Identifier (H5I)

R2026b

HDF5 object identifiers

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Description

Use the MATLAB® HDF5 identifier interface, H5I, to handle HDF5 identifiers and access information about them.

HDF5 identifiers uniquely identify common HDF5 resources, such as files, groups, datasets, dataspaces, attributes and properties. They are returned by the functions that create or open these resources and are passed to functions that operate on or with these resources. You must close an object identifier after it is processed.

Functions

H5I.dec_ref

Decrement reference count

refcount = H5I.dec_ref(objID) decrements the reference count of the object specified by objID and returns the new count.

H5I.get_file_id

File identifier for specified object

fileID = H5I.get_file_id(objID) returns the identifier of the file associated with the object specified by objID.

H5I.get_name

Name of object

name = H5I.get_name(objID) returns the name of the group, dataset, or datatype specified by objID. If no name is attached to the object, H5I.get_name returns an empty character vector.

name = H5I.get_name(objID,"TextEncoding",encoding) additionally specifies the text encoding to use to interpret the object name.

Input Arguments

  • objID — Group, dataset, or datatype identifier.

  • encoding — Text encoding, specified as one of these values:

    • "system" — Use the system default encoding to interpret the object name. "system" is the default value of "TextEncoding".

    • "UTF-8" — Use UTF-8 encoding to interpret the object name.

Note

Starting in R2020a, the H5I.get_name function only accepts committed (previously called named) HDF5 datatypes as input arguments, and will error if you pass other datatypes as input. In releases R2019b and earlier, H5I.get_name does not error if you pass other datatypes as input.

To verify that the input is a committed HDF5 datatype, call the H5T.committed function on it. The H5T.committed function returns a value of 1 if the input is a committed HDF5 datatype, and a value of 0 if it is not.

H5I.get_ref

Reference count of object

refcount = H5I.get_ref(objID) returns the reference count of the object specified by objID.

H5I.get_type

Type of object

objType = H5I.get_type(objID) returns the type of the object identified by objID.

Output Arguments

  • objType — Object type, interpreted as one of these:

    • "H5I_FILE" — File. The numeric equivalent is 1.

    • "H5I_GROUP" — Group. The numeric equivalent is 2.

    • "H5I_DATATYPE" — Datatype. The numeric equivalent is 3.

    • "H5I_DATASPACE" — Dataspace. The numeric equivalent is 4.

    • "H5I_DATASET" — Dataset. The numeric equivalent is 5.

    • "H5I_ATTR" — Attribute. The numeric equivalent is 6.

H5I.inc_ref

Increment reference count of specified object

refcount = H5I.inc_ref(objID) increments the reference count of the object specified by objID and returns the new count.

H5I.is_valid

Determine if specified identifier is valid

output = H5I.is_valid(objID) returns a positive value if the identifier objID is valid, and 0 if it is not.

Examples

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Open Live Script
fid = H5F.open("example.h5");
gid = H5G.open(fid,"/g4");
fid2 = H5I.get_file_id(gid);
name = H5F.get_filesize(fid2);
fprintf("The file size is %d bytes.\n",name)
The file size is 35072 bytes.

H5G.close(gid)
H5F.close(fid)
H5F.close(fid2)

Version History

Introduced before R2006a

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See Also

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