Add IteratorPrefix method to Iterator

db/db.go

@@ -11,6 +11,7 @@ type DB interface {
 	Close()
 	NewBatch() Batch
 	Iterator() Iterator
+	IteratorPrefix([]byte) Iterator
 
 	// For debugging
 	Print()

db/go_level_db.go

@@ -7,6 +7,7 @@ import (
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/errors"
 	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
 
 	. "github.com/tendermint/tmlibs/common"
 )
@@ -119,6 +120,10 @@ func (db *GoLevelDB) Iterator() Iterator {
 	return db.db.NewIterator(nil, nil)
 }
 
+func (db *GoLevelDB) IteratorPrefix(prefix []byte) Iterator {
+	return db.db.NewIterator(util.BytesPrefix(prefix), nil)
+}
+
 func (db *GoLevelDB) NewBatch() Batch {
 	batch := new(leveldb.Batch)
 	return &goLevelDBBatch{db, batch}

db/mem_db.go

@@ -2,6 +2,7 @@ package db
 
 import (
 	"fmt"
+	"strings"
 	"sync"
 )
 
@@ -108,6 +109,10 @@ func (it *memDBIterator) Error() error {
 }
 
 func (db *MemDB) Iterator() Iterator {
+	return db.IteratorPrefix([]byte{})
+}
+
+func (db *MemDB) IteratorPrefix(prefix []byte) Iterator {
 	it := newMemDBIterator()
 	it.db = db
 	it.last = -1
@@ -117,7 +122,9 @@ func (db *MemDB) Iterator() Iterator {
 
 	// unfortunately we need a copy of all of the keys
 	for key, _ := range db.db {
-		it.keys = append(it.keys, key)
+		if strings.HasPrefix(key, string(prefix)) {
+			it.keys = append(it.keys, key)
+		}
 	}
 	return it
 }