1 // Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
2 // All rights reserved.
4 // Use of this source code is governed by a BSD-style license that can be
5 // found in the LICENSE file.
7 // Package comparer provides interface and implementation for ordering
11 // BasicComparer is the interface that wraps the basic Compare method.
12 type BasicComparer interface {
13 // Compare returns -1, 0, or +1 depending on whether a is 'less than',
14 // 'equal to' or 'greater than' b. The two arguments can only be 'equal'
15 // if their contents are exactly equal. Furthermore, the empty slice
16 // must be 'less than' any non-empty slice.
17 Compare(a, b []byte) int
20 // Comparer defines a total ordering over the space of []byte keys: a 'less
21 // than' relationship.
22 type Comparer interface {
25 // Name returns name of the comparer.
27 // The Level-DB on-disk format stores the comparer name, and opening a
28 // database with a different comparer from the one it was created with
29 // will result in an error.
31 // An implementation to a new name whenever the comparer implementation
32 // changes in a way that will cause the relative ordering of any two keys
35 // Names starting with "leveldb." are reserved and should not be used
36 // by any users of this package.
39 // Bellow are advanced functions used used to reduce the space requirements
40 // for internal data structures such as index blocks.
42 // Separator appends a sequence of bytes x to dst such that a <= x && x < b,
43 // where 'less than' is consistent with Compare. An implementation should
44 // return nil if x equal to a.
46 // Either contents of a or b should not by any means modified. Doing so
47 // may cause corruption on the internal state.
48 Separator(dst, a, b []byte) []byte
50 // Successor appends a sequence of bytes x to dst such that x >= b, where
51 // 'less than' is consistent with Compare. An implementation should return
52 // nil if x equal to b.
54 // Contents of b should not by any means modified. Doing so may cause
55 // corruption on the internal state.
56 Successor(dst, b []byte) []byte