Question

I’ve created an array with 3 doubles and one boolen using numpy and written them to file using h5py:

import numpy as np
import h5py

data = np.zeros(10, dtype=[("THETA",np.double),("PHI",np.double),("PSI",np. double),("FLAG",np.bool)])

with h5py.File("testout.h5") as f:
    f.create_dataset("data", data=data)

h5py creates an enum type for the boolean field:

HDF5 "testout.h5" {
GROUP "/" {
   DATASET "data" {
      DATATYPE  H5T_COMPOUND {
         H5T_IEEE_F64LE "THETA";
         H5T_IEEE_F64LE "PHI";
         H5T_IEEE_F64LE "PSI";
         H5T_ENUM {
            H5T_STD_I8LE;
            "FALSE"            0;
            "TRUE"             1;
         } "FLAG";
      }
      DATASPACE  SIMPLE { ( 10 ) / ( 10 ) }
   }
}
}

now I need to read this file using C, and things get complicated:

typedef enum {
    false = 0;
    true
} bool;

typedef struct {
    double THETA, PHI, PSI;
    bool FLAG;
} pointing_t;

I do not understand how to define a type that has an enum:

hid_t memtype = H5Tcreate (H5T_COMPOUND, sizeof(pointing_t));
H5Tinsert (memtype, "THETA", HOFFSET (pointing_t, THETA),  H5T_NATIVE_DOUBLE);
H5Tinsert (memtype, "PHI", HOFFSET (pointing_t, PHI),  H5T_NATIVE_DOUBLE);
H5Tinsert (memtype, "PSI", HOFFSET (pointing_t, PSI),  H5T_NATIVE_DOUBLE);
# this should be an ENUM!!
H5Tinsert (memtype, "FLAG", HOFFSET (pointing_t, FLAG),  H5T_NATIVE_DOUBLE);

I pasted a complete “not working” example on gist that tries to read the hdf5 files created with the previous python snippet:

http://gist.github.com/3168909

anybody has suggestions?
thanks!

Answer 1

Found the solution, you need to create an enum type in hdf5:

#define CPTR(VAR,CONST) ((VAR)=(CONST),&(VAR))
hid_t boolenumtype = H5Tcreate(H5T_ENUM, sizeof(bool));
status = H5Tenum_insert(boolenumtype, "FALSE",   CPTR(val, FALSE ));
printf ("H5Tenum_insert (FALSE): %i\n", status);
status = H5Tenum_insert(boolenumtype, "TRUE",   CPTR(val, TRUE ));
printf ("H5Tenum_insert (TRUE): %i\n", status);

and then add it to the memtype:

H5Tinsert (memtype, "FLAG", HOFFSET (pointing_t, FLAG),  boolenumtype);

the example on github is now working.