key-gen.h revision 299742 
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#include "private/svn_skel.h"  /* ### for svn_fs_base__{get,put}size() */
30
31#ifdef __cplusplus
32extern "C" {
33#endif /* __cplusplus */
34
35
36/* The alphanumeric keys passed in and out of svn_fs_base__next_key
37   are guaranteed never to be longer than this many bytes,
38   *including* the trailing null byte.  It is therefore safe
39   to declare a key as "char key[MAX_KEY_SIZE]".
40
41   Note that this limit will be a problem if the number of
42   keys in a table ever exceeds
43
44       18217977168218728251394687124089371267338971528174
45       76066745969754933395997209053270030282678007662838
46       67331479599455916367452421574456059646801054954062
47       15017704234999886990788594743994796171248406730973
48       80736524850563115569208508785942830080999927310762
49       50733948404739350551934565743979678824151197232629
50       947748581376,
51
52   but that's a risk we'll live with for now. */
53#define MAX_KEY_SIZE 200
54
55/* In many of the databases, the value at this key is the key to use
56   when storing a new record. */
57#define NEXT_KEY_KEY "next-key"
58
59
60/* Generate the next key after a given alphanumeric key.
61 *
62 * The first *LEN bytes of THIS are an ascii representation of a
63 * number in base 36: digits 0-9 have their usual values, and a-z have
64 * values 10-35.
65 *
66 * The new key is stored in NEXT, null-terminated.  NEXT must be at
67 * least *LEN + 2 bytes long -- one extra byte to hold a possible
68 * overflow column, and one for null termination.  On return, *LEN
69 * will be set to the length of the new key, not counting the null
70 * terminator.  In other words, the outgoing *LEN will be either equal
71 * to the incoming, or to the incoming + 1.
72 *
73 * If THIS contains anything other than digits and lower-case
74 * alphabetic characters, or if it starts with `0' but is not the
75 * string "0", then *LEN is set to zero and the effect on NEXT
76 * is undefined.
77 */
78void svn_fs_base__next_key(const char *this, apr_size_t *len, char *next);
79
80
81/* Compare two strings A and B as base-36 alphanumber keys.
82 *
83 * Return TRUE iff both keys are NULL or both keys have the same
84 * contents.
85 */
86svn_boolean_t svn_fs_base__same_keys(const char *a, const char *b);
87
88
89#ifdef __cplusplus
90}
91#endif /* __cplusplus */
92
93#endif /* SVN_LIBSVN_FS_KEY_GEN_H */
94