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Compound Datatypes


Contents:


Creating Compound Datatypes

A compound datatype is similar to a struct in C or a common block in FORTRAN. It is a collection of one or more datatypes and can include compound datatypes. To create and use a compound datatype you need to be familiar with various properties of the compound datatype: Properties of members of a compound datatype are defined when the member is added to the compound datatype and cannot be subsequently modified.

Compound datatypes must be built out of other datatypes. First, one creates an empty compound datatype and specifies its total size. Then members are added to the compound datatype in any order.

Programming Example

Description

This example shows how to create a compound datatype, write an array to the file which uses the compound datatype, and read back subsets of the members.

The program outputs the following:

Field c : 
1.0000 0.5000 0.3333 0.2500 0.2000 0.1667 0.1429 0.1250 0.1111 0.1000 

Field a : 
0 1 2 3 4 5 6 7 8 9 

Field b : 
0.0000 1.0000 4.0000 9.0000 16.0000 25.0000 36.0000 49.0000 64.0000 81.0000 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Remarks

File Contents

HDF5 "SDScompound.h5" {
GROUP "/" {
   DATASET "ArrayOfStructures" {
      DATATYPE {
         H5T_STD_I32BE "a_name";
         H5T_IEEE_F32BE "b_name";
         H5T_IEEE_F64BE "c_name";
      }
      DATASPACE { SIMPLE ( 10 ) / ( 10 ) }
      DATA {
         {
            [ 0 ],
            [ 0 ],
            [ 1 ]
         },
         {
            [ 1 ],
            [ 1 ],
            [ 0.5 ]
         },
         {
            [ 2 ],
            [ 4 ],
            [ 0.333333 ]
         },
         {
            [ 3 ],
            [ 9 ],
            [ 0.25 ]
         },
         {
            [ 4 ],
            [ 16 ],
            [ 0.2 ]
         },
         {
            [ 5 ],
            [ 25 ],
            [ 0.166667 ]
         },
         {
            [ 6 ],
            [ 36 ],
            [ 0.142857 ]
         },
         {
            [ 7 ],
            [ 49 ],
            [ 0.125 ]
         },
         {
            [ 8 ],
            [ 64 ],
            [ 0.111111 ]
         },
         {
            [ 9 ],
            [ 81 ],
            [ 0.1 ]
         }
      }
   }
}
}


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Last Modified: November 21, 2001