X-Git-Url: http://git.osdn.net/view?a=blobdiff_plain;f=database%2Fleveldb%2Fmem_db.go;fp=database%2Fleveldb%2Fmem_db.go;h=e70aa9d0ba06a1040fcfa3ce84139122739ed7a2;hb=041a74394dd18dc0abbee21dd6e6e18bbdbd630a;hp=62f40fc69bbf9016feb51fb39b7fe95221c9e79b;hpb=e3f88c0fd58293b5d6651ba83c908c6fb2788ce0;p=bytom%2Fbytom.git

diff --git a/database/leveldb/mem_db.go b/database/leveldb/mem_db.go
index 62f40fc6..e70aa9d0 100644
--- a/database/leveldb/mem_db.go
+++ b/database/leveldb/mem_db.go
@@ -1,6 +1,7 @@
 package db
 
 import (
+	"bytes"
 	"fmt"
 	"sort"
 	"strings"
@@ -78,13 +79,29 @@ func (db *MemDB) Stats() map[string]string {
 type memDBIterator struct {
 	last int
 	keys []string
-	db   *MemDB
+	db   DB
+
+	start []byte
 }
 
 func newMemDBIterator() *memDBIterator {
 	return &memDBIterator{}
 }
 
+// Keys is expected to be in reverse order for reverse iterators.
+func newMemDBIteratorWithArgs(db DB, keys []string, start []byte) *memDBIterator {
+	itr := &memDBIterator{
+		db:    db,
+		keys:  keys,
+		start: start,
+		last:  -1,
+	}
+	if start != nil {
+		itr.Seek(start)
+	}
+	return itr
+}
+
 func (it *memDBIterator) Next() bool {
 	if it.last >= len(it.keys)-1 {
 		return false
@@ -143,10 +160,38 @@ func (db *MemDB) IteratorPrefix(prefix []byte) Iterator {
 	return it
 }
 
+func (db *MemDB) IteratorPrefixWithStart(Prefix, start []byte, isReverse bool) Iterator {
+	db.mtx.Lock()
+	defer db.mtx.Unlock()
+
+	keys := db.getSortedKeys(start, isReverse)
+	return newMemDBIteratorWithArgs(db, keys, start)
+}
+
 func (db *MemDB) NewBatch() Batch {
 	return &memDBBatch{db, nil}
 }
 
+func (db *MemDB) getSortedKeys(start []byte, reverse bool) []string {
+	keys := []string{}
+	for key := range db.db {
+		if bytes.Compare([]byte(key), start) < 0 {
+			continue
+		}
+		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
+}
+
 //--------------------------------------------------------------------------------
 
 type memDBBatch struct {