fix paging (#235)

[bytom/vapor.git] / database / leveldb / go_level_db.go

diff --git a/database/leveldb/go_level_db.go b/database/leveldb/go_level_db.go
index 7a2b892..99c28e0 100644 (file)
--- a/database/leveldb/go_level_db.go
+++ b/database/leveldb/go_level_db.go
@@ -118,18 +118,27 @@ func (db *GoLevelDB) Stats() map[string]string {
 }
 
 type goLevelDBIterator struct {
-       source iterator.Iterator
-       start  []byte
+       source    iterator.Iterator
+       start     []byte
+       isReverse bool
 }
 
-func newGoLevelDBIterator(source iterator.Iterator, start []byte) *goLevelDBIterator {
+func newGoLevelDBIterator(source iterator.Iterator, start []byte, isReverse bool) *goLevelDBIterator {
        if start != nil {
-               source.Seek(start)
+               valid := source.Seek(start)
+               if !valid && isReverse {
+                       source.Last()
+                       source.Next()
+               }
+       } else if isReverse {
+               source.Last()
+               source.Next()
        }
 
        return &goLevelDBIterator{
-               source: source,
-               start:  start,
+               source:    source,
+               start:     start,
+               isReverse: isReverse,
        }
 }
 
@@ -161,6 +170,9 @@ func (it *goLevelDBIterator) Error() error {
 
 func (it *goLevelDBIterator) Next() bool {
        it.assertNoError()
+       if it.isReverse {
+               return it.source.Prev()
+       }
        return it.source.Next()
 }
 
@@ -182,9 +194,9 @@ func (db *GoLevelDB) IteratorPrefix(prefix []byte) Iterator {
        return &goLevelDBIterator{source: db.db.NewIterator(util.BytesPrefix(prefix), nil)}
 }
 
-func (db *GoLevelDB) IteratorPrefixWithStart(Prefix, start []byte) Iterator {
+func (db *GoLevelDB) IteratorPrefixWithStart(Prefix, start []byte, isReverse bool) Iterator {
        itr := db.db.NewIterator(util.BytesPrefix(Prefix), nil)
-       return newGoLevelDBIterator(itr, start)
+       return newGoLevelDBIterator(itr, start, isReverse)
 }
 
 func (db *GoLevelDB) NewBatch() Batch {