add other session providers (#5963)

vendor/github.com/syndtr/goleveldb/leveldb/util/range.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+// Range is a key range.
+type Range struct {
+	// Start of the key range, include in the range.
+	Start []byte
+
+	// Limit of the key range, not include in the range.
+	Limit []byte
+}
+
+// BytesPrefix returns key range that satisfy the given prefix.
+// This only applicable for the standard 'bytes comparer'.
+func BytesPrefix(prefix []byte) *Range {
+	var limit []byte
+	for i := len(prefix) - 1; i >= 0; i-- {
+		c := prefix[i]
+		if c < 0xff {
+			limit = make([]byte, i+1)
+			copy(limit, prefix)
+			limit[i] = c + 1
+			break
+		}
+	}
+	return &Range{prefix, limit}
+}