1/* key-gen.c --- manufacturing sequential keys for some db tables
2 *
3 * ====================================================================
4 *    Licensed to the Apache Software Foundation (ASF) under one
5 *    or more contributor license agreements.  See the NOTICE file
6 *    distributed with this work for additional information
7 *    regarding copyright ownership.  The ASF licenses this file
8 *    to you under the Apache License, Version 2.0 (the
9 *    "License"); you may not use this file except in compliance
10 *    with the License.  You may obtain a copy of the License at
11 *
12 *      http://www.apache.org/licenses/LICENSE-2.0
13 *
14 *    Unless required by applicable law or agreed to in writing,
15 *    software distributed under the License is distributed on an
16 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 *    KIND, either express or implied.  See the License for the
18 *    specific language governing permissions and limitations
19 *    under the License.
20 * ====================================================================
21 */
22
23#ifndef SVN_LIBSVN_FS_KEY_GEN_H
24#define SVN_LIBSVN_FS_KEY_GEN_H
25
26#include <apr.h>
27
28#include "svn_types.h"
29
30#ifdef __cplusplus
31extern "C" {
32#endif /* __cplusplus */
33
34
35/* The alphanumeric keys passed in and out of svn_fs_fs__next_key
36   are guaranteed never to be longer than this many bytes,
37   *including* the trailing null byte.  It is therefore safe
38   to declare a key as "char key[MAX_KEY_SIZE]".
39
40   Note that this limit will be a problem if the number of
41   keys in a table ever exceeds
42
43       18217977168218728251394687124089371267338971528174
44       76066745969754933395997209053270030282678007662838
45       67331479599455916367452421574456059646801054954062
46       15017704234999886990788594743994796171248406730973
47       80736524850563115569208508785942830080999927310762
48       50733948404739350551934565743979678824151197232629
49       947748581376,
50
51   but that's a risk we'll live with for now. */
52#define MAX_KEY_SIZE 200
53
54
55/* Generate the next key after a given alphanumeric key.
56 *
57 * The first *LEN bytes of THIS are an ascii representation of a
58 * number in base 36: digits 0-9 have their usual values, and a-z have
59 * values 10-35.
60 *
61 * The new key is stored in NEXT, null-terminated.  NEXT must be at
62 * least *LEN + 2 bytes long -- one extra byte to hold a possible
63 * overflow column, and one for null termination.  On return, *LEN
64 * will be set to the length of the new key, not counting the null
65 * terminator.  In other words, the outgoing *LEN will be either equal
66 * to the incoming, or to the incoming + 1.
67 *
68 * If THIS contains anything other than digits and lower-case
69 * alphabetic characters, or if it starts with `0' but is not the
70 * string "0", then *LEN is set to zero and the effect on NEXT
71 * is undefined.
72 */
73void svn_fs_fs__next_key(const char *this, apr_size_t *len, char *next);
74
75
76/* Compare two strings A and B as base-36 alphanumeric keys.
77 *
78 * Return -1, 0, or 1 if A is less than, equal to, or greater than B,
79 * respectively.
80 */
81int svn_fs_fs__key_compare(const char *a, const char *b);
82
83/* Add two base-36 alphanumeric keys to get a third, the result. */
84void svn_fs_fs__add_keys(const char *key1, const char *key2, char *result);
85
86
87#ifdef __cplusplus
88}
89#endif /* __cplusplus */
90
91#endif /* SVN_LIBSVN_FS_KEY_GEN_H */
92