!
! This example opens a file, and extracts
! the bit field from a subset of a dataset. 
! The values are returned as a base-10 integer.
! Main illustrative function: H5LTread_bitfield_value_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 = &
       "SVI01-GIMFG_NPP_d2003125_t101038_e10116_b9_c2005829153351_dev.h5"

  CHARACTER(LEN=78), PARAMETER :: DATASET = &
       "/All_Data/VIIRS-I1-SDR_All/QF_VIIRSI1SDR_Array"
  
  INTEGER, PARAMETER :: num_flags = 1

  INTEGER, DIMENSION(1:3) :: dim_qf_data =(/6,5,num_flags/) ! Dimensions of qf_data
  INTEGER, DIMENSION(1:num_flags,1:6,1:5) :: qf_data ! Read buffer, transposed because data written with C convention
  INTEGER, DIMENSION(1:1) :: offset = (/2/)  ! Starting bits to be extracted from element 
  INTEGER, DIMENSION(1:1) :: length = (/2/)  ! Number of bits to be extracted for each value 
  INTEGER(hid_t) :: file, space ! Handles 
  INTEGER(hid_t) :: qf_dset
  INTEGER :: status
  INTEGER(hsize_t), DIMENSION(1:3) :: start = (/0,0,0/) 
  INTEGER(hsize_t), DIMENSION(1:3) :: count = (/num_flags,6,5/)
  INTEGER :: i, j
  !
  ! Initialize FORTRAN interface.
  !
  CALL H5open_f(status)
  !
  ! Open file.
  CALL H5Fopen_f(FILENAME, H5F_ACC_RDONLY_F, file, status)
  ! 
  ! Open the data set
  CALL H5Dopen_f(file, DATASET, qf_dset, status)
  !
  ! Get dataspace and allocate memory for read buffer. Quality flags dataset
  ! has the same dimensionality as corresponding product dataset
  ! we are using its dimensions for illustration purposes only.
   
  CALL H5Dget_space_f(qf_dset, space, status)
  CALL H5Sselect_hyperslab_f(space, H5S_SELECT_SET_F, start, count, status)

  !
  ! For each element read the value that takes first two bits and 
  ! store it in a char buffer. This selects all the elements (H5S_ALL)
   
  CALL H5LTread_bitfield_value_f(qf_dset, num_flags, offset, length, space, qf_data, dim_qf_data, status)

  CALL H5Sclose_f(space, status)

  ! Print out the bit field
  WRITE(*,'("Bit Field:")')
  DO i = 1, 6
     WRITE( *, '(A)', ADVANCE = "NO") "["
     DO j = 1, 5
        WRITE( *, '(A)', ADVANCE = "NO") " {"
        WRITE( *, '(20i2)', ADVANCE = "NO") qf_data(1,i,j)
        WRITE( *, '(A)', ADVANCE = "NO") "} "
     ENDDO
     WRITE(*,'(A)',ADVANCE="YES") "]"
  ENDDO
END PROGRAM main