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// Copyright 2013 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. //! Non-blocking access to stdin, stdout, and stderr. //! //! This module provides bindings to the local event loop's TTY interface, using it //! to offer synchronous but non-blocking versions of stdio. These handles can be //! inspected for information about terminal dimensions or for related information //! about the stream or terminal to which it is attached. //! //! # Example //! //! ```rust //! # #![allow(unused_must_use)] //! use std::io; //! //! let mut out = io::stdout(); //! out.write(b"Hello, world!"); //! ``` use self::StdSource::*; use boxed::Box; use cell::RefCell; use clone::Clone; use failure::LOCAL_STDERR; use fmt; use io::{Reader, Writer, IoResult, IoError, OtherIoError, Buffer, standard_error, EndOfFile, LineBufferedWriter, BufferedReader}; use kinds::{Sync, Send}; use libc; use mem; use option::Option; use option::Option::{Some, None}; use ops::{Deref, DerefMut, FnOnce}; use result::Result::{Ok, Err}; use rt; use slice::SliceExt; use str::StrExt; use string::String; use sys::{fs, tty}; use sync::{Arc, Mutex, MutexGuard, Once, ONCE_INIT}; use uint; use vec::Vec; // And so begins the tale of acquiring a uv handle to a stdio stream on all // platforms in all situations. Our story begins by splitting the world into two // categories, windows and unix. Then one day the creators of unix said let // there be redirection! And henceforth there was redirection away from the // console for standard I/O streams. // // After this day, the world split into four factions: // // 1. Unix with stdout on a terminal. // 2. Unix with stdout redirected. // 3. Windows with stdout on a terminal. // 4. Windows with stdout redirected. // // Many years passed, and then one day the nation of libuv decided to unify this // world. After months of toiling, uv created three ideas: TTY, Pipe, File. // These three ideas propagated throughout the lands and the four great factions // decided to settle among them. // // The groups of 1, 2, and 3 all worked very hard towards the idea of TTY. Upon // doing so, they even enhanced themselves further then their Pipe/File // brethren, becoming the dominant powers. // // The group of 4, however, decided to work independently. They abandoned the // common TTY belief throughout, and even abandoned the fledgling Pipe belief. // The members of the 4th faction decided to only align themselves with File. // // tl;dr; TTY works on everything but when windows stdout is redirected, in that // case pipe also doesn't work, but magically file does! enum StdSource { TTY(tty::TTY), File(fs::FileDesc), } fn src<T, F>(fd: libc::c_int, _readable: bool, f: F) -> T where F: FnOnce(StdSource) -> T, { match tty::TTY::new(fd) { Ok(tty) => f(TTY(tty)), Err(_) => f(File(fs::FileDesc::new(fd, false))), } } thread_local! { static LOCAL_STDOUT: RefCell<Option<Box<Writer + Send>>> = { RefCell::new(None) } } struct RaceBox(BufferedReader<StdReader>); unsafe impl Send for RaceBox {} unsafe impl Sync for RaceBox {} /// A synchronized wrapper around a buffered reader from stdin #[deriving(Clone)] pub struct StdinReader { inner: Arc<Mutex<RaceBox>>, } unsafe impl Send for StdinReader {} unsafe impl Sync for StdinReader {} /// A guard for exclusive access to `StdinReader`'s internal `BufferedReader`. pub struct StdinReaderGuard<'a> { inner: MutexGuard<'a, RaceBox>, } impl<'a> Deref<BufferedReader<StdReader>> for StdinReaderGuard<'a> { fn deref(&self) -> &BufferedReader<StdReader> { &self.inner.0 } } impl<'a> DerefMut<BufferedReader<StdReader>> for StdinReaderGuard<'a> { fn deref_mut(&mut self) -> &mut BufferedReader<StdReader> { &mut self.inner.0 } } impl StdinReader { /// Locks the `StdinReader`, granting the calling thread exclusive access /// to the underlying `BufferedReader`. /// /// This provides access to methods like `chars` and `lines`. /// /// # Examples /// /// ```rust /// use std::io; /// /// for line in io::stdin().lock().lines() { /// println!("{}", line.unwrap()); /// } /// ``` pub fn lock<'a>(&'a mut self) -> StdinReaderGuard<'a> { StdinReaderGuard { inner: self.inner.lock().unwrap() } } /// Like `Buffer::read_line`. /// /// The read is performed atomically - concurrent read calls in other /// threads will not interleave with this one. pub fn read_line(&mut self) -> IoResult<String> { self.inner.lock().unwrap().0.read_line() } /// Like `Buffer::read_until`. /// /// The read is performed atomically - concurrent read calls in other /// threads will not interleave with this one. pub fn read_until(&mut self, byte: u8) -> IoResult<Vec<u8>> { self.inner.lock().unwrap().0.read_until(byte) } /// Like `Buffer::read_char`. /// /// The read is performed atomically - concurrent read calls in other /// threads will not interleave with this one. pub fn read_char(&mut self) -> IoResult<char> { self.inner.lock().unwrap().0.read_char() } } impl Reader for StdinReader { fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> { self.inner.lock().unwrap().0.read(buf) } // We have to manually delegate all of these because the default impls call // read more than once and we don't want those calls to interleave (or // incur the costs of repeated locking). fn read_at_least(&mut self, min: uint, buf: &mut [u8]) -> IoResult<uint> { self.inner.lock().unwrap().0.read_at_least(min, buf) } fn push_at_least(&mut self, min: uint, len: uint, buf: &mut Vec<u8>) -> IoResult<uint> { self.inner.lock().unwrap().0.push_at_least(min, len, buf) } fn read_to_end(&mut self) -> IoResult<Vec<u8>> { self.inner.lock().unwrap().0.read_to_end() } fn read_le_uint_n(&mut self, nbytes: uint) -> IoResult<u64> { self.inner.lock().unwrap().0.read_le_uint_n(nbytes) } fn read_be_uint_n(&mut self, nbytes: uint) -> IoResult<u64> { self.inner.lock().unwrap().0.read_be_uint_n(nbytes) } } /// Creates a new handle to the stdin of the current process. /// /// The returned handle is a wrapper around a global `BufferedReader` shared /// by all threads. If buffered access is not desired, the `stdin_raw` function /// is provided to provided unbuffered access to stdin. /// /// See `stdout()` for more notes about this function. pub fn stdin() -> StdinReader { // We're following the same strategy as kimundi's lazy_static library static mut STDIN: *const StdinReader = 0 as *const StdinReader; static ONCE: Once = ONCE_INIT; unsafe { ONCE.doit(|| { // 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. let stdin = if cfg!(windows) { BufferedReader::with_capacity(8 * 1024, stdin_raw()) } else { BufferedReader::new(stdin_raw()) }; let stdin = StdinReader { inner: Arc::new(Mutex::new(RaceBox(stdin))) }; STDIN = mem::transmute(box stdin); // Make sure to free it at exit rt::at_exit(|| { mem::transmute::<_, Box<StdinReader>>(STDIN); STDIN = 0 as *const _; }); }); (*STDIN).clone() } } /// Creates a new non-blocking handle to the stdin of the current process. /// /// Unlike `stdin()`, the returned reader is *not* a buffered reader. /// /// See `stdout()` for more notes about this function. pub fn stdin_raw() -> StdReader { src(libc::STDIN_FILENO, true, |src| StdReader { inner: src }) } /// Creates a line-buffered handle to the stdout of the current process. /// /// Note that this is a fairly expensive operation in that at least one memory /// allocation is performed. Additionally, this must be called from a runtime /// task context because the stream returned will be a non-blocking object using /// the local scheduler to perform the I/O. /// /// Care should be taken when creating multiple handles to an output stream for /// a single process. While usage is still safe, the output may be surprising if /// no synchronization is performed to ensure a sane output. pub fn stdout() -> LineBufferedWriter<StdWriter> { LineBufferedWriter::new(stdout_raw()) } /// Creates an unbuffered handle to the stdout of the current process /// /// See notes in `stdout()` for more information. pub fn stdout_raw() -> StdWriter { src(libc::STDOUT_FILENO, false, |src| StdWriter { inner: src }) } /// Creates a line-buffered handle to the stderr of the current process. /// /// See `stdout()` for notes about this function. pub fn stderr() -> LineBufferedWriter<StdWriter> { LineBufferedWriter::new(stderr_raw()) } /// Creates an unbuffered handle to the stderr of the current process /// /// See notes in `stdout()` for more information. pub fn stderr_raw() -> StdWriter { src(libc::STDERR_FILENO, false, |src| StdWriter { inner: src }) } /// 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. pub fn set_stdout(stdout: Box<Writer + Send>) -> Option<Box<Writer + Send>> { let mut new = Some(stdout); LOCAL_STDOUT.with(|slot| { mem::replace(&mut *slot.borrow_mut(), new.take()) }).and_then(|mut s| { let _ = s.flush(); Some(s) }) } /// Resets the task-local stderr handle to the specified writer /// /// This will replace the current task's stderr handle, returning the old /// handle. Currently, the stderr handle is used for printing panic messages /// during task panic. /// /// Note that this does not need to be called for all new tasks; the default /// output handle is to the process's stderr stream. pub fn set_stderr(stderr: Box<Writer + Send>) -> Option<Box<Writer + Send>> { let mut new = Some(stderr); LOCAL_STDERR.with(|slot| { mem::replace(&mut *slot.borrow_mut(), new.take()) }).and_then(|mut s| { let _ = s.flush(); Some(s) }) } // Helper to access the local task's stdout handle // // Note that this is not a safe function to expose because you can create an // aliased pointer very easily: // // with_task_stdout(|io1| { // with_task_stdout(|io2| { // // io1 aliases io2 // }) // }) fn with_task_stdout<F>(f: F) where F: FnOnce(&mut Writer) -> IoResult<()> { let mut my_stdout = LOCAL_STDOUT.with(|slot| { slot.borrow_mut().take() }).unwrap_or_else(|| { box stdout() as Box<Writer + Send> }); let result = f(&mut *my_stdout); let mut var = Some(my_stdout); LOCAL_STDOUT.with(|slot| { *slot.borrow_mut() = var.take(); }); match result { Ok(()) => {} Err(e) => panic!("failed printing to stdout: {}", e), } } /// Flushes the local task's stdout handle. /// /// By default, this stream is a line-buffering stream, so flushing may be /// necessary to ensure that all output is printed to the screen (if there are /// no newlines printed). /// /// Note that logging macros do not use this stream. Using the logging macros /// will emit output to stderr, and while they are line buffered the log /// messages are always terminated in a newline (no need to flush). pub fn flush() { with_task_stdout(|io| io.flush()) } /// Prints a string to the stdout of the current process. No newline is emitted /// after the string is printed. pub fn print(s: &str) { with_task_stdout(|io| io.write(s.as_bytes())) } /// Prints a string to the stdout of the current process. A literal /// `\n` character is printed to the console after the string. pub fn println(s: &str) { with_task_stdout(|io| { io.write(s.as_bytes()).and_then(|()| io.write(&[b'\n'])) }) } /// Similar to `print`, but takes a `fmt::Arguments` structure to be compatible /// with the `format_args!` macro. pub fn print_args(fmt: fmt::Arguments) { with_task_stdout(|io| write!(io, "{}", fmt)) } /// Similar to `println`, but takes a `fmt::Arguments` structure to be /// compatible with the `format_args!` macro. pub fn println_args(fmt: fmt::Arguments) { with_task_stdout(|io| writeln!(io, "{}", fmt)) } /// Representation of a reader of a standard input stream pub struct StdReader { inner: StdSource } impl StdReader { /// Returns whether this stream is attached to a TTY instance or not. pub fn isatty(&self) -> bool { match self.inner { TTY(..) => true, File(..) => false, } } } impl Reader for StdReader { fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> { let ret = match self.inner { TTY(ref mut tty) => { // Flush the task-local stdout so that weird issues like a // print!'d prompt not being shown until after the user hits // enter. flush(); tty.read(buf).map(|i| i as uint) }, File(ref mut file) => file.read(buf).map(|i| i as uint), }; match ret { // When reading a piped stdin, libuv will return 0-length reads when // stdin reaches EOF. For pretty much all other streams it will // return an actual EOF error, but apparently for stdin it's a // little different. Hence, here we convert a 0 length read to an // end-of-file indicator so the caller knows to stop reading. Ok(0) => { Err(standard_error(EndOfFile)) } ret @ Ok(..) | ret @ Err(..) => ret, } } } /// Representation of a writer to a standard output stream pub struct StdWriter { inner: StdSource } unsafe impl Send for StdWriter {} unsafe impl Sync for StdWriter {} impl StdWriter { /// Gets the size of this output window, if possible. This is typically used /// when the writer is attached to something like a terminal, this is used /// to fetch the dimensions of the terminal. /// /// If successful, returns `Ok((width, height))`. /// /// # Error /// /// This function will return an error if the output stream is not actually /// connected to a TTY instance, or if querying the TTY instance fails. pub fn winsize(&mut self) -> IoResult<(int, int)> { match self.inner { TTY(ref mut tty) => { tty.get_winsize() } File(..) => { Err(IoError { kind: OtherIoError, desc: "stream is not a tty", detail: None, }) } } } /// Controls whether this output stream is a "raw stream" or simply a normal /// stream. /// /// # Error /// /// This function will return an error if the output stream is not actually /// connected to a TTY instance, or if querying the TTY instance fails. pub fn set_raw(&mut self, raw: bool) -> IoResult<()> { match self.inner { TTY(ref mut tty) => { tty.set_raw(raw) } File(..) => { Err(IoError { kind: OtherIoError, desc: "stream is not a tty", detail: None, }) } } } /// Returns whether this stream is attached to a TTY instance or not. pub fn isatty(&self) -> bool { match self.inner { TTY(..) => true, File(..) => false, } } } impl Writer for StdWriter { fn write(&mut self, buf: &[u8]) -> IoResult<()> { // As with stdin on windows, stdout often can't handle writes of large // sizes. For an example, see #14940. For this reason, chunk the output // buffer on windows, but 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 let max_size = if cfg!(windows) {8192} else {uint::MAX}; for chunk in buf.chunks(max_size) { try!(match self.inner { TTY(ref mut tty) => tty.write(chunk), File(ref mut file) => file.write(chunk), }) } Ok(()) } } #[cfg(test)] mod tests { use super::*; use prelude::*; #[test] fn smoke() { // Just make sure we can acquire handles stdin(); stdout(); stderr(); } #[test] fn capture_stdout() { use io::{ChanReader, ChanWriter}; let (tx, rx) = channel(); let (mut r, w) = (ChanReader::new(rx), ChanWriter::new(tx)); spawn(move|| { set_stdout(box w); println!("hello!"); }); assert_eq!(r.read_to_string().unwrap(), "hello!\n"); } #[test] fn capture_stderr() { use io::{ChanReader, ChanWriter, Reader}; let (tx, rx) = channel(); let (mut r, w) = (ChanReader::new(rx), ChanWriter::new(tx)); spawn(move|| { set_stderr(box w); panic!("my special message"); }); let s = r.read_to_string().unwrap(); assert!(s.contains("my special message")); } }