cpp/io/basic streambuf/sputn

@1@ Calls of the most derived class.

@2@ Writes characters to the output sequence from the character array whose first element is pointed to by. The characters are written as if by repeated calls to sputc. Writing stops when either characters are written or a call to sputc would have returned.

If the put area becomes full, it is unspecified whether overflow is actually called or its effect is achieved by other means.

Parameters
(none)

Return value
The number of characters successfully written.