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 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 funcstr | Function Syntax | Description |
|---|---|---|
'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 organize, label, and add data objects to vgroups.
Value of funcstr | Function Syntax | Description |
|---|---|---|
'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 return information about how vgroups are stored in a file. They are useful for locating vgroups in a file.
Value of funcstr | Function Syntax | Description |
|---|---|---|
'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 provide specific information about a specific vgroup. This information includes the class, name, member count, and additional member information.
Value of funcstr | Function Syntax | Description |
|---|---|---|
'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. |
A status or identifier output of -1 indicates
that the operation failed.
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