protected member function
Advance get pointer
Adds n to the get pointer.
The get pointer (gptr) is the internal pointer that points to the current location in the array with the buffered portion of the controlled input sequence.
- Value by which to increase the get pointer.
This shall be a value such that
gptr()+n is in the range between eback and egptr.
Modifies the stream buffer object.
Concurrent access to the same stream buffer object may cause data races.
Basic guarantee: if an exception is thrown, the stream buffer is in a valid state.
Invalid arguments cause undefined behavior.