!
!   This example copies subregions of the satellite data 'SatelliteZenithAngle'
!   'SatelliteAzimuthAngle' and 'SatelliteRange' under '/All_Data/VIIRS-MOD-GTM-EDR-GEO_All'
!   to one dataset,'Satellite', located at '/Data_Products/Subset' of the NPP
!   file. 
!   Main illustrative functions: H5LRcreate_region_references_f and H5LRmake_dataset_f
!

PROGRAM main
  
  USE ISO_C_BINDING
  USE HDF5 ! module of HDF5 library
  USE H5LT ! module of H5LT
  USE H5HL_REGION

  IMPLICIT NONE
  CHARACTER(LEN=78), PARAMETER :: filename = &
       "GMGTO_npp_d20030125_t0657104_e0659047_b00014_c20090811150425926728_unkn_SCI.h5"

  INTEGER(hid_t) :: file_id  ! file identifier
  INTEGER(hsize_t), DIMENSION(1:12) :: block_coord = (/52,4,54,8,52,4,54,8,52,4,54,8/) ! hyperslab coordinates, (52,4)-(54,8), for
                                                                                       ! 'SatelliteZenithAngle', 'SatelliteAzimuthAngle', 'SatelliteRange'
  TYPE(hdset_reg_ref_t_f), DIMENSION(1:3) ::  ref_subset ! region references to hyperslabs of 'SatelliteZenithAngle', 'SatelliteAzimuthAngle', 'SatelliteRange'
  CHARACTER(LEN=80), DIMENSION(1:3) :: path ! full paths to the satellite target datasets for the region references
  INTEGER(hsize_t), DIMENSION(1:1) :: dims = (/3/)
  INTEGER(hid_t), DIMENSION(1:3) ::  file_id_array  ! identifiers describing which HDF5 file the corresponding region reference belongs to
  INTEGER :: status

  path(1)= "/All_Data/VIIRS-MOD-GTM-EDR-GEO_All/SatelliteZenithAngle"
  path(2)= "/All_Data/VIIRS-MOD-GTM-EDR-GEO_All/SatelliteAzimuthAngle"
  path(3)= "/All_Data/VIIRS-MOD-GTM-EDR-GEO_All/SatelliteRange"

  !
  ! Initialize FORTRAN interface.
  !
  CALL H5open_f(status)
  !
  ! OPEN the NPP file.
  !
  CALL H5Fopen_f(filename, H5F_ACC_RDWR_F, file_id, status)
  !
  ! We are creating the data set in the same file, so fill the file_id path with the same file id.
  !
  file_id_array(1:3) = file_id
  !
  ! Create three region references pointing to hyperslabs with block coordinates (52,4)-(54,8) in
  ! 'SatelliteZenithAngle', 'SatelliteAzimuthAngle' and 'SatelliteRange' datasets. 
  !
  CALL H5LRcreate_region_references_f(file_id, 3_size_t, path, block_coord, ref_subset, status);
  ! 
  ! Combine the three datasets into one dataset, 'Satellite', under '/Data_Products/Subset', 
  ! resulting in a final dataset of size (0,0)-(14,2). Notice the group 'Subset' did not exist
  ! so the FUNCTION automatically created the necessary intermediate group.
  !
  CALL H5LRmake_dataset_f(file_id, "/Data_Products/Subset/Satellite", H5T_NATIVE_REAL, 3_size_t, file_id_array, ref_subset, status)
  
  CALL H5Fclose_f(file_id, status)
  
END PROGRAM main