1 files changed, 62 insertions, 0 deletions
diff --git a/src/pkg/time/tick.go b/src/pkg/time/tick.go
new file mode 100644
index 000000000..53e2234f8
--- /dev/null
+++ b/src/pkg/time/tick.go
@@ -0,0 +1,62 @@
+// 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 (
+	"syscall";
+	"time";
+	"unsafe";
+)
+
+// TODO(rsc): This implementation of time.Tick is a
+// simple placeholder.  Eventually, there will need to be
+// a single central time server no matter how many tickers
+// are active.  There also needs to be a way to cancel a ticker.
+//
+// Also, if timeouts become part of the select statement,
+// perhaps the Ticker is just:
+//
+//	func Ticker(ns int64, c chan int64) {
+//		for {
+//			select { timeout ns: }
+//			nsec, err := time.Nanoseconds();
+//			c <- nsec;
+//		}
+
+func ticker(ns int64, c chan int64) {
+	var tv syscall.Timeval;
+	now := time.Nanoseconds();
+	when := now;
+	for {
+		when += ns;	// next alarm
+
+		// if c <- now took too long, skip ahead
+		if when < now {
+			// one big step
+			when += (now-when)/ns * ns;
+		}
+		for when <= now {
+			// little steps until when > now
+			when += ns
+		}
+
+		time.Sleep(when - now);
+		now = time.Nanoseconds();
+		c <- now;
+	}
+}
+
+// Tick creates a synchronous channel that will send the time, in nanoseconds,
+// every ns nanoseconds.  It adjusts the intervals to make up for pauses in
+// delivery of the ticks.
+func Tick(ns int64) chan int64 {
+	if ns <= 0 {
+		return nil
+	}
+	c := make(chan int64);
+	go ticker(ns, c);
+	return c;
+}
+