use an in memory store for containers

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

oci/history.go

@@ -0,0 +1,31 @@
+package oci
+
+import "sort"
+
+// History is a convenience type for storing a list of containers,
+// sorted by creation date in descendant order.
+type History []*Container
+
+// Len returns the number of containers in the history.
+func (history *History) Len() int {
+	return len(*history)
+}
+
+// Less compares two containers and returns true if the second one
+// was created before the first one.
+func (history *History) Less(i, j int) bool {
+	containers := *history
+	// FIXME: state access should be serialized
+	return containers[j].state.Created.Before(containers[i].state.Created)
+}
+
+// Swap switches containers i and j positions in the history.
+func (history *History) Swap(i, j int) {
+	containers := *history
+	containers[i], containers[j] = containers[j], containers[i]
+}
+
+// sort orders the history by creation date in descendant order.
+func (history *History) sort() {
+	sort.Sort(history)
+}