1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef SQL_META_TABLE_H_
6#define SQL_META_TABLE_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "sql/sql_export.h"
12
13namespace sql {
14
15class Connection;
16class Statement;
17
18class SQL_EXPORT MetaTable {
19 public:
20  MetaTable();
21  ~MetaTable();
22
23  // Returns true if the 'meta' table exists.
24  static bool DoesTableExist(Connection* db);
25
26  // Initializes the MetaTableHelper, creating the meta table if necessary. For
27  // new tables, it will initialize the version number to |version| and the
28  // compatible version number to |compatible_version|.  Versions must be
29  // greater than 0 to distinguish missing versions (see GetVersionNumber()).
30  bool Init(Connection* db, int version, int compatible_version);
31
32  // Resets this MetaTable object, making another call to Init() possible.
33  void Reset();
34
35  // The version number of the database. This should be the version number of
36  // the creator of the file. The version number will be 0 if there is no
37  // previously set version number.
38  //
39  // See also Get/SetCompatibleVersionNumber().
40  void SetVersionNumber(int version);
41  int GetVersionNumber();
42
43  // The compatible version number is the lowest version of the code that this
44  // database can be read by. If there are minor changes or additions, old
45  // versions of the code can still work with the database without failing.
46  //
47  // For example, if an optional column is added to a table in version 3, the
48  // new code will set the version to 3, and the compatible version to 2, since
49  // the code expecting version 2 databases can still read and write the table.
50  //
51  // Rule of thumb: check the version number when you're upgrading, but check
52  // the compatible version number to see if you can read the file at all. If
53  // it's larger than you code is expecting, fail.
54  //
55  // The compatible version number will be 0 if there is no previously set
56  // compatible version number.
57  void SetCompatibleVersionNumber(int version);
58  int GetCompatibleVersionNumber();
59
60  // Set the given arbitrary key with the given data. Returns true on success.
61  bool SetValue(const char* key, const std::string& value);
62  bool SetValue(const char* key, int value);
63  bool SetValue(const char* key, int64 value);
64
65  // Retrieves the value associated with the given key. This will use sqlite's
66  // type conversion rules. It will return true on success.
67  bool GetValue(const char* key, std::string* value);
68  bool GetValue(const char* key, int* value);
69  bool GetValue(const char* key, int64* value);
70
71  // Deletes the key from the table.
72  bool DeleteKey(const char* key);
73
74 private:
75  // Conveniences to prepare the two types of statements used by
76  // MetaTableHelper.
77  void PrepareSetStatement(Statement* statement, const char* key);
78  bool PrepareGetStatement(Statement* statement, const char* key);
79
80  Connection* db_;
81
82  DISALLOW_COPY_AND_ASSIGN(MetaTable);
83};
84
85}  // namespace sql
86
87#endif  // SQL_META_TABLE_H_
88