1 files changed, 66 insertions, 0 deletions
diff --git a/vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go b/vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go
new file mode 100644
index 00000000..0a43d4d4
--- /dev/null
+++ b/vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go
@@ -0,0 +1,66 @@
+package shadow
+
+import (
+	"container/list"
+	"sync"
+)
+
+// OrderedValue is a struct that keeps track of a value in the order
+// it is set. Each time Value() is called, it will return the most recent
+// calls value then discard it.
+//
+// This is unlike Value that returns the same value once it is set.
+type OrderedValue struct {
+	lock    sync.Mutex
+	values  *list.List
+	waiters *list.List
+}
+
+// Value returns the last value that was set, or blocks until one
+// is received.
+func (w *OrderedValue) Value() interface{} {
+	w.lock.Lock()
+
+	// If we have a pending value already, use it
+	if w.values != nil && w.values.Len() > 0 {
+		front := w.values.Front()
+		w.values.Remove(front)
+		w.lock.Unlock()
+		return front.Value
+	}
+
+	// No pending value, create a waiter
+	if w.waiters == nil {
+		w.waiters = list.New()
+	}
+
+	var val Value
+	w.waiters.PushBack(&val)
+	w.lock.Unlock()
+
+	// Return the value once we have it
+	return val.Value()
+}
+
+// SetValue sets the latest value.
+func (w *OrderedValue) SetValue(v interface{}) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	// If we have a waiter, notify it
+	if w.waiters != nil && w.waiters.Len() > 0 {
+		front := w.waiters.Front()
+		w.waiters.Remove(front)
+
+		val := front.Value.(*Value)
+		val.SetValue(v)
+		return
+	}
+
+	// Add it to the list of values
+	if w.values == nil {
+		w.values = list.New()
+	}
+
+	w.values.PushBack(v)
+}