1 files changed, 79 insertions, 0 deletions
diff --git a/vendor/github.com/hashicorp/terraform/helper/shadow/value.go b/vendor/github.com/hashicorp/terraform/helper/shadow/value.go
new file mode 100644
index 00000000..2413335b
--- /dev/null
+++ b/vendor/github.com/hashicorp/terraform/helper/shadow/value.go
@@ -0,0 +1,79 @@
+package shadow
+
+import (
+	"errors"
+	"sync"
+)
+
+// ErrClosed is returned by any closed values.
+//
+// A "closed value" is when the shadow has been notified that the real
+// side is complete and any blocking values will _never_ be satisfied
+// in the future. In this case, this error is returned. If a value is already
+// available, that is still returned.
+var ErrClosed = errors.New("shadow closed")
+
+// Value is a struct that coordinates a value between two
+// parallel routines. It is similar to atomic.Value except that when
+// Value is called if it isn't set it will wait for it.
+//
+// The Value can be closed with Close, which will cause any future
+// blocking operations to return immediately with ErrClosed.
+type Value struct {
+	lock     sync.Mutex
+	cond     *sync.Cond
+	value    interface{}
+	valueSet bool
+}
+
+// Close closes the value. This can never fail. For a definition of
+// "close" see the struct docs.
+func (w *Value) Close() error {
+	w.lock.Lock()
+	set := w.valueSet
+	w.lock.Unlock()
+
+	// If we haven't set the value, set it
+	if !set {
+		w.SetValue(ErrClosed)
+	}
+
+	// Done
+	return nil
+}
+
+// Value returns the value that was set.
+func (w *Value) Value() interface{} {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	// If we already have a value just return
+	for !w.valueSet {
+		// No value, setup the condition variable if we have to
+		if w.cond == nil {
+			w.cond = sync.NewCond(&w.lock)
+		}
+
+		// Wait on it
+		w.cond.Wait()
+	}
+
+	// Return the value
+	return w.value
+}
+
+// SetValue sets the value.
+func (w *Value) SetValue(v interface{}) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	// Set the value
+	w.valueSet = true
+	w.value = v
+
+	// If we have a condition, clear it
+	if w.cond != nil {
+		w.cond.Broadcast()
+		w.cond = nil
+	}
+}