src/libstd/sys/windows/pipe.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 os::windows::prelude::*;
  13
  14 use ffi::OsStr;
  15 use path::Path;
  16 use io;
  17 use mem;
  18 use rand::{self, Rng};
  19 use slice;
  20 use sys::c;
  21 use sys::fs::{File, OpenOptions};
  22 use sys::handle::Handle;
  23
  24 ////////////////////////////////////////////////////////////////////////////////
  25 // Anonymous pipes
  26 ////////////////////////////////////////////////////////////////////////////////
  27
  28 pub struct AnonPipe {
  29     inner: Handle,
  30 }
  31
  32 pub fn anon_pipe() -> io::Result<(AnonPipe, AnonPipe)> {
  33     // Note that we specifically do *not* use `CreatePipe` here because
  34     // unfortunately the anonymous pipes returned do not support overlapped
  35     // operations.
  36     //
  37     // Instead, we create a "hopefully unique" name and create a named pipe
  38     // which has overlapped operations enabled.
  39     //
  40     // Once we do this, we connect do it as usual via `CreateFileW`, and then we
  41     // return those reader/writer halves.
  42     unsafe {
  43         let reader;
  44         let mut name;
  45         let mut tries = 0;
  46         loop {
  47             tries += 1;
  48             let key: u64 = rand::thread_rng().gen();
  49             name = format!(r"\\.\pipe\__rust_anonymous_pipe1__.{}.{}",
  50                            c::GetCurrentProcessId(),
  51                            key);
  52             let wide_name = OsStr::new(&name)
  53                                   .encode_wide()
  54                                   .chain(Some(0))
  55                                   .collect::<Vec<_>>();
  56
  57             let handle = c::CreateNamedPipeW(wide_name.as_ptr(),
  58                                              c::PIPE_ACCESS_INBOUND |
  59                                               c::FILE_FLAG_FIRST_PIPE_INSTANCE |
  60                                               c::FILE_FLAG_OVERLAPPED,
  61                                              c::PIPE_TYPE_BYTE |
  62                                               c::PIPE_READMODE_BYTE |
  63                                               c::PIPE_WAIT |
  64                                               c::PIPE_REJECT_REMOTE_CLIENTS,
  65                                              1,
  66                                              4096,
  67                                              4096,
  68                                              0,
  69                                              0 as *mut _);
  70
  71             // We pass the FILE_FLAG_FIRST_PIPE_INSTANCE flag above, and we're
  72             // also just doing a best effort at selecting a unique name. If
  73             // ERROR_ACCESS_DENIED is returned then it could mean that we
  74             // accidentally conflicted with an already existing pipe, so we try
  75             // again.
  76             //
  77             // Don't try again too much though as this could also perhaps be a
  78             // legit error.
  79             if handle == c::INVALID_HANDLE_VALUE {
  80                 let err = io::Error::last_os_error();
  81                 if tries < 10 &&
  82                    err.raw_os_error() == Some(c::ERROR_ACCESS_DENIED as i32) {
  83                     continue
  84                 }
  85                 return Err(err)
  86             }
  87             reader = Handle::new(handle);
  88             break
  89         }
  90
  91         // Connect to the named pipe we just created in write-only mode (also
  92         // overlapped for async I/O below).
  93         let mut opts = OpenOptions::new();
  94         opts.write(true);
  95         opts.read(false);
  96         opts.share_mode(0);
  97         opts.attributes(c::FILE_FLAG_OVERLAPPED);
  98         let writer = File::open(Path::new(&name), &opts)?;
  99         let writer = AnonPipe { inner: writer.into_handle() };
 100
 101         Ok((AnonPipe { inner: reader }, AnonPipe { inner: writer.into_handle() }))
 102     }
 103 }
 104
 105 impl AnonPipe {
 106     pub fn handle(&self) -> &Handle { &self.inner }
 107     pub fn into_handle(self) -> Handle { self.inner }
 108
 109     pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
 110         self.inner.read(buf)
 111     }
 112
 113     pub fn read_to_end(&self, buf: &mut Vec<u8>) -> io::Result<usize> {
 114         self.inner.read_to_end(buf)
 115     }
 116
 117     pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
 118         self.inner.write(buf)
 119     }
 120 }
 121
 122 pub fn read2(p1: AnonPipe,
 123              v1: &mut Vec<u8>,
 124              p2: AnonPipe,
 125              v2: &mut Vec<u8>) -> io::Result<()> {
 126     let p1 = p1.into_handle();
 127     let p2 = p2.into_handle();
 128
 129     let mut p1 = AsyncPipe::new(p1, v1)?;
 130     let mut p2 = AsyncPipe::new(p2, v2)?;
 131     let objs = [p1.event.raw(), p2.event.raw()];
 132
 133     // In a loop we wait for either pipe's scheduled read operation to complete.
 134     // If the operation completes with 0 bytes, that means EOF was reached, in
 135     // which case we just finish out the other pipe entirely.
 136     //
 137     // Note that overlapped I/O is in general super unsafe because we have to
 138     // be careful to ensure that all pointers in play are valid for the entire
 139     // duration of the I/O operation (where tons of operations can also fail).
 140     // The destructor for `AsyncPipe` ends up taking care of most of this.
 141     loop {
 142         let res = unsafe {
 143             c::WaitForMultipleObjects(2, objs.as_ptr(), c::FALSE, c::INFINITE)
 144         };
 145         if res == c::WAIT_OBJECT_0 {
 146             if !p1.result()? || !p1.schedule_read()? {
 147                 return p2.finish()
 148             }
 149         } else if res == c::WAIT_OBJECT_0 + 1 {
 150             if !p2.result()? || !p2.schedule_read()? {
 151                 return p1.finish()
 152             }
 153         } else {
 154             return Err(io::Error::last_os_error())
 155         }
 156     }
 157 }
 158
 159 struct AsyncPipe<'a> {
 160     pipe: Handle,
 161     event: Handle,
 162     overlapped: Box<c::OVERLAPPED>, // needs a stable address
 163     dst: &'a mut Vec<u8>,
 164     state: State,
 165 }
 166
 167 #[derive(PartialEq, Debug)]
 168 enum State {
 169     NotReading,
 170     Reading,
 171     Read(usize),
 172 }
 173
 174 impl<'a> AsyncPipe<'a> {
 175     fn new(pipe: Handle, dst: &'a mut Vec<u8>) -> io::Result<AsyncPipe<'a>> {
 176         // Create an event which we'll use to coordinate our overlapped
 177         // opreations, this event will be used in WaitForMultipleObjects
 178         // and passed as part of the OVERLAPPED handle.
 179         //
 180         // Note that we do a somewhat clever thing here by flagging the
 181         // event as being manually reset and setting it initially to the
 182         // signaled state. This means that we'll naturally fall through the
 183         // WaitForMultipleObjects call above for pipes created initially,
 184         // and the only time an even will go back to "unset" will be once an
 185         // I/O operation is successfully scheduled (what we want).
 186         let event = Handle::new_event(true, true)?;
 187         let mut overlapped: Box<c::OVERLAPPED> = unsafe {
 188             Box::new(mem::zeroed())
 189         };
 190         overlapped.hEvent = event.raw();
 191         Ok(AsyncPipe {
 192             pipe: pipe,
 193             overlapped: overlapped,
 194             event: event,
 195             dst: dst,
 196             state: State::NotReading,
 197         })
 198     }
 199
 200     /// Executes an overlapped read operation.
 201     ///
 202     /// Must not currently be reading, and returns whether the pipe is currently
 203     /// at EOF or not. If the pipe is not at EOF then `result()` must be called
 204     /// to complete the read later on (may block), but if the pipe is at EOF
 205     /// then `result()` should not be called as it will just block forever.
 206     fn schedule_read(&mut self) -> io::Result<bool> {
 207         assert_eq!(self.state, State::NotReading);
 208         let amt = unsafe {
 209             let slice = slice_to_end(self.dst);
 210             self.pipe.read_overlapped(slice, &mut *self.overlapped)?
 211         };
 212
 213         // If this read finished immediately then our overlapped event will
 214         // remain signaled (it was signaled coming in here) and we'll progress
 215         // down to the method below.
 216         //
 217         // Otherwise the I/O operation is scheduled and the system set our event
 218         // to not signaled, so we flag ourselves into the reading state and move
 219         // on.
 220         self.state = match amt {
 221             Some(0) => return Ok(false),
 222             Some(amt) => State::Read(amt),
 223             None => State::Reading,
 224         };
 225         Ok(true)
 226     }
 227
 228     /// Wait for the result of the overlapped operation previously executed.
 229     ///
 230     /// Takes a parameter `wait` which indicates if this pipe is currently being
 231     /// read whether the function should block waiting for the read to complete.
 232     ///
 233     /// Return values:
 234     ///
 235     /// * `true` - finished any pending read and the pipe is not at EOF (keep
 236     ///            going)
 237     /// * `false` - finished any pending read and pipe is at EOF (stop issuing
 238     ///             reads)
 239     fn result(&mut self) -> io::Result<bool> {
 240         let amt = match self.state {
 241             State::NotReading => return Ok(true),
 242             State::Reading => {
 243                 self.pipe.overlapped_result(&mut *self.overlapped, true)?
 244             }
 245             State::Read(amt) => amt,
 246         };
 247         self.state = State::NotReading;
 248         unsafe {
 249             let len = self.dst.len();
 250             self.dst.set_len(len + amt);
 251         }
 252         Ok(amt != 0)
 253     }
 254
 255     /// Finishes out reading this pipe entirely.
 256     ///
 257     /// Waits for any pending and schedule read, and then calls `read_to_end`
 258     /// if necessary to read all the remaining information.
 259     fn finish(&mut self) -> io::Result<()> {
 260         while self.result()? && self.schedule_read()? {
 261             // ...
 262         }
 263         Ok(())
 264     }
 265 }
 266
 267 impl<'a> Drop for AsyncPipe<'a> {
 268     fn drop(&mut self) {
 269         match self.state {
 270             State::Reading => {}
 271             _ => return,
 272         }
 273
 274         // If we have a pending read operation, then we have to make sure that
 275         // it's *done* before we actually drop this type. The kernel requires
 276         // that the `OVERLAPPED` and buffer pointers are valid for the entire
 277         // I/O operation.
 278         //
 279         // To do that, we call `CancelIo` to cancel any pending operation, and
 280         // if that succeeds we wait for the overlapped result.
 281         //
 282         // If anything here fails, there's not really much we can do, so we leak
 283         // the buffer/OVERLAPPED pointers to ensure we're at least memory safe.
 284         if self.pipe.cancel_io().is_err() || self.result().is_err() {
 285             let buf = mem::replace(self.dst, Vec::new());
 286             let overlapped = Box::new(unsafe { mem::zeroed() });
 287             let overlapped = mem::replace(&mut self.overlapped, overlapped);
 288             mem::forget((buf, overlapped));
 289         }
 290     }
 291 }
 292
 293 unsafe fn slice_to_end(v: &mut Vec<u8>) -> &mut [u8] {
 294     if v.capacity() == 0 {
 295         v.reserve(16);
 296     }
 297     if v.capacity() == v.len() {
 298         v.reserve(1);
 299     }
 300     slice::from_raw_parts_mut(v.as_mut_ptr().offset(v.len() as isize),
 301                               v.capacity() - v.len())
 302 }