1// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
2// All rights reserved.
3//
4// Use of this source code is governed by a BSD-style license that can be
5// found in the LICENSE file.
6
7package comparer
8
9import "bytes"
10
11type bytesComparer struct{}
12
13func (bytesComparer) Compare(a, b []byte) int {
14	return bytes.Compare(a, b)
15}
16
17func (bytesComparer) Name() string {
18	return "leveldb.BytewiseComparator"
19}
20
21func (bytesComparer) Separator(dst, a, b []byte) []byte {
22	i, n := 0, len(a)
23	if n > len(b) {
24		n = len(b)
25	}
26	for ; i < n && a[i] == b[i]; i++ {
27	}
28	if i >= n {
29		// Do not shorten if one string is a prefix of the other
30	} else if c := a[i]; c < 0xff && c+1 < b[i] {
31		dst = append(dst, a[:i+1]...)
32		dst[len(dst)-1]++
33		return dst
34	}
35	return nil
36}
37
38func (bytesComparer) Successor(dst, b []byte) []byte {
39	for i, c := range b {
40		if c != 0xff {
41			dst = append(dst, b[:i+1]...)
42			dst[len(dst)-1]++
43			return dst
44		}
45	}
46	return nil
47}
48
49// DefaultComparer are default implementation of the Comparer interface.
50// It uses the natural ordering, consistent with bytes.Compare.
51var DefaultComparer = bytesComparer{}
52