add other session providers (#5963)

vendor/github.com/syndtr/goleveldb/leveldb/comparer.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2012, 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 leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+)
+
+type iComparer struct {
+	ucmp comparer.Comparer
+}
+
+func (icmp *iComparer) uName() string {
+	return icmp.ucmp.Name()
+}
+
+func (icmp *iComparer) uCompare(a, b []byte) int {
+	return icmp.ucmp.Compare(a, b)
+}
+
+func (icmp *iComparer) uSeparator(dst, a, b []byte) []byte {
+	return icmp.ucmp.Separator(dst, a, b)
+}
+
+func (icmp *iComparer) uSuccessor(dst, b []byte) []byte {
+	return icmp.ucmp.Successor(dst, b)
+}
+
+func (icmp *iComparer) Name() string {
+	return icmp.uName()
+}
+
+func (icmp *iComparer) Compare(a, b []byte) int {
+	x := icmp.uCompare(internalKey(a).ukey(), internalKey(b).ukey())
+	if x == 0 {
+		if m, n := internalKey(a).num(), internalKey(b).num(); m > n {
+			return -1
+		} else if m < n {
+			return 1
+		}
+	}
+	return x
+}
+
+func (icmp *iComparer) Separator(dst, a, b []byte) []byte {
+	ua, ub := internalKey(a).ukey(), internalKey(b).ukey()
+	dst = icmp.uSeparator(dst, ua, ub)
+	if dst != nil && len(dst) < len(ua) && icmp.uCompare(ua, dst) < 0 {
+		// Append earliest possible number.
+		return append(dst, keyMaxNumBytes...)
+	}
+	return nil
+}
+
+func (icmp *iComparer) Successor(dst, b []byte) []byte {
+	ub := internalKey(b).ukey()
+	dst = icmp.uSuccessor(dst, ub)
+	if dst != nil && len(dst) < len(ub) && icmp.uCompare(ub, dst) < 0 {
+		// Append earliest possible number.
+		return append(dst, keyMaxNumBytes...)
+	}
+	return nil
+}