NAME

       comedi_mark_buffer_read - streaming buffer control

SYNOPSIS

       #include <comedilib.h>

       int comedi_mark_buffer_read(comedi_t * device, unsigned int subdevice,
                                   unsigned int num_bytes);

DESCRIPTION

       The function comedi_mark_buffer_read is used on a subdevice that has a Comedi input
       command in progress. It should only be used if you are using a mmap mapping to read data
       from Comedi's buffer (as opposed to calling read on the device file), since Comedi will
       automatically keep track of how many bytes have been transferred via read calls. This
       function is used to indicate that the next num_bytes bytes in the buffer are no longer
       needed and may be discarded.

RETURN VALUE

       The function comedi_mark_buffer_read returns the number of bytes successfully marked as
       read, or -1 on error. The return value may be less than num_bytes if you attempt to mark
       more bytes read than are currently available for reading, or if num_bytes must be rounded
       down to be an exact multiple of the subdevice's sample size (either sizeof(sampl_t) or
       sizeof(lsampl_t)).

AUTHORS

       David Schleef <ds@schleef.org>
           Author.

       Frank Mori Hess <fmhess@users.sourceforge.net>
           Author.

       Herman Bruyninckx <Herman.Bruyninckx@mech.kuleuven.ac.be>
           Author.

       Bernd Porr <tech@linux-usb-daq.co.uk>
           Author.

       Ian Abbott <abbotti@mev.co.uk>
           Author.

       Éric Piel <piel@delmic.com>
           Author.

COPYRIGHT

       Copyright © 1998-2003 David Schleef
       Copyright © 2001-2003, 2005, 2008 Frank Mori Hess
       Copyright © 2002-2003 Herman Bruyninckx
       Copyright © 2012 Bernd Porr
       Copyright © 2012 Ian Abbott
       Copyright © 2012 Éric Piel

       This document is part of Comedilib. In the context of this document, the term "source
       code" as defined by the license is interpreted as the XML source.

       This library is free software; you can redistribute it and/or modify it under the terms of
       the GNU Lesser General Public License as published by the Free Software Foundation,
       version 2.1 of the License.

       This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
       without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
       See the GNU Lesser General Public License for more details.

       You should have received a copy of the GNU Lesser General Public License along with this
       library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
       Boston, MA 02111-1307 USA.