src/libstd/io/stdio.rs

   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 use prelude::v1::*;
  12 use io::prelude::*;
  13
  14 use cell::{RefCell, BorrowState};
  15 use cmp;
  16 use fmt;
  17 use io::lazy::Lazy;
  18 use io::{self, BufReader, LineWriter};
  19 use sync::{Arc, Mutex, MutexGuard};
  20 use sys::stdio;
  21 use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
  22
  23 /// Stdout used by print! and println! macros
  24 thread_local! {
  25     static LOCAL_STDOUT: RefCell<Option<Box<Write + Send>>> = {
  26         RefCell::new(None)
  27     }
  28 }
  29
  30 /// A handle to a raw instance of the standard input stream of this process.
  31 ///
  32 /// This handle is not synchronized or buffered in any fashion. Constructed via
  33 /// the `std::io::stdio::stdin_raw` function.
  34 struct StdinRaw(stdio::Stdin);
  35
  36 /// A handle to a raw instance of the standard output stream of this process.
  37 ///
  38 /// This handle is not synchronized or buffered in any fashion. Constructed via
  39 /// the `std::io::stdio::stdout_raw` function.
  40 struct StdoutRaw(stdio::Stdout);
  41
  42 /// A handle to a raw instance of the standard output stream of this process.
  43 ///
  44 /// This handle is not synchronized or buffered in any fashion. Constructed via
  45 /// the `std::io::stdio::stderr_raw` function.
  46 struct StderrRaw(stdio::Stderr);
  47
  48 /// Constructs a new raw handle to the standard input of this process.
  49 ///
  50 /// The returned handle does not interact with any other handles created nor
  51 /// handles returned by `std::io::stdin`. Data buffered by the `std::io::stdin`
  52 /// handles is **not** available to raw handles returned from this function.
  53 ///
  54 /// The returned handle has no external synchronization or buffering.
  55 fn stdin_raw() -> StdinRaw { StdinRaw(stdio::Stdin::new()) }
  56
  57 /// Constructs a new raw handle to the standard input stream of this process.
  58 ///
  59 /// The returned handle does not interact with any other handles created nor
  60 /// handles returned by `std::io::stdout`. Note that data is buffered by the
  61 /// `std::io::stdin` handles so writes which happen via this raw handle may
  62 /// appear before previous writes.
  63 ///
  64 /// The returned handle has no external synchronization or buffering layered on
  65 /// top.
  66 fn stdout_raw() -> StdoutRaw { StdoutRaw(stdio::Stdout::new()) }
  67
  68 /// Constructs a new raw handle to the standard input stream of this process.
  69 ///
  70 /// The returned handle does not interact with any other handles created nor
  71 /// handles returned by `std::io::stdout`.
  72 ///
  73 /// The returned handle has no external synchronization or buffering layered on
  74 /// top.
  75 fn stderr_raw() -> StderrRaw { StderrRaw(stdio::Stderr::new()) }
  76
  77 impl Read for StdinRaw {
  78     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }
  79 }
  80 impl Write for StdoutRaw {
  81     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
  82     fn flush(&mut self) -> io::Result<()> { Ok(()) }
  83 }
  84 impl Write for StderrRaw {
  85     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
  86     fn flush(&mut self) -> io::Result<()> { Ok(()) }
  87 }
  88
  89 /// A handle to the standard input stream of a process.
  90 ///
  91 /// Each handle is a shared reference to a global buffer of input data to this
  92 /// process. A handle can be `lock`'d to gain full access to `BufRead` methods
  93 /// (e.g. `.lines()`). Writes to this handle are otherwise locked with respect
  94 /// to other writes.
  95 ///
  96 /// This handle implements the `Read` trait, but beware that concurrent reads
  97 /// of `Stdin` must be executed with care.
  98 ///
  99 /// Created by the function `io::stdin()`.
 100 #[stable(feature = "rust1", since = "1.0.0")]
 101 pub struct Stdin {
 102     inner: Arc<Mutex<BufReader<StdinRaw>>>,
 103 }
 104
 105 /// A locked reference to the a `Stdin` handle.
 106 ///
 107 /// This handle implements both the `Read` and `BufRead` traits and is
 108 /// constructed via the `lock` method on `Stdin`.
 109 #[stable(feature = "rust1", since = "1.0.0")]
 110 pub struct StdinLock<'a> {
 111     inner: MutexGuard<'a, BufReader<StdinRaw>>,
 112 }
 113
 114 /// Creates a new handle to the global standard input stream of this process.
 115 ///
 116 /// The handle returned refers to a globally shared buffer between all threads.
 117 /// Access is synchronized and can be explicitly controlled with the `lock()`
 118 /// method.
 119 ///
 120 /// The `Read` trait is implemented for the returned value but the `BufRead`
 121 /// trait is not due to the global nature of the standard input stream. The
 122 /// locked version, `StdinLock`, implements both `Read` and `BufRead`, however.
 123 #[stable(feature = "rust1", since = "1.0.0")]
 124 pub fn stdin() -> Stdin {
 125     static INSTANCE: Lazy<Mutex<BufReader<StdinRaw>>> = lazy_init!(stdin_init);
 126     return Stdin {
 127         inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
 128     };
 129
 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())
 137         } else {
 138             BufReader::new(stdin_raw())
 139         }))
 140     }
 141 }
 142
 143 impl Stdin {
 144     /// Locks this handle to the standard input stream, returning a readable
 145     /// guard.
 146     ///
 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_or_else(|e| e.into_inner()) }
 153     }
 154
 155     /// Locks this handle and reads a line of input into the specified buffer.
 156     ///
 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)
 162     }
 163 }
 164
 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)
 169     }
 170     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
 171         self.lock().read_to_end(buf)
 172     }
 173     fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
 174         self.lock().read_to_string(buf)
 175     }
 176 }
 177
 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> {
 181         self.inner.read(buf)
 182     }
 183 }
 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) }
 188 }
 189
 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.
 194 //
 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.
 198 //
 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
 201 #[cfg(windows)]
 202 const OUT_MAX: usize = 8192;
 203 #[cfg(unix)]
 204 const OUT_MAX: usize = ::usize::MAX;
 205
 206 /// A handle to the global standard output stream of the current process.
 207 ///
 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 ///
 212 /// Created by the function `io::stdout()`.
 213 #[stable(feature = "rust1", since = "1.0.0")]
 214 pub struct Stdout {
 215     // FIXME: this should be LineWriter or BufWriter depending on the state of
 216     //        stdout (tty or not). Note that if this is not line buffered it
 217     //        should also flush-on-panic or some form of flush-on-abort.
 218     inner: Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>>,
 219 }
 220
 221 /// A locked reference to the a `Stdout` handle.
 222 ///
 223 /// This handle implements the `Write` trait and is constructed via the `lock`
 224 /// method on `Stdout`.
 225 #[stable(feature = "rust1", since = "1.0.0")]
 226 pub struct StdoutLock<'a> {
 227     inner: ReentrantMutexGuard<'a, RefCell<LineWriter<StdoutRaw>>>,
 228 }
 229
 230 /// Constructs a new reference to the standard output of the current process.
 231 ///
 232 /// Each handle returned is a reference to a shared global buffer whose access
 233 /// is synchronized via a mutex. Explicit control over synchronization is
 234 /// provided via the `lock` method.
 235 ///
 236 /// The returned handle implements the `Write` trait.
 237 #[stable(feature = "rust1", since = "1.0.0")]
 238 pub fn stdout() -> Stdout {
 239     static INSTANCE: Lazy<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = lazy_init!(stdout_init);
 240     return Stdout {
 241         inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
 242     };
 243
 244     fn stdout_init() -> Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> {
 245         Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw()))))
 246     }
 247 }
 248
 249 impl Stdout {
 250     /// Locks this handle to the standard output stream, returning a writable
 251     /// guard.
 252     ///
 253     /// The lock is released when the returned lock goes out of scope. The
 254     /// returned guard also implements the `Write` trait for writing data.
 255     #[stable(feature = "rust1", since = "1.0.0")]
 256     pub fn lock(&self) -> StdoutLock {
 257         StdoutLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
 258     }
 259 }
 260
 261 #[stable(feature = "rust1", since = "1.0.0")]
 262 impl Write for Stdout {
 263     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 264         self.lock().write(buf)
 265     }
 266     fn flush(&mut self) -> io::Result<()> {
 267         self.lock().flush()
 268     }
 269     fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
 270         self.lock().write_all(buf)
 271     }
 272     fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
 273         self.lock().write_fmt(args)
 274     }
 275 }
 276 #[stable(feature = "rust1", since = "1.0.0")]
 277 impl<'a> Write for StdoutLock<'a> {
 278     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 279         self.inner.borrow_mut().write(&buf[..cmp::min(buf.len(), OUT_MAX)])
 280     }
 281     fn flush(&mut self) -> io::Result<()> {
 282         self.inner.borrow_mut().flush()
 283     }
 284 }
 285
 286 /// A handle to the standard error stream of a process.
 287 ///
 288 /// For more information, see `stderr`
 289 #[stable(feature = "rust1", since = "1.0.0")]
 290 pub struct Stderr {
 291     inner: Arc<ReentrantMutex<RefCell<StderrRaw>>>,
 292 }
 293
 294 /// A locked reference to the a `Stderr` handle.
 295 ///
 296 /// This handle implements the `Write` trait and is constructed via the `lock`
 297 /// method on `Stderr`.
 298 #[stable(feature = "rust1", since = "1.0.0")]
 299 pub struct StderrLock<'a> {
 300     inner: ReentrantMutexGuard<'a, RefCell<StderrRaw>>,
 301 }
 302
 303 /// Constructs a new reference to the standard error stream of a process.
 304 ///
 305 /// Each returned handle is synchronized amongst all other handles created from
 306 /// this function. No handles are buffered, however.
 307 ///
 308 /// The returned handle implements the `Write` trait.
 309 #[stable(feature = "rust1", since = "1.0.0")]
 310 pub fn stderr() -> Stderr {
 311     static INSTANCE: Lazy<ReentrantMutex<RefCell<StderrRaw>>> = lazy_init!(stderr_init);
 312     return Stderr {
 313         inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
 314     };
 315
 316     fn stderr_init() -> Arc<ReentrantMutex<RefCell<StderrRaw>>> {
 317         Arc::new(ReentrantMutex::new(RefCell::new(stderr_raw())))
 318     }
 319 }
 320
 321 impl Stderr {
 322     /// Locks this handle to the standard error stream, returning a writable
 323     /// guard.
 324     ///
 325     /// The lock is released when the returned lock goes out of scope. The
 326     /// returned guard also implements the `Write` trait for writing data.
 327     #[stable(feature = "rust1", since = "1.0.0")]
 328     pub fn lock(&self) -> StderrLock {
 329         StderrLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
 330     }
 331 }
 332
 333 #[stable(feature = "rust1", since = "1.0.0")]
 334 impl Write for Stderr {
 335     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 336         self.lock().write(buf)
 337     }
 338     fn flush(&mut self) -> io::Result<()> {
 339         self.lock().flush()
 340     }
 341     fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
 342         self.lock().write_all(buf)
 343     }
 344     fn write_fmt(&mut self, args: fmt::Arguments) -> io::Result<()> {
 345         self.lock().write_fmt(args)
 346     }
 347 }
 348 #[stable(feature = "rust1", since = "1.0.0")]
 349 impl<'a> Write for StderrLock<'a> {
 350     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
 351         self.inner.borrow_mut().write(&buf[..cmp::min(buf.len(), OUT_MAX)])
 352     }
 353     fn flush(&mut self) -> io::Result<()> {
 354         self.inner.borrow_mut().flush()
 355     }
 356 }
 357
 358 /// Resets the thread-local stderr handle to the specified writer
 359 ///
 360 /// This will replace the current thread's stderr handle, returning the old
 361 /// handle. All future calls to `panic!` and friends will emit their output to
 362 /// this specified handle.
 363 ///
 364 /// Note that this does not need to be called for all new threads; 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")]
 369 #[doc(hidden)]
 370 pub fn set_panic(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
 371     use panicking::LOCAL_STDERR;
 372     use mem;
 373     LOCAL_STDERR.with(move |slot| {
 374         mem::replace(&mut *slot.borrow_mut(), Some(sink))
 375     }).and_then(|mut s| {
 376         let _ = s.flush();
 377         Some(s)
 378     })
 379 }
 380
 381 /// Resets the thread-local stdout handle to the specified writer
 382 ///
 383 /// This will replace the current thread's stdout handle, returning the old
 384 /// handle. All future calls to `print!` and friends will emit their output to
 385 /// this specified handle.
 386 ///
 387 /// Note that this does not need to be called for all new threads; 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")]
 392 #[doc(hidden)]
 393 pub fn set_print(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
 394     use mem;
 395     LOCAL_STDOUT.with(move |slot| {
 396         mem::replace(&mut *slot.borrow_mut(), Some(sink))
 397     }).and_then(|mut s| {
 398         let _ = s.flush();
 399         Some(s)
 400     })
 401 }
 402
 403 #[unstable(feature = "print",
 404            reason = "implementation detail which may disappear or be replaced at any time")]
 405 #[doc(hidden)]
 406 pub fn _print(args: fmt::Arguments) {
 407     let result = LOCAL_STDOUT.with(|s| {
 408         if s.borrow_state() == BorrowState::Unused {
 409             if let Some(w) = s.borrow_mut().as_mut() {
 410                 return w.write_fmt(args);
 411             }
 412         }
 413         stdout().write_fmt(args)
 414     });
 415     if let Err(e) = result {
 416         panic!("failed printing to stdout: {}", e);
 417     }
 418 }
 419
 420 #[cfg(test)]
 421 mod tests {
 422     use thread;
 423     use super::*;
 424
 425     #[test]
 426     fn panic_doesnt_poison() {
 427         thread::spawn(|| {
 428             let _a = stdin();
 429             let _a = _a.lock();
 430             let _a = stdout();
 431             let _a = _a.lock();
 432             let _a = stderr();
 433             let _a = _a.lock();
 434             panic!();
 435         }).join().unwrap_err();
 436
 437         let _a = stdin();
 438         let _a = _a.lock();
 439         let _a = stdout();
 440         let _a = _a.lock();
 441         let _a = stderr();
 442         let _a = _a.lock();
 443     }
 444 }