HDF5 Fortran90 Flags, Datatypes and User’s Notes

Fortran90 Datatypes

The Fortran90 HDF5 datatypes are listed in HDF5 Predefined Datatypes

Fortran90 Flags

The Fortran90 HDF5 flags have the same meanings as the C flags defined in the HDF5 Reference Manual and the HDF5 User's Guide.

File access flags

      H5F_ACC_RDWR_F 
      H5F_ACC_RDONLY_F
      H5F_ACC_TRUNC_F

      H5F_ACC_EXCL_F
      H5F_ACC_DEBUG_F

      H5F_SCOPE_LOCAL_F
      H5F_SCOPE_GLOBAL_F

Group management flags

      H5G_UNKNOWN_F
      H5G_LINK_F
      H5G_GROUP_F

      H5G_DATASET_F
      H5G_TYPE_F
      H5G_LINK_ERROR_F

      H5G_LINK_HARD_F
      H5G_LINK_SOFT_F

Dataset format flags

      H5D_COMPACT_F

      H5D_CONTIGUOUS_F

      H5D_CHUNKED_F

MPI IO data transfer flags

      H5FD_MPIO_INDEPENDENT_F

      H5FD_MPIO_COLLECTIVE_F

Error flags

      H5E_NONE_MAJOR_F 
      H5E_ARGS_F 
      H5E_RESOURCE_F 
      H5E_INTERNAL_F 
      H5E_FILE_F 
      H5E_IO_F 
      H5E_FUNC_F 
      H5E_ATOM_F

      H5E_CACHE_F 
      H5E_BTREE_F 
      H5E_SYM_F 
      H5E_HEAP_F 
      H5E_OHDR_F 
      H5E_DATATYPE_F 
      H5E_DATASPACE_F 
      H5E_DATASET_F

      H5E_STORAGE_F 
      H5E_PLIST_F 
      H5E_ATTR_F 
      H5E_PLINE_F 
      H5E_EFL_F 
      H5E_REFERENCE_F
      H5E_VFL_F 
      H5E_TBBT_F

Object identifier flags

      H5I_FILE_F
      H5I_GROUP_F
      H5I_DATATYPE_F

      H5I_DATASPACE_F
      H5I_DATASET_F
      H5I_ATTR_F

      H5I_BADID_F

Property list flags

      H5P_FILE_CREATE_F 
      H5P_FILE_ACCESS_F

      H5P_DATASET_CREATE_F
      H5P_DATASET_XFER_F

      H5P_MOUNT_F 
      H5P_DEFAULT_F

Reference pointer flags

      H5R_OBJECT_F

      H5R_DATASET_REGION_F

Dataspace flags

      H5S_SCALAR_F 
      H5S_SIMPLE_F

      H5S_SELECT_SET_F
      H5S_SELECT_OR_F

      H5S_UNLIMITED_F
      H5S_ALL_F

Datatype flags

      H5T_NO_CLASS_F 
      H5T_INTEGER_F 
      H5T_FLOAT_F  
      H5T_TIME_F 
      H5T_STRING_F 
      H5T_BITFIELD_F
      H5T_OPAQUE_F 
      H5T_COMPOUND_F 
      H5T_REFERENCE_F
      H5T_ENUM_F

      H5T_ORDER_LE_F 
      H5T_ORDER_BE_F
      H5T_ORDER_VAX_F
      H5T_PAD_ZERO_F
      H5T_PAD_ONE_F
      H5T_PAD_BACKGROUND_F
      H5T_PAD_ERROR_F    
      H5T_SGN_NONE_F   
      H5T_SGN_2_F     
      H5T_SGN_ERROR_F

      H5T_NORM_IMPLIED_F
      H5T_NORM_MSBSET_F
      H5T_NORM_NONE_F 
      H5T_CSET_ASCII_F
      H5T_STR_NULLTERM_F 
      H5T_STR_NULLPAD_F 
      H5T_STR_SPACEPAD_F
      H5T_STR_ERROR_F

HDF5 Fortran90 User’s Notes

About the source code organization

The Fortran APIs are organized in modules parallel to the HDF5 Interfaces. Each module is in a separate file with the name H5*ff.f. Corresponding C stubs are in the H5*f.c files. For example, the Fortran File APIs are in the file H5Fff.f and the corresponding C stubs are in the file H5Ff.c.

Each module contains Fortran definitions of the constants, interfaces to the subroutines if needed, and the subroutines themselves.

Users must use constant names in their programs instead of the numerical values, as the numerical values are subject to change without notice.

About the Fortran APIs

The Fortran APIs come in the form of Fortran subroutines with the following characteristics:

Each Fortran subroutine name is derived from the corresponding C function name by adding "_f" to the name. For example, the name of the C function to create an HDF5 file is H5Fcreate; the corresponding Fortran subroutine is h5fcreate_f.
A description of each implemented Fortran subroutine and its parameters can be found following the description of the corresponding C function in the HDF5 Reference Manual provided with this release.
The parameter list for each Fortran subroutine has two more parameters than the corresponding C function. These additional parameters hold the return value and an error code. The order of the Fortran subroutine parameters may differ from the order of the C function parameters. The Fortran subroutine parameters are listed in the following order:
- Required input parameters
- Output parameters, including return value and error code
- Optional input parameters
For example, the C function to create a dataset has the following prototype:
```
       hid_t H5Dcreate(hid_it loc_id, char *name, hid_t type_id, 
             hid_t space_id, hid_t creation_prp);
```
The corresponding Fortran subroutine has the following form:
```
       SUBROUTINE h5dcreate_f(loc_id, name, type_id, space_id, dset_id, 
             hdferr, creation_prp)
```
The first four parameters of the Fortran subroutine correspond to the C function parameters. The fifth parameter, dset_id, is an output parameter and contains a valid dataset identifier if the value of the sixth output parameter hdferr indicates successful completion. (Error code descriptions are provided with the subroutine descriptions in the Reference Manual.) The seventh input parameter, creation_prp, is optional, and may be omitted when the default creation property list is used.
Parameters to the Fortran subroutines have one of the following predefined datatypes (see the file H5fortran_types.f90 for KIND definitions):
- INTEGER(HID_T) compares with the hid_t datatype in the HDF5 C APIs.
- INTEGER(HSIZE_T) compares with hsize_t in the HDF5 C APIs.
- INTEGER(HSSIZE_T) compares with hssize_t in the HDF5 C APIs.
- INTEGER(SIZE_T) compares with the C size_t datatype.
These integer types usually correspond to 4 or 8 byte integers, depending on the FORTRAN90 compiler and the corresponding HDF5 C library definitions.

The H5R module defines two types of references:
- TYPE(HOBJ_REF_T_F) compares to hobj_ref_t in the HDF5 C API.
- TYPE(HDSET_REG_REF_T_F) compares to hdset_reg_ref_t in the HDF5 C API.
Each Fortran application must call the h5open_f subroutine to initialize the Fortran interface and the HDF5 C Library before calling any HDF5 Fortran subroutine. The application must call the h5close_f subroutine after all calls to the HDF5 Fortran Library to close the Fortran interface and HDF5 C Library.
List of the predefined datatypes can be found in the HDF5 Reference Manual provided with this release. See HDF5 Predefined Datatypes.
When a C application reads data stored from a Fortran program, the data will appear to be transposed due to the difference in the C and Fortran storage orders. For example, if Fortran writes a 4x6 two-dimensional dataset to the file, a C program will read it as a 6x4 two-dimensional dataset into memory. The HDF5 C utilities h5dump and h5ls will also display transposed data, if data is written from a Fortran program.
Fortran indices are 1-based.
Compound datatype datasets can be written or read by atomic fields only.

HDF5 documents and links
Introduction to HDF5
HDF5 User Guide

The HDF Group Help Desk:

Describes HDF5 Release 1.8.7, targeted for May 2011.