This avoids making a new channel and immediately closing it. `benchcmp`
says:
benchmark old ns/op new ns/op delta
BenchmarkPrecompleted-4 213 138 -35.21%
benchmark old allocs new allocs delta
BenchmarkPrecompleted-4 3 2 -33.33%
benchmark old bytes new bytes delta
BenchmarkPrecompleted-4 176 80 -54.55%
func UntilSignal(parent context.Context, sig ...os.Signal) *Context {
ctx := new(Context)
ctx.parent = parent
func UntilSignal(parent context.Context, sig ...os.Signal) *Context {
ctx := new(Context)
ctx.parent = parent
- ctx.done = make(chan struct{})
if err := parent.Err(); err != nil {
if err := parent.Err(); err != nil {
+ ctx.done = alreadyclosed
ctx.err = err
return ctx
}
ctx.err = err
return ctx
}
+ ctx.done = make(chan struct{})
ctx.c = make(chan os.Signal, 1)
signal.Notify(ctx.c, sig...)
go ctx.wait(sig...)
ctx.c = make(chan os.Signal, 1)
signal.Notify(ctx.c, sig...)
go ctx.wait(sig...)
s.m.Unlock()
return err
}
s.m.Unlock()
return err
}
+
+// Reuse the same channel for all contexts which begin life already
+// completed.
+var alreadyclosed = make(chan struct{})
+
+func init() {
+ close(alreadyclosed)
+}