auto merge of #19169 : aturon/rust/fds, r=alexcrichton

This PR adds some internal infrastructure to allow the private `std::sys` module to access internal representation details of `std::io`.

It then exposes those details in two new, platform-specific API surfaces: `std::os::unix` and `std::os::windows`.

To start with, these will provide the ability to extract file descriptors, HANDLEs, SOCKETs, and so on from `std::io` types.

More functionality, and more specific platforms (e.g. `std::os::linux`) will be added over time.

Closes #18897

4 files changed, 114 insertions, 6 deletions

diff --git a/src/libstd/sys/unix/ext.rs b/src/libstd/sys/unix/ext.rs
new file mode 100644
index 00000000000..ae3c939bf78
--- /dev/null
+++ b/src/libstd/sys/unix/ext.rs
@@ -0,0 +1,107 @@
+// Copyright 2014 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.
+
+//! Experimental extensions to `std` for Unix platforms.
+//!
+//! For now, this module is limited to extracting file descriptors,
+//! but its functionality will grow over time.
+//!
+//! # Example
+//!
+//! ```rust,ignore
+//! #![feature(globs)]
+//!
+//! use std::io::fs::File;
+//! use std::os::unix::prelude::*;
+//!
+//! fn main() {
+//!     let f = File::create(&Path::new("foo.txt")).unwrap();
+//!     let fd = f.as_raw_fd();
+//!
+//!     // use fd with native unix bindings
+//! }
+//! ```
+
+#![experimental]
+
+use sys_common::AsInner;
+use libc;
+
+use io;
+
+/// Raw file descriptors.
+pub type Fd = libc::c_int;
+
+/// Extract raw file descriptor
+pub trait AsRawFd {
+    /// Extract the raw file descriptor, without taking any ownership.
+    fn as_raw_fd(&self) -> Fd;
+}
+
+impl AsRawFd for io::fs::File {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::pipe::PipeStream {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::pipe::UnixStream {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::pipe::UnixListener {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::pipe::UnixAcceptor {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::tcp::TcpStream {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::tcp::TcpListener {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::tcp::TcpAcceptor {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+impl AsRawFd for io::net::udp::UdpSocket {
+    fn as_raw_fd(&self) -> Fd {
+        self.as_inner().fd()
+    }
+}
+
+/// A prelude for conveniently writing platform-specific code.
+///
+/// Includes all extension traits, and some important type definitions.
+pub mod prelude {
+    pub use super::{Fd, AsRawFd};
+}
diff --git a/src/libstd/sys/unix/mod.rs b/src/libstd/sys/unix/mod.rs
index 7a5317b578d..af238905119 100644
--- a/src/libstd/sys/unix/mod.rs
+++ b/src/libstd/sys/unix/mod.rs
@@ -33,6 +33,7 @@ macro_rules! helper_init( (static $name:ident: Helper<$m:ty>) => (
 ) )
 
 pub mod c;
+pub mod ext;
 pub mod fs;
 pub mod helper_signal;
 pub mod os;
diff --git a/src/libstd/sys/unix/pipe.rs b/src/libstd/sys/unix/pipe.rs
index 4d3469a9c24..3f70fb5c1a5 100644
--- a/src/libstd/sys/unix/pipe.rs
+++ b/src/libstd/sys/unix/pipe.rs
@@ -133,7 +133,7 @@ impl UnixStream {
         }
     }
 
-    fn fd(&self) -> fd_t { self.inner.fd }
+    pub fn fd(&self) -> fd_t { self.inner.fd }
 
     #[cfg(target_os = "linux")]
     fn lock_nonblocking(&self) {}
@@ -222,7 +222,7 @@ impl UnixListener {
         })
     }
 
-    fn fd(&self) -> fd_t { self.inner.fd }
+    pub fn fd(&self) -> fd_t { self.inner.fd }
 
     pub fn listen(self) -> IoResult<UnixAcceptor> {
         match unsafe { libc::listen(self.fd(), 128) } {
@@ -260,7 +260,7 @@ struct AcceptorInner {
 }
 
 impl UnixAcceptor {
-    fn fd(&self) -> fd_t { self.inner.listener.fd() }
+    pub fn fd(&self) -> fd_t { self.inner.listener.fd() }
 
     pub fn accept(&mut self) -> IoResult<UnixStream> {
         let deadline = if self.deadline == 0 {None} else {Some(self.deadline)};
diff --git a/src/libstd/sys/unix/process.rs b/src/libstd/sys/unix/process.rs
index 81bc138ca91..76c316076f9 100644
--- a/src/libstd/sys/unix/process.rs
+++ b/src/libstd/sys/unix/process.rs
@@ -24,7 +24,7 @@ use hash::Hash;
 use sys::{mod, retry, c, wouldblock, set_nonblocking, ms_to_timeval};
 use sys::fs::FileDesc;
 use sys_common::helper_thread::Helper;
-use sys_common::{AsFileDesc, mkerr_libc, timeout};
+use sys_common::{AsInner, mkerr_libc, timeout};
 
 pub use sys_common::ProcessConfig;
 
@@ -56,7 +56,7 @@ impl Process {
     pub fn spawn<K, V, C, P>(cfg: &C, in_fd: Option<P>,
                               out_fd: Option<P>, err_fd: Option<P>)
                               -> IoResult<Process>
-        where C: ProcessConfig<K, V>, P: AsFileDesc,
+        where C: ProcessConfig<K, V>, P: AsInner<FileDesc>,
               K: BytesContainer + Eq + Hash, V: BytesContainer
     {
         use libc::funcs::posix88::unistd::{fork, dup2, close, chdir, execvp};
@@ -183,7 +183,7 @@ impl Process {
                             libc::open(devnull.as_ptr(), flags, 0)
                         }
                         Some(obj) => {
-                            let fd = obj.as_fd().fd();
+                            let fd = obj.as_inner().fd();
                             // Leak the memory and the file descriptor. We're in the
                             // child now an all our resources are going to be
                             // cleaned up very soon