Hide unnecessary error checking from the user

This affects the `set_non_blocking` function which cannot fail for Unix or
Windows, given correct parameters. Additionally, the short UDP write error case
has been removed as there is no such thing as "short UDP writes", instead, the
operating system will error out if the application tries to send a packet
larger than the MTU of the network path.

3 files changed, 16 insertions, 5 deletions

diff --git a/src/libstd/sys/windows/mod.rs b/src/libstd/sys/windows/mod.rs
index a756fb29f81..a13c03c7448 100644
--- a/src/libstd/sys/windows/mod.rs
+++ b/src/libstd/sys/windows/mod.rs
@@ -192,13 +192,13 @@ pub fn wouldblock() -> bool {
     err == libc::WSAEWOULDBLOCK as i32
 }
 
-pub fn set_nonblocking(fd: sock_t, nb: bool) -> IoResult<()> {
+pub fn set_nonblocking(fd: sock_t, nb: bool) {
     let mut set = nb as libc::c_ulong;
-    if unsafe { c::ioctlsocket(fd, c::FIONBIO, &mut set) != 0 } {
+    (if unsafe { c::ioctlsocket(fd, c::FIONBIO, &mut set) } != 0 {
         Err(last_error())
     } else {
         Ok(())
-    }
+    }).unwrap();
 }
 
 pub fn init_net() {
diff --git a/src/libstd/sys/windows/net.rs b/src/libstd/sys/windows/net.rs
index 3451232f40a..6caa4df5dfe 100644
--- a/src/libstd/sys/windows/net.rs
+++ b/src/libstd/sys/windows/net.rs
@@ -25,6 +25,8 @@ pub type wrlen_t = i32;
 
 pub struct Socket(libc::SOCKET);
 
+/// Checks whether the Windows socket interface has been started already, and
+/// if not, starts it.
 pub fn init() {
     static START: Once = ONCE_INIT;
 
@@ -38,10 +40,16 @@ pub fn init() {
     });
 }
 
+/// Returns the last error from the Windows socket interface.
 fn last_error() -> io::Error {
     io::Error::from_os_error(unsafe { c::WSAGetLastError() })
 }
 
+/// Checks if the signed integer is the Windows constant `SOCKET_ERROR` (-1)
+/// and if so, returns the last error from the Windows socket interface. . This
+/// function must be called before another call to the socket API is made.
+///
+/// FIXME: generics needed?
 pub fn cvt<T: SignedInt>(t: T) -> io::Result<T> {
     let one: T = Int::one();
     if t == -one {
@@ -51,11 +59,14 @@ pub fn cvt<T: SignedInt>(t: T) -> io::Result<T> {
     }
 }
 
+/// Provides the functionality of `cvt` for the return values of `getaddrinfo`
+/// and similar, meaning that they return an error if the return value is 0.
 pub fn cvt_gai(err: c_int) -> io::Result<()> {
     if err == 0 { return Ok(()) }
     cvt(err).map(|_| ())
 }
 
+/// Provides the functionality of `cvt` for a closure.
 pub fn cvt_r<T: SignedInt, F>(mut f: F) -> io::Result<T> where F: FnMut() -> T {
     cvt(f())
 }
@@ -112,7 +123,7 @@ impl Socket {
 
 impl Drop for Socket {
     fn drop(&mut self) {
-        unsafe { let _ = libc::closesocket(self.0); }
+        unsafe { cvt(libc::closesocket(self.0)).unwrap(); }
     }
 }
 
diff --git a/src/libstd/sys/windows/tcp.rs b/src/libstd/sys/windows/tcp.rs
index 4804ca510cb..25b70918591 100644
--- a/src/libstd/sys/windows/tcp.rs
+++ b/src/libstd/sys/windows/tcp.rs
@@ -192,7 +192,7 @@ impl TcpAcceptor {
                         c::WSAEventSelect(socket, events[1], 0)
                     };
                     if ret != 0 { return Err(last_net_error()) }
-                    try!(set_nonblocking(socket, false));
+                    set_nonblocking(socket, false);
                     return Ok(stream)
                 }
             }