cleaner testing, leveldb can sort and limit

leveldb.go

@@ -2,10 +2,12 @@ package storage
 
 import (
 	"path"
+	"strconv"
 	"strings"
 
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/filter"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/util"
 )
@@ -33,31 +35,6 @@ func NewLevelDB(path string) (*LevelDB, error) {
 	}, err
 }
 
-func (ldb *LevelDB) List(ns []string, limits ...string) ([]string, error) {
-	namespace := resolveNamespace(ns)
-	namespace = path.Join(namespace)
-	limits = resolveLimits(limits)
-	limits[0] = path.Join(namespace, limits[0])
-	limits[1] = path.Join(namespace, limits[1])
-
-	keys := []string{}
-	r := util.BytesPrefix([]byte(namespace))
-	it := ldb.db.NewIterator(r, nil)
-	defer it.Release()
-	for it.Next() {
-		k := string(it.Key())
-		if k < limits[0] {
-			continue
-		} else if k > limits[1] {
-			break
-		}
-		k = strings.TrimPrefix(k, namespace+"/")
-		keys = append(keys, k)
-	}
-	err := it.Error()
-	return keys, err
-}
-
 func (ldb *LevelDB) Get(key string, ns ...string) ([]byte, error) {
 	namespace := resolveNamespace(ns)
 	snapshot, err := ldb.db.GetSnapshot()
@@ -91,3 +68,57 @@ func (ldb *LevelDB) Set(key string, value []byte, ns ...string) error {
 func (ldb *LevelDB) Close() error {
 	return ldb.db.Close()
 }
+
+func (ldb *LevelDB) List(ns []string, limits ...string) ([]string, error) {
+	namespace := path.Join(resolveNamespace(ns))
+	limits = resolveLimits(limits)
+	it, next := ldb.getIterator(namespace, limits)
+	defer it.Release()
+	keys := ldb.useIterator(it, next, namespace, limits)
+	err := it.Error()
+	return keys, err
+}
+
+func (ldb *LevelDB) getIterator(namespace string, limits []string) (iterator.Iterator, func() bool) {
+	limits[0] = path.Join(namespace, limits[0])
+	limits[1] = path.Join(namespace, limits[1])
+	asc := limits[3] == "true"
+
+	r := util.BytesPrefix([]byte(namespace))
+	it := ldb.db.NewIterator(r, nil)
+	next := it.Next
+	it.First()
+	if !asc {
+		next = it.Prev
+		it.Last()
+	}
+	return it, next
+}
+
+func (ldb *LevelDB) useIterator(it iterator.Iterator, next func() bool, namespace string, limits []string) []string {
+	limits = resolveLimits(limits)
+	n, _ := strconv.Atoi(limits[2])
+	m := 0
+
+	for it.Error() == nil && !ldb.inRange(string(it.Key()), limits[0], limits[1]) && next() {
+	}
+
+	keys := []string{}
+	for it.Error() == nil && ldb.inRange(string(it.Key()), limits[0], limits[1]) {
+		k := string(it.Key())
+		k = strings.TrimPrefix(k, namespace+"/")
+		keys = append(keys, k)
+		m += 1
+		if n > 0 && m >= n {
+			break
+		}
+		if !next() {
+			break
+		}
+	}
+	return keys
+}
+
+func (ldb *LevelDB) inRange(k, start, stop string) bool {
+	return k != "" && k >= start && k <= stop
+}