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1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 //! Traits, helpers, and type definitions for core I/O functionality.
12 //!
13 //! The `std::io` module contains a number of common things you'll need
14 //! when doing input and output. The most core part of this module is
15 //! the [`Read`][read] and [`Write`][write] traits, which provide the
16 //! most general interface for reading and writing input and output.
17 //!
18 //! [read]: trait.Read.html
19 //! [write]: trait.Write.html
20 //!
21 //! # Read and Write
22 //!
23 //! Because they are traits, `Read` and `Write` are implemented by a number
24 //! of other types, and you can implement them for your types too. As such,
25 //! you'll see a few different types of I/O throughout the documentation in
26 //! this module: `File`s, `TcpStream`s, and sometimes even `Vec<T>`s. For
27 //! example, `Read` adds a `read()` method, which we can use on `File`s:
28 //!
29 //! ```
30 //! use std::io;
31 //! use std::io::prelude::*;
32 //! use std::fs::File;
33 //!
34 //! # fn foo() -> io::Result<()> {
35 //! let mut f = try!(File::open("foo.txt"));
36 //! let mut buffer = [0; 10];
37 //!
38 //! // read up to 10 bytes
39 //! try!(f.read(&mut buffer));
40 //!
41 //! println!("The bytes: {:?}", buffer);
42 //! # Ok(())
43 //! # }
44 //! ```
45 //!
46 //! `Read` and `Write` are so important, implementors of the two traits have a
47 //! nickname: readers and writers. So you'll sometimes see 'a reader' instead
48 //! of 'a type that implements the `Read` trait'. Much easier!
49 //!
50 //! ## Seek and BufRead
51 //!
52 //! Beyond that, there are two important traits that are provided: [`Seek`][seek]
53 //! and [`BufRead`][bufread]. Both of these build on top of a reader to control
54 //! how the reading happens. `Seek` lets you control where the next byte is
55 //! coming from:
56 //!
57 //! ```
58 //! use std::io;
59 //! use std::io::prelude::*;
60 //! use std::io::SeekFrom;
61 //! use std::fs::File;
62 //!
63 //! # fn foo() -> io::Result<()> {
64 //! let mut f = try!(File::open("foo.txt"));
65 //! let mut buffer = [0; 10];
66 //!
67 //! // skip to the last 10 bytes of the file
68 //! try!(f.seek(SeekFrom::End(-10)));
69 //!
70 //! // read up to 10 bytes
71 //! try!(f.read(&mut buffer));
72 //!
73 //! println!("The bytes: {:?}", buffer);
74 //! # Ok(())
75 //! # }
76 //! ```
77 //!
78 //! [seek]: trait.Seek.html
79 //! [bufread]: trait.BufRead.html
80 //!
81 //! `BufRead` uses an internal buffer to provide a number of other ways to read, but
82 //! to show it off, we'll need to talk about buffers in general. Keep reading!
83 //!
84 //! ## BufReader and BufWriter
85 //!
86 //! Byte-based interfaces are unwieldy and can be inefficient, as we'd need to be
87 //! making near-constant calls to the operating system. To help with this,
88 //! `std::io` comes with two structs, `BufReader` and `BufWriter`, which wrap
89 //! readers and writers. The wrapper uses a buffer, reducing the number of
90 //! calls and providing nicer methods for accessing exactly what you want.
91 //!
92 //! For example, `BufReader` works with the `BufRead` trait to add extra
93 //! methods to any reader:
94 //!
95 //! ```
96 //! use std::io;
97 //! use std::io::prelude::*;
98 //! use std::io::BufReader;
99 //! use std::fs::File;
100 //!
101 //! # fn foo() -> io::Result<()> {
102 //! let f = try!(File::open("foo.txt"));
103 //! let mut reader = BufReader::new(f);
104 //! let mut buffer = String::new();
105 //!
106 //! // read a line into buffer
107 //! try!(reader.read_line(&mut buffer));
108 //!
109 //! println!("{}", buffer);
110 //! # Ok(())
111 //! # }
112 //! ```
113 //!
114 //! `BufWriter` doesn't add any new ways of writing; it just buffers every call
115 //! to [`write()`][write()]:
116 //!
117 //! ```
118 //! use std::io;
119 //! use std::io::prelude::*;
120 //! use std::io::BufWriter;
121 //! use std::fs::File;
122 //!
123 //! # fn foo() -> io::Result<()> {
124 //! let f = try!(File::create("foo.txt"));
125 //! {
126 //! let mut writer = BufWriter::new(f);
127 //!
128 //! // write a byte to the buffer
129 //! try!(writer.write(&[42]));
130 //!
131 //! } // the buffer is flushed once writer goes out of scope
132 //!
133 //! # Ok(())
134 //! # }
135 //! ```
136 //!
137 //! [write()]: trait.Write.html#tymethod.write
138 //!
139 //! ## Standard input and output
140 //!
141 //! A very common source of input is standard input:
142 //!
143 //! ```
144 //! use std::io;
145 //!
146 //! # fn foo() -> io::Result<()> {
147 //! let mut input = String::new();
148 //!
149 //! try!(io::stdin().read_line(&mut input));
150 //!
151 //! println!("You typed: {}", input.trim());
152 //! # Ok(())
153 //! # }
154 //! ```
155 //!
156 //! And a very common source of output is standard output:
157 //!
158 //! ```
159 //! use std::io;
160 //! use std::io::prelude::*;
161 //!
162 //! # fn foo() -> io::Result<()> {
163 //! try!(io::stdout().write(&[42]));
164 //! # Ok(())
165 //! # }
166 //! ```
167 //!
168 //! Of course, using `io::stdout()` directly is less common than something like
169 //! `println!`.
170 //!
171 //! ## Iterator types
172 //!
173 //! A large number of the structures provided by `std::io` are for various
174 //! ways of iterating over I/O. For example, `Lines` is used to split over
175 //! lines:
176 //!
177 //! ```
178 //! use std::io;
179 //! use std::io::prelude::*;
180 //! use std::io::BufReader;
181 //! use std::fs::File;
182 //!
183 //! # fn foo() -> io::Result<()> {
184 //! let f = try!(File::open("foo.txt"));
185 //! let mut reader = BufReader::new(f);
186 //!
187 //! for line in reader.lines() {
188 //! let line = try!(line);
189 //! println!("{}", line);
190 //! }
191 //!
192 //! # Ok(())
193 //! # }
194 //! ```
195 //!
196 //! ## Functions
197 //!
198 //! There are a number of [functions][functions] that offer access to various
199 //! features. For example, we can use three of these functions to copy everything
200 //! from standard input to standard output:
201 //!
202 //! ```
203 //! use std::io;
204 //!
205 //! # fn foo() -> io::Result<()> {
206 //! try!(io::copy(&mut io::stdin(), &mut io::stdout()));
207 //! # Ok(())
208 //! # }
209 //! ```
210 //!
211 //! [functions]: #functions
212 //!
213 //! ## io::Result
214 //!
215 //! Last, but certainly not least, is [`io::Result`][result]. This type is used
216 //! as the return type of many `std::io` functions that can cause an error, and
217 //! can be returned from your own functions as well. Many of the examples in this
218 //! module use the [`try!`][try] macro:
219 //!
220 //! ```
221 //! use std::io;
222 //!
223 //! fn read_input() -> io::Result<()> {
224 //! let mut input = String::new();
225 //!
226 //! try!(io::stdin().read_line(&mut input));
227 //!
228 //! println!("You typed: {}", input.trim());
229 //!
230 //! Ok(())
231 //! }
232 //! ```
233 //!
234 //! The return type of `read_input()`, `io::Result<()>`, is a very common type
235 //! for functions which don't have a 'real' return value, but do want to return
236 //! errors if they happen. In this case, the only purpose of this function is
237 //! to read the line and print it, so we use `()`.
238 //!
239 //! [result]: type.Result.html
240 //! [try]: ../macro.try!.html
241 //!
242 //! ## Platform-specific behavior
243 //!
244 //! Many I/O functions throughout the standard library are documented to indicate
245 //! what various library or syscalls they are delegated to. This is done to help
246 //! applications both understand what's happening under the hood as well as investigate
247 //! any possibly unclear semantics. Note, however, that this is informative, not a binding
248 //! contract. The implementation of many of these functions are subject to change over
249 //! time and may call fewer or more syscalls/library functions.
250
251 #![stable(feature = "rust1", since = "1.0.0")]
252
253 use cmp;
254 use rustc_unicode::str as core_str;
255 use error as std_error;
256 use fmt;
257 use iter::{Iterator};
258 use marker::Sized;
259 use ops::{Drop, FnOnce};
260 use option::Option::{self, Some, None};
261 use result::Result::{Ok, Err};
262 use result;
263 use string::String;
264 use str;
265 use vec::Vec;
266 use memchr;
267
268 #[stable(feature = "rust1", since = "1.0.0")]
269 pub use self::buffered::{BufReader, BufWriter, LineWriter};
270 #[stable(feature = "rust1", since = "1.0.0")]
271 pub use self::buffered::IntoInnerError;
272 #[stable(feature = "rust1", since = "1.0.0")]
273 pub use self::cursor::Cursor;
274 #[stable(feature = "rust1", since = "1.0.0")]
275 pub use self::error::{Result, Error, ErrorKind};
276 #[stable(feature = "rust1", since = "1.0.0")]
277 pub use self::util::{copy, sink, Sink, empty, Empty, repeat, Repeat};
278 #[stable(feature = "rust1", since = "1.0.0")]
279 pub use self::stdio::{stdin, stdout, stderr, _print, Stdin, Stdout, Stderr};
280 #[stable(feature = "rust1", since = "1.0.0")]
281 pub use self::stdio::{StdoutLock, StderrLock, StdinLock};
282 #[unstable(feature = "libstd_io_internals", issue = "0")]
283 #[doc(no_inline, hidden)]
284 pub use self::stdio::{set_panic, set_print};
285
286 pub mod prelude;
287 mod buffered;
288 mod cursor;
289 mod error;
290 mod impls;
291 mod lazy;
292 mod util;
293 mod stdio;
294
295 const DEFAULT_BUF_SIZE: usize = 8 * 1024;
296
297 // A few methods below (read_to_string, read_line) will append data into a
298 // `String` buffer, but we need to be pretty careful when doing this. The
299 // implementation will just call `.as_mut_vec()` and then delegate to a
300 // byte-oriented reading method, but we must ensure that when returning we never
301 // leave `buf` in a state such that it contains invalid UTF-8 in its bounds.
302 //
303 // To this end, we use an RAII guard (to protect against panics) which updates
304 // the length of the string when it is dropped. This guard initially truncates
305 // the string to the prior length and only after we've validated that the
306 // new contents are valid UTF-8 do we allow it to set a longer length.
307 //
308 // The unsafety in this function is twofold:
309 //
310 // 1. We're looking at the raw bytes of `buf`, so we take on the burden of UTF-8
311 // checks.
312 // 2. We're passing a raw buffer to the function `f`, and it is expected that
313 // the function only *appends* bytes to the buffer. We'll get undefined
314 // behavior if existing bytes are overwritten to have non-UTF-8 data.
315 fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize>
316 where F: FnOnce(&mut Vec<u8>) -> Result<usize>
317 {
318 struct Guard<'a> { s: &'a mut Vec<u8>, len: usize }
319 impl<'a> Drop for Guard<'a> {
320 fn drop(&mut self) {
321 unsafe { self.s.set_len(self.len); }
322 }
323 }
324
325 unsafe {
326 let mut g = Guard { len: buf.len(), s: buf.as_mut_vec() };
327 let ret = f(g.s);
328 if str::from_utf8(&g.s[g.len..]).is_err() {
329 ret.and_then(|_| {
330 Err(Error::new(ErrorKind::InvalidData,
331 "stream did not contain valid UTF-8"))
332 })
333 } else {
334 g.len = g.s.len();
335 ret
336 }
337 }
338 }
339
340 // This uses an adaptive system to extend the vector when it fills. We want to
341 // avoid paying to allocate and zero a huge chunk of memory if the reader only
342 // has 4 bytes while still making large reads if the reader does have a ton
343 // of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every
344 // time is 4,500 times (!) slower than this if the reader has a very small
345 // amount of data to return.
346 fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> {
347 let start_len = buf.len();
348 let mut len = start_len;
349 let mut new_write_size = 16;
350 let ret;
351 loop {
352 if len == buf.len() {
353 if new_write_size < DEFAULT_BUF_SIZE {
354 new_write_size *= 2;
355 }
356 buf.resize(len + new_write_size, 0);
357 }
358
359 match r.read(&mut buf[len..]) {
360 Ok(0) => {
361 ret = Ok(len - start_len);
362 break;
363 }
364 Ok(n) => len += n,
365 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
366 Err(e) => {
367 ret = Err(e);
368 break;
369 }
370 }
371 }
372
373 buf.truncate(len);
374 ret
375 }
376
377 /// The `Read` trait allows for reading bytes from a source.
378 ///
379 /// Implementors of the `Read` trait are sometimes called 'readers'.
380 ///
381 /// Readers are defined by one required method, `read()`. Each call to `read`
382 /// will attempt to pull bytes from this source into a provided buffer. A
383 /// number of other methods are implemented in terms of `read()`, giving
384 /// implementors a number of ways to read bytes while only needing to implement
385 /// a single method.
386 ///
387 /// Readers are intended to be composable with one another. Many implementors
388 /// throughout `std::io` take and provide types which implement the `Read`
389 /// trait.
390 ///
391 /// Please note that each call to `read` may involve a system call, and
392 /// therefore, using something that implements [`BufRead`][bufread], such as
393 /// [`BufReader`][bufreader], will be more efficient.
394 ///
395 /// [bufread]: trait.BufRead.html
396 /// [bufreader]: struct.BufReader.html
397 ///
398 /// # Examples
399 ///
400 /// [`File`][file]s implement `Read`:
401 ///
402 /// [file]: ../fs/struct.File.html
403 ///
404 /// ```
405 /// use std::io;
406 /// use std::io::prelude::*;
407 /// use std::fs::File;
408 ///
409 /// # fn foo() -> io::Result<()> {
410 /// let mut f = try!(File::open("foo.txt"));
411 /// let mut buffer = [0; 10];
412 ///
413 /// // read up to 10 bytes
414 /// try!(f.read(&mut buffer));
415 ///
416 /// let mut buffer = vec![0; 10];
417 /// // read the whole file
418 /// try!(f.read_to_end(&mut buffer));
419 ///
420 /// // read into a String, so that you don't need to do the conversion.
421 /// let mut buffer = String::new();
422 /// try!(f.read_to_string(&mut buffer));
423 ///
424 /// // and more! See the other methods for more details.
425 /// # Ok(())
426 /// # }
427 /// ```
428 #[stable(feature = "rust1", since = "1.0.0")]
429 pub trait Read {
430 /// Pull some bytes from this source into the specified buffer, returning
431 /// how many bytes were read.
432 ///
433 /// This function does not provide any guarantees about whether it blocks
434 /// waiting for data, but if an object needs to block for a read but cannot
435 /// it will typically signal this via an `Err` return value.
436 ///
437 /// If the return value of this method is `Ok(n)`, then it must be
438 /// guaranteed that `0 <= n <= buf.len()`. A nonzero `n` value indicates
439 /// that the buffer `buf` has been filled in with `n` bytes of data from this
440 /// source. If `n` is `0`, then it can indicate one of two scenarios:
441 ///
442 /// 1. This reader has reached its "end of file" and will likely no longer
443 /// be able to produce bytes. Note that this does not mean that the
444 /// reader will *always* no longer be able to produce bytes.
445 /// 2. The buffer specified was 0 bytes in length.
446 ///
447 /// No guarantees are provided about the contents of `buf` when this
448 /// function is called, implementations cannot rely on any property of the
449 /// contents of `buf` being true. It is recommended that implementations
450 /// only write data to `buf` instead of reading its contents.
451 ///
452 /// # Errors
453 ///
454 /// If this function encounters any form of I/O or other error, an error
455 /// variant will be returned. If an error is returned then it must be
456 /// guaranteed that no bytes were read.
457 ///
458 /// # Examples
459 ///
460 /// [`File`][file]s implement `Read`:
461 ///
462 /// [file]: ../fs/struct.File.html
463 ///
464 /// ```
465 /// use std::io;
466 /// use std::io::prelude::*;
467 /// use std::fs::File;
468 ///
469 /// # fn foo() -> io::Result<()> {
470 /// let mut f = try!(File::open("foo.txt"));
471 /// let mut buffer = [0; 10];
472 ///
473 /// // read 10 bytes
474 /// try!(f.read(&mut buffer[..]));
475 /// # Ok(())
476 /// # }
477 /// ```
478 #[stable(feature = "rust1", since = "1.0.0")]
479 fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
480
481 /// Read all bytes until EOF in this source, placing them into `buf`.
482 ///
483 /// All bytes read from this source will be appended to the specified buffer
484 /// `buf`. This function will continuously call `read` to append more data to
485 /// `buf` until `read` returns either `Ok(0)` or an error of
486 /// non-`ErrorKind::Interrupted` kind.
487 ///
488 /// If successful, this function will return the total number of bytes read.
489 ///
490 /// # Errors
491 ///
492 /// If this function encounters an error of the kind
493 /// `ErrorKind::Interrupted` then the error is ignored and the operation
494 /// will continue.
495 ///
496 /// If any other read error is encountered then this function immediately
497 /// returns. Any bytes which have already been read will be appended to
498 /// `buf`.
499 ///
500 /// # Examples
501 ///
502 /// [`File`][file]s implement `Read`:
503 ///
504 /// [file]: ../fs/struct.File.html
505 ///
506 /// ```
507 /// use std::io;
508 /// use std::io::prelude::*;
509 /// use std::fs::File;
510 ///
511 /// # fn foo() -> io::Result<()> {
512 /// let mut f = try!(File::open("foo.txt"));
513 /// let mut buffer = Vec::new();
514 ///
515 /// // read the whole file
516 /// try!(f.read_to_end(&mut buffer));
517 /// # Ok(())
518 /// # }
519 /// ```
520 #[stable(feature = "rust1", since = "1.0.0")]
521 fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
522 read_to_end(self, buf)
523 }
524
525 /// Read all bytes until EOF in this source, placing them into `buf`.
526 ///
527 /// If successful, this function returns the number of bytes which were read
528 /// and appended to `buf`.
529 ///
530 /// # Errors
531 ///
532 /// If the data in this stream is *not* valid UTF-8 then an error is
533 /// returned and `buf` is unchanged.
534 ///
535 /// See [`read_to_end()`][readtoend] for other error semantics.
536 ///
537 /// [readtoend]: #method.read_to_end
538 ///
539 /// # Examples
540 ///
541 /// [`File`][file]s implement `Read`:
542 ///
543 /// [file]: ../fs/struct.File.html
544 ///
545 /// ```
546 /// use std::io;
547 /// use std::io::prelude::*;
548 /// use std::fs::File;
549 ///
550 /// # fn foo() -> io::Result<()> {
551 /// let mut f = try!(File::open("foo.txt"));
552 /// let mut buffer = String::new();
553 ///
554 /// try!(f.read_to_string(&mut buffer));
555 /// # Ok(())
556 /// # }
557 /// ```
558 #[stable(feature = "rust1", since = "1.0.0")]
559 fn read_to_string(&mut self, buf: &mut String) -> Result<usize> {
560 // Note that we do *not* call `.read_to_end()` here. We are passing
561 // `&mut Vec<u8>` (the raw contents of `buf`) into the `read_to_end`
562 // method to fill it up. An arbitrary implementation could overwrite the
563 // entire contents of the vector, not just append to it (which is what
564 // we are expecting).
565 //
566 // To prevent extraneously checking the UTF-8-ness of the entire buffer
567 // we pass it to our hardcoded `read_to_end` implementation which we
568 // know is guaranteed to only read data into the end of the buffer.
569 append_to_string(buf, |b| read_to_end(self, b))
570 }
571
572 /// Read the exact number of bytes required to fill `buf`.
573 ///
574 /// This function reads as many bytes as necessary to completely fill the
575 /// specified buffer `buf`.
576 ///
577 /// No guarantees are provided about the contents of `buf` when this
578 /// function is called, implementations cannot rely on any property of the
579 /// contents of `buf` being true. It is recommended that implementations
580 /// only write data to `buf` instead of reading its contents.
581 ///
582 /// # Errors
583 ///
584 /// If this function encounters an error of the kind
585 /// `ErrorKind::Interrupted` then the error is ignored and the operation
586 /// will continue.
587 ///
588 /// If this function encounters an "end of file" before completely filling
589 /// the buffer, it returns an error of the kind `ErrorKind::UnexpectedEof`.
590 /// The contents of `buf` are unspecified in this case.
591 ///
592 /// If any other read error is encountered then this function immediately
593 /// returns. The contents of `buf` are unspecified in this case.
594 ///
595 /// If this function returns an error, it is unspecified how many bytes it
596 /// has read, but it will never read more than would be necessary to
597 /// completely fill the buffer.
598 ///
599 /// # Examples
600 ///
601 /// [`File`][file]s implement `Read`:
602 ///
603 /// [file]: ../fs/struct.File.html
604 ///
605 /// ```
606 /// use std::io;
607 /// use std::io::prelude::*;
608 /// use std::fs::File;
609 ///
610 /// # fn foo() -> io::Result<()> {
611 /// let mut f = try!(File::open("foo.txt"));
612 /// let mut buffer = [0; 10];
613 ///
614 /// // read exactly 10 bytes
615 /// try!(f.read_exact(&mut buffer));
616 /// # Ok(())
617 /// # }
618 /// ```
619 #[stable(feature = "read_exact", since = "1.6.0")]
620 fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<()> {
621 while !buf.is_empty() {
622 match self.read(buf) {
623 Ok(0) => break,
624 Ok(n) => { let tmp = buf; buf = &mut tmp[n..]; }
625 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
626 Err(e) => return Err(e),
627 }
628 }
629 if !buf.is_empty() {
630 Err(Error::new(ErrorKind::UnexpectedEof,
631 "failed to fill whole buffer"))
632 } else {
633 Ok(())
634 }
635 }
636
637 /// Creates a "by reference" adaptor for this instance of `Read`.
638 ///
639 /// The returned adaptor also implements `Read` and will simply borrow this
640 /// current reader.
641 ///
642 /// # Examples
643 ///
644 /// [`File`][file]s implement `Read`:
645 ///
646 /// [file]: ../fs/struct.File.html
647 ///
648 /// ```
649 /// use std::io;
650 /// use std::io::Read;
651 /// use std::fs::File;
652 ///
653 /// # fn foo() -> io::Result<()> {
654 /// let mut f = try!(File::open("foo.txt"));
655 /// let mut buffer = Vec::new();
656 /// let mut other_buffer = Vec::new();
657 ///
658 /// {
659 /// let reference = f.by_ref();
660 ///
661 /// // read at most 5 bytes
662 /// try!(reference.take(5).read_to_end(&mut buffer));
663 ///
664 /// } // drop our &mut reference so we can use f again
665 ///
666 /// // original file still usable, read the rest
667 /// try!(f.read_to_end(&mut other_buffer));
668 /// # Ok(())
669 /// # }
670 /// ```
671 #[stable(feature = "rust1", since = "1.0.0")]
672 fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
673
674 /// Transforms this `Read` instance to an `Iterator` over its bytes.
675 ///
676 /// The returned type implements `Iterator` where the `Item` is `Result<u8,
677 /// R::Err>`. The yielded item is `Ok` if a byte was successfully read and
678 /// `Err` otherwise for I/O errors. EOF is mapped to returning `None` from
679 /// this iterator.
680 ///
681 /// # Examples
682 ///
683 /// [`File`][file]s implement `Read`:
684 ///
685 /// [file]: ../fs/struct.File.html
686 ///
687 /// ```
688 /// use std::io;
689 /// use std::io::prelude::*;
690 /// use std::fs::File;
691 ///
692 /// # fn foo() -> io::Result<()> {
693 /// let mut f = try!(File::open("foo.txt"));
694 ///
695 /// for byte in f.bytes() {
696 /// println!("{}", byte.unwrap());
697 /// }
698 /// # Ok(())
699 /// # }
700 /// ```
701 #[stable(feature = "rust1", since = "1.0.0")]
702 fn bytes(self) -> Bytes<Self> where Self: Sized {
703 Bytes { inner: self }
704 }
705
706 /// Transforms this `Read` instance to an `Iterator` over `char`s.
707 ///
708 /// This adaptor will attempt to interpret this reader as a UTF-8 encoded
709 /// sequence of characters. The returned iterator will return `None` once
710 /// EOF is reached for this reader. Otherwise each element yielded will be a
711 /// `Result<char, E>` where `E` may contain information about what I/O error
712 /// occurred or where decoding failed.
713 ///
714 /// Currently this adaptor will discard intermediate data read, and should
715 /// be avoided if this is not desired.
716 ///
717 /// # Examples
718 ///
719 /// [`File`][file]s implement `Read`:
720 ///
721 /// [file]: ../fs/struct.File.html
722 ///
723 /// ```
724 /// #![feature(io)]
725 /// use std::io;
726 /// use std::io::prelude::*;
727 /// use std::fs::File;
728 ///
729 /// # fn foo() -> io::Result<()> {
730 /// let mut f = try!(File::open("foo.txt"));
731 ///
732 /// for c in f.chars() {
733 /// println!("{}", c.unwrap());
734 /// }
735 /// # Ok(())
736 /// # }
737 /// ```
738 #[unstable(feature = "io", reason = "the semantics of a partial read/write \
739 of where errors happen is currently \
740 unclear and may change",
741 issue = "27802")]
742 fn chars(self) -> Chars<Self> where Self: Sized {
743 Chars { inner: self }
744 }
745
746 /// Creates an adaptor which will chain this stream with another.
747 ///
748 /// The returned `Read` instance will first read all bytes from this object
749 /// until EOF is encountered. Afterwards the output is equivalent to the
750 /// output of `next`.
751 ///
752 /// # Examples
753 ///
754 /// [`File`][file]s implement `Read`:
755 ///
756 /// [file]: ../fs/struct.File.html
757 ///
758 /// ```
759 /// use std::io;
760 /// use std::io::prelude::*;
761 /// use std::fs::File;
762 ///
763 /// # fn foo() -> io::Result<()> {
764 /// let mut f1 = try!(File::open("foo.txt"));
765 /// let mut f2 = try!(File::open("bar.txt"));
766 ///
767 /// let mut handle = f1.chain(f2);
768 /// let mut buffer = String::new();
769 ///
770 /// // read the value into a String. We could use any Read method here,
771 /// // this is just one example.
772 /// try!(handle.read_to_string(&mut buffer));
773 /// # Ok(())
774 /// # }
775 /// ```
776 #[stable(feature = "rust1", since = "1.0.0")]
777 fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized {
778 Chain { first: self, second: next, done_first: false }
779 }
780
781 /// Creates an adaptor which will read at most `limit` bytes from it.
782 ///
783 /// This function returns a new instance of `Read` which will read at most
784 /// `limit` bytes, after which it will always return EOF (`Ok(0)`). Any
785 /// read errors will not count towards the number of bytes read and future
786 /// calls to `read` may succeed.
787 ///
788 /// # Examples
789 ///
790 /// [`File`][file]s implement `Read`:
791 ///
792 /// [file]: ../fs/struct.File.html
793 ///
794 /// ```
795 /// use std::io;
796 /// use std::io::prelude::*;
797 /// use std::fs::File;
798 ///
799 /// # fn foo() -> io::Result<()> {
800 /// let mut f = try!(File::open("foo.txt"));
801 /// let mut buffer = [0; 5];
802 ///
803 /// // read at most five bytes
804 /// let mut handle = f.take(5);
805 ///
806 /// try!(handle.read(&mut buffer));
807 /// # Ok(())
808 /// # }
809 /// ```
810 #[stable(feature = "rust1", since = "1.0.0")]
811 fn take(self, limit: u64) -> Take<Self> where Self: Sized {
812 Take { inner: self, limit: limit }
813 }
814 }
815
816 /// A trait for objects which are byte-oriented sinks.
817 ///
818 /// Implementors of the `Write` trait are sometimes called 'writers'.
819 ///
820 /// Writers are defined by two required methods, `write()` and `flush()`:
821 ///
822 /// * The `write()` method will attempt to write some data into the object,
823 /// returning how many bytes were successfully written.
824 ///
825 /// * The `flush()` method is useful for adaptors and explicit buffers
826 /// themselves for ensuring that all buffered data has been pushed out to the
827 /// 'true sink'.
828 ///
829 /// Writers are intended to be composable with one another. Many implementors
830 /// throughout `std::io` take and provide types which implement the `Write`
831 /// trait.
832 ///
833 /// # Examples
834 ///
835 /// ```
836 /// use std::io::prelude::*;
837 /// use std::fs::File;
838 ///
839 /// # fn foo() -> std::io::Result<()> {
840 /// let mut buffer = try!(File::create("foo.txt"));
841 ///
842 /// try!(buffer.write(b"some bytes"));
843 /// # Ok(())
844 /// # }
845 /// ```
846 #[stable(feature = "rust1", since = "1.0.0")]
847 pub trait Write {
848 /// Write a buffer into this object, returning how many bytes were written.
849 ///
850 /// This function will attempt to write the entire contents of `buf`, but
851 /// the entire write may not succeed, or the write may also generate an
852 /// error. A call to `write` represents *at most one* attempt to write to
853 /// any wrapped object.
854 ///
855 /// Calls to `write` are not guaranteed to block waiting for data to be
856 /// written, and a write which would otherwise block can be indicated through
857 /// an `Err` variant.
858 ///
859 /// If the return value is `Ok(n)` then it must be guaranteed that
860 /// `0 <= n <= buf.len()`. A return value of `0` typically means that the
861 /// underlying object is no longer able to accept bytes and will likely not
862 /// be able to in the future as well, or that the buffer provided is empty.
863 ///
864 /// # Errors
865 ///
866 /// Each call to `write` may generate an I/O error indicating that the
867 /// operation could not be completed. If an error is returned then no bytes
868 /// in the buffer were written to this writer.
869 ///
870 /// It is **not** considered an error if the entire buffer could not be
871 /// written to this writer.
872 ///
873 /// # Examples
874 ///
875 /// ```
876 /// use std::io::prelude::*;
877 /// use std::fs::File;
878 ///
879 /// # fn foo() -> std::io::Result<()> {
880 /// let mut buffer = try!(File::create("foo.txt"));
881 ///
882 /// try!(buffer.write(b"some bytes"));
883 /// # Ok(())
884 /// # }
885 /// ```
886 #[stable(feature = "rust1", since = "1.0.0")]
887 fn write(&mut self, buf: &[u8]) -> Result<usize>;
888
889 /// Flush this output stream, ensuring that all intermediately buffered
890 /// contents reach their destination.
891 ///
892 /// # Errors
893 ///
894 /// It is considered an error if not all bytes could be written due to
895 /// I/O errors or EOF being reached.
896 ///
897 /// # Examples
898 ///
899 /// ```
900 /// use std::io::prelude::*;
901 /// use std::io::BufWriter;
902 /// use std::fs::File;
903 ///
904 /// # fn foo() -> std::io::Result<()> {
905 /// let mut buffer = BufWriter::new(try!(File::create("foo.txt")));
906 ///
907 /// try!(buffer.write(b"some bytes"));
908 /// try!(buffer.flush());
909 /// # Ok(())
910 /// # }
911 /// ```
912 #[stable(feature = "rust1", since = "1.0.0")]
913 fn flush(&mut self) -> Result<()>;
914
915 /// Attempts to write an entire buffer into this write.
916 ///
917 /// This method will continuously call `write` while there is more data to
918 /// write. This method will not return until the entire buffer has been
919 /// successfully written or an error occurs. The first error generated from
920 /// this method will be returned.
921 ///
922 /// # Errors
923 ///
924 /// This function will return the first error that `write` returns.
925 ///
926 /// # Examples
927 ///
928 /// ```
929 /// use std::io::prelude::*;
930 /// use std::fs::File;
931 ///
932 /// # fn foo() -> std::io::Result<()> {
933 /// let mut buffer = try!(File::create("foo.txt"));
934 ///
935 /// try!(buffer.write_all(b"some bytes"));
936 /// # Ok(())
937 /// # }
938 /// ```
939 #[stable(feature = "rust1", since = "1.0.0")]
940 fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
941 while !buf.is_empty() {
942 match self.write(buf) {
943 Ok(0) => return Err(Error::new(ErrorKind::WriteZero,
944 "failed to write whole buffer")),
945 Ok(n) => buf = &buf[n..],
946 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
947 Err(e) => return Err(e),
948 }
949 }
950 Ok(())
951 }
952
953 /// Writes a formatted string into this writer, returning any error
954 /// encountered.
955 ///
956 /// This method is primarily used to interface with the
957 /// [`format_args!`][formatargs] macro, but it is rare that this should
958 /// explicitly be called. The [`write!`][write] macro should be favored to
959 /// invoke this method instead.
960 ///
961 /// [formatargs]: ../macro.format_args!.html
962 /// [write]: ../macro.write!.html
963 ///
964 /// This function internally uses the [`write_all`][writeall] method on
965 /// this trait and hence will continuously write data so long as no errors
966 /// are received. This also means that partial writes are not indicated in
967 /// this signature.
968 ///
969 /// [writeall]: #method.write_all
970 ///
971 /// # Errors
972 ///
973 /// This function will return any I/O error reported while formatting.
974 ///
975 /// # Examples
976 ///
977 /// ```
978 /// use std::io::prelude::*;
979 /// use std::fs::File;
980 ///
981 /// # fn foo() -> std::io::Result<()> {
982 /// let mut buffer = try!(File::create("foo.txt"));
983 ///
984 /// // this call
985 /// try!(write!(buffer, "{:.*}", 2, 1.234567));
986 /// // turns into this:
987 /// try!(buffer.write_fmt(format_args!("{:.*}", 2, 1.234567)));
988 /// # Ok(())
989 /// # }
990 /// ```
991 #[stable(feature = "rust1", since = "1.0.0")]
992 fn write_fmt(&mut self, fmt: fmt::Arguments) -> Result<()> {
993 // Create a shim which translates a Write to a fmt::Write and saves
994 // off I/O errors. instead of discarding them
995 struct Adaptor<'a, T: ?Sized + 'a> {
996 inner: &'a mut T,
997 error: Result<()>,
998 }
999
1000 impl<'a, T: Write + ?Sized> fmt::Write for Adaptor<'a, T> {
1001 fn write_str(&mut self, s: &str) -> fmt::Result {
1002 match self.inner.write_all(s.as_bytes()) {
1003 Ok(()) => Ok(()),
1004 Err(e) => {
1005 self.error = Err(e);
1006 Err(fmt::Error)
1007 }
1008 }
1009 }
1010 }
1011
1012 let mut output = Adaptor { inner: self, error: Ok(()) };
1013 match fmt::write(&mut output, fmt) {
1014 Ok(()) => Ok(()),
1015 Err(..) => {
1016 // check if the error came from the underlying `Write` or not
1017 if output.error.is_err() {
1018 output.error
1019 } else {
1020 Err(Error::new(ErrorKind::Other, "formatter error"))
1021 }
1022 }
1023 }
1024 }
1025
1026 /// Creates a "by reference" adaptor for this instance of `Write`.
1027 ///
1028 /// The returned adaptor also implements `Write` and will simply borrow this
1029 /// current writer.
1030 ///
1031 /// # Examples
1032 ///
1033 /// ```
1034 /// use std::io::Write;
1035 /// use std::fs::File;
1036 ///
1037 /// # fn foo() -> std::io::Result<()> {
1038 /// let mut buffer = try!(File::create("foo.txt"));
1039 ///
1040 /// let reference = buffer.by_ref();
1041 ///
1042 /// // we can use reference just like our original buffer
1043 /// try!(reference.write_all(b"some bytes"));
1044 /// # Ok(())
1045 /// # }
1046 /// ```
1047 #[stable(feature = "rust1", since = "1.0.0")]
1048 fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
1049 }
1050
1051 /// The `Seek` trait provides a cursor which can be moved within a stream of
1052 /// bytes.
1053 ///
1054 /// The stream typically has a fixed size, allowing seeking relative to either
1055 /// end or the current offset.
1056 ///
1057 /// # Examples
1058 ///
1059 /// [`File`][file]s implement `Seek`:
1060 ///
1061 /// [file]: ../fs/struct.File.html
1062 ///
1063 /// ```
1064 /// use std::io;
1065 /// use std::io::prelude::*;
1066 /// use std::fs::File;
1067 /// use std::io::SeekFrom;
1068 ///
1069 /// # fn foo() -> io::Result<()> {
1070 /// let mut f = try!(File::open("foo.txt"));
1071 ///
1072 /// // move the cursor 42 bytes from the start of the file
1073 /// try!(f.seek(SeekFrom::Start(42)));
1074 /// # Ok(())
1075 /// # }
1076 /// ```
1077 #[stable(feature = "rust1", since = "1.0.0")]
1078 pub trait Seek {
1079 /// Seek to an offset, in bytes, in a stream.
1080 ///
1081 /// A seek beyond the end of a stream is allowed, but implementation
1082 /// defined.
1083 ///
1084 /// If the seek operation completed successfully,
1085 /// this method returns the new position from the start of the stream.
1086 /// That position can be used later with `SeekFrom::Start`.
1087 ///
1088 /// # Errors
1089 ///
1090 /// Seeking to a negative offset is considered an error.
1091 #[stable(feature = "rust1", since = "1.0.0")]
1092 fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
1093 }
1094
1095 /// Enumeration of possible methods to seek within an I/O object.
1096 #[derive(Copy, PartialEq, Eq, Clone, Debug)]
1097 #[stable(feature = "rust1", since = "1.0.0")]
1098 pub enum SeekFrom {
1099 /// Set the offset to the provided number of bytes.
1100 #[stable(feature = "rust1", since = "1.0.0")]
1101 Start(#[stable(feature = "rust1", since = "1.0.0")] u64),
1102
1103 /// Set the offset to the size of this object plus the specified number of
1104 /// bytes.
1105 ///
1106 /// It is possible to seek beyond the end of an object, but it's an error to
1107 /// seek before byte 0.
1108 #[stable(feature = "rust1", since = "1.0.0")]
1109 End(#[stable(feature = "rust1", since = "1.0.0")] i64),
1110
1111 /// Set the offset to the current position plus the specified number of
1112 /// bytes.
1113 ///
1114 /// It is possible to seek beyond the end of an object, but it's an error to
1115 /// seek before byte 0.
1116 #[stable(feature = "rust1", since = "1.0.0")]
1117 Current(#[stable(feature = "rust1", since = "1.0.0")] i64),
1118 }
1119
1120 fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>)
1121 -> Result<usize> {
1122 let mut read = 0;
1123 loop {
1124 let (done, used) = {
1125 let available = match r.fill_buf() {
1126 Ok(n) => n,
1127 Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
1128 Err(e) => return Err(e)
1129 };
1130 match memchr::memchr(delim, available) {
1131 Some(i) => {
1132 buf.extend_from_slice(&available[..i + 1]);
1133 (true, i + 1)
1134 }
1135 None => {
1136 buf.extend_from_slice(available);
1137 (false, available.len())
1138 }
1139 }
1140 };
1141 r.consume(used);
1142 read += used;
1143 if done || used == 0 {
1144 return Ok(read);
1145 }
1146 }
1147 }
1148
1149 /// A `BufRead` is a type of `Read`er which has an internal buffer, allowing it
1150 /// to perform extra ways of reading.
1151 ///
1152 /// For example, reading line-by-line is inefficient without using a buffer, so
1153 /// if you want to read by line, you'll need `BufRead`, which includes a
1154 /// [`read_line()`][readline] method as well as a [`lines()`][lines] iterator.
1155 ///
1156 /// [readline]: #method.read_line
1157 /// [lines]: #method.lines
1158 ///
1159 /// # Examples
1160 ///
1161 /// A locked standard input implements `BufRead`:
1162 ///
1163 /// ```
1164 /// use std::io;
1165 /// use std::io::prelude::*;
1166 ///
1167 /// let stdin = io::stdin();
1168 /// for line in stdin.lock().lines() {
1169 /// println!("{}", line.unwrap());
1170 /// }
1171 /// ```
1172 ///
1173 /// If you have something that implements `Read`, you can use the [`BufReader`
1174 /// type][bufreader] to turn it into a `BufRead`.
1175 ///
1176 /// For example, [`File`][file] implements `Read`, but not `BufRead`.
1177 /// `BufReader` to the rescue!
1178 ///
1179 /// [bufreader]: struct.BufReader.html
1180 /// [file]: ../fs/struct.File.html
1181 ///
1182 /// ```
1183 /// use std::io::{self, BufReader};
1184 /// use std::io::prelude::*;
1185 /// use std::fs::File;
1186 ///
1187 /// # fn foo() -> io::Result<()> {
1188 /// let f = try!(File::open("foo.txt"));
1189 /// let f = BufReader::new(f);
1190 ///
1191 /// for line in f.lines() {
1192 /// println!("{}", line.unwrap());
1193 /// }
1194 ///
1195 /// # Ok(())
1196 /// # }
1197 /// ```
1198 ///
1199 #[stable(feature = "rust1", since = "1.0.0")]
1200 pub trait BufRead: Read {
1201 /// Fills the internal buffer of this object, returning the buffer contents.
1202 ///
1203 /// This function is a lower-level call. It needs to be paired with the
1204 /// [`consume`][consume] method to function properly. When calling this
1205 /// method, none of the contents will be "read" in the sense that later
1206 /// calling `read` may return the same contents. As such, `consume` must be
1207 /// called with the number of bytes that are consumed from this buffer to
1208 /// ensure that the bytes are never returned twice.
1209 ///
1210 /// [consume]: #tymethod.consume
1211 ///
1212 /// An empty buffer returned indicates that the stream has reached EOF.
1213 ///
1214 /// # Errors
1215 ///
1216 /// This function will return an I/O error if the underlying reader was
1217 /// read, but returned an error.
1218 ///
1219 /// # Examples
1220 ///
1221 /// A locked standard input implements `BufRead`:
1222 ///
1223 /// ```
1224 /// use std::io;
1225 /// use std::io::prelude::*;
1226 ///
1227 /// let stdin = io::stdin();
1228 /// let mut stdin = stdin.lock();
1229 ///
1230 /// // we can't have two `&mut` references to `stdin`, so use a block
1231 /// // to end the borrow early.
1232 /// let length = {
1233 /// let buffer = stdin.fill_buf().unwrap();
1234 ///
1235 /// // work with buffer
1236 /// println!("{:?}", buffer);
1237 ///
1238 /// buffer.len()
1239 /// };
1240 ///
1241 /// // ensure the bytes we worked with aren't returned again later
1242 /// stdin.consume(length);
1243 /// ```
1244 #[stable(feature = "rust1", since = "1.0.0")]
1245 fn fill_buf(&mut self) -> Result<&[u8]>;
1246
1247 /// Tells this buffer that `amt` bytes have been consumed from the buffer,
1248 /// so they should no longer be returned in calls to `read`.
1249 ///
1250 /// This function is a lower-level call. It needs to be paired with the
1251 /// [`fill_buf`][fillbuf] method to function properly. This function does
1252 /// not perform any I/O, it simply informs this object that some amount of
1253 /// its buffer, returned from `fill_buf`, has been consumed and should no
1254 /// longer be returned. As such, this function may do odd things if
1255 /// `fill_buf` isn't called before calling it.
1256 ///
1257 /// [fillbuf]: #tymethod.fill_buf
1258 ///
1259 /// The `amt` must be `<=` the number of bytes in the buffer returned by
1260 /// `fill_buf`.
1261 ///
1262 /// # Examples
1263 ///
1264 /// Since `consume()` is meant to be used with [`fill_buf()`][fillbuf],
1265 /// that method's example includes an example of `consume()`.
1266 #[stable(feature = "rust1", since = "1.0.0")]
1267 fn consume(&mut self, amt: usize);
1268
1269 /// Read all bytes into `buf` until the delimiter `byte` is reached.
1270 ///
1271 /// This function will read bytes from the underlying stream until the
1272 /// delimiter or EOF is found. Once found, all bytes up to, and including,
1273 /// the delimiter (if found) will be appended to `buf`.
1274 ///
1275 /// If this reader is currently at EOF then this function will not modify
1276 /// `buf` and will return `Ok(n)` where `n` is the number of bytes which
1277 /// were read.
1278 ///
1279 /// # Errors
1280 ///
1281 /// This function will ignore all instances of `ErrorKind::Interrupted` and
1282 /// will otherwise return any errors returned by `fill_buf`.
1283 ///
1284 /// If an I/O error is encountered then all bytes read so far will be
1285 /// present in `buf` and its length will have been adjusted appropriately.
1286 ///
1287 /// # Examples
1288 ///
1289 /// A locked standard input implements `BufRead`. In this example, we'll
1290 /// read from standard input until we see an `a` byte.
1291 ///
1292 /// ```
1293 /// use std::io;
1294 /// use std::io::prelude::*;
1295 ///
1296 /// fn foo() -> io::Result<()> {
1297 /// let stdin = io::stdin();
1298 /// let mut stdin = stdin.lock();
1299 /// let mut buffer = Vec::new();
1300 ///
1301 /// try!(stdin.read_until(b'a', &mut buffer));
1302 ///
1303 /// println!("{:?}", buffer);
1304 /// # Ok(())
1305 /// # }
1306 /// ```
1307 #[stable(feature = "rust1", since = "1.0.0")]
1308 fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> {
1309 read_until(self, byte, buf)
1310 }
1311
1312 /// Read all bytes until a newline (the 0xA byte) is reached, and append
1313 /// them to the provided buffer.
1314 ///
1315 /// This function will read bytes from the underlying stream until the
1316 /// newline delimiter (the 0xA byte) or EOF is found. Once found, all bytes
1317 /// up to, and including, the delimiter (if found) will be appended to
1318 /// `buf`.
1319 ///
1320 /// If this reader is currently at EOF then this function will not modify
1321 /// `buf` and will return `Ok(n)` where `n` is the number of bytes which
1322 /// were read.
1323 ///
1324 /// # Errors
1325 ///
1326 /// This function has the same error semantics as `read_until` and will also
1327 /// return an error if the read bytes are not valid UTF-8. If an I/O error
1328 /// is encountered then `buf` may contain some bytes already read in the
1329 /// event that all data read so far was valid UTF-8.
1330 ///
1331 /// # Examples
1332 ///
1333 /// A locked standard input implements `BufRead`. In this example, we'll
1334 /// read all of the lines from standard input. If we were to do this in
1335 /// an actual project, the [`lines()`][lines] method would be easier, of
1336 /// course.
1337 ///
1338 /// [lines]: #method.lines
1339 ///
1340 /// ```
1341 /// use std::io;
1342 /// use std::io::prelude::*;
1343 ///
1344 /// let stdin = io::stdin();
1345 /// let mut stdin = stdin.lock();
1346 /// let mut buffer = String::new();
1347 ///
1348 /// while stdin.read_line(&mut buffer).unwrap() > 0 {
1349 /// // work with buffer
1350 /// println!("{:?}", buffer);
1351 ///
1352 /// buffer.clear();
1353 /// }
1354 /// ```
1355 #[stable(feature = "rust1", since = "1.0.0")]
1356 fn read_line(&mut self, buf: &mut String) -> Result<usize> {
1357 // Note that we are not calling the `.read_until` method here, but
1358 // rather our hardcoded implementation. For more details as to why, see
1359 // the comments in `read_to_end`.
1360 append_to_string(buf, |b| read_until(self, b'\n', b))
1361 }
1362
1363 /// Returns an iterator over the contents of this reader split on the byte
1364 /// `byte`.
1365 ///
1366 /// The iterator returned from this function will return instances of
1367 /// `io::Result<Vec<u8>>`. Each vector returned will *not* have the
1368 /// delimiter byte at the end.
1369 ///
1370 /// This function will yield errors whenever `read_until` would have also
1371 /// yielded an error.
1372 ///
1373 /// # Examples
1374 ///
1375 /// A locked standard input implements `BufRead`. In this example, we'll
1376 /// read some input from standard input, splitting on commas.
1377 ///
1378 /// ```
1379 /// use std::io;
1380 /// use std::io::prelude::*;
1381 ///
1382 /// let stdin = io::stdin();
1383 ///
1384 /// for content in stdin.lock().split(b',') {
1385 /// println!("{:?}", content.unwrap());
1386 /// }
1387 /// ```
1388 #[stable(feature = "rust1", since = "1.0.0")]
1389 fn split(self, byte: u8) -> Split<Self> where Self: Sized {
1390 Split { buf: self, delim: byte }
1391 }
1392
1393 /// Returns an iterator over the lines of this reader.
1394 ///
1395 /// The iterator returned from this function will yield instances of
1396 /// `io::Result<String>`. Each string returned will *not* have a newline
1397 /// byte (the 0xA byte) or CRLF (0xD, 0xA bytes) at the end.
1398 ///
1399 /// # Examples
1400 ///
1401 /// A locked standard input implements `BufRead`:
1402 ///
1403 /// ```
1404 /// use std::io;
1405 /// use std::io::prelude::*;
1406 ///
1407 /// let stdin = io::stdin();
1408 ///
1409 /// for line in stdin.lock().lines() {
1410 /// println!("{}", line.unwrap());
1411 /// }
1412 /// ```
1413 #[stable(feature = "rust1", since = "1.0.0")]
1414 fn lines(self) -> Lines<Self> where Self: Sized {
1415 Lines { buf: self }
1416 }
1417 }
1418
1419 /// Adaptor to chain together two readers.
1420 ///
1421 /// This struct is generally created by calling [`chain()`][chain] on a reader.
1422 /// Please see the documentation of `chain()` for more details.
1423 ///
1424 /// [chain]: trait.Read.html#method.chain
1425 #[stable(feature = "rust1", since = "1.0.0")]
1426 pub struct Chain<T, U> {
1427 first: T,
1428 second: U,
1429 done_first: bool,
1430 }
1431
1432 #[stable(feature = "rust1", since = "1.0.0")]
1433 impl<T: Read, U: Read> Read for Chain<T, U> {
1434 fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
1435 if !self.done_first {
1436 match self.first.read(buf)? {
1437 0 => { self.done_first = true; }
1438 n => return Ok(n),
1439 }
1440 }
1441 self.second.read(buf)
1442 }
1443 }
1444
1445 #[stable(feature = "chain_bufread", since = "1.9.0")]
1446 impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
1447 fn fill_buf(&mut self) -> Result<&[u8]> {
1448 if !self.done_first {
1449 match self.first.fill_buf()? {
1450 buf if buf.len() == 0 => { self.done_first = true; }
1451 buf => return Ok(buf),
1452 }
1453 }
1454 self.second.fill_buf()
1455 }
1456
1457 fn consume(&mut self, amt: usize) {
1458 if !self.done_first {
1459 self.first.consume(amt)
1460 } else {
1461 self.second.consume(amt)
1462 }
1463 }
1464 }
1465
1466 /// Reader adaptor which limits the bytes read from an underlying reader.
1467 ///
1468 /// This struct is generally created by calling [`take()`][take] on a reader.
1469 /// Please see the documentation of `take()` for more details.
1470 ///
1471 /// [take]: trait.Read.html#method.take
1472 #[stable(feature = "rust1", since = "1.0.0")]
1473 pub struct Take<T> {
1474 inner: T,
1475 limit: u64,
1476 }
1477
1478 impl<T> Take<T> {
1479 /// Returns the number of bytes that can be read before this instance will
1480 /// return EOF.
1481 ///
1482 /// # Note
1483 ///
1484 /// This instance may reach EOF after reading fewer bytes than indicated by
1485 /// this method if the underlying `Read` instance reaches EOF.
1486 #[stable(feature = "rust1", since = "1.0.0")]
1487 pub fn limit(&self) -> u64 { self.limit }
1488 }
1489
1490 #[stable(feature = "rust1", since = "1.0.0")]
1491 impl<T: Read> Read for Take<T> {
1492 fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
1493 // Don't call into inner reader at all at EOF because it may still block
1494 if self.limit == 0 {
1495 return Ok(0);
1496 }
1497
1498 let max = cmp::min(buf.len() as u64, self.limit) as usize;
1499 let n = self.inner.read(&mut buf[..max])?;
1500 self.limit -= n as u64;
1501 Ok(n)
1502 }
1503 }
1504
1505 #[stable(feature = "rust1", since = "1.0.0")]
1506 impl<T: BufRead> BufRead for Take<T> {
1507 fn fill_buf(&mut self) -> Result<&[u8]> {
1508 let buf = self.inner.fill_buf()?;
1509 let cap = cmp::min(buf.len() as u64, self.limit) as usize;
1510 Ok(&buf[..cap])
1511 }
1512
1513 fn consume(&mut self, amt: usize) {
1514 // Don't let callers reset the limit by passing an overlarge value
1515 let amt = cmp::min(amt as u64, self.limit) as usize;
1516 self.limit -= amt as u64;
1517 self.inner.consume(amt);
1518 }
1519 }
1520
1521 /// An iterator over `u8` values of a reader.
1522 ///
1523 /// This struct is generally created by calling [`bytes()`][bytes] on a reader.
1524 /// Please see the documentation of `bytes()` for more details.
1525 ///
1526 /// [bytes]: trait.Read.html#method.bytes
1527 #[stable(feature = "rust1", since = "1.0.0")]
1528 pub struct Bytes<R> {
1529 inner: R,
1530 }
1531
1532 #[stable(feature = "rust1", since = "1.0.0")]
1533 impl<R: Read> Iterator for Bytes<R> {
1534 type Item = Result<u8>;
1535
1536 fn next(&mut self) -> Option<Result<u8>> {
1537 let mut buf = [0];
1538 match self.inner.read(&mut buf) {
1539 Ok(0) => None,
1540 Ok(..) => Some(Ok(buf[0])),
1541 Err(e) => Some(Err(e)),
1542 }
1543 }
1544 }
1545
1546 /// An iterator over the `char`s of a reader.
1547 ///
1548 /// This struct is generally created by calling [`chars()`][chars] on a reader.
1549 /// Please see the documentation of `chars()` for more details.
1550 ///
1551 /// [chars]: trait.Read.html#method.chars
1552 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
1553 issue = "27802")]
1554 pub struct Chars<R> {
1555 inner: R,
1556 }
1557
1558 /// An enumeration of possible errors that can be generated from the `Chars`
1559 /// adapter.
1560 #[derive(Debug)]
1561 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
1562 issue = "27802")]
1563 pub enum CharsError {
1564 /// Variant representing that the underlying stream was read successfully
1565 /// but it did not contain valid utf8 data.
1566 NotUtf8,
1567
1568 /// Variant representing that an I/O error occurred.
1569 Other(Error),
1570 }
1571
1572 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
1573 issue = "27802")]
1574 impl<R: Read> Iterator for Chars<R> {
1575 type Item = result::Result<char, CharsError>;
1576
1577 fn next(&mut self) -> Option<result::Result<char, CharsError>> {
1578 let mut buf = [0];
1579 let first_byte = match self.inner.read(&mut buf) {
1580 Ok(0) => return None,
1581 Ok(..) => buf[0],
1582 Err(e) => return Some(Err(CharsError::Other(e))),
1583 };
1584 let width = core_str::utf8_char_width(first_byte);
1585 if width == 1 { return Some(Ok(first_byte as char)) }
1586 if width == 0 { return Some(Err(CharsError::NotUtf8)) }
1587 let mut buf = [first_byte, 0, 0, 0];
1588 {
1589 let mut start = 1;
1590 while start < width {
1591 match self.inner.read(&mut buf[start..width]) {
1592 Ok(0) => return Some(Err(CharsError::NotUtf8)),
1593 Ok(n) => start += n,
1594 Err(e) => return Some(Err(CharsError::Other(e))),
1595 }
1596 }
1597 }
1598 Some(match str::from_utf8(&buf[..width]).ok() {
1599 Some(s) => Ok(s.chars().next().unwrap()),
1600 None => Err(CharsError::NotUtf8),
1601 })
1602 }
1603 }
1604
1605 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
1606 issue = "27802")]
1607 impl std_error::Error for CharsError {
1608 fn description(&self) -> &str {
1609 match *self {
1610 CharsError::NotUtf8 => "invalid utf8 encoding",
1611 CharsError::Other(ref e) => std_error::Error::description(e),
1612 }
1613 }
1614 fn cause(&self) -> Option<&std_error::Error> {
1615 match *self {
1616 CharsError::NotUtf8 => None,
1617 CharsError::Other(ref e) => e.cause(),
1618 }
1619 }
1620 }
1621
1622 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
1623 issue = "27802")]
1624 impl fmt::Display for CharsError {
1625 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1626 match *self {
1627 CharsError::NotUtf8 => {
1628 "byte stream did not contain valid utf8".fmt(f)
1629 }
1630 CharsError::Other(ref e) => e.fmt(f),
1631 }
1632 }
1633 }
1634
1635 /// An iterator over the contents of an instance of `BufRead` split on a
1636 /// particular byte.
1637 ///
1638 /// This struct is generally created by calling [`split()`][split] on a
1639 /// `BufRead`. Please see the documentation of `split()` for more details.
1640 ///
1641 /// [split]: trait.BufRead.html#method.split
1642 #[stable(feature = "rust1", since = "1.0.0")]
1643 pub struct Split<B> {
1644 buf: B,
1645 delim: u8,
1646 }
1647
1648 #[stable(feature = "rust1", since = "1.0.0")]
1649 impl<B: BufRead> Iterator for Split<B> {
1650 type Item = Result<Vec<u8>>;
1651
1652 fn next(&mut self) -> Option<Result<Vec<u8>>> {
1653 let mut buf = Vec::new();
1654 match self.buf.read_until(self.delim, &mut buf) {
1655 Ok(0) => None,
1656 Ok(_n) => {
1657 if buf[buf.len() - 1] == self.delim {
1658 buf.pop();
1659 }
1660 Some(Ok(buf))
1661 }
1662 Err(e) => Some(Err(e))
1663 }
1664 }
1665 }
1666
1667 /// An iterator over the lines of an instance of `BufRead`.
1668 ///
1669 /// This struct is generally created by calling [`lines()`][lines] on a
1670 /// `BufRead`. Please see the documentation of `lines()` for more details.
1671 ///
1672 /// [lines]: trait.BufRead.html#method.lines
1673 #[stable(feature = "rust1", since = "1.0.0")]
1674 pub struct Lines<B> {
1675 buf: B,
1676 }
1677
1678 #[stable(feature = "rust1", since = "1.0.0")]
1679 impl<B: BufRead> Iterator for Lines<B> {
1680 type Item = Result<String>;
1681
1682 fn next(&mut self) -> Option<Result<String>> {
1683 let mut buf = String::new();
1684 match self.buf.read_line(&mut buf) {
1685 Ok(0) => None,
1686 Ok(_n) => {
1687 if buf.ends_with("\n") {
1688 buf.pop();
1689 if buf.ends_with("\r") {
1690 buf.pop();
1691 }
1692 }
1693 Some(Ok(buf))
1694 }
1695 Err(e) => Some(Err(e))
1696 }
1697 }
1698 }
1699
1700 #[cfg(test)]
1701 mod tests {
1702 use prelude::v1::*;
1703 use io::prelude::*;
1704 use io;
1705 use super::Cursor;
1706 use test;
1707 use super::repeat;
1708
1709 #[test]
1710 fn read_until() {
1711 let mut buf = Cursor::new(&b"12"[..]);
1712 let mut v = Vec::new();
1713 assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 2);
1714 assert_eq!(v, b"12");
1715
1716 let mut buf = Cursor::new(&b"1233"[..]);
1717 let mut v = Vec::new();
1718 assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 3);
1719 assert_eq!(v, b"123");
1720 v.truncate(0);
1721 assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 1);
1722 assert_eq!(v, b"3");
1723 v.truncate(0);
1724 assert_eq!(buf.read_until(b'3', &mut v).unwrap(), 0);
1725 assert_eq!(v, []);
1726 }
1727
1728 #[test]
1729 fn split() {
1730 let buf = Cursor::new(&b"12"[..]);
1731 let mut s = buf.split(b'3');
1732 assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']);
1733 assert!(s.next().is_none());
1734
1735 let buf = Cursor::new(&b"1233"[..]);
1736 let mut s = buf.split(b'3');
1737 assert_eq!(s.next().unwrap().unwrap(), vec![b'1', b'2']);
1738 assert_eq!(s.next().unwrap().unwrap(), vec![]);
1739 assert!(s.next().is_none());
1740 }
1741
1742 #[test]
1743 fn read_line() {
1744 let mut buf = Cursor::new(&b"12"[..]);
1745 let mut v = String::new();
1746 assert_eq!(buf.read_line(&mut v).unwrap(), 2);
1747 assert_eq!(v, "12");
1748
1749 let mut buf = Cursor::new(&b"12\n\n"[..]);
1750 let mut v = String::new();
1751 assert_eq!(buf.read_line(&mut v).unwrap(), 3);
1752 assert_eq!(v, "12\n");
1753 v.truncate(0);
1754 assert_eq!(buf.read_line(&mut v).unwrap(), 1);
1755 assert_eq!(v, "\n");
1756 v.truncate(0);
1757 assert_eq!(buf.read_line(&mut v).unwrap(), 0);
1758 assert_eq!(v, "");
1759 }
1760
1761 #[test]
1762 fn lines() {
1763 let buf = Cursor::new(&b"12\r"[..]);
1764 let mut s = buf.lines();
1765 assert_eq!(s.next().unwrap().unwrap(), "12\r".to_string());
1766 assert!(s.next().is_none());
1767
1768 let buf = Cursor::new(&b"12\r\n\n"[..]);
1769 let mut s = buf.lines();
1770 assert_eq!(s.next().unwrap().unwrap(), "12".to_string());
1771 assert_eq!(s.next().unwrap().unwrap(), "".to_string());
1772 assert!(s.next().is_none());
1773 }
1774
1775 #[test]
1776 fn read_to_end() {
1777 let mut c = Cursor::new(&b""[..]);
1778 let mut v = Vec::new();
1779 assert_eq!(c.read_to_end(&mut v).unwrap(), 0);
1780 assert_eq!(v, []);
1781
1782 let mut c = Cursor::new(&b"1"[..]);
1783 let mut v = Vec::new();
1784 assert_eq!(c.read_to_end(&mut v).unwrap(), 1);
1785 assert_eq!(v, b"1");
1786
1787 let cap = 1024 * 1024;
1788 let data = (0..cap).map(|i| (i / 3) as u8).collect::<Vec<_>>();
1789 let mut v = Vec::new();
1790 let (a, b) = data.split_at(data.len() / 2);
1791 assert_eq!(Cursor::new(a).read_to_end(&mut v).unwrap(), a.len());
1792 assert_eq!(Cursor::new(b).read_to_end(&mut v).unwrap(), b.len());
1793 assert_eq!(v, data);
1794 }
1795
1796 #[test]
1797 fn read_to_string() {
1798 let mut c = Cursor::new(&b""[..]);
1799 let mut v = String::new();
1800 assert_eq!(c.read_to_string(&mut v).unwrap(), 0);
1801 assert_eq!(v, "");
1802
1803 let mut c = Cursor::new(&b"1"[..]);
1804 let mut v = String::new();
1805 assert_eq!(c.read_to_string(&mut v).unwrap(), 1);
1806 assert_eq!(v, "1");
1807
1808 let mut c = Cursor::new(&b"\xff"[..]);
1809 let mut v = String::new();
1810 assert!(c.read_to_string(&mut v).is_err());
1811 }
1812
1813 #[test]
1814 fn read_exact() {
1815 let mut buf = [0; 4];
1816
1817 let mut c = Cursor::new(&b""[..]);
1818 assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(),
1819 io::ErrorKind::UnexpectedEof);
1820
1821 let mut c = Cursor::new(&b"123"[..]).chain(Cursor::new(&b"456789"[..]));
1822 c.read_exact(&mut buf).unwrap();
1823 assert_eq!(&buf, b"1234");
1824 c.read_exact(&mut buf).unwrap();
1825 assert_eq!(&buf, b"5678");
1826 assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(),
1827 io::ErrorKind::UnexpectedEof);
1828 }
1829
1830 #[test]
1831 fn read_exact_slice() {
1832 let mut buf = [0; 4];
1833
1834 let mut c = &b""[..];
1835 assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(),
1836 io::ErrorKind::UnexpectedEof);
1837
1838 let mut c = &b"123"[..];
1839 assert_eq!(c.read_exact(&mut buf).unwrap_err().kind(),
1840 io::ErrorKind::UnexpectedEof);
1841 // make sure the optimized (early returning) method is being used
1842 assert_eq!(&buf, &[0; 4]);
1843
1844 let mut c = &b"1234"[..];
1845 c.read_exact(&mut buf).unwrap();
1846 assert_eq!(&buf, b"1234");
1847
1848 let mut c = &b"56789"[..];
1849 c.read_exact(&mut buf).unwrap();
1850 assert_eq!(&buf, b"5678");
1851 assert_eq!(c, b"9");
1852 }
1853
1854 #[test]
1855 fn take_eof() {
1856 struct R;
1857
1858 impl Read for R {
1859 fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
1860 Err(io::Error::new(io::ErrorKind::Other, ""))
1861 }
1862 }
1863
1864 let mut buf = [0; 1];
1865 assert_eq!(0, R.take(0).read(&mut buf).unwrap());
1866 }
1867
1868 fn cmp_bufread<Br1: BufRead, Br2: BufRead>(mut br1: Br1, mut br2: Br2, exp: &[u8]) {
1869 let mut cat = Vec::new();
1870 loop {
1871 let consume = {
1872 let buf1 = br1.fill_buf().unwrap();
1873 let buf2 = br2.fill_buf().unwrap();
1874 let minlen = if buf1.len() < buf2.len() { buf1.len() } else { buf2.len() };
1875 assert_eq!(buf1[..minlen], buf2[..minlen]);
1876 cat.extend_from_slice(&buf1[..minlen]);
1877 minlen
1878 };
1879 if consume == 0 {
1880 break;
1881 }
1882 br1.consume(consume);
1883 br2.consume(consume);
1884 }
1885 assert_eq!(br1.fill_buf().unwrap().len(), 0);
1886 assert_eq!(br2.fill_buf().unwrap().len(), 0);
1887 assert_eq!(&cat[..], &exp[..])
1888 }
1889
1890 #[test]
1891 fn chain_bufread() {
1892 let testdata = b"ABCDEFGHIJKL";
1893 let chain1 = (&testdata[..3]).chain(&testdata[3..6])
1894 .chain(&testdata[6..9])
1895 .chain(&testdata[9..]);
1896 let chain2 = (&testdata[..4]).chain(&testdata[4..8])
1897 .chain(&testdata[8..]);
1898 cmp_bufread(chain1, chain2, &testdata[..]);
1899 }
1900
1901 #[bench]
1902 fn bench_read_to_end(b: &mut test::Bencher) {
1903 b.iter(|| {
1904 let mut lr = repeat(1).take(10000000);
1905 let mut vec = Vec::with_capacity(1024);
1906 super::read_to_end(&mut lr, &mut vec)
1907 });
1908 }
1909 }