1 files changed, 51 insertions, 0 deletions
diff --git a/updates.go b/updates.go
new file mode 100644
index 0000000..c36bda8
--- /dev/null
+++ b/updates.go
@@ -0,0 +1,51 @@
+package main
+
+import (
+	"time"
+)
+
+const (
+	addAction    = 0
+	removeAction = 1
+)
+type Update struct {
+	Song *Song
+	Action uint8
+	Timestamp int64
+	Next *Update
+}
+var headUpdates map[int]*Update
+var tailUpdates map[int]*Update
+
+func init() {
+	headUpdates = make(map[int]*Update)
+	tailUpdates = make(map[int]*Update)
+}
+
+func addUpdate(pid int, action uint8, song *Song) {
+	update := new(Update)
+	update.Song = song
+	update.Action = action
+	update.Timestamp = time.Nanoseconds()
+	pup, ok := tailUpdates[pid]
+	if ok {
+		pup.Next = update
+	} else {
+		headUpdates[pid] = update
+	}
+	tailUpdates[pid] = update
+}
+
+func getUpdates(pid int, timestamp int64) *Update {
+	pup, ok := headUpdates[pid]
+	if !ok {
+		return nil
+	}
+	for pup != nil {
+		if pup.Timestamp > timestamp {
+			return pup
+		}
+		pup = pup.Next
+	}
+	return nil
+}