Returns the number of bars of a corresponding symbol and period, available in history.
[in] The symbol name of the financial instrument. NULL means the current symbol.
[in] Period. It can be one of the values of the ENUM_TIMEFRAMES enumeration. 0 means the current chart period.
The number of bars of a corresponding symbol and period, available in history, but no more than allowed by the "Max bars in chart" parameter in platform settings.