// that it gives you less control over performance. For example, you can't | |
965 | /// pre-allocate memory like you can using [`String::with_capacity`] and | |
966 | /// [`Read::read_to_string`]. Also, you can't re-use the buffer if an error | |
967 | /// occurs while reading. | |
968 | /// | |
969 | /// In many cases, this function's performance will be adequate and the ease of use | |
970 | /// and type safety tradeoffs will be worth it. However, there are cases where you | |
971 | /// need more control over performance, and in those cases you should definitely use | |
972 | /// [`Read::read_to_string`] directly. | |
973 | /// | |
974 | /// # Errors | |
975 | /// | |
976 | /// This function forces you to handle errors because the output (the `String`) | |
977 | /// is wrapped in a [`Result`]. See [`Read::read_to_string`] for the errors | |
978 | /// that can occur. If any error occurs, you will get an [`Err`], so you | |
979 | /// don't have to worry about your buffer being empty or partially full. | |
980 | /// | |
981 | /// # Examples | |
982 | /// | |
983 | /// ```no_run | |
984 | /// #![feature(io_read_to_string)] | |
985 | /// | |
986 | /// # use std::io; | |
987 | /// fn main() -> io::Result<()> { | |
988 | /// let stdin = io::read_to_string(&mut io::stdin())?; | |
989 | /// println!("Stdin was:"); | |
990 | /// println!("{}", stdin); | |
991 | /// Ok(()) | |
992 | /// } | |
993 | /// ``` | |
994 | #[unstable(feature = "io_read_to_string", issue = "80218")] | |
995 | pub fn read_to_string<R: Read>(reader: &mut R) -> Result<String> { | |
996 | let mut buf = String::new(); | |
997 | reader.read_to_string(&mut buf)?; | |
998 | Ok(buf) | |
999 | } | |
1000 | ||
9fa01778 XL |
1001 | /// A buffer type used with `Read::read_vectored`. |
1002 | /// | |
1003 | /// It is semantically a wrapper around an `&mut [u8]`, but is guaranteed to be | |
1004 | /// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on | |
1005 | /// Windows. | |
48663c56 | 1006 | #[stable(feature = "iovec", since = "1.36.0")] |
9fa01778 | 1007 | #[repr(transparent)] |
48663c56 | 1008 | pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>); |
9fa01778 | 1009 | |
ba9703b0 XL |
1010 | #[stable(feature = "iovec-send-sync", since = "1.44.0")] |
1011 | unsafe impl<'a> Send for IoSliceMut<'a> {} | |
1012 | ||
1013 | #[stable(feature = "iovec-send-sync", since = "1.44.0")] | |
1014 | unsafe impl<'a> Sync for IoSliceMut<'a> {} | |
1015 | ||
48663c56 XL |
1016 | #[stable(feature = "iovec", since = "1.36.0")] |
1017 | impl<'a> fmt::Debug for IoSliceMut<'a> { | |
532ac7d7 | 1018 | fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { |
9fa01778 XL |
1019 | fmt::Debug::fmt(self.0.as_slice(), fmt) |
1020 | } | |
1021 | } | |
1022 | ||
48663c56 XL |
1023 | impl<'a> IoSliceMut<'a> { |
1024 | /// Creates a new `IoSliceMut` wrapping a byte slice. | |
9fa01778 XL |
1025 | /// |
1026 | /// # Panics | |
1027 | /// | |
1028 | /// Panics on Windows if the slice is larger than 4GB. | |
48663c56 | 1029 | #[stable(feature = "iovec", since = "1.36.0")] |
9fa01778 | 1030 | #[inline] |
48663c56 XL |
1031 | pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> { |
1032 | IoSliceMut(sys::io::IoSliceMut::new(buf)) | |
9fa01778 | 1033 | } |
416331ca XL |
1034 | |
1035 | /// Advance the internal cursor of the slice. | |
1036 | /// | |
1037 | /// # Notes | |
1038 | /// | |
1039 | /// Elements in the slice may be modified if the cursor is not advanced to | |
1040 | /// the end of the slice. For example if we have a slice of buffers with 2 | |
1041 | /// `IoSliceMut`s, both of length 8, and we advance the cursor by 10 bytes | |
1042 | /// the first `IoSliceMut` will be untouched however the second will be | |
1043 | /// modified to remove the first 2 bytes (10 - 8). | |
1044 | /// | |
1045 | /// # Examples | |
1046 | /// | |
1047 | /// ``` | |
1048 | /// #![feature(io_slice_advance)] | |
1049 | /// | |
1050 | /// use std::io::IoSliceMut; | |
416331ca XL |
1051 | /// use std::ops::Deref; |
1052 | /// | |
1053 | /// let mut buf1 = [1; 8]; | |
1054 | /// let mut buf2 = [2; 16]; | |
1055 | /// let mut buf3 = [3; 8]; | |
1056 | /// let mut bufs = &mut [ | |
1057 | /// IoSliceMut::new(&mut buf1), | |
1058 | /// IoSliceMut::new(&mut buf2), | |
1059 | /// IoSliceMut::new(&mut buf3), | |
1060 | /// ][..]; | |
1061 | /// | |
1062 | /// // Mark 10 bytes as read. | |
60c5eb7d | 1063 | /// bufs = IoSliceMut::advance(bufs, 10); |
416331ca XL |
1064 | /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); |
1065 | /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); | |
1066 | /// ``` | |
1067 | #[unstable(feature = "io_slice_advance", issue = "62726")] | |
1068 | #[inline] | |
1069 | pub fn advance<'b>(bufs: &'b mut [IoSliceMut<'a>], n: usize) -> &'b mut [IoSliceMut<'a>] { | |
1070 | // Number of buffers to remove. | |
1071 | let mut remove = 0; | |
1072 | // Total length of all the to be removed buffers. | |
1073 | let mut accumulated_len = 0; | |
1074 | for buf in bufs.iter() { | |
1075 | if accumulated_len + buf.len() > n { | |
1076 | break; | |
1077 | } else { | |
1078 | accumulated_len += buf.len(); | |
1079 | remove += 1; | |
1080 | } | |
1081 | } | |
1082 | ||
1083 | let bufs = &mut bufs[remove..]; | |
1084 | if !bufs.is_empty() { | |
1085 | bufs[0].0.advance(n - accumulated_len) | |
1086 | } | |
1087 | bufs | |
1088 | } | |
9fa01778 XL |
1089 | } |
1090 | ||
48663c56 XL |
1091 | #[stable(feature = "iovec", since = "1.36.0")] |
1092 | impl<'a> Deref for IoSliceMut<'a> { | |
9fa01778 XL |
1093 | type Target = [u8]; |
1094 | ||
1095 | #[inline] | |
1096 | fn deref(&self) -> &[u8] { | |
1097 | self.0.as_slice() | |
1098 | } | |
1099 | } | |
1100 | ||
48663c56 XL |
1101 | #[stable(feature = "iovec", since = "1.36.0")] |
1102 | impl<'a> DerefMut for IoSliceMut<'a> { | |
9fa01778 XL |
1103 | #[inline] |
1104 | fn deref_mut(&mut self) -> &mut [u8] { | |
1105 | self.0.as_mut_slice() | |
1106 | } | |
1107 | } | |
1108 | ||
1109 | /// A buffer type used with `Write::write_vectored`. | |
1110 | /// | |
1111 | /// It is semantically a wrapper around an `&[u8]`, but is guaranteed to be | |
1112 | /// ABI compatible with the `iovec` type on Unix platforms and `WSABUF` on | |
1113 | /// Windows. | |
48663c56 | 1114 | #[stable(feature = "iovec", since = "1.36.0")] |
ba9703b0 | 1115 | #[derive(Copy, Clone)] |
9fa01778 | 1116 | #[repr(transparent)] |
48663c56 | 1117 | pub struct IoSlice<'a>(sys::io::IoSlice<'a>); |
9fa01778 | 1118 | |
ba9703b0 XL |
1119 | #[stable(feature = "iovec-send-sync", since = "1.44.0")] |
1120 | unsafe impl<'a> Send for IoSlice<'a> {} | |
1121 | ||
1122 | #[stable(feature = "iovec-send-sync", since = "1.44.0")] | |
1123 | unsafe impl<'a> Sync for IoSlice<'a> {} | |
1124 | ||
48663c56 XL |
1125 | #[stable(feature = "iovec", since = "1.36.0")] |
1126 | impl<'a> fmt::Debug for IoSlice<'a> { | |
532ac7d7 | 1127 | fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { |
9fa01778 XL |
1128 | fmt::Debug::fmt(self.0.as_slice(), fmt) |
1129 | } | |
1130 | } | |
1131 | ||
48663c56 XL |
1132 | impl<'a> IoSlice<'a> { |
1133 | /// Creates a new `IoSlice` wrapping a byte slice. | |
9fa01778 XL |
1134 | /// |
1135 | /// # Panics | |
1136 | /// | |
1137 | /// Panics on Windows if the slice is larger than 4GB. | |
48663c56 | 1138 | #[stable(feature = "iovec", since = "1.36.0")] |
9fa01778 | 1139 | #[inline] |
48663c56 XL |
1140 | pub fn new(buf: &'a [u8]) -> IoSlice<'a> { |
1141 | IoSlice(sys::io::IoSlice::new(buf)) | |
9fa01778 | 1142 | } |
416331ca XL |
1143 | |
1144 | /// Advance the internal cursor of the slice. | |
1145 | /// | |
1146 | /// # Notes | |
1147 | /// | |
1148 | /// Elements in the slice may be modified if the cursor is not advanced to | |
1149 | /// the end of the slice. For example if we have a slice of buffers with 2 | |
1150 | /// `IoSlice`s, both of length 8, and we advance the cursor by 10 bytes the | |
1151 | /// first `IoSlice` will be untouched however the second will be modified to | |
1152 | /// remove the first 2 bytes (10 - 8). | |
1153 | /// | |
1154 | /// # Examples | |
1155 | /// | |
1156 | /// ``` | |
1157 | /// #![feature(io_slice_advance)] | |
1158 | /// | |
1159 | /// use std::io::IoSlice; | |
416331ca XL |
1160 | /// use std::ops::Deref; |
1161 | /// | |
60c5eb7d XL |
1162 | /// let buf1 = [1; 8]; |
1163 | /// let buf2 = [2; 16]; | |
1164 | /// let buf3 = [3; 8]; | |
416331ca | 1165 | /// let mut bufs = &mut [ |
60c5eb7d XL |
1166 | /// IoSlice::new(&buf1), |
1167 | /// IoSlice::new(&buf2), | |
1168 | /// IoSlice::new(&buf3), | |
416331ca XL |
1169 | /// ][..]; |
1170 | /// | |
1171 | /// // Mark 10 bytes as written. | |
60c5eb7d | 1172 | /// bufs = IoSlice::advance(bufs, 10); |
416331ca XL |
1173 | /// assert_eq!(bufs[0].deref(), [2; 14].as_ref()); |
1174 | /// assert_eq!(bufs[1].deref(), [3; 8].as_ref()); | |
1175 | #[unstable(feature = "io_slice_advance", issue = "62726")] | |
1176 | #[inline] | |
1177 | pub fn advance<'b>(bufs: &'b mut [IoSlice<'a>], n: usize) -> &'b mut [IoSlice<'a>] { | |
1178 | // Number of buffers to remove. | |
1179 | let mut remove = 0; | |
1180 | // Total length of all the to be removed buffers. | |
1181 | let mut accumulated_len = 0; | |
1182 | for buf in bufs.iter() { | |
1183 | if accumulated_len + buf.len() > n { | |
1184 | break; | |
1185 | } else { | |
1186 | accumulated_len += buf.len(); | |
1187 | remove += 1; | |
1188 | } | |
1189 | } | |
1190 | ||
1191 | let bufs = &mut bufs[remove..]; | |
1192 | if !bufs.is_empty() { | |
1193 | bufs[0].0.advance(n - accumulated_len) | |
1194 | } | |
1195 | bufs | |
1196 | } | |
9fa01778 XL |
1197 | } |
1198 | ||
48663c56 XL |
1199 | #[stable(feature = "iovec", since = "1.36.0")] |
1200 | impl<'a> Deref for IoSlice<'a> { | |
9fa01778 XL |
1201 | type Target = [u8]; |
1202 | ||
1203 | #[inline] | |
1204 | fn deref(&self) -> &[u8] { | |
1205 | self.0.as_slice() | |
1206 | } | |
1207 | } | |
1208 | ||
041b39d2 XL |
1209 | /// A type used to conditionally initialize buffers passed to `Read` methods. |
1210 | #[unstable(feature = "read_initializer", issue = "42788")] | |
1211 | #[derive(Debug)] | |
1212 | pub struct Initializer(bool); | |
1213 | ||
1214 | impl Initializer { | |
1215 | /// Returns a new `Initializer` which will zero out buffers. | |
1216 | #[unstable(feature = "read_initializer", issue = "42788")] | |
1217 | #[inline] | |
1218 | pub fn zeroing() -> Initializer { | |
1219 | Initializer(true) | |
1220 | } | |
1221 | ||
1222 | /// Returns a new `Initializer` which will not zero out buffers. | |
1223 | /// | |
3b2f2976 | 1224 | /// # Safety |
041b39d2 XL |
1225 | /// |
1226 | /// This may only be called by `Read`ers which guarantee that they will not | |
1227 | /// read from buffers passed to `Read` methods, and that the return value of | |
1228 | /// the method accurately reflects the number of bytes that have been | |
1229 | /// written to the head of the buffer. | |
1230 | #[unstable(feature = "read_initializer", issue = "42788")] | |
1231 | #[inline] | |
1232 | pub unsafe fn nop() -> Initializer { | |
1233 | Initializer(false) | |
1234 | } | |
1235 | ||
1236 | /// Indicates if a buffer should be initialized. | |
1237 | #[unstable(feature = "read_initializer", issue = "42788")] | |
1238 | #[inline] | |
1239 | pub fn should_initialize(&self) -> bool { | |
1240 | self.0 | |
1241 | } | |
1242 | ||
1243 | /// Initializes a buffer if necessary. | |
1244 | #[unstable(feature = "read_initializer", issue = "42788")] | |
1245 | #[inline] | |
1246 | pub fn initialize(&self, buf: &mut [u8]) { | |
1247 | if self.should_initialize() { | |
1248 | unsafe { ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len()) } | |
1249 | } | |
1250 | } | |
1251 | } | |
1252 | ||
85aaf69f SL |
1253 | /// A trait for objects which are byte-oriented sinks. |
1254 | /// | |
c1a9b12d SL |
1255 | /// Implementors of the `Write` trait are sometimes called 'writers'. |
1256 | /// | |
cc61c64b | 1257 | /// Writers are defined by two required methods, [`write`] and [`flush`]: |
c1a9b12d | 1258 | /// |
cc61c64b | 1259 | /// * The [`write`] method will attempt to write some data into the object, |
c1a9b12d SL |
1260 | /// returning how many bytes were successfully written. |
1261 | /// | |
cc61c64b | 1262 | /// * The [`flush`] method is useful for adaptors and explicit buffers |
c1a9b12d SL |
1263 | /// themselves for ensuring that all buffered data has been pushed out to the |
1264 | /// 'true sink'. | |
1265 | /// | |
1266 | /// Writers are intended to be composable with one another. Many implementors | |
476ff2be | 1267 | /// throughout [`std::io`] take and provide types which implement the `Write` |
c1a9b12d SL |
1268 | /// trait. |
1269 | /// | |
3dfed10e XL |
1270 | /// [`write`]: Write::write |
1271 | /// [`flush`]: Write::flush | |
1272 | /// [`std::io`]: self | |
476ff2be | 1273 | /// |
c1a9b12d SL |
1274 | /// # Examples |
1275 | /// | |
0531ce1d | 1276 | /// ```no_run |
c1a9b12d SL |
1277 | /// use std::io::prelude::*; |
1278 | /// use std::fs::File; | |
85aaf69f | 1279 | /// |
0531ce1d | 1280 | /// fn main() -> std::io::Result<()> { |
532ac7d7 XL |
1281 | /// let data = b"some bytes"; |
1282 | /// | |
1283 | /// let mut pos = 0; | |
0531ce1d | 1284 | /// let mut buffer = File::create("foo.txt")?; |
85aaf69f | 1285 | /// |
532ac7d7 XL |
1286 | /// while pos < data.len() { |
1287 | /// let bytes_written = buffer.write(&data[pos..])?; | |
1288 | /// pos += bytes_written; | |
1289 | /// } | |
0531ce1d XL |
1290 | /// Ok(()) |
1291 | /// } | |
c1a9b12d | 1292 | /// ``` |
532ac7d7 XL |
1293 | /// |
1294 | /// The trait also provides convenience methods like [`write_all`], which calls | |
1295 | /// `write` in a loop until its entire input has been written. | |
1296 | /// | |
3dfed10e | 1297 | /// [`write_all`]: Write::write_all |
c34b1796 | 1298 | #[stable(feature = "rust1", since = "1.0.0")] |
3dfed10e | 1299 | #[doc(spotlight)] |
85aaf69f | 1300 | pub trait Write { |
0731742a | 1301 | /// Write a buffer into this writer, returning how many bytes were written. |
1a4d82fc | 1302 | /// |
85aaf69f SL |
1303 | /// This function will attempt to write the entire contents of `buf`, but |
1304 | /// the entire write may not succeed, or the write may also generate an | |
1305 | /// error. A call to `write` represents *at most one* attempt to write to | |
1306 | /// any wrapped object. | |
1a4d82fc | 1307 | /// |
85aaf69f | 1308 | /// Calls to `write` are not guaranteed to block waiting for data to be |
62682a34 | 1309 | /// written, and a write which would otherwise block can be indicated through |
2c00a5a8 | 1310 | /// an [`Err`] variant. |
1a4d82fc | 1311 | /// |
2c00a5a8 | 1312 | /// If the return value is [`Ok(n)`] then it must be guaranteed that |
416331ca | 1313 | /// `n <= buf.len()`. A return value of `0` typically means that the |
85aaf69f SL |
1314 | /// underlying object is no longer able to accept bytes and will likely not |
1315 | /// be able to in the future as well, or that the buffer provided is empty. | |
1a4d82fc | 1316 | /// |
85aaf69f | 1317 | /// # Errors |
1a4d82fc | 1318 | /// |
85aaf69f SL |
1319 | /// Each call to `write` may generate an I/O error indicating that the |
1320 | /// operation could not be completed. If an error is returned then no bytes | |
1321 | /// in the buffer were written to this writer. | |
1a4d82fc | 1322 | /// |
85aaf69f SL |
1323 | /// It is **not** considered an error if the entire buffer could not be |
1324 | /// written to this writer. | |
c1a9b12d | 1325 | /// |
2c00a5a8 | 1326 | /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the |
7cac9316 XL |
1327 | /// write operation should be retried if there is nothing else to do. |
1328 | /// | |
c1a9b12d SL |
1329 | /// # Examples |
1330 | /// | |
0531ce1d | 1331 | /// ```no_run |
c1a9b12d SL |
1332 | /// use std::io::prelude::*; |
1333 | /// use std::fs::File; | |
1334 | /// | |
0531ce1d XL |
1335 | /// fn main() -> std::io::Result<()> { |
1336 | /// let mut buffer = File::create("foo.txt")?; | |
c1a9b12d | 1337 | /// |
0531ce1d XL |
1338 | /// // Writes some prefix of the byte string, not necessarily all of it. |
1339 | /// buffer.write(b"some bytes")?; | |
1340 | /// Ok(()) | |
1341 | /// } | |
c1a9b12d | 1342 | /// ``` |
3dfed10e XL |
1343 | /// |
1344 | /// [`Ok(n)`]: Ok | |
c34b1796 | 1345 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1346 | fn write(&mut self, buf: &[u8]) -> Result<usize>; |
1a4d82fc | 1347 | |
3dfed10e | 1348 | /// Like [`write`], except that it writes from a slice of buffers. |
9fa01778 | 1349 | /// |
416331ca | 1350 | /// Data is copied from each buffer in order, with the final buffer |
9fa01778 | 1351 | /// read from possibly being only partially consumed. This method must |
3dfed10e | 1352 | /// behave as a call to [`write`] with the buffers concatenated would. |
9fa01778 | 1353 | /// |
3dfed10e | 1354 | /// The default implementation calls [`write`] with either the first nonempty |
532ac7d7 | 1355 | /// buffer provided, or an empty one if none exists. |
3dfed10e XL |
1356 | /// |
1357 | /// [`write`]: Write::write | |
48663c56 XL |
1358 | #[stable(feature = "iovec", since = "1.36.0")] |
1359 | fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> { | |
532ac7d7 | 1360 | default_write_vectored(|b| self.write(b), bufs) |
9fa01778 XL |
1361 | } |
1362 | ||
fc512014 | 1363 | /// Determines if this `Write`r has an efficient [`write_vectored`] |
f9f354fc XL |
1364 | /// implementation. |
1365 | /// | |
fc512014 | 1366 | /// If a `Write`r does not override the default [`write_vectored`] |
f9f354fc XL |
1367 | /// implementation, code using it may want to avoid the method all together |
1368 | /// and coalesce writes into a single buffer for higher performance. | |
1369 | /// | |
1370 | /// The default implementation returns `false`. | |
3dfed10e XL |
1371 | /// |
1372 | /// [`write_vectored`]: Write::write_vectored | |
f9f354fc XL |
1373 | #[unstable(feature = "can_vector", issue = "69941")] |
1374 | fn is_write_vectored(&self) -> bool { | |
1375 | false | |
1376 | } | |
1377 | ||
85aaf69f SL |
1378 | /// Flush this output stream, ensuring that all intermediately buffered |
1379 | /// contents reach their destination. | |
1a4d82fc | 1380 | /// |
85aaf69f | 1381 | /// # Errors |
1a4d82fc | 1382 | /// |
85aaf69f SL |
1383 | /// It is considered an error if not all bytes could be written due to |
1384 | /// I/O errors or EOF being reached. | |
c1a9b12d SL |
1385 | /// |
1386 | /// # Examples | |
1387 | /// | |
0531ce1d | 1388 | /// ```no_run |
c1a9b12d SL |
1389 | /// use std::io::prelude::*; |
1390 | /// use std::io::BufWriter; | |
1391 | /// use std::fs::File; | |
1392 | /// | |
0531ce1d XL |
1393 | /// fn main() -> std::io::Result<()> { |
1394 | /// let mut buffer = BufWriter::new(File::create("foo.txt")?); | |
c1a9b12d | 1395 | /// |
532ac7d7 | 1396 | /// buffer.write_all(b"some bytes")?; |
0531ce1d XL |
1397 | /// buffer.flush()?; |
1398 | /// Ok(()) | |
1399 | /// } | |
c1a9b12d | 1400 | /// ``` |
c34b1796 | 1401 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1402 | fn flush(&mut self) -> Result<()>; |
1a4d82fc | 1403 | |
0731742a | 1404 | /// Attempts to write an entire buffer into this writer. |
1a4d82fc | 1405 | /// |
2c00a5a8 XL |
1406 | /// This method will continuously call [`write`] until there is no more data |
1407 | /// to be written or an error of non-[`ErrorKind::Interrupted`] kind is | |
7cac9316 XL |
1408 | /// returned. This method will not return until the entire buffer has been |
1409 | /// successfully written or such an error occurs. The first error that is | |
2c00a5a8 | 1410 | /// not of [`ErrorKind::Interrupted`] kind generated from this method will be |
7cac9316 | 1411 | /// returned. |
1a4d82fc | 1412 | /// |
74b04a01 XL |
1413 | /// If the buffer contains no data, this will never call [`write`]. |
1414 | /// | |
1a4d82fc JJ |
1415 | /// # Errors |
1416 | /// | |
7cac9316 | 1417 | /// This function will return the first error of |
2c00a5a8 XL |
1418 | /// non-[`ErrorKind::Interrupted`] kind that [`write`] returns. |
1419 | /// | |
3dfed10e | 1420 | /// [`write`]: Write::write |
c1a9b12d SL |
1421 | /// |
1422 | /// # Examples | |
1423 | /// | |
0531ce1d | 1424 | /// ```no_run |
c1a9b12d SL |
1425 | /// use std::io::prelude::*; |
1426 | /// use std::fs::File; | |
1427 | /// | |
0531ce1d XL |
1428 | /// fn main() -> std::io::Result<()> { |
1429 | /// let mut buffer = File::create("foo.txt")?; | |
c1a9b12d | 1430 | /// |
0531ce1d XL |
1431 | /// buffer.write_all(b"some bytes")?; |
1432 | /// Ok(()) | |
1433 | /// } | |
c1a9b12d | 1434 | /// ``` |
c34b1796 | 1435 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1436 | fn write_all(&mut self, mut buf: &[u8]) -> Result<()> { |
9346a6ac | 1437 | while !buf.is_empty() { |
85aaf69f | 1438 | match self.write(buf) { |
60c5eb7d XL |
1439 | Ok(0) => { |
1440 | return Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer")); | |
1441 | } | |
85aaf69f SL |
1442 | Ok(n) => buf = &buf[n..], |
1443 | Err(ref e) if e.kind() == ErrorKind::Interrupted => {} | |
1444 | Err(e) => return Err(e), | |
1445 | } | |
1446 | } | |
1447 | Ok(()) | |
1448 | } | |
1a4d82fc | 1449 | |
ba9703b0 XL |
1450 | /// Attempts to write multiple buffers into this writer. |
1451 | /// | |
1452 | /// This method will continuously call [`write_vectored`] until there is no | |
1453 | /// more data to be written or an error of non-[`ErrorKind::Interrupted`] | |
1454 | /// kind is returned. This method will not return until all buffers have | |
1455 | /// been successfully written or such an error occurs. The first error that | |
1456 | /// is not of [`ErrorKind::Interrupted`] kind generated from this method | |
1457 | /// will be returned. | |
1458 | /// | |
1459 | /// If the buffer contains no data, this will never call [`write_vectored`]. | |
1460 | /// | |
ba9703b0 XL |
1461 | /// # Notes |
1462 | /// | |
3dfed10e XL |
1463 | /// Unlike [`write_vectored`], this takes a *mutable* reference to |
1464 | /// a slice of [`IoSlice`]s, not an immutable one. That's because we need to | |
ba9703b0 XL |
1465 | /// modify the slice to keep track of the bytes already written. |
1466 | /// | |
1467 | /// Once this function returns, the contents of `bufs` are unspecified, as | |
3dfed10e | 1468 | /// this depends on how many calls to [`write_vectored`] were necessary. It is |
ba9703b0 XL |
1469 | /// best to understand this function as taking ownership of `bufs` and to |
1470 | /// not use `bufs` afterwards. The underlying buffers, to which the | |
3dfed10e | 1471 | /// [`IoSlice`]s point (but not the [`IoSlice`]s themselves), are unchanged and |
ba9703b0 XL |
1472 | /// can be reused. |
1473 | /// | |
3dfed10e XL |
1474 | /// [`write_vectored`]: Write::write_vectored |
1475 | /// | |
ba9703b0 XL |
1476 | /// # Examples |
1477 | /// | |
1478 | /// ``` | |
1479 | /// #![feature(write_all_vectored)] | |
1480 | /// # fn main() -> std::io::Result<()> { | |
1481 | /// | |
1482 | /// use std::io::{Write, IoSlice}; | |
1483 | /// | |
1484 | /// let mut writer = Vec::new(); | |
1485 | /// let bufs = &mut [ | |
1486 | /// IoSlice::new(&[1]), | |
1487 | /// IoSlice::new(&[2, 3]), | |
1488 | /// IoSlice::new(&[4, 5, 6]), | |
1489 | /// ]; | |
1490 | /// | |
1491 | /// writer.write_all_vectored(bufs)?; | |
1492 | /// // Note: the contents of `bufs` is now undefined, see the Notes section. | |
1493 | /// | |
1494 | /// assert_eq!(writer, &[1, 2, 3, 4, 5, 6]); | |
1495 | /// # Ok(()) } | |
1496 | /// ``` | |
1497 | #[unstable(feature = "write_all_vectored", issue = "70436")] | |
1498 | fn write_all_vectored(&mut self, mut bufs: &mut [IoSlice<'_>]) -> Result<()> { | |
3dfed10e XL |
1499 | // Guarantee that bufs is empty if it contains no data, |
1500 | // to avoid calling write_vectored if there is no data to be written. | |
1501 | bufs = IoSlice::advance(bufs, 0); | |
ba9703b0 XL |
1502 | while !bufs.is_empty() { |
1503 | match self.write_vectored(bufs) { | |
1504 | Ok(0) => { | |
1505 | return Err(Error::new(ErrorKind::WriteZero, "failed to write whole buffer")); | |
1506 | } | |
3dfed10e | 1507 | Ok(n) => bufs = IoSlice::advance(bufs, n), |
ba9703b0 XL |
1508 | Err(ref e) if e.kind() == ErrorKind::Interrupted => {} |
1509 | Err(e) => return Err(e), | |
1510 | } | |
1511 | } | |
1512 | Ok(()) | |
1513 | } | |
1514 | ||
1a4d82fc JJ |
1515 | /// Writes a formatted string into this writer, returning any error |
1516 | /// encountered. | |
1517 | /// | |
c1a9b12d | 1518 | /// This method is primarily used to interface with the |
3dfed10e XL |
1519 | /// [`format_args!()`] macro, but it is rare that this should |
1520 | /// explicitly be called. The [`write!()`] macro should be favored to | |
c1a9b12d SL |
1521 | /// invoke this method instead. |
1522 | /// | |
3dfed10e | 1523 | /// This function internally uses the [`write_all`] method on |
c1a9b12d SL |
1524 | /// this trait and hence will continuously write data so long as no errors |
1525 | /// are received. This also means that partial writes are not indicated in | |
1526 | /// this signature. | |
1527 | /// | |
3dfed10e | 1528 | /// [`write_all`]: Write::write_all |
85aaf69f | 1529 | /// |
1a4d82fc JJ |
1530 | /// # Errors |
1531 | /// | |
1532 | /// This function will return any I/O error reported while formatting. | |
c1a9b12d SL |
1533 | /// |
1534 | /// # Examples | |
1535 | /// | |
0531ce1d | 1536 | /// ```no_run |
c1a9b12d SL |
1537 | /// use std::io::prelude::*; |
1538 | /// use std::fs::File; | |
1539 | /// | |
0531ce1d XL |
1540 | /// fn main() -> std::io::Result<()> { |
1541 | /// let mut buffer = File::create("foo.txt")?; | |
c1a9b12d | 1542 | /// |
0531ce1d XL |
1543 | /// // this call |
1544 | /// write!(buffer, "{:.*}", 2, 1.234567)?; | |
1545 | /// // turns into this: | |
1546 | /// buffer.write_fmt(format_args!("{:.*}", 2, 1.234567))?; | |
1547 | /// Ok(()) | |
1548 | /// } | |
c1a9b12d | 1549 | /// ``` |
c34b1796 | 1550 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 1551 | fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> Result<()> { |
85aaf69f | 1552 | // Create a shim which translates a Write to a fmt::Write and saves |
1a4d82fc | 1553 | // off I/O errors. instead of discarding them |
85aaf69f | 1554 | struct Adaptor<'a, T: ?Sized + 'a> { |
1a4d82fc | 1555 | inner: &'a mut T, |
85aaf69f | 1556 | error: Result<()>, |
1a4d82fc JJ |
1557 | } |
1558 | ||
9fa01778 | 1559 | impl<T: Write + ?Sized> fmt::Write for Adaptor<'_, T> { |
1a4d82fc | 1560 | fn write_str(&mut self, s: &str) -> fmt::Result { |
85aaf69f | 1561 | match self.inner.write_all(s.as_bytes()) { |
1a4d82fc JJ |
1562 | Ok(()) => Ok(()), |
1563 | Err(e) => { | |
1564 | self.error = Err(e); | |
1565 | Err(fmt::Error) | |
1566 | } | |
1567 | } | |
1568 | } | |
1569 | } | |
1570 | ||
1571 | let mut output = Adaptor { inner: self, error: Ok(()) }; | |
1572 | match fmt::write(&mut output, fmt) { | |
1573 | Ok(()) => Ok(()), | |
7453a54e SL |
1574 | Err(..) => { |
1575 | // check if the error came from the underlying `Write` or not | |
1576 | if output.error.is_err() { | |
1577 | output.error | |
1578 | } else { | |
1579 | Err(Error::new(ErrorKind::Other, "formatter error")) | |
1580 | } | |
1581 | } | |
1a4d82fc JJ |
1582 | } |
1583 | } | |
1a4d82fc | 1584 | |
9346a6ac | 1585 | /// Creates a "by reference" adaptor for this instance of `Write`. |
1a4d82fc | 1586 | /// |
85aaf69f SL |
1587 | /// The returned adaptor also implements `Write` and will simply borrow this |
1588 | /// current writer. | |
c1a9b12d SL |
1589 | /// |
1590 | /// # Examples | |
1591 | /// | |
0531ce1d | 1592 | /// ```no_run |
c1a9b12d SL |
1593 | /// use std::io::Write; |
1594 | /// use std::fs::File; | |
1595 | /// | |
0531ce1d XL |
1596 | /// fn main() -> std::io::Result<()> { |
1597 | /// let mut buffer = File::create("foo.txt")?; | |
c1a9b12d | 1598 | /// |
0531ce1d | 1599 | /// let reference = buffer.by_ref(); |
c1a9b12d | 1600 | /// |
0531ce1d XL |
1601 | /// // we can use reference just like our original buffer |
1602 | /// reference.write_all(b"some bytes")?; | |
1603 | /// Ok(()) | |
1604 | /// } | |
c1a9b12d | 1605 | /// ``` |
c34b1796 | 1606 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
1607 | fn by_ref(&mut self) -> &mut Self |
1608 | where | |
1609 | Self: Sized, | |
1610 | { | |
1611 | self | |
1612 | } | |
1a4d82fc JJ |
1613 | } |
1614 | ||
c1a9b12d SL |
1615 | /// The `Seek` trait provides a cursor which can be moved within a stream of |
1616 | /// bytes. | |
1a4d82fc | 1617 | /// |
85aaf69f SL |
1618 | /// The stream typically has a fixed size, allowing seeking relative to either |
1619 | /// end or the current offset. | |
c1a9b12d SL |
1620 | /// |
1621 | /// # Examples | |
1622 | /// | |
3dfed10e | 1623 | /// [`File`]s implement `Seek`: |
c1a9b12d | 1624 | /// |
3dfed10e | 1625 | /// [`File`]: crate::fs::File |
c1a9b12d | 1626 | /// |
0531ce1d | 1627 | /// ```no_run |
c1a9b12d SL |
1628 | /// use std::io; |
1629 | /// use std::io::prelude::*; | |
1630 | /// use std::fs::File; | |
1631 | /// use std::io::SeekFrom; | |
1632 | /// | |
0531ce1d XL |
1633 | /// fn main() -> io::Result<()> { |
1634 | /// let mut f = File::open("foo.txt")?; | |
c1a9b12d | 1635 | /// |
0531ce1d XL |
1636 | /// // move the cursor 42 bytes from the start of the file |
1637 | /// f.seek(SeekFrom::Start(42))?; | |
1638 | /// Ok(()) | |
1639 | /// } | |
c1a9b12d | 1640 | /// ``` |
c34b1796 | 1641 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1642 | pub trait Seek { |
c1a9b12d | 1643 | /// Seek to an offset, in bytes, in a stream. |
85aaf69f | 1644 | /// |
0bf4aa26 XL |
1645 | /// A seek beyond the end of a stream is allowed, but behavior is defined |
1646 | /// by the implementation. | |
85aaf69f | 1647 | /// |
c1a9b12d SL |
1648 | /// If the seek operation completed successfully, |
1649 | /// this method returns the new position from the start of the stream. | |
5bcae85e | 1650 | /// That position can be used later with [`SeekFrom::Start`]. |
85aaf69f SL |
1651 | /// |
1652 | /// # Errors | |
1653 | /// | |
c1a9b12d | 1654 | /// Seeking to a negative offset is considered an error. |
c34b1796 | 1655 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1656 | fn seek(&mut self, pos: SeekFrom) -> Result<u64>; |
532ac7d7 XL |
1657 | |
1658 | /// Returns the length of this stream (in bytes). | |
1659 | /// | |
1660 | /// This method is implemented using up to three seek operations. If this | |
1661 | /// method returns successfully, the seek position is unchanged (i.e. the | |
1662 | /// position before calling this method is the same as afterwards). | |
1663 | /// However, if this method returns an error, the seek position is | |
1664 | /// unspecified. | |
1665 | /// | |
1666 | /// If you need to obtain the length of *many* streams and you don't care | |
1667 | /// about the seek position afterwards, you can reduce the number of seek | |
1668 | /// operations by simply calling `seek(SeekFrom::End(0))` and using its | |
1669 | /// return value (it is also the stream length). | |
1670 | /// | |
1671 | /// Note that length of a stream can change over time (for example, when | |
1672 | /// data is appended to a file). So calling this method multiple times does | |
1673 | /// not necessarily return the same length each time. | |
1674 | /// | |
532ac7d7 XL |
1675 | /// # Example |
1676 | /// | |
1677 | /// ```no_run | |
5869c6ff | 1678 | /// #![feature(seek_stream_len)] |
532ac7d7 XL |
1679 | /// use std::{ |
1680 | /// io::{self, Seek}, | |
1681 | /// fs::File, | |
1682 | /// }; | |
1683 | /// | |
1684 | /// fn main() -> io::Result<()> { | |
1685 | /// let mut f = File::open("foo.txt")?; | |
1686 | /// | |
1687 | /// let len = f.stream_len()?; | |
1688 | /// println!("The file is currently {} bytes long", len); | |
1689 | /// Ok(()) | |
1690 | /// } | |
1691 | /// ``` | |
5869c6ff | 1692 | #[unstable(feature = "seek_stream_len", issue = "59359")] |
532ac7d7 XL |
1693 | fn stream_len(&mut self) -> Result<u64> { |
1694 | let old_pos = self.stream_position()?; | |
1695 | let len = self.seek(SeekFrom::End(0))?; | |
1696 | ||
1697 | // Avoid seeking a third time when we were already at the end of the | |
1698 | // stream. The branch is usually way cheaper than a seek operation. | |
1699 | if old_pos != len { | |
1700 | self.seek(SeekFrom::Start(old_pos))?; | |
1701 | } | |
1702 | ||
1703 | Ok(len) | |
1704 | } | |
1705 | ||
1706 | /// Returns the current seek position from the start of the stream. | |
1707 | /// | |
1708 | /// This is equivalent to `self.seek(SeekFrom::Current(0))`. | |
1709 | /// | |
532ac7d7 XL |
1710 | /// # Example |
1711 | /// | |
1712 | /// ```no_run | |
532ac7d7 XL |
1713 | /// use std::{ |
1714 | /// io::{self, BufRead, BufReader, Seek}, | |
1715 | /// fs::File, | |
1716 | /// }; | |
1717 | /// | |
1718 | /// fn main() -> io::Result<()> { | |
1719 | /// let mut f = BufReader::new(File::open("foo.txt")?); | |
1720 | /// | |
1721 | /// let before = f.stream_position()?; | |
1722 | /// f.read_line(&mut String::new())?; | |
1723 | /// let after = f.stream_position()?; | |
1724 | /// | |
1725 | /// println!("The first line was {} bytes long", after - before); | |
1726 | /// Ok(()) | |
1727 | /// } | |
1728 | /// ``` | |
5869c6ff | 1729 | #[stable(feature = "seek_convenience", since = "1.51.0")] |
532ac7d7 XL |
1730 | fn stream_position(&mut self) -> Result<u64> { |
1731 | self.seek(SeekFrom::Current(0)) | |
1732 | } | |
1a4d82fc JJ |
1733 | } |
1734 | ||
85aaf69f | 1735 | /// Enumeration of possible methods to seek within an I/O object. |
5bcae85e SL |
1736 | /// |
1737 | /// It is used by the [`Seek`] trait. | |
85aaf69f | 1738 | #[derive(Copy, PartialEq, Eq, Clone, Debug)] |
c34b1796 | 1739 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1740 | pub enum SeekFrom { |
9fa01778 | 1741 | /// Sets the offset to the provided number of bytes. |
c34b1796 | 1742 | #[stable(feature = "rust1", since = "1.0.0")] |
7453a54e | 1743 | Start(#[stable(feature = "rust1", since = "1.0.0")] u64), |
1a4d82fc | 1744 | |
9fa01778 | 1745 | /// Sets the offset to the size of this object plus the specified number of |
85aaf69f SL |
1746 | /// bytes. |
1747 | /// | |
9cc50fc6 | 1748 | /// It is possible to seek beyond the end of an object, but it's an error to |
85aaf69f | 1749 | /// seek before byte 0. |
c34b1796 | 1750 | #[stable(feature = "rust1", since = "1.0.0")] |
7453a54e | 1751 | End(#[stable(feature = "rust1", since = "1.0.0")] i64), |
1a4d82fc | 1752 | |
9fa01778 | 1753 | /// Sets the offset to the current position plus the specified number of |
85aaf69f SL |
1754 | /// bytes. |
1755 | /// | |
9cc50fc6 | 1756 | /// It is possible to seek beyond the end of an object, but it's an error to |
85aaf69f | 1757 | /// seek before byte 0. |
c34b1796 | 1758 | #[stable(feature = "rust1", since = "1.0.0")] |
7453a54e | 1759 | Current(#[stable(feature = "rust1", since = "1.0.0")] i64), |
1a4d82fc JJ |
1760 | } |
1761 | ||
60c5eb7d | 1762 | fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>) -> Result<usize> { |
c34b1796 | 1763 | let mut read = 0; |
85aaf69f SL |
1764 | loop { |
1765 | let (done, used) = { | |
1766 | let available = match r.fill_buf() { | |
1767 | Ok(n) => n, | |
1768 | Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, | |
60c5eb7d | 1769 | Err(e) => return Err(e), |
85aaf69f | 1770 | }; |
9cc50fc6 | 1771 | match memchr::memchr(delim, available) { |
85aaf69f | 1772 | Some(i) => { |
0731742a | 1773 | buf.extend_from_slice(&available[..=i]); |
85aaf69f SL |
1774 | (true, i + 1) |
1775 | } | |
1776 | None => { | |
92a42be0 | 1777 | buf.extend_from_slice(available); |
85aaf69f SL |
1778 | (false, available.len()) |
1779 | } | |
1780 | } | |
1781 | }; | |
1782 | r.consume(used); | |
c34b1796 | 1783 | read += used; |
85aaf69f | 1784 | if done || used == 0 { |
c34b1796 | 1785 | return Ok(read); |
1a4d82fc JJ |
1786 | } |
1787 | } | |
1788 | } | |
1789 | ||
c1a9b12d SL |
1790 | /// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it |
1791 | /// to perform extra ways of reading. | |
1792 | /// | |
1793 | /// For example, reading line-by-line is inefficient without using a buffer, so | |
1794 | /// if you want to read by line, you'll need `BufRead`, which includes a | |
cc61c64b | 1795 | /// [`read_line`] method as well as a [`lines`] iterator. |
c1a9b12d SL |
1796 | /// |
1797 | /// # Examples | |
1798 | /// | |
1799 | /// A locked standard input implements `BufRead`: | |
1800 | /// | |
0531ce1d | 1801 | /// ```no_run |
c1a9b12d SL |
1802 | /// use std::io; |
1803 | /// use std::io::prelude::*; | |
1804 | /// | |
1805 | /// let stdin = io::stdin(); | |
1806 | /// for line in stdin.lock().lines() { | |
1807 | /// println!("{}", line.unwrap()); | |
1808 | /// } | |
1809 | /// ``` | |
1810 | /// | |
c30ab7b3 SL |
1811 | /// If you have something that implements [`Read`], you can use the [`BufReader` |
1812 | /// type][`BufReader`] to turn it into a `BufRead`. | |
c1a9b12d | 1813 | /// |
c30ab7b3 SL |
1814 | /// For example, [`File`] implements [`Read`], but not `BufRead`. |
1815 | /// [`BufReader`] to the rescue! | |
85aaf69f | 1816 | /// |
3dfed10e XL |
1817 | /// [`File`]: crate::fs::File |
1818 | /// [`read_line`]: BufRead::read_line | |
1819 | /// [`lines`]: BufRead::lines | |
c1a9b12d | 1820 | /// |
0531ce1d | 1821 | /// ```no_run |
c1a9b12d SL |
1822 | /// use std::io::{self, BufReader}; |
1823 | /// use std::io::prelude::*; | |
1824 | /// use std::fs::File; | |
1825 | /// | |
0531ce1d XL |
1826 | /// fn main() -> io::Result<()> { |
1827 | /// let f = File::open("foo.txt")?; | |
1828 | /// let f = BufReader::new(f); | |
c1a9b12d | 1829 | /// |
0531ce1d XL |
1830 | /// for line in f.lines() { |
1831 | /// println!("{}", line.unwrap()); | |
1832 | /// } | |
c1a9b12d | 1833 | /// |
0531ce1d XL |
1834 | /// Ok(()) |
1835 | /// } | |
c1a9b12d | 1836 | /// ``` |
c34b1796 | 1837 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1838 | pub trait BufRead: Read { |
b7449926 XL |
1839 | /// Returns the contents of the internal buffer, filling it with more data |
1840 | /// from the inner reader if it is empty. | |
85aaf69f | 1841 | /// |
c1a9b12d | 1842 | /// This function is a lower-level call. It needs to be paired with the |
cc61c64b | 1843 | /// [`consume`] method to function properly. When calling this |
c1a9b12d | 1844 | /// method, none of the contents will be "read" in the sense that later |
cc61c64b | 1845 | /// calling `read` may return the same contents. As such, [`consume`] must |
c30ab7b3 | 1846 | /// be called with the number of bytes that are consumed from this buffer to |
c1a9b12d | 1847 | /// ensure that the bytes are never returned twice. |
1a4d82fc | 1848 | /// |
3dfed10e | 1849 | /// [`consume`]: BufRead::consume |
1a4d82fc | 1850 | /// |
85aaf69f SL |
1851 | /// An empty buffer returned indicates that the stream has reached EOF. |
1852 | /// | |
1853 | /// # Errors | |
1a4d82fc JJ |
1854 | /// |
1855 | /// This function will return an I/O error if the underlying reader was | |
85aaf69f | 1856 | /// read, but returned an error. |
c1a9b12d SL |
1857 | /// |
1858 | /// # Examples | |
1859 | /// | |
1860 | /// A locked standard input implements `BufRead`: | |
1861 | /// | |
0531ce1d | 1862 | /// ```no_run |
c1a9b12d SL |
1863 | /// use std::io; |
1864 | /// use std::io::prelude::*; | |
1865 | /// | |
1866 | /// let stdin = io::stdin(); | |
1867 | /// let mut stdin = stdin.lock(); | |
1868 | /// | |
48663c56 | 1869 | /// let buffer = stdin.fill_buf().unwrap(); |
c1a9b12d | 1870 | /// |
48663c56 XL |
1871 | /// // work with buffer |
1872 | /// println!("{:?}", buffer); | |
c1a9b12d SL |
1873 | /// |
1874 | /// // ensure the bytes we worked with aren't returned again later | |
48663c56 | 1875 | /// let length = buffer.len(); |
c1a9b12d SL |
1876 | /// stdin.consume(length); |
1877 | /// ``` | |
c34b1796 | 1878 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1879 | fn fill_buf(&mut self) -> Result<&[u8]>; |
1a4d82fc JJ |
1880 | |
1881 | /// Tells this buffer that `amt` bytes have been consumed from the buffer, | |
1882 | /// so they should no longer be returned in calls to `read`. | |
c34b1796 | 1883 | /// |
c1a9b12d | 1884 | /// This function is a lower-level call. It needs to be paired with the |
cc61c64b | 1885 | /// [`fill_buf`] method to function properly. This function does |
c1a9b12d | 1886 | /// not perform any I/O, it simply informs this object that some amount of |
cc61c64b | 1887 | /// its buffer, returned from [`fill_buf`], has been consumed and should |
c30ab7b3 | 1888 | /// no longer be returned. As such, this function may do odd things if |
cc61c64b | 1889 | /// [`fill_buf`] isn't called before calling it. |
c1a9b12d SL |
1890 | /// |
1891 | /// The `amt` must be `<=` the number of bytes in the buffer returned by | |
cc61c64b | 1892 | /// [`fill_buf`]. |
c34b1796 | 1893 | /// |
c1a9b12d | 1894 | /// # Examples |
c34b1796 | 1895 | /// |
cc61c64b | 1896 | /// Since `consume()` is meant to be used with [`fill_buf`], |
c1a9b12d | 1897 | /// that method's example includes an example of `consume()`. |
c30ab7b3 | 1898 | /// |
3dfed10e | 1899 | /// [`fill_buf`]: BufRead::fill_buf |
c34b1796 | 1900 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 1901 | fn consume(&mut self, amt: usize); |
1a4d82fc | 1902 | |
c30ab7b3 | 1903 | /// Read all bytes into `buf` until the delimiter `byte` or EOF is reached. |
1a4d82fc | 1904 | /// |
c1a9b12d SL |
1905 | /// This function will read bytes from the underlying stream until the |
1906 | /// delimiter or EOF is found. Once found, all bytes up to, and including, | |
1907 | /// the delimiter (if found) will be appended to `buf`. | |
1a4d82fc | 1908 | /// |
c30ab7b3 | 1909 | /// If successful, this function will return the total number of bytes read. |
1a4d82fc | 1910 | /// |
f035d41b XL |
1911 | /// This function is blocking and should be used carefully: it is possible for |
1912 | /// an attacker to continuously send bytes without ever sending the delimiter | |
1913 | /// or EOF. | |
1914 | /// | |
85aaf69f | 1915 | /// # Errors |
1a4d82fc | 1916 | /// |
c30ab7b3 | 1917 | /// This function will ignore all instances of [`ErrorKind::Interrupted`] and |
cc61c64b | 1918 | /// will otherwise return any errors returned by [`fill_buf`]. |
1a4d82fc | 1919 | /// |
85aaf69f SL |
1920 | /// If an I/O error is encountered then all bytes read so far will be |
1921 | /// present in `buf` and its length will have been adjusted appropriately. | |
c1a9b12d | 1922 | /// |
3dfed10e | 1923 | /// [`fill_buf`]: BufRead::fill_buf |
c30ab7b3 | 1924 | /// |
cc61c64b | 1925 | /// # Examples |
c1a9b12d | 1926 | /// |
cc61c64b XL |
1927 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
1928 | /// this example, we use [`Cursor`] to read all the bytes in a byte slice | |
1929 | /// in hyphen delimited segments: | |
c1a9b12d | 1930 | /// |
cc61c64b XL |
1931 | /// ``` |
1932 | /// use std::io::{self, BufRead}; | |
1933 | /// | |
1934 | /// let mut cursor = io::Cursor::new(b"lorem-ipsum"); | |
1935 | /// let mut buf = vec![]; | |
1936 | /// | |
1937 | /// // cursor is at 'l' | |
1938 | /// let num_bytes = cursor.read_until(b'-', &mut buf) | |
1939 | /// .expect("reading from cursor won't fail"); | |
1940 | /// assert_eq!(num_bytes, 6); | |
1941 | /// assert_eq!(buf, b"lorem-"); | |
1942 | /// buf.clear(); | |
1943 | /// | |
1944 | /// // cursor is at 'i' | |
1945 | /// let num_bytes = cursor.read_until(b'-', &mut buf) | |
1946 | /// .expect("reading from cursor won't fail"); | |
1947 | /// assert_eq!(num_bytes, 5); | |
1948 | /// assert_eq!(buf, b"ipsum"); | |
1949 | /// buf.clear(); | |
1950 | /// | |
1951 | /// // cursor is at EOF | |
1952 | /// let num_bytes = cursor.read_until(b'-', &mut buf) | |
1953 | /// .expect("reading from cursor won't fail"); | |
1954 | /// assert_eq!(num_bytes, 0); | |
1955 | /// assert_eq!(buf, b""); | |
c1a9b12d | 1956 | /// ``` |
c34b1796 AL |
1957 | #[stable(feature = "rust1", since = "1.0.0")] |
1958 | fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> { | |
85aaf69f | 1959 | read_until(self, byte, buf) |
1a4d82fc JJ |
1960 | } |
1961 | ||
3dfed10e | 1962 | /// Read all bytes until a newline (the `0xA` byte) is reached, and append |
c1a9b12d | 1963 | /// them to the provided buffer. |
1a4d82fc | 1964 | /// |
c1a9b12d | 1965 | /// This function will read bytes from the underlying stream until the |
3dfed10e | 1966 | /// newline delimiter (the `0xA` byte) or EOF is found. Once found, all bytes |
c1a9b12d SL |
1967 | /// up to, and including, the delimiter (if found) will be appended to |
1968 | /// `buf`. | |
1a4d82fc | 1969 | /// |
c30ab7b3 | 1970 | /// If successful, this function will return the total number of bytes read. |
85aaf69f | 1971 | /// |
3dfed10e | 1972 | /// If this function returns [`Ok(0)`], the stream has reached EOF. |
abe05a73 | 1973 | /// |
f035d41b XL |
1974 | /// This function is blocking and should be used carefully: it is possible for |
1975 | /// an attacker to continuously send bytes without ever sending a newline | |
1976 | /// or EOF. | |
1977 | /// | |
3dfed10e XL |
1978 | /// [`Ok(0)`]: Ok |
1979 | /// | |
85aaf69f SL |
1980 | /// # Errors |
1981 | /// | |
cc61c64b | 1982 | /// This function has the same error semantics as [`read_until`] and will |
c30ab7b3 SL |
1983 | /// also return an error if the read bytes are not valid UTF-8. If an I/O |
1984 | /// error is encountered then `buf` may contain some bytes already read in | |
1985 | /// the event that all data read so far was valid UTF-8. | |
c1a9b12d | 1986 | /// |
3dfed10e | 1987 | /// [`read_until`]: BufRead::read_until |
0531ce1d | 1988 | /// |
c1a9b12d SL |
1989 | /// # Examples |
1990 | /// | |
cc61c64b XL |
1991 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
1992 | /// this example, we use [`Cursor`] to read all the lines in a byte slice: | |
c1a9b12d | 1993 | /// |
c1a9b12d | 1994 | /// ``` |
cc61c64b XL |
1995 | /// use std::io::{self, BufRead}; |
1996 | /// | |
1997 | /// let mut cursor = io::Cursor::new(b"foo\nbar"); | |
1998 | /// let mut buf = String::new(); | |
1999 | /// | |
2000 | /// // cursor is at 'f' | |
2001 | /// let num_bytes = cursor.read_line(&mut buf) | |
2002 | /// .expect("reading from cursor won't fail"); | |
2003 | /// assert_eq!(num_bytes, 4); | |
2004 | /// assert_eq!(buf, "foo\n"); | |
2005 | /// buf.clear(); | |
2006 | /// | |
2007 | /// // cursor is at 'b' | |
2008 | /// let num_bytes = cursor.read_line(&mut buf) | |
2009 | /// .expect("reading from cursor won't fail"); | |
2010 | /// assert_eq!(num_bytes, 3); | |
2011 | /// assert_eq!(buf, "bar"); | |
2012 | /// buf.clear(); | |
2013 | /// | |
2014 | /// // cursor is at EOF | |
2015 | /// let num_bytes = cursor.read_line(&mut buf) | |
2016 | /// .expect("reading from cursor won't fail"); | |
2017 | /// assert_eq!(num_bytes, 0); | |
2018 | /// assert_eq!(buf, ""); | |
c1a9b12d | 2019 | /// ``` |
c34b1796 AL |
2020 | #[stable(feature = "rust1", since = "1.0.0")] |
2021 | fn read_line(&mut self, buf: &mut String) -> Result<usize> { | |
85aaf69f SL |
2022 | // Note that we are not calling the `.read_until` method here, but |
2023 | // rather our hardcoded implementation. For more details as to why, see | |
2024 | // the comments in `read_to_end`. | |
2025 | append_to_string(buf, |b| read_until(self, b'\n', b)) | |
1a4d82fc | 2026 | } |
1a4d82fc | 2027 | |
85aaf69f SL |
2028 | /// Returns an iterator over the contents of this reader split on the byte |
2029 | /// `byte`. | |
1a4d82fc | 2030 | /// |
85aaf69f | 2031 | /// The iterator returned from this function will return instances of |
c30ab7b3 SL |
2032 | /// [`io::Result`]`<`[`Vec<u8>`]`>`. Each vector returned will *not* have |
2033 | /// the delimiter byte at the end. | |
1a4d82fc | 2034 | /// |
cc61c64b | 2035 | /// This function will yield errors whenever [`read_until`] would have |
c30ab7b3 | 2036 | /// also yielded an error. |
c1a9b12d | 2037 | /// |
3dfed10e | 2038 | /// [`io::Result`]: self::Result |
3dfed10e | 2039 | /// [`read_until`]: BufRead::read_until |
cc61c64b | 2040 | /// |
c1a9b12d SL |
2041 | /// # Examples |
2042 | /// | |
cc61c64b XL |
2043 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
2044 | /// this example, we use [`Cursor`] to iterate over all hyphen delimited | |
2045 | /// segments in a byte slice | |
c1a9b12d SL |
2046 | /// |
2047 | /// ``` | |
cc61c64b | 2048 | /// use std::io::{self, BufRead}; |
c1a9b12d | 2049 | /// |
cc61c64b | 2050 | /// let cursor = io::Cursor::new(b"lorem-ipsum-dolor"); |
c1a9b12d | 2051 | /// |
cc61c64b XL |
2052 | /// let mut split_iter = cursor.split(b'-').map(|l| l.unwrap()); |
2053 | /// assert_eq!(split_iter.next(), Some(b"lorem".to_vec())); | |
2054 | /// assert_eq!(split_iter.next(), Some(b"ipsum".to_vec())); | |
2055 | /// assert_eq!(split_iter.next(), Some(b"dolor".to_vec())); | |
2056 | /// assert_eq!(split_iter.next(), None); | |
c1a9b12d | 2057 | /// ``` |
c34b1796 | 2058 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
2059 | fn split(self, byte: u8) -> Split<Self> |
2060 | where | |
2061 | Self: Sized, | |
2062 | { | |
85aaf69f SL |
2063 | Split { buf: self, delim: byte } |
2064 | } | |
1a4d82fc | 2065 | |
85aaf69f | 2066 | /// Returns an iterator over the lines of this reader. |
1a4d82fc | 2067 | /// |
85aaf69f | 2068 | /// The iterator returned from this function will yield instances of |
c30ab7b3 | 2069 | /// [`io::Result`]`<`[`String`]`>`. Each string returned will *not* have a newline |
3dfed10e | 2070 | /// byte (the `0xA` byte) or `CRLF` (`0xD`, `0xA` bytes) at the end. |
c1a9b12d | 2071 | /// |
3dfed10e | 2072 | /// [`io::Result`]: self::Result |
c30ab7b3 | 2073 | /// |
c1a9b12d SL |
2074 | /// # Examples |
2075 | /// | |
cc61c64b XL |
2076 | /// [`std::io::Cursor`][`Cursor`] is a type that implements `BufRead`. In |
2077 | /// this example, we use [`Cursor`] to iterate over all the lines in a byte | |
2078 | /// slice. | |
2079 | /// | |
c1a9b12d | 2080 | /// ``` |
cc61c64b | 2081 | /// use std::io::{self, BufRead}; |
c1a9b12d | 2082 | /// |
cc61c64b | 2083 | /// let cursor = io::Cursor::new(b"lorem\nipsum\r\ndolor"); |
c1a9b12d | 2084 | /// |
cc61c64b XL |
2085 | /// let mut lines_iter = cursor.lines().map(|l| l.unwrap()); |
2086 | /// assert_eq!(lines_iter.next(), Some(String::from("lorem"))); | |
2087 | /// assert_eq!(lines_iter.next(), Some(String::from("ipsum"))); | |
2088 | /// assert_eq!(lines_iter.next(), Some(String::from("dolor"))); | |
2089 | /// assert_eq!(lines_iter.next(), None); | |
c1a9b12d | 2090 | /// ``` |
32a655c1 SL |
2091 | /// |
2092 | /// # Errors | |
2093 | /// | |
cc61c64b | 2094 | /// Each line of the iterator has the same error semantics as [`BufRead::read_line`]. |
c34b1796 | 2095 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
2096 | fn lines(self) -> Lines<Self> |
2097 | where | |
2098 | Self: Sized, | |
2099 | { | |
85aaf69f SL |
2100 | Lines { buf: self } |
2101 | } | |
2102 | } | |
2103 | ||
c1a9b12d SL |
2104 | /// Adaptor to chain together two readers. |
2105 | /// | |
cc61c64b XL |
2106 | /// This struct is generally created by calling [`chain`] on a reader. |
2107 | /// Please see the documentation of [`chain`] for more details. | |
85aaf69f | 2108 | /// |
3dfed10e | 2109 | /// [`chain`]: Read::chain |
c34b1796 | 2110 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2111 | pub struct Chain<T, U> { |
2112 | first: T, | |
2113 | second: U, | |
2114 | done_first: bool, | |
1a4d82fc JJ |
2115 | } |
2116 | ||
7cac9316 XL |
2117 | impl<T, U> Chain<T, U> { |
2118 | /// Consumes the `Chain`, returning the wrapped readers. | |
2119 | /// | |
2120 | /// # Examples | |
2121 | /// | |
0531ce1d XL |
2122 | /// ```no_run |
2123 | /// use std::io; | |
7cac9316 XL |
2124 | /// use std::io::prelude::*; |
2125 | /// use std::fs::File; | |
2126 | /// | |
0531ce1d XL |
2127 | /// fn main() -> io::Result<()> { |
2128 | /// let mut foo_file = File::open("foo.txt")?; | |
2129 | /// let mut bar_file = File::open("bar.txt")?; | |
7cac9316 | 2130 | /// |
0531ce1d XL |
2131 | /// let chain = foo_file.chain(bar_file); |
2132 | /// let (foo_file, bar_file) = chain.into_inner(); | |
2133 | /// Ok(()) | |
2134 | /// } | |
7cac9316 | 2135 | /// ``` |
041b39d2 | 2136 | #[stable(feature = "more_io_inner_methods", since = "1.20.0")] |
7cac9316 XL |
2137 | pub fn into_inner(self) -> (T, U) { |
2138 | (self.first, self.second) | |
2139 | } | |
2140 | ||
2141 | /// Gets references to the underlying readers in this `Chain`. | |
2142 | /// | |
2143 | /// # Examples | |
2144 | /// | |
0531ce1d XL |
2145 | /// ```no_run |
2146 | /// use std::io; | |
7cac9316 XL |
2147 | /// use std::io::prelude::*; |
2148 | /// use std::fs::File; | |
2149 | /// | |
0531ce1d XL |
2150 | /// fn main() -> io::Result<()> { |
2151 | /// let mut foo_file = File::open("foo.txt")?; | |
2152 | /// let mut bar_file = File::open("bar.txt")?; | |
7cac9316 | 2153 | /// |
0531ce1d XL |
2154 | /// let chain = foo_file.chain(bar_file); |
2155 | /// let (foo_file, bar_file) = chain.get_ref(); | |
2156 | /// Ok(()) | |
2157 | /// } | |
7cac9316 | 2158 | /// ``` |
041b39d2 | 2159 | #[stable(feature = "more_io_inner_methods", since = "1.20.0")] |
7cac9316 XL |
2160 | pub fn get_ref(&self) -> (&T, &U) { |
2161 | (&self.first, &self.second) | |
2162 | } | |
2163 | ||
2164 | /// Gets mutable references to the underlying readers in this `Chain`. | |
2165 | /// | |
2166 | /// Care should be taken to avoid modifying the internal I/O state of the | |
2167 | /// underlying readers as doing so may corrupt the internal state of this | |
2168 | /// `Chain`. | |
2169 | /// | |
2170 | /// # Examples | |
2171 | /// | |
0531ce1d XL |
2172 | /// ```no_run |
2173 | /// use std::io; | |
7cac9316 XL |
2174 | /// use std::io::prelude::*; |
2175 | /// use std::fs::File; | |
2176 | /// | |
0531ce1d XL |
2177 | /// fn main() -> io::Result<()> { |
2178 | /// let mut foo_file = File::open("foo.txt")?; | |
2179 | /// let mut bar_file = File::open("bar.txt")?; | |
7cac9316 | 2180 | /// |
0531ce1d XL |
2181 | /// let mut chain = foo_file.chain(bar_file); |
2182 | /// let (foo_file, bar_file) = chain.get_mut(); | |
2183 | /// Ok(()) | |
2184 | /// } | |
7cac9316 | 2185 | /// ``` |
041b39d2 | 2186 | #[stable(feature = "more_io_inner_methods", since = "1.20.0")] |
7cac9316 XL |
2187 | pub fn get_mut(&mut self) -> (&mut T, &mut U) { |
2188 | (&mut self.first, &mut self.second) | |
2189 | } | |
2190 | } | |
2191 | ||
8bb4bdeb | 2192 | #[stable(feature = "std_debug", since = "1.16.0")] |
32a655c1 | 2193 | impl<T: fmt::Debug, U: fmt::Debug> fmt::Debug for Chain<T, U> { |
532ac7d7 | 2194 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
60c5eb7d | 2195 | f.debug_struct("Chain").field("t", &self.first).field("u", &self.second).finish() |
32a655c1 SL |
2196 | } |
2197 | } | |
2198 | ||
c34b1796 | 2199 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2200 | impl<T: Read, U: Read> Read for Chain<T, U> { |
2201 | fn read(&mut self, buf: &mut [u8]) -> Result<usize> { | |
2202 | if !self.done_first { | |
54a0048b | 2203 | match self.first.read(buf)? { |
416331ca | 2204 | 0 if !buf.is_empty() => self.done_first = true, |
85aaf69f SL |
2205 | n => return Ok(n), |
2206 | } | |
2207 | } | |
2208 | self.second.read(buf) | |
2209 | } | |
041b39d2 | 2210 | |
48663c56 | 2211 | fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> { |
9fa01778 XL |
2212 | if !self.done_first { |
2213 | match self.first.read_vectored(bufs)? { | |
2214 | 0 if bufs.iter().any(|b| !b.is_empty()) => self.done_first = true, | |
2215 | n => return Ok(n), | |
2216 | } | |
2217 | } | |
2218 | self.second.read_vectored(bufs) | |
2219 | } | |
2220 | ||
041b39d2 XL |
2221 | unsafe fn initializer(&self) -> Initializer { |
2222 | let initializer = self.first.initializer(); | |
60c5eb7d | 2223 | if initializer.should_initialize() { initializer } else { self.second.initializer() } |
041b39d2 | 2224 | } |
1a4d82fc JJ |
2225 | } |
2226 | ||
54a0048b SL |
2227 | #[stable(feature = "chain_bufread", since = "1.9.0")] |
2228 | impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> { | |
2229 | fn fill_buf(&mut self) -> Result<&[u8]> { | |
2230 | if !self.done_first { | |
2231 | match self.first.fill_buf()? { | |
60c5eb7d XL |
2232 | buf if buf.is_empty() => { |
2233 | self.done_first = true; | |
2234 | } | |
54a0048b SL |
2235 | buf => return Ok(buf), |
2236 | } | |
2237 | } | |
2238 | self.second.fill_buf() | |
2239 | } | |
2240 | ||
2241 | fn consume(&mut self, amt: usize) { | |
60c5eb7d | 2242 | if !self.done_first { self.first.consume(amt) } else { self.second.consume(amt) } |
54a0048b SL |
2243 | } |
2244 | } | |
2245 | ||
6a06907d XL |
2246 | impl<T, U> SizeHint for Chain<T, U> { |
2247 | fn lower_bound(&self) -> usize { | |
2248 | SizeHint::lower_bound(&self.first) + SizeHint::lower_bound(&self.second) | |
2249 | } | |
2250 | ||
2251 | fn upper_bound(&self) -> Option<usize> { | |
2252 | match (SizeHint::upper_bound(&self.first), SizeHint::upper_bound(&self.second)) { | |
2253 | (Some(first), Some(second)) => Some(first + second), | |
2254 | _ => None, | |
2255 | } | |
2256 | } | |
2257 | } | |
2258 | ||
85aaf69f | 2259 | /// Reader adaptor which limits the bytes read from an underlying reader. |
1a4d82fc | 2260 | /// |
cc61c64b XL |
2261 | /// This struct is generally created by calling [`take`] on a reader. |
2262 | /// Please see the documentation of [`take`] for more details. | |
c1a9b12d | 2263 | /// |
3dfed10e | 2264 | /// [`take`]: Read::take |
c34b1796 | 2265 | #[stable(feature = "rust1", since = "1.0.0")] |
32a655c1 | 2266 | #[derive(Debug)] |
85aaf69f SL |
2267 | pub struct Take<T> { |
2268 | inner: T, | |
2269 | limit: u64, | |
1a4d82fc JJ |
2270 | } |
2271 | ||
85aaf69f SL |
2272 | impl<T> Take<T> { |
2273 | /// Returns the number of bytes that can be read before this instance will | |
2274 | /// return EOF. | |
1a4d82fc | 2275 | /// |
85aaf69f | 2276 | /// # Note |
1a4d82fc | 2277 | /// |
476ff2be SL |
2278 | /// This instance may reach `EOF` after reading fewer bytes than indicated by |
2279 | /// this method if the underlying [`Read`] instance reaches EOF. | |
2280 | /// | |
5bcae85e SL |
2281 | /// # Examples |
2282 | /// | |
0531ce1d | 2283 | /// ```no_run |
5bcae85e SL |
2284 | /// use std::io; |
2285 | /// use std::io::prelude::*; | |
2286 | /// use std::fs::File; | |
2287 | /// | |
0531ce1d XL |
2288 | /// fn main() -> io::Result<()> { |
2289 | /// let f = File::open("foo.txt")?; | |
5bcae85e | 2290 | /// |
0531ce1d XL |
2291 | /// // read at most five bytes |
2292 | /// let handle = f.take(5); | |
5bcae85e | 2293 | /// |
0531ce1d XL |
2294 | /// println!("limit: {}", handle.limit()); |
2295 | /// Ok(()) | |
2296 | /// } | |
5bcae85e | 2297 | /// ``` |
c34b1796 | 2298 | #[stable(feature = "rust1", since = "1.0.0")] |
60c5eb7d XL |
2299 | pub fn limit(&self) -> u64 { |
2300 | self.limit | |
2301 | } | |
9e0c209e | 2302 | |
041b39d2 XL |
2303 | /// Sets the number of bytes that can be read before this instance will |
2304 | /// return EOF. This is the same as constructing a new `Take` instance, so | |
2305 | /// the amount of bytes read and the previous limit value don't matter when | |
2306 | /// calling this method. | |
2307 | /// | |
2308 | /// # Examples | |
2309 | /// | |
0531ce1d | 2310 | /// ```no_run |
041b39d2 XL |
2311 | /// use std::io; |
2312 | /// use std::io::prelude::*; | |
2313 | /// use std::fs::File; | |
2314 | /// | |
0531ce1d XL |
2315 | /// fn main() -> io::Result<()> { |
2316 | /// let f = File::open("foo.txt")?; | |
041b39d2 | 2317 | /// |
0531ce1d XL |
2318 | /// // read at most five bytes |
2319 | /// let mut handle = f.take(5); | |
2320 | /// handle.set_limit(10); | |
041b39d2 | 2321 | /// |
0531ce1d XL |
2322 | /// assert_eq!(handle.limit(), 10); |
2323 | /// Ok(()) | |
2324 | /// } | |
041b39d2 | 2325 | /// ``` |
83c7162d | 2326 | #[stable(feature = "take_set_limit", since = "1.27.0")] |
041b39d2 XL |
2327 | pub fn set_limit(&mut self, limit: u64) { |
2328 | self.limit = limit; | |
2329 | } | |
2330 | ||
9e0c209e SL |
2331 | /// Consumes the `Take`, returning the wrapped reader. |
2332 | /// | |
2333 | /// # Examples | |
2334 | /// | |
0531ce1d | 2335 | /// ```no_run |
9e0c209e SL |
2336 | /// use std::io; |
2337 | /// use std::io::prelude::*; | |
2338 | /// use std::fs::File; | |
2339 | /// | |
0531ce1d XL |
2340 | /// fn main() -> io::Result<()> { |
2341 | /// let mut file = File::open("foo.txt")?; | |
9e0c209e | 2342 | /// |
0531ce1d XL |
2343 | /// let mut buffer = [0; 5]; |
2344 | /// let mut handle = file.take(5); | |
2345 | /// handle.read(&mut buffer)?; | |
9e0c209e | 2346 | /// |
0531ce1d XL |
2347 | /// let file = handle.into_inner(); |
2348 | /// Ok(()) | |
2349 | /// } | |
9e0c209e | 2350 | /// ``` |
476ff2be | 2351 | #[stable(feature = "io_take_into_inner", since = "1.15.0")] |
9e0c209e SL |
2352 | pub fn into_inner(self) -> T { |
2353 | self.inner | |
2354 | } | |
7cac9316 XL |
2355 | |
2356 | /// Gets a reference to the underlying reader. | |
2357 | /// | |
2358 | /// # Examples | |
2359 | /// | |
0531ce1d | 2360 | /// ```no_run |
7cac9316 XL |
2361 | /// use std::io; |
2362 | /// use std::io::prelude::*; | |
2363 | /// use std::fs::File; | |
2364 | /// | |
0531ce1d XL |
2365 | /// fn main() -> io::Result<()> { |
2366 | /// let mut file = File::open("foo.txt")?; | |
7cac9316 | 2367 | /// |
0531ce1d XL |
2368 | /// let mut buffer = [0; 5]; |
2369 | /// let mut handle = file.take(5); | |
2370 | /// handle.read(&mut buffer)?; | |
7cac9316 | 2371 | /// |
0531ce1d XL |
2372 | /// let file = handle.get_ref(); |
2373 | /// Ok(()) | |
2374 | /// } | |
7cac9316 | 2375 | /// ``` |
041b39d2 | 2376 | #[stable(feature = "more_io_inner_methods", since = "1.20.0")] |
7cac9316 XL |
2377 | pub fn get_ref(&self) -> &T { |
2378 | &self.inner | |
2379 | } | |
2380 | ||
2381 | /// Gets a mutable reference to the underlying reader. | |
2382 | /// | |
2383 | /// Care should be taken to avoid modifying the internal I/O state of the | |
2384 | /// underlying reader as doing so may corrupt the internal limit of this | |
2385 | /// `Take`. | |
2386 | /// | |
2387 | /// # Examples | |
2388 | /// | |
0531ce1d | 2389 | /// ```no_run |
7cac9316 XL |
2390 | /// use std::io; |
2391 | /// use std::io::prelude::*; | |
2392 | /// use std::fs::File; | |
2393 | /// | |
0531ce1d XL |
2394 | /// fn main() -> io::Result<()> { |
2395 | /// let mut file = File::open("foo.txt")?; | |
7cac9316 | 2396 | /// |
0531ce1d XL |
2397 | /// let mut buffer = [0; 5]; |
2398 | /// let mut handle = file.take(5); | |
2399 | /// handle.read(&mut buffer)?; | |
7cac9316 | 2400 | /// |
0531ce1d XL |
2401 | /// let file = handle.get_mut(); |
2402 | /// Ok(()) | |
2403 | /// } | |
7cac9316 | 2404 | /// ``` |
041b39d2 | 2405 | #[stable(feature = "more_io_inner_methods", since = "1.20.0")] |
7cac9316 XL |
2406 | pub fn get_mut(&mut self) -> &mut T { |
2407 | &mut self.inner | |
2408 | } | |
85aaf69f | 2409 | } |
1a4d82fc | 2410 | |
c34b1796 | 2411 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2412 | impl<T: Read> Read for Take<T> { |
2413 | fn read(&mut self, buf: &mut [u8]) -> Result<usize> { | |
c34b1796 AL |
2414 | // Don't call into inner reader at all at EOF because it may still block |
2415 | if self.limit == 0 { | |
2416 | return Ok(0); | |
2417 | } | |
2418 | ||
85aaf69f | 2419 | let max = cmp::min(buf.len() as u64, self.limit) as usize; |
54a0048b | 2420 | let n = self.inner.read(&mut buf[..max])?; |
85aaf69f SL |
2421 | self.limit -= n as u64; |
2422 | Ok(n) | |
1a4d82fc | 2423 | } |
041b39d2 XL |
2424 | |
2425 | unsafe fn initializer(&self) -> Initializer { | |
2426 | self.inner.initializer() | |
2427 | } | |
b7449926 XL |
2428 | |
2429 | fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> { | |
e1599b0c XL |
2430 | // Pass in a reservation_size closure that respects the current value |
2431 | // of limit for each read. If we hit the read limit, this prevents the | |
2432 | // final zero-byte read from allocating again. | |
2433 | read_to_end_with_reservation(self, buf, |self_| cmp::min(self_.limit, 32) as usize) | |
b7449926 | 2434 | } |
1a4d82fc JJ |
2435 | } |
2436 | ||
c34b1796 AL |
2437 | #[stable(feature = "rust1", since = "1.0.0")] |
2438 | impl<T: BufRead> BufRead for Take<T> { | |
2439 | fn fill_buf(&mut self) -> Result<&[u8]> { | |
a7813a04 XL |
2440 | // Don't call into inner reader at all at EOF because it may still block |
2441 | if self.limit == 0 { | |
2442 | return Ok(&[]); | |
2443 | } | |
2444 | ||
54a0048b | 2445 | let buf = self.inner.fill_buf()?; |
c34b1796 AL |
2446 | let cap = cmp::min(buf.len() as u64, self.limit) as usize; |
2447 | Ok(&buf[..cap]) | |
2448 | } | |
2449 | ||
2450 | fn consume(&mut self, amt: usize) { | |
2451 | // Don't let callers reset the limit by passing an overlarge value | |
2452 | let amt = cmp::min(amt as u64, self.limit) as usize; | |
2453 | self.limit -= amt as u64; | |
2454 | self.inner.consume(amt); | |
2455 | } | |
2456 | } | |
2457 | ||
c1a9b12d SL |
2458 | /// An iterator over `u8` values of a reader. |
2459 | /// | |
cc61c64b XL |
2460 | /// This struct is generally created by calling [`bytes`] on a reader. |
2461 | /// Please see the documentation of [`bytes`] for more details. | |
1a4d82fc | 2462 | /// |
3dfed10e | 2463 | /// [`bytes`]: Read::bytes |
c34b1796 | 2464 | #[stable(feature = "rust1", since = "1.0.0")] |
32a655c1 | 2465 | #[derive(Debug)] |
85aaf69f SL |
2466 | pub struct Bytes<R> { |
2467 | inner: R, | |
1a4d82fc JJ |
2468 | } |
2469 | ||
c34b1796 | 2470 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2471 | impl<R: Read> Iterator for Bytes<R> { |
2472 | type Item = Result<u8>; | |
1a4d82fc | 2473 | |
85aaf69f | 2474 | fn next(&mut self) -> Option<Result<u8>> { |
0731742a XL |
2475 | let mut byte = 0; |
2476 | loop { | |
2477 | return match self.inner.read(slice::from_mut(&mut byte)) { | |
2478 | Ok(0) => None, | |
2479 | Ok(..) => Some(Ok(byte)), | |
2480 | Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, | |
2481 | Err(e) => Some(Err(e)), | |
2482 | }; | |
2483 | } | |
85aaf69f | 2484 | } |
6a06907d XL |
2485 | |
2486 | fn size_hint(&self) -> (usize, Option<usize>) { | |
2487 | SizeHint::size_hint(&self.inner) | |
2488 | } | |
2489 | } | |
2490 | ||
2491 | trait SizeHint { | |
2492 | fn lower_bound(&self) -> usize; | |
2493 | ||
2494 | fn upper_bound(&self) -> Option<usize>; | |
2495 | ||
2496 | fn size_hint(&self) -> (usize, Option<usize>) { | |
2497 | (self.lower_bound(), self.upper_bound()) | |
2498 | } | |
2499 | } | |
2500 | ||
2501 | impl<T> SizeHint for T { | |
2502 | default fn lower_bound(&self) -> usize { | |
2503 | 0 | |
2504 | } | |
2505 | ||
2506 | default fn upper_bound(&self) -> Option<usize> { | |
2507 | None | |
2508 | } | |
1a4d82fc JJ |
2509 | } |
2510 | ||
85aaf69f SL |
2511 | /// An iterator over the contents of an instance of `BufRead` split on a |
2512 | /// particular byte. | |
2513 | /// | |
e1599b0c XL |
2514 | /// This struct is generally created by calling [`split`] on a `BufRead`. |
2515 | /// Please see the documentation of [`split`] for more details. | |
c1a9b12d | 2516 | /// |
3dfed10e | 2517 | /// [`split`]: BufRead::split |
c34b1796 | 2518 | #[stable(feature = "rust1", since = "1.0.0")] |
32a655c1 | 2519 | #[derive(Debug)] |
85aaf69f SL |
2520 | pub struct Split<B> { |
2521 | buf: B, | |
2522 | delim: u8, | |
2523 | } | |
1a4d82fc | 2524 | |
c34b1796 | 2525 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2526 | impl<B: BufRead> Iterator for Split<B> { |
2527 | type Item = Result<Vec<u8>>; | |
1a4d82fc | 2528 | |
85aaf69f SL |
2529 | fn next(&mut self) -> Option<Result<Vec<u8>>> { |
2530 | let mut buf = Vec::new(); | |
2531 | match self.buf.read_until(self.delim, &mut buf) { | |
c34b1796 AL |
2532 | Ok(0) => None, |
2533 | Ok(_n) => { | |
85aaf69f SL |
2534 | if buf[buf.len() - 1] == self.delim { |
2535 | buf.pop(); | |
2536 | } | |
2537 | Some(Ok(buf)) | |
2538 | } | |
60c5eb7d | 2539 | Err(e) => Some(Err(e)), |
1a4d82fc JJ |
2540 | } |
2541 | } | |
85aaf69f SL |
2542 | } |
2543 | ||
c1a9b12d | 2544 | /// An iterator over the lines of an instance of `BufRead`. |
85aaf69f | 2545 | /// |
e1599b0c XL |
2546 | /// This struct is generally created by calling [`lines`] on a `BufRead`. |
2547 | /// Please see the documentation of [`lines`] for more details. | |
c1a9b12d | 2548 | /// |
3dfed10e | 2549 | /// [`lines`]: BufRead::lines |
c34b1796 | 2550 | #[stable(feature = "rust1", since = "1.0.0")] |
32a655c1 | 2551 | #[derive(Debug)] |
85aaf69f SL |
2552 | pub struct Lines<B> { |
2553 | buf: B, | |
2554 | } | |
2555 | ||
c34b1796 | 2556 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f SL |
2557 | impl<B: BufRead> Iterator for Lines<B> { |
2558 | type Item = Result<String>; | |
1a4d82fc | 2559 | |
85aaf69f SL |
2560 | fn next(&mut self) -> Option<Result<String>> { |
2561 | let mut buf = String::new(); | |
2562 | match self.buf.read_line(&mut buf) { | |
c34b1796 AL |
2563 | Ok(0) => None, |
2564 | Ok(_n) => { | |
74b04a01 | 2565 | if buf.ends_with('\n') { |
85aaf69f | 2566 | buf.pop(); |
74b04a01 | 2567 | if buf.ends_with('\r') { |
e9174d1e SL |
2568 | buf.pop(); |
2569 | } | |
1a4d82fc | 2570 | } |
85aaf69f | 2571 | Some(Ok(buf)) |
1a4d82fc | 2572 | } |
60c5eb7d | 2573 | Err(e) => Some(Err(e)), |
1a4d82fc JJ |
2574 | } |
2575 | } | |
85aaf69f | 2576 | } |