comedi_mark_buffer_read — streaming buffer control


#include <comedilib.h>
int comedi_mark_buffer_read(comedi_t * device,
 unsigned int subdevice,
 unsigned int num_bytes);


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 descriptor), 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

On success, comedi_mark_buffer_read returns the number of bytes successfully marked as read. The return value may be less than the num_bytes. On failure, -1 is returned.