fix paging (#235)

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

diff --git a/database/leveldb/mem_db.go b/database/leveldb/mem_db.go
index 63e2b76..9ab7052 100644 (file)
--- a/database/leveldb/mem_db.go
+++ b/database/leveldb/mem_db.go
@@ -163,11 +163,11 @@ func (db *MemDB) IteratorPrefix(prefix []byte) Iterator {
        return it
 }
 
-func (db *MemDB) IteratorPrefixWithStart(Prefix, start []byte) Iterator {
+func (db *MemDB) IteratorPrefixWithStart(Prefix, start []byte, isReverse bool) Iterator {
        db.mtx.Lock()
        defer db.mtx.Unlock()
 
-       keys := db.getSortedKeys(start)
+       keys := db.getSortedKeys(start, isReverse)
        return newMemDBIteratorWithArgs(db, keys, start)
 }
 
@@ -175,7 +175,7 @@ func (db *MemDB) NewBatch() Batch {
        return &memDBBatch{db, nil}
 }
 
-func (db *MemDB) getSortedKeys(start []byte) []string {
+func (db *MemDB) getSortedKeys(start []byte, reverse bool) []string {
        keys := []string{}
        for key := range db.db {
                if bytes.Compare([]byte(key), start) < 0 {
@@ -184,6 +184,14 @@ func (db *MemDB) getSortedKeys(start []byte) []string {
                keys = append(keys, key)
        }
        sort.Strings(keys)
+       if reverse {
+               nkeys := len(keys)
+               for i := 0; i < nkeys/2; i++ {
+                       temp := keys[i]
+                       keys[i] = keys[nkeys-i-1]
+                       keys[nkeys-i-1] = temp
+               }
+       }
        return keys
 }