track prev. path

tracker/tracker.go

@@ -25,6 +25,7 @@
 package tracker
 
 import (
+	"bytes"
 	"encoding/csv"
 	"fmt"
 	"os"
@@ -106,11 +107,12 @@ type TrackerImpl struct {
 
 type Iterator struct {
 	trie.NodeIterator
-	tracker *TrackerImpl
+	tracker  *TrackerImpl
+	prevPath []byte
 }
 
 func (tr *TrackerImpl) Tracked(it trie.NodeIterator) *Iterator {
-	ret := &Iterator{it, tr}
+	ret := &Iterator{it, tr, nil}
 	tr.startChan <- ret
 	return ret
 }
@@ -128,7 +130,7 @@ func (tr *TrackerImpl) Save() error {
 	for it := range tr.started {
 		_, endPath := it.Bounds()
 		rows = append(rows, []string{
-			fmt.Sprintf("%x", it.Path()),
+			fmt.Sprintf("%x", it.prevPath),
 			fmt.Sprintf("%x", endPath),
 		})
 	}
@@ -232,6 +234,7 @@ func (tr *TrackerImpl) CloseAndSave() error {
 
 // Next advances the iterator, notifying its owning tracker when it finishes.
 func (it *Iterator) Next(descend bool) bool {
+	it.prevPath = bytes.Clone(it.Path())
 	ret := it.NodeIterator.Next(descend)
 
 	if !ret {