On Sun, 6 May 2007, Alan Cox wrote: > > However, whatever policy the buffer uses, the fundamental point it's that > > when I flush the input buffer I should be sure that each byte read > > after the flush is *new* (current) data and not old one. This because > > Define "new" and "old" in this case. I don't believe you can give a > precise definition or that such a thing is physically possible.
One can come close. It would make sense to say that after a flush, subsequent reads should retrieve _contiguous_ bytes from the input stream. In other words, rule out the possibility that the read would get bytes 1-10 (from some buffer somewhere) followed by bytes 30-60 (because bytes 11-29 were dropped by the flush). By contrast, it would be permissible for the read to obtain bytes 20-60, even though 20-29 may have been entered the input stream before the flush occurred. > The hardware itself has buffers at both ends of the link, there may be > buffers in modems, muxes and the like as well. We can certainly flush > input buffers in the kernel but it isn't clear we can always do so at the > hardware level, let alone at the remote end or buffers on devices on the > link. This is of course the fly in the ointment. Alan Stern ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
