Add Cycler

io/cycler.go

@@ -0,0 +1,28 @@
+package uio
+
+import "io"
+
+// Cycler stores any io.Closer. When the value is replaced, the old value is
+// closed.
+type Cycler struct {
+	value io.Closer
+}
+
+// Value returns the value of the Cycler. If there is no value, nil is returned.
+func (this *Cycler) Value () io.Closer {
+	return this.value
+}
+
+// Set replaces the value of the Cycler, closing the previous one if it exists.
+func (this *Cycler) Set (value io.Closer) error {
+	err := this.value.Close()
+	this.value = value
+	return err
+}
+
+// Close closes the Cycler's value early. It will be set to nil.
+func (this *Cycler) Close () error {
+	return this.Set(nil)
+}
+
+