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.
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.
18 use io::{self, BufReader, LineWriter};
19 use sync::{Arc, Mutex, MutexGuard};
22 /// Stdout used by print! and println! macroses
24 static LOCAL_STDOUT: RefCell<Option<Box<Write + Send>>> = {
29 /// A handle to a raw instance of the standard input stream of this process.
31 /// This handle is not synchronized or buffered in any fashion. Constructed via
32 /// the `std::io::stdin_raw` function.
33 pub struct StdinRaw(stdio::Stdin);
35 /// A handle to a raw instance of the standard output stream of this process.
37 /// This handle is not synchronized or buffered in any fashion. Constructed via
38 /// the `std::io::stdout_raw` function.
39 pub struct StdoutRaw(stdio::Stdout);
41 /// A handle to a raw instance of the standard output stream of this process.
43 /// This handle is not synchronized or buffered in any fashion. Constructed via
44 /// the `std::io::stderr_raw` function.
45 pub struct StderrRaw(stdio::Stderr);
47 /// Construct a new raw handle to the standard input of this process.
49 /// The returned handle does not interact with any other handles created nor
50 /// handles returned by `std::io::stdin`. Data buffered by the `std::io::stdin`
51 /// handles is **not** available to raw handles returned from this function.
53 /// The returned handle has no external synchronization or buffering.
54 pub fn stdin_raw() -> StdinRaw { StdinRaw(stdio::Stdin::new()) }
56 /// Construct a new raw handle to the standard input stream of this process.
58 /// The returned handle does not interact with any other handles created nor
59 /// handles returned by `std::io::stdout`. Note that data is buffered by the
60 /// `std::io::stdin` handles so writes which happen via this raw handle may
61 /// appear before previous writes.
63 /// The returned handle has no external synchronization or buffering layered on
65 pub fn stdout_raw() -> StdoutRaw { StdoutRaw(stdio::Stdout::new()) }
67 /// Construct a new raw handle to the standard input stream of this process.
69 /// The returned handle does not interact with any other handles created nor
70 /// handles returned by `std::io::stdout`.
72 /// The returned handle has no external synchronization or buffering layered on
74 pub fn stderr_raw() -> StderrRaw { StderrRaw(stdio::Stderr::new()) }
76 impl Read for StdinRaw {
77 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }
79 impl Write for StdoutRaw {
80 fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
81 fn flush(&mut self) -> io::Result<()> { Ok(()) }
83 impl Write for StderrRaw {
84 fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
85 fn flush(&mut self) -> io::Result<()> { Ok(()) }
88 /// A handle to the standard input stream of a process.
90 /// Each handle is a shared reference to a global buffer of input data to this
91 /// process. A handle can be `lock`'d to gain full access to `BufRead` methods
92 /// (e.g. `.lines()`). Writes to this handle are otherwise locked with respect
95 /// This handle implements the `Read` trait, but beware that concurrent reads
96 /// of `Stdin` must be executed with care.
97 #[stable(feature = "rust1", since = "1.0.0")]
99 inner: Arc<Mutex<BufReader<StdinRaw>>>,
102 /// A locked reference to the a `Stdin` handle.
104 /// This handle implements both the `Read` and `BufRead` traits and is
105 /// constructed via the `lock` method on `Stdin`.
106 #[stable(feature = "rust1", since = "1.0.0")]
107 pub struct StdinLock<'a> {
108 inner: MutexGuard<'a, BufReader<StdinRaw>>,
111 /// Create a new handle to the global standard input stream of this process.
113 /// The handle returned refers to a globally shared buffer between all threads.
114 /// Access is synchronized and can be explicitly controlled with the `lock()`
117 /// The `Read` trait is implemented for the returned value but the `BufRead`
118 /// trait is not due to the global nature of the standard input stream. The
119 /// locked version, `StdinLock`, implements both `Read` and `BufRead`, however.
121 /// To avoid locking and buffering altogether, it is recommended to use the
122 /// `stdin_raw` constructor.
123 #[stable(feature = "rust1", since = "1.0.0")]
124 pub fn stdin() -> Stdin {
125 static INSTANCE: Lazy<Mutex<BufReader<StdinRaw>>> = lazy_init!(stdin_init);
127 inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
130 fn stdin_init() -> Arc<Mutex<BufReader<StdinRaw>>> {
131 // The default buffer capacity is 64k, but apparently windows
132 // doesn't like 64k reads on stdin. See #13304 for details, but the
133 // idea is that on windows we use a slightly smaller buffer that's
134 // been seen to be acceptable.
135 Arc::new(Mutex::new(if cfg!(windows) {
136 BufReader::with_capacity(8 * 1024, stdin_raw())
138 BufReader::new(stdin_raw())
144 /// Lock this handle to the standard input stream, returning a readable
147 /// The lock is released when the returned lock goes out of scope. The
148 /// returned guard also implements the `Read` and `BufRead` traits for
149 /// accessing the underlying data.
150 #[stable(feature = "rust1", since = "1.0.0")]
151 pub fn lock(&self) -> StdinLock {
152 StdinLock { inner: self.inner.lock().unwrap() }
155 /// Locks this handle and reads a line of input into the specified buffer.
157 /// For detailed semantics of this method, see the documentation on
158 /// `BufRead::read_line`.
159 #[stable(feature = "rust1", since = "1.0.0")]
160 pub fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
161 self.lock().read_line(buf)
165 #[stable(feature = "rust1", since = "1.0.0")]
166 impl Read for Stdin {
167 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
168 self.lock().read(buf)
170 fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
171 self.lock().read_to_end(buf)
173 fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
174 self.lock().read_to_string(buf)
178 #[stable(feature = "rust1", since = "1.0.0")]
179 impl<'a> Read for StdinLock<'a> {
180 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
184 #[stable(feature = "rust1", since = "1.0.0")]
185 impl<'a> BufRead for StdinLock<'a> {
186 fn fill_buf(&mut self) -> io::Result<&[u8]> { self.inner.fill_buf() }
187 fn consume(&mut self, n: usize) { self.inner.consume(n) }
190 // As with stdin on windows, stdout often can't handle writes of large
191 // sizes. For an example, see #14940. For this reason, don't try to
192 // write the entire output buffer on windows. On unix we can just
193 // write the whole buffer all at once.
195 // For some other references, it appears that this problem has been
196 // encountered by others [1] [2]. We choose the number 8KB just because
197 // libuv does the same.
199 // [1]: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1232
200 // [2]: http://www.mail-archive.com/log4net-dev@logging.apache.org/msg00661.html
202 const OUT_MAX: usize = 8192;
204 const OUT_MAX: usize = ::usize::MAX;
206 /// A handle to the global standard output stream of the current process.
208 /// Each handle shares a global buffer of data to be written to the standard
209 /// output stream. Access is also synchronized via a lock and explicit control
210 /// over locking is available via the `lock` method.
211 #[stable(feature = "rust1", since = "1.0.0")]
213 // FIXME: this should be LineWriter or BufWriter depending on the state of
214 // stdout (tty or not). Note that if this is not line buffered it
215 // should also flush-on-panic or some form of flush-on-abort.
216 inner: Arc<Mutex<LineWriter<StdoutRaw>>>,
219 /// A locked reference to the a `Stdout` handle.
221 /// This handle implements the `Write` trait and is constructed via the `lock`
222 /// method on `Stdout`.
223 #[stable(feature = "rust1", since = "1.0.0")]
224 pub struct StdoutLock<'a> {
225 inner: MutexGuard<'a, LineWriter<StdoutRaw>>,
228 /// Constructs a new reference to the standard output of the current process.
230 /// Each handle returned is a reference to a shared global buffer whose access
231 /// is synchronized via a mutex. Explicit control over synchronization is
232 /// provided via the `lock` method.
234 /// The returned handle implements the `Write` trait.
236 /// To avoid locking and buffering altogether, it is recommended to use the
237 /// `stdout_raw` constructor.
238 #[stable(feature = "rust1", since = "1.0.0")]
239 pub fn stdout() -> Stdout {
240 static INSTANCE: Lazy<Mutex<LineWriter<StdoutRaw>>> = lazy_init!(stdout_init);
242 inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
245 fn stdout_init() -> Arc<Mutex<LineWriter<StdoutRaw>>> {
246 Arc::new(Mutex::new(LineWriter::new(stdout_raw())))
251 /// Lock this handle to the standard output stream, returning a writable
254 /// The lock is released when the returned lock goes out of scope. The
255 /// returned guard also implements the `Write` trait for writing data.
256 #[stable(feature = "rust1", since = "1.0.0")]
257 pub fn lock(&self) -> StdoutLock {
258 StdoutLock { inner: self.inner.lock().unwrap() }
262 #[stable(feature = "rust1", since = "1.0.0")]
263 impl Write for Stdout {
264 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
265 self.lock().write(buf)
267 fn flush(&mut self) -> io::Result<()> {
270 fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
271 self.lock().write_all(buf)
273 fn write_fmt(&mut self, fmt: fmt::Arguments) -> io::Result<()> {
274 self.lock().write_fmt(fmt)
277 #[stable(feature = "rust1", since = "1.0.0")]
278 impl<'a> Write for StdoutLock<'a> {
279 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
280 self.inner.write(&buf[..cmp::min(buf.len(), OUT_MAX)])
282 fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
285 /// A handle to the standard error stream of a process.
287 /// For more information, see `stderr`
288 #[stable(feature = "rust1", since = "1.0.0")]
290 inner: Arc<Mutex<StderrRaw>>,
293 /// A locked reference to the a `Stderr` handle.
295 /// This handle implements the `Write` trait and is constructed via the `lock`
296 /// method on `Stderr`.
297 #[stable(feature = "rust1", since = "1.0.0")]
298 pub struct StderrLock<'a> {
299 inner: MutexGuard<'a, StderrRaw>,
302 /// Constructs a new reference to the standard error stream of a process.
304 /// Each returned handle is synchronized amongst all other handles created from
305 /// this function. No handles are buffered, however.
307 /// The returned handle implements the `Write` trait.
309 /// To avoid locking altogether, it is recommended to use the `stderr_raw`
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub fn stderr() -> Stderr {
313 static INSTANCE: Lazy<Mutex<StderrRaw>> = lazy_init!(stderr_init);
315 inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
318 fn stderr_init() -> Arc<Mutex<StderrRaw>> {
319 Arc::new(Mutex::new(stderr_raw()))
324 /// Lock this handle to the standard error stream, returning a writable
327 /// The lock is released when the returned lock goes out of scope. The
328 /// returned guard also implements the `Write` trait for writing data.
329 #[stable(feature = "rust1", since = "1.0.0")]
330 pub fn lock(&self) -> StderrLock {
331 StderrLock { inner: self.inner.lock().unwrap() }
335 #[stable(feature = "rust1", since = "1.0.0")]
336 impl Write for Stderr {
337 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
338 self.lock().write(buf)
340 fn flush(&mut self) -> io::Result<()> {
343 fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
344 self.lock().write_all(buf)
346 fn write_fmt(&mut self, fmt: fmt::Arguments) -> io::Result<()> {
347 self.lock().write_fmt(fmt)
350 #[stable(feature = "rust1", since = "1.0.0")]
351 impl<'a> Write for StderrLock<'a> {
352 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
353 self.inner.write(&buf[..cmp::min(buf.len(), OUT_MAX)])
355 fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
358 /// Resets the task-local stderr handle to the specified writer
360 /// This will replace the current task's stderr handle, returning the old
361 /// handle. All future calls to `panic!` and friends will emit their output to
362 /// this specified handle.
364 /// Note that this does not need to be called for all new tasks; the default
365 /// output handle is to the process's stderr stream.
366 #[unstable(feature = "set_stdio",
367 reason = "this function may disappear completely or be replaced \
368 with a more general mechanism")]
370 pub fn set_panic(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
371 use panicking::LOCAL_STDERR;
373 LOCAL_STDERR.with(move |slot| {
374 mem::replace(&mut *slot.borrow_mut(), Some(sink))
375 }).and_then(|mut s| {
381 /// Resets the task-local stdout handle to the specified writer
383 /// This will replace the current task's stdout handle, returning the old
384 /// handle. All future calls to `print!` and friends will emit their output to
385 /// this specified handle.
387 /// Note that this does not need to be called for all new tasks; the default
388 /// output handle is to the process's stdout stream.
389 #[unstable(feature = "set_stdio",
390 reason = "this function may disappear completely or be replaced \
391 with a more general mechanism")]
393 pub fn set_print(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
395 LOCAL_STDOUT.with(move |slot| {
396 mem::replace(&mut *slot.borrow_mut(), Some(sink))
397 }).and_then(|mut s| {
403 #[unstable(feature = "print",
404 reason = "implementation detail which may disappear or be replaced at any time")]
406 pub fn _print(args: fmt::Arguments) {
407 if let Err(e) = LOCAL_STDOUT.with(|s| match s.borrow_mut().as_mut() {
408 Some(w) => w.write_fmt(args),
409 None => stdout().write_fmt(args)
411 panic!("failed printing to stdout: {}", e);