diff options
Diffstat (limited to 'vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go')
-rw-r--r-- | vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go | 66 |
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 0000000..0a43d4d --- /dev/null +++ b/vendor/github.com/hashicorp/terraform/helper/shadow/ordered_value.go | |||
@@ -0,0 +1,66 @@ | |||
1 | package shadow | ||
2 | |||
3 | import ( | ||
4 | "container/list" | ||
5 | "sync" | ||
6 | ) | ||
7 | |||
8 | // OrderedValue is a struct that keeps track of a value in the order | ||
9 | // it is set. Each time Value() is called, it will return the most recent | ||
10 | // calls value then discard it. | ||
11 | // | ||
12 | // This is unlike Value that returns the same value once it is set. | ||
13 | type OrderedValue struct { | ||
14 | lock sync.Mutex | ||
15 | values *list.List | ||
16 | waiters *list.List | ||
17 | } | ||
18 | |||
19 | // Value returns the last value that was set, or blocks until one | ||
20 | // is received. | ||
21 | func (w *OrderedValue) Value() interface{} { | ||
22 | w.lock.Lock() | ||
23 | |||
24 | // If we have a pending value already, use it | ||
25 | if w.values != nil && w.values.Len() > 0 { | ||
26 | front := w.values.Front() | ||
27 | w.values.Remove(front) | ||
28 | w.lock.Unlock() | ||
29 | return front.Value | ||
30 | } | ||
31 | |||
32 | // No pending value, create a waiter | ||
33 | if w.waiters == nil { | ||
34 | w.waiters = list.New() | ||
35 | } | ||
36 | |||
37 | var val Value | ||
38 | w.waiters.PushBack(&val) | ||
39 | w.lock.Unlock() | ||
40 | |||
41 | // Return the value once we have it | ||
42 | return val.Value() | ||
43 | } | ||
44 | |||
45 | // SetValue sets the latest value. | ||
46 | func (w *OrderedValue) SetValue(v interface{}) { | ||
47 | w.lock.Lock() | ||
48 | defer w.lock.Unlock() | ||
49 | |||
50 | // If we have a waiter, notify it | ||
51 | if w.waiters != nil && w.waiters.Len() > 0 { | ||
52 | front := w.waiters.Front() | ||
53 | w.waiters.Remove(front) | ||
54 | |||
55 | val := front.Value.(*Value) | ||
56 | val.SetValue(v) | ||
57 | return | ||
58 | } | ||
59 | |||
60 | // Add it to the list of values | ||
61 | if w.values == nil { | ||
62 | w.values = list.New() | ||
63 | } | ||
64 | |||
65 | w.values.PushBack(v) | ||
66 | } | ||