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 13 namespace sql { 14 15 class Connection; 16 class Statement; 17 18 class 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
