1 // Copyright (c) 2009 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 APP_SQL_META_TABLE_H_ 6 #define APP_SQL_META_TABLE_H_ 7 #pragma once 8 9 #include <string> 10 11 #include "base/basictypes.h" 12 13 namespace sql { 14 15 class Connection; 16 class Statement; 17 18 class 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|. 29 bool Init(Connection* db, int version, int compatible_version); 30 31 // Resets this MetaTable object, making another call to Init() possible. 32 void Reset(); 33 34 // The version number of the database. This should be the version number of 35 // the creator of the file. The version number will be 0 if there is no 36 // previously set version number. 37 // 38 // See also Get/SetCompatibleVersionNumber(). 39 void SetVersionNumber(int version); 40 int GetVersionNumber(); 41 42 // The compatible version number is the lowest version of the code that this 43 // database can be read by. If there are minor changes or additions, old 44 // versions of the code can still work with the database without failing. 45 // 46 // For example, if an optional column is added to a table in version 3, the 47 // new code will set the version to 3, and the compatible version to 2, since 48 // the code expecting version 2 databases can still read and write the table. 49 // 50 // Rule of thumb: check the version number when you're upgrading, but check 51 // the compatible version number to see if you can read the file at all. If 52 // it's larger than you code is expecting, fail. 53 // 54 // The compatible version number will be 0 if there is no previously set 55 // compatible version number. 56 void SetCompatibleVersionNumber(int version); 57 int GetCompatibleVersionNumber(); 58 59 // Set the given arbitrary key with the given data. Returns true on success. 60 bool SetValue(const char* key, const std::string& value); 61 bool SetValue(const char* key, int value); 62 bool SetValue(const char* key, int64 value); 63 64 // Retrieves the value associated with the given key. This will use sqlite's 65 // type conversion rules. It will return true on success. 66 bool GetValue(const char* key, std::string* value); 67 bool GetValue(const char* key, int* value); 68 bool GetValue(const char* key, int64* value); 69 70 private: 71 // Conveniences to prepare the two types of statements used by 72 // MetaTableHelper. 73 bool PrepareSetStatement(Statement* statement, const char* key); 74 bool PrepareGetStatement(Statement* statement, const char* key); 75 76 Connection* db_; 77 78 DISALLOW_COPY_AND_ASSIGN(MetaTable); 79 }; 80 81 } // namespace sql 82 83 #endif // APP_SQL_META_TABLE_H_ 84
