title: in directsound, for IDirectSoundBuffer, which method to be in charge of write position of buffer.
body: <p>In directsound, we know, call IDirectSoundBuffer::getcurrentposition(), would get the play-position and write-position in the directsound buffer.But i think copy data into buffer should change the writeposition(this behavior, changing write_position, would be caused by which method, unlock?). I think only the copying data function should only affect the data in buffer, not the write-position..</p>