Hi,
Currently the HDF5 FAQ says about bitfields ...
How are these stored then? Any sort of padding or what?
We currently do not pack them, so a 13-bit field in a 32-bit
datatype still takes up 4 bytes of space. This is not ideal, but
it is a fairly complicated problem to pack the bits on disk (in
light of using bitfields in compound, array and variable-length
datatypes mostly). Eventually we should fix this.
Is there any plan to implement packed bit fields in the near
future?
Thanks,
Steve
···
--
Steve Sullivan steves@ucar.edu 303-497-2823
FL/2, Research Applications Laboratory
National Center for Atmospheric Research
PO Box 3000
Boulder CO 80307
USA
Steve,
Hi,
Currently the HDF5 FAQ says about bitfields ...
How are these stored then? Any sort of padding or what?
We currently do not pack them, so a 13-bit field in a 32-bit
datatype still takes up 4 bytes of space. This is not ideal, but
it is a fairly complicated problem to pack the bits on disk (in
light of using bitfields in compound, array and variable-length
datatypes mostly). Eventually we should fix this.
Is there any plan to implement packed bit fields in the near
future?
We will update FAQ. In 1.8.* we provide the n-bit filter to pack data in the file; see
http://www.hdfgroup.org/HDF5/doc/RM/RM_H5P.html#Property-SetNbit.
C example is available from http://www.hdfgroup.org/ftp/HDF5/examples/examples-by-api/api18-c.html See Dataset section.
Elena
···
On Sep 20, 2010, at 10:43 AM, Steve Sullivan wrote:
Thanks,
Steve
--
Steve Sullivan steves@ucar.edu 303-497-2823
FL/2, Research Applications Laboratory
National Center for Atmospheric Research
PO Box 3000
Boulder CO 80307
USA
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