1 files changed, 73 insertions, 0 deletions
diff --git a/src/time/tick.go b/src/time/tick.go
new file mode 100644
index 0000000..babf865
--- /dev/null
+++ b/src/time/tick.go
@@ -0,0 +1,73 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package time
+
+import "errors"
+
+// A Ticker holds a channel that delivers ``ticks'' of a clock
+// at intervals.
+type Ticker struct {
+	C <-chan Time // The channel on which the ticks are delivered.
+	r runtimeTimer
+}
+
+// NewTicker returns a new Ticker containing a channel that will send
+// the current time on the channel after each tick. The period of the
+// ticks is specified by the duration argument. The ticker will adjust
+// the time interval or drop ticks to make up for slow receivers.
+// The duration d must be greater than zero; if not, NewTicker will
+// panic. Stop the ticker to release associated resources.
+func NewTicker(d Duration) *Ticker {
+	if d <= 0 {
+		panic(errors.New("non-positive interval for NewTicker"))
+	}
+	// Give the channel a 1-element time buffer.
+	// If the client falls behind while reading, we drop ticks
+	// on the floor until the client catches up.
+	c := make(chan Time, 1)
+	t := &Ticker{
+		C: c,
+		r: runtimeTimer{
+			when:   when(d),
+			period: int64(d),
+			f:      sendTime,
+			arg:    c,
+		},
+	}
+	startTimer(&t.r)
+	return t
+}
+
+// Stop turns off a ticker. After Stop, no more ticks will be sent.
+// Stop does not close the channel, to prevent a concurrent goroutine
+// reading from the channel from seeing an erroneous "tick".
+func (t *Ticker) Stop() {
+	stopTimer(&t.r)
+}
+
+// Reset stops a ticker and resets its period to the specified duration.
+// The next tick will arrive after the new period elapses. The duration d
+// must be greater than zero; if not, Reset will panic.
+func (t *Ticker) Reset(d Duration) {
+	if d <= 0 {
+		panic("non-positive interval for Ticker.Reset")
+	}
+	if t.r.f == nil {
+		panic("time: Reset called on uninitialized Ticker")
+	}
+	modTimer(&t.r, when(d), int64(d), t.r.f, t.r.arg, t.r.seq)
+}
+
+// Tick is a convenience wrapper for NewTicker providing access to the ticking
+// channel only. While Tick is useful for clients that have no need to shut down
+// the Ticker, be aware that without a way to shut it down the underlying
+// Ticker cannot be recovered by the garbage collector; it "leaks".
+// Unlike NewTicker, Tick will return nil if d <= 0.
+func Tick(d Duration) <-chan Time {
+	if d <= 0 {
+		return nil
+	}
+	return NewTicker(d).C
+}