std: Redesign Duration, implementing RFC 1040

This commit is an implementation of [RFC 1040][rfc] which is a redesign of the
currently-unstable `Duration` type. The API of the type has been scaled back to
be more conservative and it also no longer supports negative durations.

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1040-duration-reform.md

The inner `duration` module of the `time` module has now been hidden (as
`Duration` is reexported) and the feature name for this type has changed from
`std_misc` to `duration`. All APIs accepting durations have also been audited to
take a more flavorful feature name instead of `std_misc`.

Closes #24874

Author: alexcrichton

src/librustc/lib.rs

@@ -30,6 +30,8 @@
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]
+#![feature(duration)]
+#![feature(duration_span)]
 #![feature(fs_canonicalize)]
 #![feature(hash)]
 #![feature(into_cow)]

src/librustc/metadata/loader.rs

@@ -720,8 +720,7 @@ fn get_metadata_section(is_osx: bool, filename: &Path) -> Result<MetadataBlob, S
     let dur = Duration::span(|| {
         ret = Some(get_metadata_section_imp(is_osx, filename));
     });
-    info!("reading {:?} => {}ms", filename.file_name().unwrap(),
-          dur.num_milliseconds());
+    info!("reading {:?} => {}", filename.file_name().unwrap(), dur);
     return ret.unwrap();;
 }
 

src/librustc/util/common.rs

@@ -55,8 +55,8 @@ pub fn time<T, U, F>(do_it: bool, what: &str, u: U, f: F) -> T where
     };
     let rv = rv.unwrap();
 
-    println!("{}time: {}.{:03} \t{}", repeat("  ").take(old).collect::<String>(),
-             dur.num_seconds(), dur.num_milliseconds() % 1000, what);
+    println!("{}time: {} \t{}", repeat("  ").take(old).collect::<String>(),
+             dur, what);
     DEPTH.with(|slot| slot.set(old));
 
     rv

src/libstd/sync/condvar.rs

@@ -69,20 +69,20 @@ pub struct Condvar { inner: Box<StaticCondvar> }
 /// # Examples
 ///
 /// ```
-/// # #![feature(std_misc)]
+/// # #![feature(static_condvar)]
 /// use std::sync::{StaticCondvar, CONDVAR_INIT};
 ///
 /// static CVAR: StaticCondvar = CONDVAR_INIT;
 /// ```
-#[unstable(feature = "std_misc",
+#[unstable(feature = "static_condvar",
            reason = "may be merged with Condvar in the future")]
 pub struct StaticCondvar {
     inner: sys::Condvar,
     mutex: AtomicUsize,
 }
 
 /// Constant initializer for a statically allocated condition variable.
-#[unstable(feature = "std_misc",
+#[unstable(feature = "static_condvar",
            reason = "may be merged with Condvar in the future")]
 pub const CONDVAR_INIT: StaticCondvar = StaticCondvar {
     inner: sys::CONDVAR_INIT,
@@ -161,6 +161,30 @@ impl Condvar {
         }
     }
 
+    /// Waits on this condition variable for a notification, timing out after a
+    /// specified duration.
+    ///
+    /// The semantics of this function are equivalent to `wait()` except that
+    /// the thread will be blocked for roughly no longer than `dur`. This
+    /// method should not be used for precise timing due to anomalies such as
+    /// preemption or platform differences that may not cause the maximum
+    /// amount of time waited to be precisely `dur`.
+    ///
+    /// The returned boolean is `false` only if the timeout is known
+    /// to have elapsed.
+    ///
+    /// Like `wait`, the lock specified will be re-acquired when this function
+    /// returns, regardless of whether the timeout elapsed or not.
+    #[unstable(feature = "wait_timeout", reason = "waiting for Duration")]
+    pub fn wait_timeout<'a, T>(&self, guard: MutexGuard<'a, T>,
+                               dur: Duration)
+                               -> LockResult<(MutexGuard<'a, T>, bool)> {
+        unsafe {
+            let me: &'static Condvar = &*(self as *const _);
+            me.inner.wait_timeout(guard, dur)
+        }
+    }
+
     /// Waits on this condition variable for a notification, timing out after a
     /// specified duration.
     ///
@@ -214,7 +238,7 @@ impl StaticCondvar {
     /// notification.
     ///
     /// See `Condvar::wait`.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub fn wait<'a, T>(&'static self, guard: MutexGuard<'a, T>)
                        -> LockResult<MutexGuard<'a, T>> {
@@ -235,14 +259,27 @@ impl StaticCondvar {
     /// specified duration.
     ///
     /// See `Condvar::wait_timeout`.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub fn wait_timeout_ms<'a, T>(&'static self, guard: MutexGuard<'a, T>, ms: u32)
                                   -> LockResult<(MutexGuard<'a, T>, bool)> {
+        self.wait_timeout(guard, Duration::from_millis(ms as u64))
+    }
+
+    /// Waits on this condition variable for a notification, timing out after a
+    /// specified duration.
+    ///
+    /// See `Condvar::wait_timeout`.
+    #[unstable(feature = "static_condvar",
+               reason = "may be merged with Condvar in the future")]
+    pub fn wait_timeout<'a, T>(&'static self,
+                               guard: MutexGuard<'a, T>,
+                               timeout: Duration)
+                               -> LockResult<(MutexGuard<'a, T>, bool)> {
         let (poisoned, success) = unsafe {
             let lock = mutex::guard_lock(&guard);
             self.verify(lock);
-            let success = self.inner.wait_timeout(lock, Duration::milliseconds(ms as i64));
+            let success = self.inner.wait_timeout(lock, timeout);
             (mutex::guard_poison(&guard).get(), success)
         };
         if poisoned {
@@ -259,15 +296,16 @@ impl StaticCondvar {
     /// passed and the function returns `false`.
     ///
     /// See `Condvar::wait_timeout_with`.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub fn wait_timeout_with<'a, T, F>(&'static self,
                                        guard: MutexGuard<'a, T>,
                                        dur: Duration,
                                        mut f: F)
                                        -> LockResult<(MutexGuard<'a, T>, bool)>
             where F: FnMut(LockResult<&mut T>) -> bool {
-        // This could be made more efficient by pushing the implementation into sys::condvar
+        // This could be made more efficient by pushing the implementation into
+        // sys::condvar
         let start = SteadyTime::now();
         let mut guard_result: LockResult<MutexGuard<'a, T>> = Ok(guard);
         while !f(guard_result
@@ -277,12 +315,15 @@ impl StaticCondvar {
             let now = SteadyTime::now();
             let consumed = &now - &start;
             let guard = guard_result.unwrap_or_else(|e| e.into_inner());
-            let res = self.wait_timeout_ms(guard, (dur - consumed).num_milliseconds() as u32);
-            let (new_guard_result, no_timeout) = match res {
-                Ok((new_guard, no_timeout)) => (Ok(new_guard), no_timeout),
-                Err(err) => {
-                    let (new_guard, no_timeout) = err.into_inner();
-                    (Err(PoisonError::new(new_guard)), no_timeout)
+            let (new_guard_result, no_timeout) = if consumed > dur {
+                (Ok(guard), false)
+            } else {
+                match self.wait_timeout(guard, dur - consumed) {
+                    Ok((new_guard, no_timeout)) => (Ok(new_guard), no_timeout),
+                    Err(err) => {
+                        let (new_guard, no_timeout) = err.into_inner();
+                        (Err(PoisonError::new(new_guard)), no_timeout)
+                    }
                 }
             };
             guard_result = new_guard_result;
@@ -301,14 +342,14 @@ impl StaticCondvar {
     /// Wakes up one blocked thread on this condvar.
     ///
     /// See `Condvar::notify_one`.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub fn notify_one(&'static self) { unsafe { self.inner.notify_one() } }
 
     /// Wakes up all blocked threads on this condvar.
     ///
     /// See `Condvar::notify_all`.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub fn notify_all(&'static self) { unsafe { self.inner.notify_all() } }
 
@@ -318,7 +359,7 @@ impl StaticCondvar {
     /// active users of the condvar, and this also doesn't prevent any future
     /// users of the condvar. This method is required to be called to not leak
     /// memory on all platforms.
-    #[unstable(feature = "std_misc",
+    #[unstable(feature = "static_condvar",
                reason = "may be merged with Condvar in the future")]
     pub unsafe fn destroy(&'static self) {
         self.inner.destroy()
@@ -447,7 +488,9 @@ mod tests {
         static S: AtomicUsize = ATOMIC_USIZE_INIT;
 
         let g = M.lock().unwrap();
-        let (g, success) = C.wait_timeout_with(g, Duration::nanoseconds(1000), |_| false).unwrap();
+        let (g, success) = C.wait_timeout_with(g, Duration::new(0, 1000), |_| {
+            false
+        }).unwrap();
         assert!(!success);
 
         let (tx, rx) = channel();
@@ -471,7 +514,8 @@ mod tests {
         });
 
         let mut state = 0;
-        let (_g, success) = C.wait_timeout_with(g, Duration::days(1), |_| {
+        let day = 24 * 60 * 60;
+        let (_g, success) = C.wait_timeout_with(g, Duration::new(day, 0), |_| {
             assert_eq!(state, S.load(Ordering::SeqCst));
             tx.send(()).unwrap();
             state += 1;

src/libstd/sys/unix/condvar.rs

@@ -57,25 +57,20 @@ impl Condvar {
     // https://github.com/llvm-mirror/libcxx/blob/release_35/src/condition_variable.cpp#L46
     // https://github.com/llvm-mirror/libcxx/blob/release_35/include/__mutex_base#L367
     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
-        if dur <= Duration::zero() {
-            return false;
-        }
-
-        // First, figure out what time it currently is, in both system and stable time.
-        // pthread_cond_timedwait uses system time, but we want to report timeout based on stable
-        // time.
+        // First, figure out what time it currently is, in both system and
+        // stable time.  pthread_cond_timedwait uses system time, but we want to
+        // report timeout based on stable time.
         let mut sys_now = libc::timeval { tv_sec: 0, tv_usec: 0 };
         let stable_now = time::SteadyTime::now();
         let r = ffi::gettimeofday(&mut sys_now, ptr::null_mut());
         debug_assert_eq!(r, 0);
 
-        let seconds = dur.num_seconds() as libc::time_t;
+        let seconds = dur.secs() as libc::time_t;
         let timeout = match sys_now.tv_sec.checked_add(seconds) {
             Some(sec) => {
                 libc::timespec {
                     tv_sec: sec,
-                    tv_nsec: (dur - Duration::seconds(dur.num_seconds()))
-                        .num_nanoseconds().unwrap() as libc::c_long,
+                    tv_nsec: dur.extra_nanos() as libc::c_long,
                 }
             }
             None => {
@@ -87,11 +82,12 @@ impl Condvar {
         };
 
         // And wait!
-        let r = ffi::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex), &timeout);
+        let r = ffi::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex),
+                                            &timeout);
         debug_assert!(r == libc::ETIMEDOUT || r == 0);
 
-        // ETIMEDOUT is not a totally reliable method of determining timeout due to clock shifts,
-        // so do the check ourselves
+        // ETIMEDOUT is not a totally reliable method of determining timeout due
+        // to clock shifts, so do the check ourselves
         &time::SteadyTime::now() - &stable_now < dur
     }
 

src/libstd/sys/unix/thread.rs

@@ -129,14 +129,9 @@ impl Thread {
     }
 
     pub fn sleep(dur: Duration) {
-        if dur < Duration::zero() {
-            return Thread::yield_now()
-        }
-        let seconds = dur.num_seconds();
-        let ns = dur - Duration::seconds(seconds);
         let mut ts = libc::timespec {
-            tv_sec: seconds as libc::time_t,
-            tv_nsec: ns.num_nanoseconds().unwrap() as libc::c_long,
+            tv_sec: dur.secs() as libc::time_t,
+            tv_nsec: dur.extra_nanos() as libc::c_long,
         };
 
         // If we're awoken with a signal then the return value will be -1 and

src/libstd/sys/unix/time.rs

@@ -10,12 +10,15 @@
 
 pub use self::inner::SteadyTime;
 
+const NSEC_PER_SEC: u64 = 1_000_000_000;
+
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 mod inner {
     use libc;
     use time::Duration;
     use ops::Sub;
     use sync::{Once, ONCE_INIT};
+    use super::NSEC_PER_SEC;
 
     pub struct SteadyTime {
         t: u64
@@ -32,11 +35,6 @@ mod inner {
                 t: unsafe { mach_absolute_time() },
             }
         }
-
-        pub fn ns(&self) -> u64 {
-            let info = info();
-            self.t * info.numer as u64 / info.denom as u64
-        }
     }
 
     fn info() -> &'static libc::mach_timebase_info {
@@ -59,8 +57,9 @@ mod inner {
 
         fn sub(self, other: &SteadyTime) -> Duration {
             let info = info();
-            let diff = self.t as i64 - other.t as i64;
-            Duration::nanoseconds(diff * info.numer as i64 / info.denom as i64)
+            let diff = self.t as u64 - other.t as u64;
+            let nanos = diff * info.numer as u64 / info.denom as u64;
+            Duration::new(nanos / NSEC_PER_SEC, (nanos % NSEC_PER_SEC) as u32)
         }
     }
 }
@@ -70,8 +69,7 @@ mod inner {
     use libc;
     use time::Duration;
     use ops::Sub;
-
-    const NSEC_PER_SEC: i64 = 1_000_000_000;
+    use super::NSEC_PER_SEC;
 
     pub struct SteadyTime {
         t: libc::timespec,
@@ -104,23 +102,19 @@ mod inner {
             }
             t
         }
-
-        pub fn ns(&self) -> u64 {
-            self.t.tv_sec as u64 * NSEC_PER_SEC as u64 + self.t.tv_nsec as u64
-        }
     }
 
     impl<'a> Sub for &'a SteadyTime {
         type Output = Duration;
 
         fn sub(self, other: &SteadyTime) -> Duration {
             if self.t.tv_nsec >= other.t.tv_nsec {
-                Duration::seconds(self.t.tv_sec as i64 - other.t.tv_sec as i64) +
-                    Duration::nanoseconds(self.t.tv_nsec as i64 - other.t.tv_nsec as i64)
+                Duration::new(self.t.tv_sec as u64 - other.t.tv_sec as u64,
+                              self.t.tv_nsec as u32 - other.t.tv_nsec as u32)
             } else {
-                Duration::seconds(self.t.tv_sec as i64 - 1 - other.t.tv_sec as i64) +
-                    Duration::nanoseconds(self.t.tv_nsec as i64 + NSEC_PER_SEC -
-                                          other.t.tv_nsec as i64)
+                Duration::new(self.t.tv_sec as u64 - 1 - other.t.tv_sec as u64,
+                              self.t.tv_nsec as u32 + (NSEC_PER_SEC as u32) -
+                                          other.t.tv_nsec as u32)
             }
         }
     }

src/libstd/sys/windows/condvar.rs

@@ -42,7 +42,7 @@ impl Condvar {
     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
         let r = ffi::SleepConditionVariableSRW(self.inner.get(),
                                                mutex::raw(mutex),
-                                               dur.num_milliseconds() as DWORD,
+                                               super::dur2timeout(dur),
                                                0);
         if r == 0 {
             const ERROR_TIMEOUT: DWORD = 0x5B4;

src/libstd/sys/windows/mod.rs

@@ -20,6 +20,7 @@ use libc;
 use num::Zero;
 use os::windows::ffi::{OsStrExt, OsStringExt};
 use path::PathBuf;
+use time::Duration;
 
 pub mod backtrace;
 pub mod c;
@@ -151,6 +152,27 @@ fn cvt<I: PartialEq + Zero>(i: I) -> io::Result<I> {
     }
 }
 
+fn dur2timeout(dur: Duration) -> libc::DWORD {
+    // Note that a duration is a (u64, u32) (seconds, nanoseconds) pair, and the
+    // timeouts in windows APIs are typically u32 milliseconds. To translate, we
+    // have two pieces to take care of:
+    //
+    // * Nanosecond precision is rounded up
+    // * Greater than u32::MAX milliseconds (50 days) is rounded up to INFINITE
+    //   (never time out).
+    dur.secs().checked_mul(1000).and_then(|ms| {
+        ms.checked_add((dur.extra_nanos() as u64) / 1_000_000)
+    }).and_then(|ms| {
+        ms.checked_add(if dur.extra_nanos() % 1_000_000 > 0 {1} else {0})
+    }).map(|ms| {
+        if ms > <libc::DWORD>::max_value() as u64 {
+            libc::INFINITE
+        } else {
+            ms as libc::DWORD
+        }
+    }).unwrap_or(libc::INFINITE)
+}
+
 fn ms_to_filetime(ms: u64) -> libc::FILETIME {
     // A FILETIME is a count of 100 nanosecond intervals, so we multiply by
     // 10000 b/c there are 10000 intervals in 1 ms