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5.3 The Vgroup Interface

 The Vgroup interface consists of routines for creating and accessing vgroups, and getting information about vgroups and their members.

5.3.1 Vgroup Interface Routines

Vgroup interface routine names are prefaced by "V" in C and by "vf" in FORTRAN-77. These routines are categorized as follows:

The Vgroup interface routines are listed in Table 5A below and described in the following sections.

TABLE 5A - Vgroup Interface Routines

Category
Routine Name
Description
C
FORTRAN-77
Access/Create
 Vstart vfstart Initializes the Vdata and Vgroup interfaces (Section 5.4.1 on page 192)

Vattach vfatch Establishes access to a vgroup (Section 5.4.1 on page 192)

Vdetach vfdtch Terminates access to a vgroup (Section 5.4.2 on page 193)

Vend vfend Terminates access to the Vdata and Vgroup interfaces (Section 5.4.2 on page 193)

Manipulation
 Vaddtagref vfadtr Adds an HDF data object to a vgroup (Section 5.5.2 on page 195)

Vdelete vdelete Removes a vgroup from a file (Section 5.7.1 on page 205)

Vdeletetagref vfdtr Detaches a member from a vgroup (Section 5.7.2 on page 205)

Vinsert vfinsrt Adds a vgroup or vdata to an existing vgroup (Section 5.5.3 on page 195)

Vsetclass vfscls Assigns a class name to a vgroup (Section 5.5.1 on page 195)

Vsetname vfsnam Assigns a name to a vgroup (Section 5.5.1 on page 195)

Vgroup Inquiry
 Vfind vfind Returns the reference number of a vgroup given its name (Section 5.6.1.5 on page 200)

Vfindclass vfndcls Returns the reference number of a vgroup specified by class name (Section 5.6.1.6 on page 200)

Vgetclass vfgcls Retrieves the class of a vgroup (Section 5.6.1.4 on page 199)

Vgetid vfgid Returns the reference number for the next vgroup in the HDF file (Section 5.6.1.2 on page 198)

Vgetname vfgnam Retrieves the name of a vgroup (Section 5.6.1.3 on page 199)

Vgetversion vfgver Returns the vgroup version of a vgroup (Section 5.8.1 on page 205)

Vinquire vfinq Retrieves general information about a vgroup (Section 5.9.2 on page 209)

Vlone vflone Retrieves the reference numbers of vgroups that are not members of other vgroups (Section 5.6.1.1 on page 198)

Vntagrefs vfntr Returns the number of tag/reference number pairs contained in the specified vgroup (Section 5.6.2.1 on page 201)

VQueryref vqref Returns the reference number of a vgroup (Section 5.6.2.9 on page 204)

VQuerytag vqtag Returns the tag of a vgroup (Section 5.6.2.10 on page 204)

Member Inquiry
Vflocate vffloc Locates a vdata in a vgroup given a list of field names (Section 5.6.2.7 on page 203)

Vgetnext vfgnxt Returns the identifier of the next vgroup or vdata in a vgroup (Obsolete) (Section 5.9.1 on page 209)

Vgettagref vfgttr Retrieves a tag/reference number pair for a data object in the vgroup (Section 5.6.2.2 on page 201)

Vgettagrefs vfgttrs Retrieves the tag/reference number pairs of all of the data objects belonging to a vgroup (Section 5.6.2.3 on page 201)

Vinqtagref vfinqtr Determines whether a data object belongs to a vgroup (Section 5.6.2.4 on page 202)

Visvg vfisvg Determines whether a data object is a vgroup within another vgroup (Section 5.6.2.5 on page 202)

Visvs vfisvs Determines whether a data object is a vdata within a vgroup (Section 5.6.2.6 on page 202)

Vnrefs vnrefs Retrieves the number of tags of a given tag type in a vgroup (Section 5.6.2.8 on page 203)

Attributes
Vattrinfo vfainfo Retrieves information of a vgroup attribute (Section 5.8.2 on page 206)

Vfindattr vffdatt Returns the index of a vgroup attribute given the attribute name (Section 5.8.6 on page 208)

Vgetattr vfgnatt/ vfgcatt Retrieves the values of a vgroup attribute (Section 5.8.5 on page 208)

Vnattrs vfnatts Returns the total number of vgroup attributes (Section 5.8.3 on page 207)

Vsetattr vfsnatt/ vfscatt Sets the attribute of a vgroup (Section 5.8.4 on page 207)

5.3.2 Identifying Vgroups in the Vgroup Interface

 The Vgroup interface identifies vgroups in several ways. In some cases, a vgroup can be accessed directly through the use of its unique reference number. In other cases, the reference number and the routine Vattach are used to obtain a vgroup identifier. The reference number of a vgroup can be obtained from the name or the class of the vgroup, or by sequentially traversing the file. The concept of reference number is discussed in Section 2.2.2.1 on page 8.

When a vgroup is attached or created, it is assigned an identifier, called vgroup id. After a vgroup has been attached or created, its identifier is used by the Vgroup interface routines in accessing the vgroup.


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HDF User's Guide - 07/21/98, NCSA HDF Development Group.