src/libstd/io/stdio.rs - rust - Git at Google

 // 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 prelude::v1::*;
 use io::prelude::*;

 use cell::{RefCell, BorrowState};
 use cmp;
 use fmt;
 use io::lazy::Lazy;
 use io::{self, BufReader, LineWriter};
 use sync::{Arc, Mutex, MutexGuard};
 use sys::stdio;
 use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};

 /// 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() -> StdinRaw { StdinRaw(stdio::Stdin::new()) }

 /// Constructs a new raw handle to the standard input 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::stdin` 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() -> StdoutRaw { StdoutRaw(stdio::Stdout::new()) }

 /// Constructs a new raw handle to the standard input stream of this process.
 ///
 /// The returned handle does not interact with any other handles created nor
 /// handles returned by `std::io::stdout`.
 ///
 /// The returned handle has no external synchronization or buffering layered on
 /// top.
 fn stderr_raw() -> StderrRaw { StderrRaw(stdio::Stderr::new()) }

 impl Read for StdinRaw {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }
 }
 impl Write for StdoutRaw {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }
 impl Write for StderrRaw {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }

 /// 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()`). Writes to this handle are otherwise locked with respect
 /// to other writes.
 ///
 /// This handle implements the `Read` trait, but beware that concurrent reads
 /// of `Stdin` must be executed with care.
 ///
 /// Created by the function `io::stdin()`.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Stdin {
     inner: Arc<Mutex<BufReader<StdinRaw>>>,
 }

 /// A locked reference to the a `Stdin` handle.
 ///
 /// This handle implements both the `Read` and `BufRead` traits and is
 /// constructed via the `lock` method on `Stdin`.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct StdinLock<'a> {
     inner: MutexGuard<'a, BufReader<StdinRaw>>,
 }

 /// Creates a new handle to the global standard input stream of this process.
 ///
 /// The handle returned refers to a globally shared buffer between all threads.
 /// Access is synchronized and can be explicitly controlled with the `lock()`
 /// method.
 ///
 /// The `Read` trait is implemented for the returned value but the `BufRead`
 /// trait is not due to the global nature of the standard input stream. The
 /// locked version, `StdinLock`, implements both `Read` and `BufRead`, however.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdin() -> Stdin {
     static INSTANCE: Lazy<Mutex<BufReader<StdinRaw>>> = lazy_init!(stdin_init);
     return Stdin {
         inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
     };

     fn stdin_init() -> Arc<Mutex<BufReader<StdinRaw>>> {
         // The default buffer capacity is 64k, but apparently windows
         // doesn't like 64k reads on stdin. See #13304 for details, but the
         // idea is that on windows we use a slightly smaller buffer that's
         // been seen to be acceptable.
         Arc::new(Mutex::new(if cfg!(windows) {
             BufReader::with_capacity(8 * 1024, stdin_raw())
         } else {
             BufReader::new(stdin_raw())
         }))
     }
 }

 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.
     #[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`.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
         self.lock().read_line(buf)
     }
 }

 #[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)
     }
     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)
     }
 }

 #[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)
     }
 }
 #[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) }
 }

 // As with stdin on windows, stdout often can't handle writes of large
 // sizes. For an example, see #14940. For this reason, don't try to
 // write the entire output buffer on windows. On unix we can just
 // write the whole buffer all at once.
 //
 // For some other references, it appears that this problem has been
 // encountered by others [1] [2]. We choose the number 8KB just because
 // libuv does the same.
 //
 // [1]: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1232
 // [2]: http://www.mail-archive.com/log4net-dev@logging.apache.org/msg00661.html
 #[cfg(windows)]
 const OUT_MAX: usize = 8192;
 #[cfg(unix)]
 const OUT_MAX: usize = ::usize::MAX;

 /// 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 function `io::stdout()`.
 #[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<StdoutRaw>>>>,
 }

 /// A locked reference to the a `Stdout` handle.
 ///
 /// This handle implements the `Write` trait and is constructed via the `lock`
 /// method on `Stdout`.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct StdoutLock<'a> {
     inner: ReentrantMutexGuard<'a, RefCell<LineWriter<StdoutRaw>>>,
 }

 /// Constructs a new reference 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. Explicit control over synchronization is
 /// provided via the `lock` method.
 ///
 /// The returned handle implements the `Write` trait.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stdout() -> Stdout {
     static INSTANCE: Lazy<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = lazy_init!(stdout_init);
     return Stdout {
         inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
     };

     fn stdout_init() -> Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> {
         Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw()))))
     }
 }

 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.
     #[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 = "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[..cmp::min(buf.len(), OUT_MAX)])
     }
     fn flush(&mut self) -> io::Result<()> {
         self.inner.borrow_mut().flush()
     }
 }

 /// A handle to the standard error stream of a process.
 ///
 /// For more information, see `stderr`
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Stderr {
     inner: Arc<ReentrantMutex<RefCell<StderrRaw>>>,
 }

 /// A locked reference to the a `Stderr` handle.
 ///
 /// This handle implements the `Write` trait and is constructed via the `lock`
 /// method on `Stderr`.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct StderrLock<'a> {
     inner: ReentrantMutexGuard<'a, RefCell<StderrRaw>>,
 }

 /// Constructs a new reference to the standard error stream of a process.
 ///
 /// Each returned handle is synchronized amongst all other handles created from
 /// this function. No handles are buffered, however.
 ///
 /// The returned handle implements the `Write` trait.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stderr() -> Stderr {
     static INSTANCE: Lazy<ReentrantMutex<RefCell<StderrRaw>>> = lazy_init!(stderr_init);
     return Stderr {
         inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
     };

     fn stderr_init() -> Arc<ReentrantMutex<RefCell<StderrRaw>>> {
         Arc::new(ReentrantMutex::new(RefCell::new(stderr_raw())))
     }
 }

 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.
     #[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 = "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[..cmp::min(buf.len(), OUT_MAX)])
     }
     fn flush(&mut self) -> io::Result<()> {
         self.inner.borrow_mut().flush()
     }
 }

 /// Resets the task-local stderr handle to the specified writer
 ///
 /// This will replace the current task'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 tasks; 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")]
 #[doc(hidden)]
 pub fn set_panic(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
     use panicking::LOCAL_STDERR;
     use mem;
     LOCAL_STDERR.with(move |slot| {
         mem::replace(&mut *slot.borrow_mut(), Some(sink))
     }).and_then(|mut s| {
         let _ = s.flush();
         Some(s)
     })
 }

 /// Resets the task-local stdout handle to the specified writer
 ///
 /// This will replace the current task'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 tasks; 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")]
 #[doc(hidden)]
 pub fn set_print(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
     use mem;
     LOCAL_STDOUT.with(move |slot| {
         mem::replace(&mut *slot.borrow_mut(), Some(sink))
     }).and_then(|mut s| {
         let _ = s.flush();
         Some(s)
     })
 }

 #[unstable(feature = "print",
            reason = "implementation detail which may disappear or be replaced at any time")]
 #[doc(hidden)]
 pub fn _print(args: fmt::Arguments) {
     let result = LOCAL_STDOUT.with(|s| {
         if s.borrow_state() == BorrowState::Unused {
             if let Some(w) = s.borrow_mut().as_mut() {
                 return w.write_fmt(args);
             }
         }
         stdout().write_fmt(args)
     });
     if let Err(e) = result {
         panic!("failed printing to stdout: {}", e);
     }
 }

 #[cfg(test)]
 mod tests {
     use thread;
     use super::*;

     #[test]
     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();
     }
 }
	// 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 prelude::v1::*;
	use io::prelude::*;

	use cell::{RefCell, BorrowState};
	use cmp;
	use fmt;
	use io::lazy::Lazy;
	use io::{self, BufReader, LineWriter};
	use sync::{Arc, Mutex, MutexGuard};
	use sys::stdio;
	use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};

	/// 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() -> StdinRaw { StdinRaw(stdio::Stdin::new()) }

	/// Constructs a new raw handle to the standard input 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::stdin` 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() -> StdoutRaw { StdoutRaw(stdio::Stdout::new()) }

	/// Constructs a new raw handle to the standard input stream of this process.
	///
	/// The returned handle does not interact with any other handles created nor
	/// handles returned by `std::io::stdout`.
	///
	/// The returned handle has no external synchronization or buffering layered on
	/// top.
	fn stderr_raw() -> StderrRaw { StderrRaw(stdio::Stderr::new()) }

	impl Read for StdinRaw {
	fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { self.0.read(buf) }
	}
	impl Write for StdoutRaw {
	fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
	fn flush(&mut self) -> io::Result<()> { Ok(()) }
	}
	impl Write for StderrRaw {
	fn write(&mut self, buf: &[u8]) -> io::Result<usize> { self.0.write(buf) }
	fn flush(&mut self) -> io::Result<()> { Ok(()) }
	}

	/// 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()`). Writes to this handle are otherwise locked with respect
	/// to other writes.
	///
	/// This handle implements the `Read` trait, but beware that concurrent reads
	/// of `Stdin` must be executed with care.
	///
	/// Created by the function `io::stdin()`.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct Stdin {
	inner: Arc<Mutex<BufReader<StdinRaw>>>,
	}

	/// A locked reference to the a `Stdin` handle.
	///
	/// This handle implements both the `Read` and `BufRead` traits and is
	/// constructed via the `lock` method on `Stdin`.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct StdinLock<'a> {
	inner: MutexGuard<'a, BufReader<StdinRaw>>,
	}

	/// Creates a new handle to the global standard input stream of this process.
	///
	/// The handle returned refers to a globally shared buffer between all threads.
	/// Access is synchronized and can be explicitly controlled with the `lock()`
	/// method.
	///
	/// The `Read` trait is implemented for the returned value but the `BufRead`
	/// trait is not due to the global nature of the standard input stream. The
	/// locked version, `StdinLock`, implements both `Read` and `BufRead`, however.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn stdin() -> Stdin {
	static INSTANCE: Lazy<Mutex<BufReader<StdinRaw>>> = lazy_init!(stdin_init);
	return Stdin {
	inner: INSTANCE.get().expect("cannot access stdin during shutdown"),
	};

	fn stdin_init() -> Arc<Mutex<BufReader<StdinRaw>>> {
	// The default buffer capacity is 64k, but apparently windows
	// doesn't like 64k reads on stdin. See #13304 for details, but the
	// idea is that on windows we use a slightly smaller buffer that's
	// been seen to be acceptable.
	Arc::new(Mutex::new(if cfg!(windows) {
	BufReader::with_capacity(8 * 1024, stdin_raw())
	} else {
	BufReader::new(stdin_raw())
	}))
	}
	}

	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.
	#[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`.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
	self.lock().read_line(buf)
	}
	}

	#[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)
	}
	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)
	}
	}

	#[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)
	}
	}
	#[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) }
	}

	// As with stdin on windows, stdout often can't handle writes of large
	// sizes. For an example, see #14940. For this reason, don't try to
	// write the entire output buffer on windows. On unix we can just
	// write the whole buffer all at once.
	//
	// For some other references, it appears that this problem has been
	// encountered by others [1] [2]. We choose the number 8KB just because
	// libuv does the same.
	//
	// [1]: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1232
	// [2]: http://www.mail-archive.com/log4net-dev@logging.apache.org/msg00661.html
	#[cfg(windows)]
	const OUT_MAX: usize = 8192;
	#[cfg(unix)]
	const OUT_MAX: usize = ::usize::MAX;

	/// 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 function `io::stdout()`.
	#[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<StdoutRaw>>>>,
	}

	/// A locked reference to the a `Stdout` handle.
	///
	/// This handle implements the `Write` trait and is constructed via the `lock`
	/// method on `Stdout`.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct StdoutLock<'a> {
	inner: ReentrantMutexGuard<'a, RefCell<LineWriter<StdoutRaw>>>,
	}

	/// Constructs a new reference 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. Explicit control over synchronization is
	/// provided via the `lock` method.
	///
	/// The returned handle implements the `Write` trait.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn stdout() -> Stdout {
	static INSTANCE: Lazy<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> = lazy_init!(stdout_init);
	return Stdout {
	inner: INSTANCE.get().expect("cannot access stdout during shutdown"),
	};

	fn stdout_init() -> Arc<ReentrantMutex<RefCell<LineWriter<StdoutRaw>>>> {
	Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout_raw()))))
	}
	}

	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.
	#[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 = "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[..cmp::min(buf.len(), OUT_MAX)])
	}
	fn flush(&mut self) -> io::Result<()> {
	self.inner.borrow_mut().flush()
	}
	}

	/// A handle to the standard error stream of a process.
	///
	/// For more information, see `stderr`
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct Stderr {
	inner: Arc<ReentrantMutex<RefCell<StderrRaw>>>,
	}

	/// A locked reference to the a `Stderr` handle.
	///
	/// This handle implements the `Write` trait and is constructed via the `lock`
	/// method on `Stderr`.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub struct StderrLock<'a> {
	inner: ReentrantMutexGuard<'a, RefCell<StderrRaw>>,
	}

	/// Constructs a new reference to the standard error stream of a process.
	///
	/// Each returned handle is synchronized amongst all other handles created from
	/// this function. No handles are buffered, however.
	///
	/// The returned handle implements the `Write` trait.
	#[stable(feature = "rust1", since = "1.0.0")]
	pub fn stderr() -> Stderr {
	static INSTANCE: Lazy<ReentrantMutex<RefCell<StderrRaw>>> = lazy_init!(stderr_init);
	return Stderr {
	inner: INSTANCE.get().expect("cannot access stderr during shutdown"),
	};

	fn stderr_init() -> Arc<ReentrantMutex<RefCell<StderrRaw>>> {
	Arc::new(ReentrantMutex::new(RefCell::new(stderr_raw())))
	}
	}

	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.
	#[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 = "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[..cmp::min(buf.len(), OUT_MAX)])
	}
	fn flush(&mut self) -> io::Result<()> {
	self.inner.borrow_mut().flush()
	}
	}

	/// Resets the task-local stderr handle to the specified writer
	///
	/// This will replace the current task'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 tasks; 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")]
	#[doc(hidden)]
	pub fn set_panic(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
	use panicking::LOCAL_STDERR;
	use mem;
	LOCAL_STDERR.with(move \|slot\| {
	mem::replace(&mut *slot.borrow_mut(), Some(sink))
	}).and_then(\|mut s\| {
	let _ = s.flush();
	Some(s)
	})
	}

	/// Resets the task-local stdout handle to the specified writer
	///
	/// This will replace the current task'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 tasks; 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")]
	#[doc(hidden)]
	pub fn set_print(sink: Box<Write + Send>) -> Option<Box<Write + Send>> {
	use mem;
	LOCAL_STDOUT.with(move \|slot\| {
	mem::replace(&mut *slot.borrow_mut(), Some(sink))
	}).and_then(\|mut s\| {
	let _ = s.flush();
	Some(s)
	})
	}

	#[unstable(feature = "print",
	reason = "implementation detail which may disappear or be replaced at any time")]
	#[doc(hidden)]
	pub fn _print(args: fmt::Arguments) {
	let result = LOCAL_STDOUT.with(\|s\| {
	if s.borrow_state() == BorrowState::Unused {
	if let Some(w) = s.borrow_mut().as_mut() {
	return w.write_fmt(args);
	}
	}
	stdout().write_fmt(args)
	});
	if let Err(e) = result {
	panic!("failed printing to stdout: {}", e);
	}
	}

	#[cfg(test)]
	mod tests {
	use thread;
	use super::*;

	#[test]
	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();
	}
	}