auto merge of #21132 : sfackler/rust/wait_timeout, r=alexcrichton

**The implementation is a direct adaptation of libcxx's condition_variable implementation.**

I also added a wait_timeout_with method, which matches the second overload in C++'s condition_variable. The implementation right now is kind of dumb but it works. There is an outstanding issue with it: as is it doesn't support the use case where a user doesn't care about poisoning and wants to continue through poison.

r? @alexcrichton @aturon 

2 files changed, 51 insertions, 0 deletions

diff --git a/src/libstd/sys/windows/mod.rs b/src/libstd/sys/windows/mod.rs
index 0e706c3cc6a..72fc2f8700d 100644
--- a/src/libstd/sys/windows/mod.rs
+++ b/src/libstd/sys/windows/mod.rs
@@ -50,6 +50,7 @@ pub mod rwlock;
 pub mod sync;
 pub mod stack_overflow;
 pub mod tcp;
+pub mod time;
 pub mod thread;
 pub mod thread_local;
 pub mod timer;
diff --git a/src/libstd/sys/windows/time.rs b/src/libstd/sys/windows/time.rs
new file mode 100644
index 00000000000..20ceff0aa69
--- /dev/null
+++ b/src/libstd/sys/windows/time.rs
@@ -0,0 +1,50 @@
+// 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 libc;
+use ops::Sub;
+use time::Duration;
+use sync::{Once, ONCE_INIT};
+
+pub struct SteadyTime {
+    t: libc::LARGE_INTEGER,
+}
+
+impl SteadyTime {
+    pub fn now() -> SteadyTime {
+        let mut t = SteadyTime { t: 0 };
+        unsafe { libc::QueryPerformanceCounter(&mut t.t); }
+        t
+    }
+
+    pub fn ns(&self) -> u64 {
+        self.t as u64 * 1_000_000_000 / frequency() as u64
+    }
+}
+
+fn frequency() -> libc::LARGE_INTEGER {
+    static mut FREQUENCY: libc::LARGE_INTEGER = 0;
+    static ONCE: Once = ONCE_INIT;
+
+    unsafe {
+        ONCE.call_once(|| {
+            libc::QueryPerformanceFrequency(&mut FREQUENCY);
+        });
+        FREQUENCY
+    }
+}
+
+impl<'a> Sub for &'a SteadyTime {
+    type Output = Duration;
+
+    fn sub(self, other: &SteadyTime) -> Duration {
+        let diff = self.t as i64 - other.t as i64;
+        Duration::microseconds(diff * 1_000_000 / frequency() as i64)
+    }
+}