1 /* key-gen.c --- manufacturing sequential keys for some db tables
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
12 * http://www.apache.org/licenses/LICENSE-2.0
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
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20 * ====================================================================
23 #ifndef SVN_LIBSVN_FS_KEY_GEN_H
24 #define SVN_LIBSVN_FS_KEY_GEN_H
28 #include "svn_types.h"
32 #endif /* __cplusplus */
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]".
40 Note that this limit will be a problem if the number of
41 keys in a table ever exceeds
43 18217977168218728251394687124089371267338971528174
44 76066745969754933395997209053270030282678007662838
45 67331479599455916367452421574456059646801054954062
46 15017704234999886990788594743994796171248406730973
47 80736524850563115569208508785942830080999927310762
48 50733948404739350551934565743979678824151197232629
51 but that's a risk we'll live with for now. */
52 #define MAX_KEY_SIZE 200
55 /* Generate the next key after a given alphanumeric key.
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
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.
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
73 void svn_fs_fs__next_key(const char *this, apr_size_t *len, char *next);
76 /* Compare two strings A and B as base-36 alphanumeric keys.
78 * Return -1, 0, or 1 if A is less than, equal to, or greater than B,
81 int svn_fs_fs__key_compare(const char *a, const char *b);
83 /* Add two base-36 alphanumeric keys to get a third, the result. */
84 void svn_fs_fs__add_keys(const char *key1, const char *key2, char *result);
89 #endif /* __cplusplus */
91 #endif /* SVN_LIBSVN_FS_KEY_GEN_H */