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Retrieves the metadata for an object specified by an identifier


H5O_GET_INFO3 (loc_id, oinfo, fields)


herr_t H5Oget_info3 ( hid_t loc_id, H5O_info2_t *oinfo, unsigned fields )

SUBROUTINE h5oget_info_f(object_id, object_info, hdferr, fields)

    INTEGER(HID_T)  , INTENT(IN)            :: object_id
    TYPE(h5o_info_t), INTENT(OUT), TARGET   :: object_info
    INTEGER         , INTENT(OUT)           :: hdferr
    INTEGER         , INTENT(IN), OPTIONAL  :: fields

Related Fortran2003 Derived Type:  h5o_info_t


  TYPE, BIND(C) :: h5o_info_t
     INTEGER(C_LONG)     :: fileno     ! File number that object is located in
     TYPE(H5O_TOKEN_T_F) :: token      ! Token for object in file
     INTEGER(C_INT)      :: type       ! Basic object type (group, dataset, etc.)
     INTEGER             :: rc         ! Reference count of object

     INTEGER, DIMENSION(8) :: atime ! Access time         !    -- NOTE --
     INTEGER, DIMENSION(8) :: mtime ! Modification time   ! Returns an integer array
     INTEGER, DIMENSION(8) :: ctime ! Change time         ! as specified in the Fortran
     INTEGER, DIMENSION(8) :: btime ! Birth time          ! intrinsic DATE_AND_TIME(VALUES)

     INTEGER(hsize_t) :: num_attrs  ! # of attributes attached to object
  END TYPE h5o_info_t

hid_t   loc_idIN: Identifier for object of type specified by  H5O_type_t; may be a file, group, dataset, named datatype or attribute identifier
H5O_info2_t * oinfo    OUT: Buffer in which to return object information
unsigned int fields IN: Flags specifying the fields to include in oinfo


H5O_GET_INFO3 specifies an object by its identifier,  loc_id , and retrieves the metadata describing that object in  oinfo , an  H5O_info2_t  struct.

The H5O_info2_t  struct is defined (in  H5Opublic.h) as follows :

src / H5Opublic.h [129:141]  hdf5_1_12  HDFFV/hdf5
    } mesg;
} H5O_hdr_info_t;

/* Data model information struct for objects */
/* (For H5Oget_info / H5Oget_info_by_name / H5Oget_info_by_idx version 3) */
typedef struct H5O_info2_t {
    unsigned long fileno;    /* File number that object is located in */
    H5O_token_t   token;     /* Token representing the object        */
    H5O_type_t    type;      /* Basic object type (group, dataset, etc.) */
    unsigned      rc;        /* Reference count of object            */
    time_t        atime;     /* Access time                          */
    time_t        mtime;     /* Modification time                    */
    time_t        ctime;     /* Change time                          */

Note the following about  H50_info2_t:

  • Of the four time fields (atime,  mtime,  ctime, and  btime) only  ctime  has been implemented.
  • The  atime  value is the last time the object was read or written.
  • The  mtime  value is the last time the raw data in the object was changed.
  • The  ctime  value is the last time the metadata for the object was changed.
  • The  btime  value is the time the object was created.

H5O_token_t is defined in H5public.h as follows:

src / H5public.h [337:341]  hdf5_1_12  HDFFV/hdf5
 * Allocation statistics info struct
typedef struct H5_alloc_stats_t {
    unsigned long long total_alloc_bytes;        /* Running count of total # of bytes allocated */

The  H5O_type_t  enum indicates the object type and is defined (in  H5Opublic.h) as follows:

src / H5Opublic.h [101:109]  hdf5_1_12  HDFFV/hdf5
/* Public Typedefs */

/* Types of objects in file */
typedef enum H5O_type_t {
    H5O_TYPE_UNKNOWN = -1,   /* Unknown object type		*/
    H5O_TYPE_GROUP,          /* Object is a group		*/
    H5O_TYPE_DATASET,        /* Object is a dataset		*/
    H5O_TYPE_NAMED_DATATYPE, /* Object is a named data type	*/

Note that object_id refers only to the types specified by H5O_type_t.

The fields parameter contains flags to determine which fields will be filled in in the H5O_info2_t struct returned in oinfo. These flags are defined in the H5Opublic.h file:

H5O_INFO_BASICFill in the fileno, addr, type, and rc fields
H5O_INFO_TIMEFill in the atime, mtime, ctime, and btime fields
H5O_INFO_NUM_ATTRSFill in the num_attrs field
H5O_INFO_HDRFill in the hdr field
H5O_INFO_META_SIZEFill in the meta_size field

If you are iterating through a lot of different objects to retrieve information via the H5O_GET_INFO family of routines, you may see memory building up. This can be due to memory allocation for metadata such as  object headers and messages when the iterated objects are put into the metadata cache.

If the memory buildup is not desirable, you can configure a smaller cache via H5F_SET_MDC_CONFIG or set the file access property list via H5P_SET_MDC_CONFIG. A smaller sized cache will force metadata entries to be evicted from the cache, thus freeing the memory associated with the entries.


Returns a non-negative value if successful; otherwise returns a negative value.


examples / h5_attribute.c [189:205]  hdf5_1_12  HDFFV/hdf5
    ret = H5Oget_info3(dataset, &oinfo, H5O_INFO_NUM_ATTRS);
    for (i = 0; i < (unsigned)oinfo.num_attrs; i++) {
        attr       = H5Aopen_by_idx(dataset, ".", H5_INDEX_CRT_ORDER, H5_ITER_INC, (hsize_t)i, H5P_DEFAULT,
        atype      = H5Aget_type(attr);
        type_class = H5Tget_class(atype);
        if (type_class == H5T_STRING) {
            atype_mem = H5Tget_native_type(atype, H5T_DIR_ASCEND);
            ret       = H5Aread(attr, atype_mem, string_out);
            printf("Found string attribute; its index is %d , value =   %s \n", i, string_out);
            ret = H5Tclose(atype_mem);
        ret = H5Aclose(attr);
        ret = H5Tclose(atype);


     USE HDF5 ! This module contains all necessary modules


     CHARACTER(LEN=11), PARAMETER :: filename = "compound.h5" ! File name
     CHARACTER(LEN=8), PARAMETER :: dsetname = "Compound"     ! Dataset name
     INTEGER, PARAMETER :: dimsize = 6 ! Size of the dataset

     INTEGER(HID_T) :: file_id       ! File identifier

Release    Change
1.12.0Function was introduced in this release.

--- Last Modified: March 13, 2020 | 11:03 AM