      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370
    371
    372
    373
    374
    375
    376
    377
    378
    379
    380
    381
    382
    383
    384
    385
    386
    387
    388
    389
    390
    391
    392
    393
    394
    395
    396
    397
    398
    399
    400
    401
    402
    403
    404
    405
    406
    407
    408
    409
    410
    411
    412
    413
    414
    415
    416
    417
    418
    419
    420
    421
    422
    423
    424
    425
    426
    427
    428
    429
    430
    431
    432
    433
    434
    435
    436
    437
    438
    439
    440
    441
    442
    443
    444
    445
    446
    447
    448
    449
    450
    451
    452
    453
    454
    455
    456
    457
    458
    459
    460
    461
    462
    463
    464
    465
    466
    467
    468
    469
    470
    471
    472
    473
    474
    475
    476
    477
    478
    479
    480
    481
    482
    483
    484
    485
    486
    487
    488
    489
    490
    491
    492
    493
    494
    495
    496
    497
    498
    499
    500
    501
    502
    503
    504
    505
    506
    507
    508
    509
    510
    511
    512
    513
    514
    515
    516
    517
    518
    519
    520
    521
    522
    523
    524
    525
    526
    527
    528
    529
    530
    531
    532
    533
    534
    535
    536
    537
    538
    539
    540
    541
    542
    543
    544
    545
    546
    547
    548
    549
    550
    551
    552
    553
    554
    555
    556
    557
    558
    559
    560
    561
    562
    563
    564
    565
    566
    567
    568
    569
    570
    571
    572
    573
    574
    575
    576
    577
    578
    579
    580
    581
    582
    583
    584
    585
    586
    587
    588
    589
    590
    591
    592
    593
    594
    595
    596
    597
    598
    599
    600
    601
    602
    603
    604
    605
    606
    607
    608
    609
    610
    611
    612
    613
    614
    615
    616
    617
    618
    619
    620
    621
    622
    623
    624
    625
    626
    627
    628
    629
    630
    631
    632
    633
    634
    635
    636
    637
    638
    639
    640
    641
    642
    643
    644
    645
    646
    647
    648
    649
    650
    651
    652
    653
    654
    655
    656
    657
    658
    659
    660
    661
    662
    663
    664
    665
    666
    667
    668
    669
    670
    671
    672
    673
    674
    675
    676
    677
    678
    679
    680
    681
    682
    683
    684
    685
    686
    687
    688
    689
    690
    691
    692
    693
    694
    695
    696
    697
    698
    699
    700
    701
    702
    703
    704
    705
    706
    707
    708
    709
    710
    711
    712
    713
    714
    715
    716
    717
    718
    719
    720
    721
    722
    723
    724
    725
    726
    727
    728
    729
    730
    731
    732
    733
    734
    735
    736
    737
    738
    739
    740
    741
    742
    743
    744
    745
    746
    747
    748
    749
    750
    751
    752
    753
    754
    755
    756
    757
    758
    759
    760
    761
    762
    763
    764
    765
    766
    767
    768
    769
    770
    771
    772
    773
    774
    775
    776
    777
    778
    779
    780
    781
    782
    783
    784
    785
    786
    787
    788
    789
    790
    791
    792
    793
    794
    795
    796
    797
    798
    799
    800
    801
    802
    803
    804
    805
    806
    807
    808
    809
    810
    811
    812
    813
    814
    815
    816
    817
    818
    819
    820
    821
    822
    823
    824
    825
    826
    827
    828
    829

    use fmt;
    use sync::atomic::{AtomicUsize, Ordering};
    use sync::{mutex, MutexGuard, PoisonError};
    use sys_common::condvar as sys;
    use sys_common::mutex as sys_mutex;
    use sys_common::poison::{self, LockResult};
    use time::{Duration, Instant};

    /// A type indicating whether a timed wait on a condition variable returned
    /// due to a time out or not.
    ///
    /// It is returned by the [`wait_timeout`] method.
    ///
    /// [`wait_timeout`]: struct.Condvar.html#method.wait_timeout
    #[derive(Debug, PartialEq, Eq, Copy, Clone)]
    #[stable(feature = "wait_timeout", since = "1.5.0")]
    pub struct WaitTimeoutResult(bool);

    impl WaitTimeoutResult {
        /// Returns whether the wait was known to have timed out.
        ///
        /// # Examples
        ///
        /// This example spawns a thread which will update the boolean value and
        /// then wait 100 milliseconds before notifying the condvar.
        ///
        /// The main thread will wait with a timeout on the condvar and then leave
        /// once the boolean has been updated and notified.
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        /// use std::time::Duration;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///
        ///     // Let's wait 20 milliseconds before notifying the condvar.
        ///     thread::sleep(Duration::from_millis(20));
        ///
        ///     let mut started = lock.lock().unwrap();
        ///     // We update the boolean value.
        ///     *started = true;
        ///     cvar.notify_one();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// loop {
        ///     // Let's put a timeout on the condvar's wait.
        ///     let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
        ///     // 10 milliseconds have passed, or maybe the value changed!
        ///     started = result.0;
        ///     if *started == true {
        ///         // We received the notification and the value has been updated, we can leave.
        ///         break
        ///     }
        /// }
        /// ```
        #[stable(feature = "wait_timeout", since = "1.5.0")]
        pub fn timed_out(&self) -> bool {
            self.0
        }
    }

    /// A Condition Variable
    ///
    /// Condition variables represent the ability to block a thread such that it
    /// consumes no CPU time while waiting for an event to occur. Condition
    /// variables are typically associated with a boolean predicate (a condition)
    /// and a mutex. The predicate is always verified inside of the mutex before
    /// determining that a thread must block.
    ///
    /// Functions in this module will block the current **thread** of execution and
    /// are bindings to system-provided condition variables where possible. Note
    /// that this module places one additional restriction over the system condition
    /// variables: each condvar can be used with precisely one mutex at runtime. Any
    /// attempt to use multiple mutexes on the same condition variable will result
    /// in a runtime panic. If this is not desired, then the unsafe primitives in
    /// `sys` do not have this restriction but may result in undefined behavior.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::sync::{Arc, Mutex, Condvar};
    /// use std::thread;
    ///
    /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
    /// let pair2 = pair.clone();
    ///
    /// // Inside of our lock, spawn a new thread, and then wait for it to start.
    /// thread::spawn(move|| {
    ///     let &(ref lock, ref cvar) = &*pair2;
    ///     let mut started = lock.lock().unwrap();
    ///     *started = true;
    ///     // We notify the condvar that the value has changed.
    ///     cvar.notify_one();
    /// });
    ///
    /// // Wait for the thread to start up.
    /// let &(ref lock, ref cvar) = &*pair;
    /// let mut started = lock.lock().unwrap();
    /// while !*started {
    ///     started = cvar.wait(started).unwrap();
    /// }
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct Condvar {
        inner: Box<sys::Condvar>,
        mutex: AtomicUsize,
    }

    impl Condvar {
        /// Creates a new condition variable which is ready to be waited on and
        /// notified.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::Condvar;
        ///
        /// let condvar = Condvar::new();
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn new() -> Condvar {
            let mut c = Condvar {
                inner: box sys::Condvar::new(),
                mutex: AtomicUsize::new(0),
            };
            unsafe {
                c.inner.init();
            }
            c
        }

        /// Blocks the current thread until this condition variable receives a
        /// notification.
        ///
        /// This function will atomically unlock the mutex specified (represented by
        /// `guard`) and block the current thread. This means that any calls
        /// to [`notify_one`] or [`notify_all`] which happen logically after the
        /// mutex is unlocked are candidates to wake this thread up. When this
        /// function call returns, the lock specified will have been re-acquired.
        ///
        /// Note that this function is susceptible to spurious wakeups. Condition
        /// variables normally have a boolean predicate associated with them, and
        /// the predicate must always be checked each time this function returns to
        /// protect against spurious wakeups.
        ///
        /// # Errors
        ///
        /// This function will return an error if the mutex being waited on is
        /// poisoned when this thread re-acquires the lock. For more information,
        /// see information about [poisoning] on the [`Mutex`] type.
        ///
        /// # Panics
        ///
        /// This function will [`panic!`] if it is used with more than one mutex
        /// over time. Each condition variable is dynamically bound to exactly one
        /// mutex to ensure defined behavior across platforms. If this functionality
        /// is not desired, then unsafe primitives in `sys` are provided.
        ///
        /// [`notify_one`]: #method.notify_one
        /// [`notify_all`]: #method.notify_all
        /// [poisoning]: ../sync/struct.Mutex.html#poisoning
        /// [`Mutex`]: ../sync/struct.Mutex.html
        /// [`panic!`]: ../../std/macro.panic.html
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// // As long as the value inside the `Mutex` is false, we wait.
        /// while !*started {
        ///     started = cvar.wait(started).unwrap();
        /// }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>)
                           -> LockResult<MutexGuard<'a, T>> {
            let poisoned = unsafe {
                let lock = mutex::guard_lock(&guard);
                self.verify(lock);
                self.inner.wait(lock);
                mutex::guard_poison(&guard).get()
            };
            if poisoned {
                Err(PoisonError::new(guard))
            } else {
                Ok(guard)
            }
        }

        /// Blocks the current thread until this condition variable receives a
        /// notification and the required condition is met. Spurious wakeups are
        /// ignored and this function will only return once the condition has been
        /// met.
        ///
        /// This function will atomically unlock the mutex specified (represented by
        /// `guard`) and block the current thread. This means that any calls
        /// to [`notify_one`] or [`notify_all`] which happen logically after the
        /// mutex is unlocked are candidates to wake this thread up. When this
        /// function call returns, the lock specified will have been re-acquired.
        ///
        /// # Errors
        ///
        /// This function will return an error if the mutex being waited on is
        /// poisoned when this thread re-acquires the lock. For more information,
        /// see information about [poisoning] on the [`Mutex`] type.
        ///
        /// [`notify_one`]: #method.notify_one
        /// [`notify_all`]: #method.notify_all
        /// [poisoning]: ../sync/struct.Mutex.html#poisoning
        /// [`Mutex`]: ../sync/struct.Mutex.html
        ///
        /// # Examples
        ///
        /// ```
        /// #![feature(wait_until)]
        ///
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// // As long as the value inside the `Mutex` is false, we wait.
        /// let _guard = cvar.wait_until(lock.lock().unwrap(), |started| { *started }).unwrap();
        /// ```
        #[unstable(feature = "wait_until", issue = "47960")]
        pub fn wait_until<'a, T, F>(&self, mut guard: MutexGuard<'a, T>,
                                    mut condition: F)
                                    -> LockResult<MutexGuard<'a, T>>
                                    where F: FnMut(&mut T) -> bool {
            while !condition(&mut *guard) {
                guard = self.wait(guard)?;
            }
            Ok(guard)
        }

        /// 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 `ms` milliseconds. 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 `ms`.
        ///
        /// Note that the best effort is made to ensure that the time waited is
        /// measured with a monotonic clock, and not affected by the changes made to
        /// the system time.
        ///
        /// 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.
        ///
        /// [`wait`]: #method.wait
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// // As long as the value inside the `Mutex` is false, we wait.
        /// loop {
        ///     let result = cvar.wait_timeout_ms(started, 10).unwrap();
        ///     // 10 milliseconds have passed, or maybe the value changed!
        ///     started = result.0;
        ///     if *started == true {
        ///         // We received the notification and the value has been updated, we can leave.
        ///         break
        ///     }
        /// }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::sync::Condvar::wait_timeout`")]
        pub fn wait_timeout_ms<'a, T>(&self, guard: MutexGuard<'a, T>, ms: u32)
                                      -> LockResult<(MutexGuard<'a, T>, bool)> {
            let res = self.wait_timeout(guard, Duration::from_millis(ms as u64));
            poison::map_result(res, |(a, b)| {
                (a, !b.timed_out())
            })
        }

        /// 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`.
        ///
        /// Note that the best effort is made to ensure that the time waited is
        /// measured with a monotonic clock, and not affected by the changes made to
        /// the system time.  This function is susceptible to spurious wakeups.
        /// Condition variables normally have a boolean predicate associated with
        /// them, and the predicate must always be checked each time this function
        /// returns to protect against spurious wakeups.  Additionally, it is
        /// typically desirable for the time-out to not exceed some duration in
        /// spite of spurious wakes, thus the sleep-duration is decremented by the
        /// amount slept.  Alternatively, use the `wait_timeout_until` method
        /// to wait until a condition is met with a total time-out regardless
        /// of spurious wakes.
        ///
        /// The returned [`WaitTimeoutResult`] value indicates 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.
        ///
        /// [`wait`]: #method.wait
        /// [`wait_timeout_until`]: #method.wait_timeout_until
        /// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        /// use std::time::Duration;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // wait for the thread to start up
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// // as long as the value inside the `Mutex` is false, we wait
        /// loop {
        ///     let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap();
        ///     // 10 milliseconds have passed, or maybe the value changed!
        ///     started = result.0;
        ///     if *started == true {
        ///         // We received the notification and the value has been updated, we can leave.
        ///         break
        ///     }
        /// }
        /// ```
        #[stable(feature = "wait_timeout", since = "1.5.0")]
        pub fn wait_timeout<'a, T>(&self, guard: MutexGuard<'a, T>,
                                   dur: Duration)
                                   -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
            let (poisoned, result) = unsafe {
                let lock = mutex::guard_lock(&guard);
                self.verify(lock);
                let success = self.inner.wait_timeout(lock, dur);
                (mutex::guard_poison(&guard).get(), WaitTimeoutResult(!success))
            };
            if poisoned {
                Err(PoisonError::new((guard, result)))
            } else {
                Ok((guard, result))
            }
        }

        /// Waits on this condition variable for a notification, timing out after a
        /// specified duration.  Spurious wakes will not cause this function to
        /// return.
        ///
        /// The semantics of this function are equivalent to [`wait_until`] 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`.
        ///
        /// Note that the best effort is made to ensure that the time waited is
        /// measured with a monotonic clock, and not affected by the changes made to
        /// the system time.
        ///
        /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
        /// known to have elapsed without the condition being met.
        ///
        /// Like [`wait_until`], the lock specified will be re-acquired when this
        /// function returns, regardless of whether the timeout elapsed or not.
        ///
        /// [`wait_until`]: #method.wait_until
        /// [`wait_timeout`]: #method.wait_timeout
        /// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html
        ///
        /// # Examples
        ///
        /// ```
        /// #![feature(wait_timeout_until)]
        ///
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        /// use std::time::Duration;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // wait for the thread to start up
        /// let &(ref lock, ref cvar) = &*pair;
        /// let result = cvar.wait_timeout_until(
        ///     lock.lock().unwrap(),
        ///     Duration::from_millis(100),
        ///     |&mut started| started,
        /// ).unwrap();
        /// if result.1.timed_out() {
        ///     // timed-out without the condition ever evaluating to true.
        /// }
        /// // access the locked mutex via result.0
        /// ```
        #[unstable(feature = "wait_timeout_until", issue = "47960")]
        pub fn wait_timeout_until<'a, T, F>(&self, mut guard: MutexGuard<'a, T>,
                                            dur: Duration, mut condition: F)
                                            -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)>
                                            where F: FnMut(&mut T) -> bool {
            let start = Instant::now();
            loop {
                if condition(&mut *guard) {
                    return Ok((guard, WaitTimeoutResult(false)));
                }
                let timeout = match dur.checked_sub(start.elapsed()) {
                    Some(timeout) => timeout,
                    None => return Ok((guard, WaitTimeoutResult(true))),
                };
                guard = self.wait_timeout(guard, timeout)?.0;
            }
        }

        /// Wakes up one blocked thread on this condvar.
        ///
        /// If there is a blocked thread on this condition variable, then it will
        /// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to
        /// `notify_one` are not buffered in any way.
        ///
        /// To wake up all threads, see [`notify_all`].
        ///
        /// [`wait`]: #method.wait
        /// [`wait_timeout`]: #method.wait_timeout
        /// [`notify_all`]: #method.notify_all
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_one();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// // As long as the value inside the `Mutex` is false, we wait.
        /// while !*started {
        ///     started = cvar.wait(started).unwrap();
        /// }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn notify_one(&self) {
            unsafe { self.inner.notify_one() }
        }

        /// Wakes up all blocked threads on this condvar.
        ///
        /// This method will ensure that any current waiters on the condition
        /// variable are awoken. Calls to `notify_all()` are not buffered in any
        /// way.
        ///
        /// To wake up only one thread, see [`notify_one`].
        ///
        /// [`notify_one`]: #method.notify_one
        ///
        /// # Examples
        ///
        /// ```
        /// use std::sync::{Arc, Mutex, Condvar};
        /// use std::thread;
        ///
        /// let pair = Arc::new((Mutex::new(false), Condvar::new()));
        /// let pair2 = pair.clone();
        ///
        /// thread::spawn(move|| {
        ///     let &(ref lock, ref cvar) = &*pair2;
        ///     let mut started = lock.lock().unwrap();
        ///     *started = true;
        ///     // We notify the condvar that the value has changed.
        ///     cvar.notify_all();
        /// });
        ///
        /// // Wait for the thread to start up.
        /// let &(ref lock, ref cvar) = &*pair;
        /// let mut started = lock.lock().unwrap();
        /// // As long as the value inside the `Mutex` is false, we wait.
        /// while !*started {
        ///     started = cvar.wait(started).unwrap();
        /// }
        /// ```
        #[stable(feature = "rust1", since = "1.0.0")]
        pub fn notify_all(&self) {
            unsafe { self.inner.notify_all() }
        }

        fn verify(&self, mutex: &sys_mutex::Mutex) {
            let addr = mutex as *const _ as usize;
            match self.mutex.compare_and_swap(0, addr, Ordering::SeqCst) {
                // If we got out 0, then we have successfully bound the mutex to
                // this cvar.
                0 => {}

                // If we get out a value that's the same as `addr`, then someone
                // already beat us to the punch.
                n if n == addr => {}

                // Anything else and we're using more than one mutex on this cvar,
                // which is currently disallowed.
                _ => panic!("attempted to use a condition variable with two \
                             mutexes"),
            }
        }
    }

    #[stable(feature = "std_debug", since = "1.16.0")]
    impl fmt::Debug for Condvar {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.pad("Condvar { .. }")
        }
    }

    #[stable(feature = "condvar_default", since = "1.10.0")]
    impl Default for Condvar {
        /// Creates a `Condvar` which is ready to be waited on and notified.
        fn default() -> Condvar {
            Condvar::new()
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl Drop for Condvar {
        fn drop(&mut self) {
            unsafe { self.inner.destroy() }
        }
    }

    #[cfg(test)]
    mod tests {
        /// #![feature(wait_until)]
        use sync::mpsc::channel;
        use sync::{Condvar, Mutex, Arc};
        use sync::atomic::{AtomicBool, Ordering};
        use thread;
        use time::Duration;
        use u64;

        #[test]
        fn smoke() {
            let c = Condvar::new();
            c.notify_one();
            c.notify_all();
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn notify_one() {
            let m = Arc::new(Mutex::new(()));
            let m2 = m.clone();
            let c = Arc::new(Condvar::new());
            let c2 = c.clone();

            let g = m.lock().unwrap();
            let _t = thread::spawn(move|| {
                let _g = m2.lock().unwrap();
                c2.notify_one();
            });
            let g = c.wait(g).unwrap();
            drop(g);
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn notify_all() {
            const N: usize = 10;

            let data = Arc::new((Mutex::new(0), Condvar::new()));
            let (tx, rx) = channel();
            for _ in 0..N {
                let data = data.clone();
                let tx = tx.clone();
                thread::spawn(move|| {
                    let &(ref lock, ref cond) = &*data;
                    let mut cnt = lock.lock().unwrap();
                    *cnt += 1;
                    if *cnt == N {
                        tx.send(()).unwrap();
                    }
                    while *cnt != 0 {
                        cnt = cond.wait(cnt).unwrap();
                    }
                    tx.send(()).unwrap();
                });
            }
            drop(tx);

            let &(ref lock, ref cond) = &*data;
            rx.recv().unwrap();
            let mut cnt = lock.lock().unwrap();
            *cnt = 0;
            cond.notify_all();
            drop(cnt);

            for _ in 0..N {
                rx.recv().unwrap();
            }
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_until() {
            let pair = Arc::new((Mutex::new(false), Condvar::new()));
            let pair2 = pair.clone();

            // Inside of our lock, spawn a new thread, and then wait for it to start.
            thread::spawn(move|| {
                let &(ref lock, ref cvar) = &*pair2;
                let mut started = lock.lock().unwrap();
                *started = true;
                // We notify the condvar that the value has changed.
                cvar.notify_one();
            });

            // Wait for the thread to start up.
            let &(ref lock, ref cvar) = &*pair;
            let guard = cvar.wait_until(lock.lock().unwrap(), |started| {
                *started
            });
            assert!(*guard.unwrap());
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_timeout_wait() {
            let m = Arc::new(Mutex::new(()));
            let c = Arc::new(Condvar::new());

            loop {
                let g = m.lock().unwrap();
                let (_g, no_timeout) = c.wait_timeout(g, Duration::from_millis(1)).unwrap();
                // spurious wakeups mean this isn't necessarily true
                // so execute test again, if not timeout
                if !no_timeout.timed_out() {
                    continue;
                }

                break;
            }
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_timeout_until_wait() {
            let m = Arc::new(Mutex::new(()));
            let c = Arc::new(Condvar::new());

            let g = m.lock().unwrap();
            let (_g, wait) = c.wait_timeout_until(g, Duration::from_millis(1), |_| { false }).unwrap();
            // no spurious wakeups. ensure it timed-out
            assert!(wait.timed_out());
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_timeout_until_instant_satisfy() {
            let m = Arc::new(Mutex::new(()));
            let c = Arc::new(Condvar::new());

            let g = m.lock().unwrap();
            let (_g, wait) = c.wait_timeout_until(g, Duration::from_millis(0), |_| { true }).unwrap();
            // ensure it didn't time-out even if we were not given any time.
            assert!(!wait.timed_out());
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_timeout_until_wake() {
            let pair = Arc::new((Mutex::new(false), Condvar::new()));
            let pair_copy = pair.clone();

            let &(ref m, ref c) = &*pair;
            let g = m.lock().unwrap();
            let _t = thread::spawn(move || {
                let &(ref lock, ref cvar) = &*pair_copy;
                let mut started = lock.lock().unwrap();
                thread::sleep(Duration::from_millis(1));
                *started = true;
                cvar.notify_one();
            });
            let (g2, wait) = c.wait_timeout_until(g, Duration::from_millis(u64::MAX), |&mut notified| {
                notified
            }).unwrap();
            // ensure it didn't time-out even if we were not given any time.
            assert!(!wait.timed_out());
            assert!(*g2);
        }

        #[test]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn wait_timeout_wake() {
            let m = Arc::new(Mutex::new(()));
            let c = Arc::new(Condvar::new());

            loop {
                let g = m.lock().unwrap();

                let c2 = c.clone();
                let m2 = m.clone();

                let notified = Arc::new(AtomicBool::new(false));
                let notified_copy = notified.clone();

                let t = thread::spawn(move || {
                    let _g = m2.lock().unwrap();
                    thread::sleep(Duration::from_millis(1));
                    notified_copy.store(true, Ordering::SeqCst);
                    c2.notify_one();
                });
                let (g, timeout_res) = c.wait_timeout(g, Duration::from_millis(u64::MAX)).unwrap();
                assert!(!timeout_res.timed_out());
                // spurious wakeups mean this isn't necessarily true
                // so execute test again, if not notified
                if !notified.load(Ordering::SeqCst) {
                    t.join().unwrap();
                    continue;
                }
                drop(g);

                t.join().unwrap();

                break;
            }
        }

        #[test]
        #[should_panic]
        #[cfg_attr(target_os = "emscripten", ignore)]
        fn two_mutexes() {
            let m = Arc::new(Mutex::new(()));
            let m2 = m.clone();
            let c = Arc::new(Condvar::new());
            let c2 = c.clone();

            let mut g = m.lock().unwrap();
            let _t = thread::spawn(move|| {
                let _g = m2.lock().unwrap();
                c2.notify_one();
            });
            g = c.wait(g).unwrap();
            drop(g);

            let m = Mutex::new(());
            let _ = c.wait(m.lock().unwrap()).unwrap();
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)