subversion/libsvn_fs_fs/key-gen.h

   1 /* key-gen.c --- manufacturing sequential keys for some db tables
   2  *
   3  * ====================================================================
   4  * Copyright (c) 2000-2004 CollabNet.  All rights reserved.
   5  *
   6  * This software is licensed as described in the file COPYING, which
   7  * you should have received as part of this distribution.  The terms
   8  * are also available at http://subversion.tigris.org/license-1.html.
   9  * If newer versions of this license are posted there, you may use a
  10  * newer version instead, at your option.
  11  *
  12  * This software consists of voluntary contributions made by many
  13  * individuals.  For exact contribution history, see the revision
  14  * history and logs, available at http://subversion.tigris.org/.
  15  * ====================================================================
  16  */
  17
  18 #ifndef SVN_LIBSVN_FS_KEY_GEN_H
  19 #define SVN_LIBSVN_FS_KEY_GEN_H
  20
  21 #include <apr.h>
  22
  23 #include "svn_types.h"
  24
  25 #ifdef __cplusplus
  26 extern "C" {
  27 #endif /* __cplusplus */
  28
  29 \f
  30 /* The alphanumeric keys passed in and out of svn_fs_fs__next_key
  31    are guaranteed never to be longer than this many bytes,
  32    *including* the trailing null byte.  It is therefore safe
  33    to declare a key as "char key[MAX_KEY_SIZE]".
  34
  35    Note that this limit will be a problem if the number of
  36    keys in a table ever exceeds
  37
  38        18217977168218728251394687124089371267338971528174
  39        76066745969754933395997209053270030282678007662838
  40        67331479599455916367452421574456059646801054954062
  41        15017704234999886990788594743994796171248406730973
  42        80736524850563115569208508785942830080999927310762
  43        50733948404739350551934565743979678824151197232629
  44        947748581376,
  45
  46    but that's a risk we'll live with for now. */
  47 #define MAX_KEY_SIZE 200
  48
  49
  50 /* Generate the next key after a given alphanumeric key.
  51  *
  52  * The first *LEN bytes of THIS are an ascii representation of a
  53  * number in base 36: digits 0-9 have their usual values, and a-z have
  54  * values 10-35.
  55  *
  56  * The new key is stored in NEXT, null-terminated.  NEXT must be at
  57  * least *LEN + 2 bytes long -- one extra byte to hold a possible
  58  * overflow column, and one for null termination.  On return, *LEN
  59  * will be set to the length of the new key, not counting the null
  60  * terminator.  In other words, the outgoing *LEN will be either equal
  61  * to the incoming, or to the incoming + 1.
  62  *
  63  * If THIS contains anything other than digits and lower-case
  64  * alphabetic characters, or if it starts with `0' but is not the
  65  * string "0", then *LEN is set to zero and the effect on NEXT
  66  * is undefined.
  67  */
  68 void svn_fs_fs__next_key(const char *this, apr_size_t *len, char *next);
  69
  70
  71 /* Compare two strings A and B as base-36 alphanumeric keys.
  72  *
  73  * Return -1, 0, or 1 if A is less than, equal to, or greater than B,
  74  * respectively.
  75  */
  76 int svn_fs_fs__key_compare(const char *a, const char *b);
  77
  78 /* Add two base-36 alphanumeric keys to get a third, the result. */
  79 void svn_fs_fs__add_keys(const char *key1, const char *key2, char *result);
  80
  81
  82 #ifdef __cplusplus
  83 }
  84 #endif /* __cplusplus */
  85
  86 #endif /* SVN_LIBSVN_FS_KEY_GEN_H */