MXS-2544 Add utility class for handling SQLite

Preparation and cleanup for adding more data to handle user roles in PAM
authenticator.

server/modules/authenticator/PAM/PAMAuth/pam_auth.hh

@@ -37,3 +37,77 @@ extern const int NUM_FIELDS;
 
 extern const char* SQLITE_OPEN_FAIL;
 extern const char* SQLITE_OPEN_OOM;
+
+struct sqlite3;
+
+class SQLite;
+
+/**
+ * Convenience class for working with SQLite.
+ */
+class SQLite
+{
+public:
+    SQLite(const SQLite& rhs) = delete;
+    SQLite& operator=(const SQLite& rhs) = delete;
+
+    using SSQLite = std::unique_ptr<SQLite>;
+
+    template<class T>
+    using Callback = int (*)(T* data, int n_columns, char** rows, char** field_names);
+
+    /**
+     * Create a new database handle.
+     *
+     * @param filename The filename/url given to sqlite3_open_v2
+     * @param flags Flags given to sqlite3_open_v2
+     * @return New handle if successful, null otherwise.
+     */
+    static SSQLite create(const std::string& filename, int flags, std::string* error_out);
+    ~SQLite();
+
+    /**
+     * Run a simple query which returns no data.
+     *
+     * @param sql SQL to run
+     * @return True on success
+     */
+    bool exec(const std::string& sql);
+
+    /**
+     * Run a query which may return data.
+     *
+     * @param sql SQL to run
+     * @param cb Callback given to sqlite3_exec
+     * @param cb_data Data pointer given to sqlite3_exec
+     * @return True on success
+     */
+    template <class T>
+    bool exec(const std::string& sql, Callback<T> cb, T* cb_data)
+    {
+        return exec_impl(sql, reinterpret_cast<CallbackVoid>(cb), cb_data);
+    }
+
+    /**
+     * Calls sqlite3_busy_timeout.
+     *
+     * @param ms The timeout in ms
+     */
+    void set_timeout(int ms);
+
+    /**
+     * Get latest error.
+     *
+     * @return Error string
+     */
+    const char* error() const;
+
+private:
+    using CallbackVoid = int (*)(void* data, int n_columns, char** rows, char** field_names);
+    bool exec_impl(const std::string& sql, CallbackVoid cb, void* cb_data);
+
+    SQLite(sqlite3* handle);
+
+    sqlite3* m_dbhandle {nullptr};
+    std::string m_errormsg;
+};