-
Notifications
You must be signed in to change notification settings - Fork 12.9k
/
stdio.rs
736 lines (684 loc) · 22.2 KB
/
stdio.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use io::prelude::*;
use cell::RefCell;
use fmt;
use io::lazy::Lazy;
use io::{self, Initializer, BufReader, LineWriter};
use sync::{Arc, Mutex, MutexGuard};
use sys::stdio;
use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
use thread::{LocalKey, LocalKeyState};
/// Stdout used by print! and println! macros
thread_local! {
static LOCAL_STDOUT: RefCell<Option<Box<Write + Send>>> = {
RefCell::new(None)
}
}
/// A handle to a raw instance of the standard input stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stdin_raw` function.
struct StdinRaw(stdio::Stdin);
/// A handle to a raw instance of the standard output stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stdout_raw` function.
struct StdoutRaw(stdio::Stdout);
/// A handle to a raw instance of the standard output stream of this process.
///
/// This handle is not synchronized or buffered in any fashion. Constructed via
/// the `std::io::stdio::stderr_raw` function.
struct StderrRaw(stdio::Stderr);
/// Constructs a new raw handle to the standard input of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stdin`. Data buffered by the `std::io::stdin`
/// handles is **not** available to raw handles returned from this function.
///
/// The returned handle has no external synchronization or buffering.
fn stdin_raw() -> io::Result<StdinRaw> { stdio::Stdin::new().map(StdinRaw) }
/// Constructs a new raw handle to the standard output stream of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stdout`. Note that data is buffered by the
/// `std::io::stdout` handles so writes which happen via this raw handle may
/// appear before previous writes.
///
/// The returned handle has no external synchronization or buffering layered on
/// top.
fn stdout_raw() -> io::Result<StdoutRaw> { stdio::Stdout::new().map(StdoutRaw) }
/// Constructs a new raw handle to the standard error stream of this process.
///
/// The returned handle does not interact with any other handles created nor
/// handles returned by `std::io::stderr`.
///
/// The returned handle has no external synchronization or buffering layered on
/// top.
fn stderr_raw() -> io::Result<StderrRaw> { stdio::Stderr::new().map(StderrRaw) }
impl Read for StdinRaw {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }
#[inline]
unsafe fn initializer(&self) -> Initializer {
Initializer::nop()
}
}
impl Write for StdoutRaw {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
fn flush(&mut self) -> io::Result<()> { self.0.flush() }
}
impl Write for StderrRaw {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
fn flush(&mut self) -> io::Result<()> { self.0.flush() }
}
enum Maybe<T> {
Real(T),
Fake,
}
impl<W: io::Write> io::Write for Maybe<W> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
match *self {
Maybe::Real(ref mut w) => handle_ebadf(w.write(buf), buf.len()),
Maybe::Fake => Ok(buf.len())
}
}
fn flush(&mut self) -> io::Result<()> {
match *self {
Maybe::Real(ref mut w) => handle_ebadf(w.flush(), ()),
Maybe::Fake => Ok(())
}
}
}
impl<R: io::Read> io::Read for Maybe<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
match *self {
Maybe::Real(ref mut r) => handle_ebadf(r.read(buf), 0),
Maybe::Fake => Ok(0)
}
}
}
fn handle_ebadf<T>(r: io::Result<T>, default: T) -> io::Result<T> {
match r {
Err(ref e) if stdio::is_ebadf(e) => Ok(default),
r => r
}
}
/// A handle to the standard input stream of a process.
///
/// Each handle is a shared reference to a global buffer of input data to this
/// process. A handle can be `lock`'d to gain full access to [`BufRead`] methods
/// (e.g. `.lines()`). Reads to this handle are otherwise locked with respect
/// to other reads.
///
/// This handle implements the `Read` trait, but beware that concurrent reads
/// of `Stdin` must be executed with care.
///
/// Created by the [`io::stdin`] method.
///
/// [`io::stdin`]: fn.stdin.html
/// [`BufRead`]: trait.BufRead.html
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Stdin {
inner: Arc<Mutex<BufReader<Maybe<StdinRaw>>>>,
}
/// A locked reference to the `Stdin` handle.
///
/// This handle implements both the [`Read`] and [`BufRead`] traits, and
/// is constructed via the [`Stdin::lock`] method.
///
/// [`Read`]: trait.Read.html
/// [`BufRead`]: trait.BufRead.html
/// [`Stdin::lock`]: struct.Stdin.html#method.lock
#[stable(feature = "rust1", since = "1.0.0")]
pub struct StdinLock<'a> {
inner: MutexGuard<'a, BufReader<Maybe<StdinRaw>>>,
}
/// Constructs a new handle to the standard input of the current process.
///
/// Each handle returned is a reference to a shared global buffer whose access
/// is synchronized via a mutex. If you need more explicit control over
/// locking, see the [`lock() method`][lock].
///
/// [lock]: struct.Stdin.html#method.lock
///
/// # Examples
///
/// Using implicit synchronization:
///
/// ```
/// use std::io::{self, Read};
///
/// # fn foo() -> io::Result<String> {
/// let mut buffer = String::new();
/// io::stdin().read_to_string(&mut buffer)?;
/// # Ok(buffer)
/// # }
/// ```
///
/// Using explicit synchronization:
///
/// ```
/// use std::io::{self, Read};
///
/// # fn foo() -> io::Result<String> {
/// let mut buffer = String::new();
/// let stdin = io::stdin();
/// let mut handle = stdin.lock();
///
/// handle.read_to_string(&mut buffer)?;
/// # Ok(buffer)
/// # }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn stdin() -> Stdin {
static INSTANCE: Lazy<Mutex<BufReader<Maybe<StdinRaw>>>> = Lazy::new(stdin_init);
return Stdin {
inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
};
fn stdin_init() -> Arc<Mutex<BufReader<Maybe<StdinRaw>>>> {
let stdin = match stdin_raw() {
Ok(stdin) => Maybe::Real(stdin),
_ => Maybe::Fake
};
Arc::new(Mutex::new(BufReader::with_capacity(stdio::STDIN_BUF_SIZE, stdin)))
}
}
impl Stdin {
/// Locks this handle to the standard input stream, returning a readable
/// guard.
///
/// The lock is released when the returned lock goes out of scope. The
/// returned guard also implements the [`Read`] and [`BufRead`] traits for
/// accessing the underlying data.
///
/// [`Read`]: trait.Read.html
/// [`BufRead`]: trait.BufRead.html
///
/// # Examples
///
/// ```
/// use std::io::{self, Read};
///
/// # fn foo() -> io::Result<String> {
/// let mut buffer = String::new();
/// let stdin = io::stdin();
/// let mut handle = stdin.lock();
///
/// handle.read_to_string(&mut buffer)?;
/// # Ok(buffer)
/// # }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StdinLock {
StdinLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
}
/// Locks this handle and reads a line of input into the specified buffer.
///
/// For detailed semantics of this method, see the documentation on
/// [`BufRead::read_line`].
///
/// [`BufRead::read_line`]: trait.BufRead.html#method.read_line
///
/// # Examples
///
/// ```no_run
/// use std::io;
///
/// let mut input = String::new();
/// match io::stdin().read_line(&mut input) {
/// Ok(n) => {
/// println!("{} bytes read", n);
/// println!("{}", input);
/// }
/// Err(error) => println!("error: {}", error),
/// }
/// ```
///
/// You can run the example one of two ways:
///
/// - Pipe some text to it, e.g. `printf foo | path/to/executable`
/// - Give it text interactively by running the executable directly,
/// in which case it will wait for the Enter key to be pressed before
/// continuing
#[stable(feature = "rust1", since = "1.0.0")]
pub fn read_line(&self, buf: &mut String) -> io::Result<usize> {
self.lock().read_line(buf)
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Stdin {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("Stdin { .. }")
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Read for Stdin {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.lock().read(buf)
}
#[inline]
unsafe fn initializer(&self) -> Initializer {
Initializer::nop()
}
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
self.lock().read_to_end(buf)
}
fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
self.lock().read_to_string(buf)
}
fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
self.lock().read_exact(buf)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> Read for StdinLock<'a> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.inner.read(buf)
}
#[inline]
unsafe fn initializer(&self) -> Initializer {
Initializer::nop()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> BufRead for StdinLock<'a> {
fn fill_buf(&mut self) -> io::Result<&[u8]> { self.inner.fill_buf() }
fn consume(&mut self, n: usize) { self.inner.consume(n) }
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<'a> fmt::Debug for StdinLock<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("StdinLock { .. }")
}
}
/// A handle to the global standard output stream of the current process.
///
/// Each handle shares a global buffer of data to be written to the standard
/// output stream. Access is also synchronized via a lock and explicit control
/// over locking is available via the [`lock`] method.
///
/// Created by the [`io::stdout`] method.
///
/// [`lock`]: #method.lock
/// [`io::stdout`]: fn.stdout.html
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Stdout {
// FIXME: this should be LineWriter or BufWriter depending on the state of
// stdout (tty or not). Note that if this is not line buffered it
// should also flush-on-panic or some form of flush-on-abort.
inner: Arc<ReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>>,
}
/// A locked reference to the `Stdout` handle.
///
/// This handle implements the [`Write`] trait, and is constructed via
/// the [`Stdout::lock`] method.
///
/// [`Write`]: trait.Write.html
/// [`Stdout::lock`]: struct.Stdout.html#method.lock
#[stable(feature = "rust1", since = "1.0.0")]
pub struct StdoutLock<'a> {
inner: ReentrantMutexGuard<'a, RefCell<LineWriter<Maybe<StdoutRaw>>>>,
}
/// Constructs a new handle to the standard output of the current process.
///
/// Each handle returned is a reference to a shared global buffer whose access
/// is synchronized via a mutex. If you need more explicit control over
/// locking, see the [Stdout::lock] method.
///
/// [Stdout::lock]: struct.Stdout.html#method.lock
///
/// # Examples
///
/// Using implicit synchronization:
///
/// ```
/// use std::io::{self, Write};
///
/// # fn foo() -> io::Result<()> {
/// io::stdout().write(b"hello world")?;
///
/// # Ok(())
/// # }
/// ```
///
/// Using explicit synchronization:
///
/// ```
/// use std::io::{self, Write};
///
/// # fn foo() -> io::Result<()> {
/// let stdout = io::stdout();
/// let mut handle = stdout.lock();
///
/// handle.write(b"hello world")?;
///
/// # Ok(())
/// # }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn stdout() -> Stdout {
static INSTANCE: Lazy<ReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>>
= Lazy::new(stdout_init);
return Stdout {
inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
};
fn stdout_init() -> Arc<ReentrantMutex<RefCell<LineWriter<Maybe<StdoutRaw>>>>> {
let stdout = match stdout_raw() {
Ok(stdout) => Maybe::Real(stdout),
_ => Maybe::Fake,
};
Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout))))
}
}
impl Stdout {
/// Locks this handle to the standard output stream, returning a writable
/// guard.
///
/// The lock is released when the returned lock goes out of scope. The
/// returned guard also implements the `Write` trait for writing data.
///
/// # Examples
///
/// ```
/// use std::io::{self, Write};
///
/// # fn foo() -> io::Result<()> {
/// let stdout = io::stdout();
/// let mut handle = stdout.lock();
///
/// handle.write(b"hello world")?;
///
/// # Ok(())
/// # }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StdoutLock {
StdoutLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Stdout {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("Stdout { .. }")
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Write for Stdout {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.lock().write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.lock().flush()
}
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
self.lock().write_all(buf)
}
fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
self.lock().write_fmt(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> Write for StdoutLock<'a> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.inner.borrow_mut().write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.inner.borrow_mut().flush()
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<'a> fmt::Debug for StdoutLock<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("StdoutLock { .. }")
}
}
/// A handle to the standard error stream of a process.
///
/// For more information, see the [`io::stderr`] method.
///
/// [`io::stderr`]: fn.stderr.html
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Stderr {
inner: Arc<ReentrantMutex<RefCell<Maybe<StderrRaw>>>>,
}
/// A locked reference to the `Stderr` handle.
///
/// This handle implements the `Write` trait and is constructed via
/// the [`Stderr::lock`] method.
///
/// [`Stderr::lock`]: struct.Stderr.html#method.lock
#[stable(feature = "rust1", since = "1.0.0")]
pub struct StderrLock<'a> {
inner: ReentrantMutexGuard<'a, RefCell<Maybe<StderrRaw>>>,
}
/// Constructs a new handle to the standard error of the current process.
///
/// This handle is not buffered.
///
/// # Examples
///
/// Using implicit synchronization:
///
/// ```
/// use std::io::{self, Write};
///
/// # fn foo() -> io::Result<()> {
/// io::stderr().write(b"hello world")?;
///
/// # Ok(())
/// # }
/// ```
///
/// Using explicit synchronization:
///
/// ```
/// use std::io::{self, Write};
///
/// # fn foo() -> io::Result<()> {
/// let stderr = io::stderr();
/// let mut handle = stderr.lock();
///
/// handle.write(b"hello world")?;
///
/// # Ok(())
/// # }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn stderr() -> Stderr {
static INSTANCE: Lazy<ReentrantMutex<RefCell<Maybe<StderrRaw>>>> = Lazy::new(stderr_init);
return Stderr {
inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
};
fn stderr_init() -> Arc<ReentrantMutex<RefCell<Maybe<StderrRaw>>>> {
let stderr = match stderr_raw() {
Ok(stderr) => Maybe::Real(stderr),
_ => Maybe::Fake,
};
Arc::new(ReentrantMutex::new(RefCell::new(stderr)))
}
}
impl Stderr {
/// Locks this handle to the standard error stream, returning a writable
/// guard.
///
/// The lock is released when the returned lock goes out of scope. The
/// returned guard also implements the `Write` trait for writing data.
///
/// # Examples
///
/// ```
/// use std::io::{self, Write};
///
/// fn foo() -> io::Result<()> {
/// let stderr = io::stderr();
/// let mut handle = stderr.lock();
///
/// handle.write(b"hello world")?;
///
/// Ok(())
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn lock(&self) -> StderrLock {
StderrLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Stderr {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("Stderr { .. }")
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Write for Stderr {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.lock().write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.lock().flush()
}
fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
self.lock().write_all(buf)
}
fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
self.lock().write_fmt(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> Write for StderrLock<'a> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.inner.borrow_mut().write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.inner.borrow_mut().flush()
}
}
#[stable(feature = "std_debug", since = "1.16.0")]
impl<'a> fmt::Debug for StderrLock<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.pad("StderrLock { .. }")
}
}
/// Resets the thread-local stderr handle to the specified writer
///
/// This will replace the current thread's stderr handle, returning the old
/// handle. All future calls to `panic!` and friends will emit their output to
/// this specified handle.
///
/// Note that this does not need to be called for all new threads; the default
/// output handle is to the process's stderr stream.
#[unstable(feature = "set_stdio",
reason = "this function may disappear completely or be replaced \
with a more general mechanism",
issue = "0")]
#[doc(hidden)]
pub fn set_panic(sink: Option<Box<Write + Send>>) -> Option<Box<Write + Send>> {
use panicking::LOCAL_STDERR;
use mem;
LOCAL_STDERR.with(move |slot| {
mem::replace(&mut *slot.borrow_mut(), sink)
}).and_then(|mut s| {
let _ = s.flush();
Some(s)
})
}
/// Resets the thread-local stdout handle to the specified writer
///
/// This will replace the current thread's stdout handle, returning the old
/// handle. All future calls to `print!` and friends will emit their output to
/// this specified handle.
///
/// Note that this does not need to be called for all new threads; the default
/// output handle is to the process's stdout stream.
#[unstable(feature = "set_stdio",
reason = "this function may disappear completely or be replaced \
with a more general mechanism",
issue = "0")]
#[doc(hidden)]
pub fn set_print(sink: Option<Box<Write + Send>>) -> Option<Box<Write + Send>> {
use mem;
LOCAL_STDOUT.with(move |slot| {
mem::replace(&mut *slot.borrow_mut(), sink)
}).and_then(|mut s| {
let _ = s.flush();
Some(s)
})
}
/// Write `args` to output stream `local_s` if possible, `global_s`
/// otherwise. `label` identifies the stream in a panic message.
///
/// This function is used to print error messages, so it takes extra
/// care to avoid causing a panic when `local_stream` is unusable.
/// For instance, if the TLS key for the local stream is uninitialized
/// or already destroyed, or if the local stream is locked by another
/// thread, it will just fall back to the global stream.
///
/// However, if the actual I/O causes an error, this function does panic.
fn print_to<T>(args: fmt::Arguments,
local_s: &'static LocalKey<RefCell<Option<Box<Write+Send>>>>,
global_s: fn() -> T,
label: &str) where T: Write {
let result = match local_s.state() {
LocalKeyState::Uninitialized |
LocalKeyState::Destroyed => global_s().write_fmt(args),
LocalKeyState::Valid => {
local_s.with(|s| {
if let Ok(mut borrowed) = s.try_borrow_mut() {
if let Some(w) = borrowed.as_mut() {
return w.write_fmt(args);
}
}
global_s().write_fmt(args)
})
}
};
if let Err(e) = result {
panic!("failed printing to {}: {}", label, e);
}
}
#[unstable(feature = "print_internals",
reason = "implementation detail which may disappear or be replaced at any time",
issue = "0")]
#[doc(hidden)]
pub fn _print(args: fmt::Arguments) {
print_to(args, &LOCAL_STDOUT, stdout, "stdout");
}
#[unstable(feature = "print_internals",
reason = "implementation detail which may disappear or be replaced at any time",
issue = "0")]
#[doc(hidden)]
pub fn _eprint(args: fmt::Arguments) {
use panicking::LOCAL_STDERR;
print_to(args, &LOCAL_STDERR, stderr, "stderr");
}
#[cfg(test)]
mod tests {
use thread;
use super::*;
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn panic_doesnt_poison() {
thread::spawn(|| {
let _a = stdin();
let _a = _a.lock();
let _a = stdout();
let _a = _a.lock();
let _a = stderr();
let _a = _a.lock();
panic!();
}).join().unwrap_err();
let _a = stdin();
let _a = _a.lock();
let _a = stdout();
let _a = _a.lock();
let _a = stderr();
let _a = _a.lock();
}
}