Main Content


Gateway to HDF Vgroup (V) interface


[out1,...,outN] = hdfv(funcstr,input1,...,inputN)


hdfv is the MATLAB® gateway to the HDF Vgroup (V) interface.

[out1,...,outN] = hdfv(funcstr,input1,...,inputN) returns one or more outputs corresponding to the V function in the HDF library specified by functstr.

There is a one-to-one correspondence between V functions in the HDF library and valid values for funcstr. For example, hdfv('nattrs',vgroup_id) corresponds to the C library call Vnattrs(vgroup_id).

Access Functions

Access functions open files, initialize the Vgroup interface, and access individual groups. They also terminate access to vgroups and the Vgroup interface and close HDF files.

Value of funcstrFunction SyntaxDescription
'start'status = hdfv('start',file_id)Initializes the V interface.
'attach'vgroup_id = hdfv('attach',file_id,vgroup_ref,access)Establishes access to a vgroup. access can be 'r' or 'w'.
'detach'status = hdfv('detach',vgroup_id)Terminates access to a vgroup.
'end'status = hdfv('end',file_id)Terminates access to the V interface.

Create Functions

Create functions organize, label, and add data objects to vgroups.

Value of funcstrFunction SyntaxDescription
'setclass'status = hdfv('setclass',vgroup_id,class)Assigns a class to a vgroup.
'setname'status = hdfv('setname',vgroup_id,name)Assigns a name to a vgroup.
'insert'ref = hdfv('insert',vgroup_id, id)Adds a vgroup or vdata to an existing group. id can be a vdata id or a vgroup id.
'addtagref'status = hdfv('addtagref',vgroup_id,tag,ref)Adds any HDF data object to an existing vgroup.
'setattr'status = hdfv('setattr',vgroup_id,name,A)Sets the attribute of a vgroup.

File Inquiry Functions

File inquiry functions return information about how vgroups are stored in a file. They are useful for locating vgroups in a file.

Value of funcstrFunction SyntaxDescription
'lone'[refs,count] = hdfv('lone',file_id,maxsize)Returns the reference numbers of vgroups not included in other vgroups.
'getid'next_ref = hdfv('getid',file_id,vgroup_ref)Returns the reference number for the next vgroup in the HDF file.
'find'vgroup_ref = hdfv('find',file_id,vgroup_name)Returns the reference number of the vgroup with the specified name if successful and zero otherwise.
'findclass'vgroup_ref = hdfv('findclass',file_id,class)Returns the reference number of the vgroup with the specified class.

Vgroup Inquiry Functions

Vgroup inquiry functions provide specific information about a specific vgroup. This information includes the class, name, member count, and additional member information.

Value of funcstrFunction SyntaxDescription
'getclass'[class_name,status] = hdfv('getclass',vgroup_id)Returns the name of the class of the specified group.
'getname'[vgroup_name,status] = hdfv('getname',vgroup_id)Returns the name of the specified group.
'inquire'[num_entries,name,status] = hdfv('inquire',vgroup_id)Returns the number of entries and the name of a vgroup.
'isvg'status = hdfv('isvg',vgroup_id,ref)Checks if the object specified by ref refers to a child vgroup of the vgroup specified by vgroup_id.
'isvs'status = hdfv('isvs',vgroup_id,vdata_ref)Checks if the object specified by vdata_ref refers to a child vdata of the vgroup specified by vgroup_id.
'gettagref'[tag,ref,status] = hdfv('gettagref',vgroup_id,index)Retrieves a tag/reference number pair for a data object in the specified vgroup.
'ntagrefs'count = hdfv('ntagrefs',vgroup_id)Returns the number of tag/reference number pairs contained in the specified vgroup.
'gettagrefs'[tag,refs,count] = hdfv('gettagrefs',vgroup_id,maxsize)Retrieves the tag/reference pairs of all the data objects within a vgroup.
'inqtagref'tf = hdfv('inqtagref',vgroup_id,tag,ref)Checks if an object belongs to a vgroup.
'getversion'version = hdfv('getversion',vgroup_id)Queries the vgroup version of a given vgroup.
'nattrs'count = hdfv('nattrs',vgroup_id)Queries the total number of vgroup attributes.
'attrinfo'[name,data_type,count,nbytes,status] = hdfv('attrinfo',vgroup_id,... attr_index)Queries information on a given vgroup attribute.
'getattr'[values,status] = hdfv('getattr',vgroup_id,attr_index)Queries the values of a given attribute.
'Queryref'ref = hdfv('Queryref',vgroup_id)Returns the reference number of the specified vgroup.
'Querytag'tag = hdfv('Querytag',vgroup_id)Returns the tag of the specified vgroup.
'flocate'vdata_ref = hdfv('flocate',vgroup_id,field)Returns the reference number of the vdata containing the specified field name in the specified vgroup.
'nrefs'count = hdfv('nrefs',vgroup_id,tag)Returns the number of data objects with the specified tag in the specified vgroup.

Output Arguments

A status or identifier output of -1 indicates that the operation failed.

Version History

Introduced before R2006a