add btree for volume index

weed/storage/needle/btree_map.go

@@ -0,0 +1,52 @@
+package needle
+
+import (
+	"github.com/google/btree"
+)
+
+//This map assumes mostly inserting increasing keys
+type BtreeMap struct {
+	tree *btree.BTree
+}
+
+func NewBtreeMap() *BtreeMap {
+	return &BtreeMap{
+		tree: btree.New(32),
+	}
+}
+
+func (cm *BtreeMap) Set(key Key, offset, size uint32) (oldOffset, oldSize uint32) {
+	found := cm.tree.ReplaceOrInsert(NeedleValue{key, offset, size})
+	if found != nil {
+		old := found.(NeedleValue)
+		return old.Offset, old.Size
+	}
+	return
+}
+
+func (cm *BtreeMap) Delete(key Key) (oldSize uint32) {
+	found := cm.tree.Delete(NeedleValue{key, 0, 0})
+	if found != nil {
+		old := found.(NeedleValue)
+		return old.Size
+	}
+	return
+}
+func (cm *BtreeMap) Get(key Key) (*NeedleValue, bool) {
+	found := cm.tree.Get(NeedleValue{key, 0, 0})
+	if found != nil {
+		old := found.(NeedleValue)
+		return &old, true
+	}
+	return nil, false
+}
+
+// Visit visits all entries or stop if any error when visiting
+func (cm *BtreeMap) Visit(visit func(NeedleValue) error) (ret error) {
+	cm.tree.Ascend(func(item btree.Item) bool {
+		needle := item.(NeedleValue)
+		ret = visit(needle)
+		return ret == nil
+	})
+	return ret
+}