NAME¶
xdf_set_chconf, xdf_get_chconf - set or get the configuration of a channel
descriptor handle
SYNOPSIS¶
#include <xdfio.h>
int xdf_set_chconf(struct xdfch* ch, enum xdffield
field, ...);
int xdf_get_chconf(const struct xdfch* ch, enum xdffield
field, ...);
DESCRIPTION¶
xdf_set_chconf() sets the configuration of the channel referenced by
ch according to the variable list of argument. This list is composed of
successive couple grouping one variable of type enum xdffield defining the
feature to be set and a value whose type depends on the previous field type.
The list
must finish by
XDF_NOF.
xdf_get_chconf() gets the configuration of the channel referenced by
ch according to the variable list of argument. The variable list is the
same list terminated by
XDF_NOF as for
xdf_set_chconf()
excepting that the second part of the couple is not that value but a
pointer to the value.
Both functions process the argument list
from left to right. This means
that if a particular field request provokes an error, none of the field
requests on its right will be processed. The order of processing is also
important for field requests that influences the value of other fields (like
XDF_CF_STOTYPE).
Here is the list of admissible value. The expected type of value is provided in
the parenthesis (the expected type of the value for
xdf_set_chconf(),
or a pointer to this type for
xdf_get_chconf()). The default value of
each field is provided in squared brackets (however these defaults can be
overridden by a call to
xdf_set_conf(3) if the file is open for
writing. If the file is opened for reading, the default are meaningful only
for the fields
XDF_CF_ARR*). If a list of data formats is specified in
curl brackets, it means that the field is supported only in those formats (no
list means that all formats support the field):
- XDF_CF_ARRINDEX (int) [0]
- Specify the array from/to which the channel value should be
transfered. If the mode of the file is XDF_READ and the value is
negative, the channel will not be read. If the mode is XDF_WRITE
and the value is negative, the function will fail.
- XDF_CF_ARROFFSET (int) [0 for channel 0, packed
channels for the rest]
- Specify the offset in the array from/to which the channel
value should be transfered.
- XDF_CF_ARRDIGITAL (int) [0 if writing, 1 if
reading]
- Indicate that the data in the array from/to which the
channel value should be transfered is provided in digital unit. This means
in practice that no scaling is performed during the transfer from/to the
disk (non zero indicate no scaling).
- XDF_CF_ARRTYPE (enum xdftype) [same as
XDF_CF_STOTYPE]
- specify the type in the channel should casted to/from when
accessed in the array.
- XDF_CF_PMIN (double) [min of
XDF_CF_ARRTYPE]
- Set/get the minimal value that a physical value can get.
Cannot be set if XDF_READ.
- XDF_CF_PMAX (double) [max of
XDF_CF_ARRTYPE]
- Set/get the maximal value that a physical value can get.
Cannot be set if XDF_READ.
- XDF_CF_STOTYPE (enum xdftype) [any datatype
supported by file type]
- Specify the type stored in the file of the channel value.
If the XDF file has been opened in XDF_READ, this field cannot be set. If
this field is successfully set, it will set as well the digital minimum (
XDF_CF_DMIN) and the digital maximum (XDF_CF_MAX) to the
minimum and maximum values allowed by the data type.
- XDF_CF_DMIN (double) [min of
XDF_CF_STOTYPE]
- Set/get the minimal value that a digital value can get.
Cannot be set if XDF_READ. This is also automatically set by
XDF_CF_STOTYPE.
- XDF_CF_DMAX (double) [min of
XDF_CF_STOTYPE]
- Set/get the maximal value that a digital value can get.
Cannot be set if XDF_READ. This is also automatically set by
XDF_CF_STOTYPE.
- XDF_CF_LABEL (const char*) [""]
- Set/get the label of the channel. Cannot be set if
XDF_READ.
- XDF_CF_UNIT (const char*) [""] {EDF BDF
GDF}
- Set/get the unit of the channel. Cannot be set if
XDF_READ.
- XDF_CF_TRANSDUCTER (const char*) [""] {EDF
BDF GDF}
- Set/get the type of sensor used for this channel. Cannot be
set if XDF_READ.
- XDF_CF_PREFILTERING (const char*) [""]
{EDF BDF GDF}
- Set/get the information about the filters already applied
on channel data. Cannot be set if XDF_READ.
- XDF_CF_ELECPOS (double[3]) [0,0,0] {GDF}
- Position of the sensor/electrode expressed in X,Y,Z
components Cannot be set if XDF_READ.
- XDF_CF_IMPEDANCE (double) [0] {GDF}
- Impedance of the sensor/electrode. Cannot be set if
XDF_READ.
RETURN VALUE¶
The two functions returns 0 in case of success. Otherwise -1 is returned and
errno is set appropriately.
ERROR¶
- EINVAL
- ch is NULL or field is not a proper value of
the enumeration xdffield
- EPERM
- The request submitted to xdf_set_chconf() is not
allowed for this channel or is forbidden for file opened with the mode
XDF_READ.
- EDOM
- The value set in xdf_set_chconf() as digital or
physical min/max (fields XDF_CF_{D/P}{MIN/MAX}) goes beyond the limits of
respectively the stored or array data type.
EXAMPLES¶
Example of usage of
xdf_set_chconf():
/* Assume xdf referenced an XDF file opened for writing */
unsigned int iarray = 2, offset = 0;
const char label[] = "Channel EEG";
hchxdf ch = xdf_add_channel(xdf);
xdf_set_chconf(ch, XDF_CF_ARRINDEX, iarray,
XDF_CF_ARROFFSET, offset,
XDF_CF_LABEL, label,
XDF_NOF);
Example of usage of
xdf_get_chconf():
/* Assume xdf referenced an XDF file opened for reading */
unsigned int iarray, offset;
const char label[128];
hchxdf ch = xdf_get_channel(xdf, 1);
xdf_get_chconf(ch, XDF_CF_ARRINDEX, &iarray,
XDF_CF_ARROFFSET, &offset,
XDF_CF_LABEL, &label,
XDF_NOF);
printf("iarray = %u\n", iarray);
printf("offset = %u\n", offset);
printf("label = %s\n", label);
SEE ALSO¶
xdf_copy_chconf(3)