MXS-1703 Add convenience function + class for querying and storing results

An object of the class is returned as an auto_ptr to simplify memory management.

server/modules/monitor/mariadbmon/utilities.hh

@@ -71,3 +71,79 @@ string get_connection_errors(const ServerVector& servers);
  * @return Server names
  */
 string monitored_servers_to_string(const ServerVector& array);
+
+/**
+ * Helper class for simplifying working with resultsets. Used in MariaDBServer.
+ */
+class QueryResult
+{
+    // These need to be banned to avoid premature destruction.
+    QueryResult(const QueryResult&) = delete;
+    QueryResult& operator = (const QueryResult&) = delete;
+
+public:
+    QueryResult(MYSQL_RES* resultset = NULL);
+    ~QueryResult();
+
+    /**
+     * Advance to next row. Affects all result returning functions.
+     *
+     * @return True if the next row has data, false if the current row was the last one.
+     */
+    bool next_row();
+
+    /**
+     * Get the index of the current row.
+     *
+     * @return Current row index, or -1 if no data or next_row() has not been called yet.
+     */
+    int64_t get_row_index() const;
+
+    /**
+     * How many columns the result set has.
+     *
+     * @return Column count, or -1 if no data.
+     */
+    int64_t get_column_count() const;
+
+    /**
+     * Get a numeric index for a column name. May give wrong results if column names are not unique.
+     *
+     * @param col_name Column name
+     * @return Index or -1 if not found.
+     */
+    int64_t get_col_index(const string& col_name) const;
+
+    /**
+     * Read a string value from the current row and given column. Empty string and (null) are both interpreted
+     * as the empty string.
+     *
+     * @param column_ind Column index
+     * @return Value as string
+     */
+    string get_string(int64_t column_ind) const;
+
+    /**
+     * Read an integer value from the current row and given column. No error checking is done on the parsing.
+     * The parsing is performed by @c strtoll(), so the caller may check errno for errors.
+     *
+     * @param column_ind Column index
+     * @return Value as integer
+     */
+    int64_t get_int(int64_t column_ind) const;
+
+    /**
+     * Read a boolean value from the current row and given column.
+     *
+     * @param column_ind Column index
+     * @return Value as boolean. Returns true if the text is either 'Y' or '1'.
+     */
+    bool get_bool(int64_t column_ind) const;
+
+private:
+    MYSQL_RES* m_resultset; // Underlying result set, freed at dtor.
+    std::tr1::unordered_map<string, int64_t> m_col_indexes; // Map of column name -> index
+    int64_t m_columns;     // How many columns does the data have. Usually equal to column index map size.
+    MYSQL_ROW m_rowdata;   // Data for current row
+    int64_t m_current_row; // Index of current row
+};