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Source file src/time/sleep.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package time
     6	
     7	// Sleep pauses the current goroutine for at least the duration d.
     8	// A negative or zero duration causes Sleep to return immediately.
     9	func Sleep(d Duration)
    10	
    11	// runtimeNano returns the current value of the runtime clock in nanoseconds.
    12	func runtimeNano() int64
    13	
    14	// Interface to timers implemented in package runtime.
    15	// Must be in sync with ../runtime/runtime.h:/^struct.Timer$
    16	type runtimeTimer struct {
    17		i      int
    18		when   int64
    19		period int64
    20		f      func(interface{}, uintptr) // NOTE: must not be closure
    21		arg    interface{}
    22		seq    uintptr
    23	}
    24	
    25	// when is a helper function for setting the 'when' field of a runtimeTimer.
    26	// It returns what the time will be, in nanoseconds, Duration d in the future.
    27	// If d is negative, it is ignored.  If the returned value would be less than
    28	// zero because of an overflow, MaxInt64 is returned.
    29	func when(d Duration) int64 {
    30		if d <= 0 {
    31			return runtimeNano()
    32		}
    33		t := runtimeNano() + int64(d)
    34		if t < 0 {
    35			t = 1<<63 - 1 // math.MaxInt64
    36		}
    37		return t
    38	}
    39	
    40	func startTimer(*runtimeTimer)
    41	func stopTimer(*runtimeTimer) bool
    42	
    43	// The Timer type represents a single event.
    44	// When the Timer expires, the current time will be sent on C,
    45	// unless the Timer was created by AfterFunc.
    46	// A Timer must be created with NewTimer or AfterFunc.
    47	type Timer struct {
    48		C <-chan Time
    49		r runtimeTimer
    50	}
    51	
    52	// Stop prevents the Timer from firing.
    53	// It returns true if the call stops the timer, false if the timer has already
    54	// expired or been stopped.
    55	// Stop does not close the channel, to prevent a read from the channel succeeding
    56	// incorrectly.
    57	func (t *Timer) Stop() bool {
    58		if t.r.f == nil {
    59			panic("time: Stop called on uninitialized Timer")
    60		}
    61		return stopTimer(&t.r)
    62	}
    63	
    64	// NewTimer creates a new Timer that will send
    65	// the current time on its channel after at least duration d.
    66	func NewTimer(d Duration) *Timer {
    67		c := make(chan Time, 1)
    68		t := &Timer{
    69			C: c,
    70			r: runtimeTimer{
    71				when: when(d),
    72				f:    sendTime,
    73				arg:  c,
    74			},
    75		}
    76		startTimer(&t.r)
    77		return t
    78	}
    79	
    80	// Reset changes the timer to expire after duration d.
    81	// It returns true if the timer had been active, false if the timer had
    82	// expired or been stopped.
    83	func (t *Timer) Reset(d Duration) bool {
    84		if t.r.f == nil {
    85			panic("time: Reset called on uninitialized Timer")
    86		}
    87		w := when(d)
    88		active := stopTimer(&t.r)
    89		t.r.when = w
    90		startTimer(&t.r)
    91		return active
    92	}
    93	
    94	func sendTime(c interface{}, seq uintptr) {
    95		// Non-blocking send of time on c.
    96		// Used in NewTimer, it cannot block anyway (buffer).
    97		// Used in NewTicker, dropping sends on the floor is
    98		// the desired behavior when the reader gets behind,
    99		// because the sends are periodic.
   100		select {
   101		case c.(chan Time) <- Now():
   102		default:
   103		}
   104	}
   105	
   106	// After waits for the duration to elapse and then sends the current time
   107	// on the returned channel.
   108	// It is equivalent to NewTimer(d).C.
   109	func After(d Duration) <-chan Time {
   110		return NewTimer(d).C
   111	}
   112	
   113	// AfterFunc waits for the duration to elapse and then calls f
   114	// in its own goroutine. It returns a Timer that can
   115	// be used to cancel the call using its Stop method.
   116	func AfterFunc(d Duration, f func()) *Timer {
   117		t := &Timer{
   118			r: runtimeTimer{
   119				when: when(d),
   120				f:    goFunc,
   121				arg:  f,
   122			},
   123		}
   124		startTimer(&t.r)
   125		return t
   126	}
   127	
   128	func goFunc(arg interface{}, seq uintptr) {
   129		go arg.(func())()
   130	}
   131	

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