function [vginfo, children] = hdfvgroupinfo(filename,dataset,fileID,sdID,anID)
%HDFVGROUPINFO Information about HDF Vgroup
%
%   VGINFO = HDFVGROUPINFO(FILENAME,DATASET) returns a structure whose
%   fields contain information about an HDF Vgroup.  FILENAME is a string
%   that specifies the name of the HDF file.   DATASET is a string
%   specifying the name of the Vgroup (?) or a number specifying the zero based
%   index of the data set.  FILEID is the file identifier returned by
%   hdfh('open',... and SDID is the sds identifier returned by
%   hdfsd('start',...
%
%   Assumptions: 
%               1.  The file has been open.  FILEID is a valid file
%                   identifier.
%               2.  The V, AN and SD interfaces have been started.
%               3.  anID may be -1.
%               4.  The V, AN and SD interface and file will be closed elsewhere.
% 
%   The fields of VGINFO depend on the contents of the file.
%
%   Possible fields of VGINFO are:
%
%   Filename  A string containing the name of the file
%		   
%   Name      A string containing the name of the data set
%
%   Class     A string containing the name of the class of the data set
%
%   Vgroup    An array of structures describing Vgroups
%
%   SDS       An array of structures describing Scientific Data sets
%
%   Vdata     An array of structures describing Vdata sets
%
%   Raster24  An array of structures describing 24-bit raster images  
%
%   Raster8   An array of structures describing 8-bit raster images
%
%   Type      A string describing the type of HDF object 
%
%   Tag       The tag number of this Vgroup
%
%   Ref       The reference number of this vgroup
%

%   Copyright 1984-2002 The MathWorks, Inc. 
%   $Revision: 1.1.6.2 $  $Date: 2004/02/01 22:04:21 $

%Check input arguments
error(nargchk(5,5,nargin, 'struct'));

if ~ischar(filename)
  error('MATLAB:hdfvgroupinfo:badFilename', ...
        'FILENAME must be a string.');
end

%if ~isnumeric(dataset)
%  error('DATASET must be a number.');
%end

%Initialization 
vginfo = struct('Filename',[],'Name',[],'Class',[],'Vgroup',[],'SDS',[],'Vdata',[],'Raster24',[],'Raster8',[],'Tag',[],'Ref',[]);
vgroup = [];
sds = [];
raster8 = [];
raster24 = [];
vdata = [];
children.Tag = [];
children.Ref = [];

msg ='Problem connecting to Vgroup. File may be corrupt or Vgroup may not exist.';
vgID = hdfv('attach',fileID,dataset,'r');
if vgID == -1
  warning('MATLAB:hdfvgroupinfo:vgroupAttach', '%s', msg);
  return;
end

%Get name and class of Vgroup
[numEntries, name, status] = hdfv('inquire',vgID);
hdfwarn(status)
[class, status] = hdfv('getclass',vgID);
hdfwarn(status)

%Get child/tag reference pairs
childTags = [];
childRefs = [];
numChildren = hdfv('ntagrefs',vgID);
hdfwarn(numChildren)
if numChildren>0
  [childTags, childRefs, status] = hdfv('gettagrefs',vgID,numChildren);
  hdfwarn(status)
  children.Tag = childTags;
  children.Ref = childRefs;
end

%Close interfaces
status = hdfv('detach',vgID);
hdfwarn(status)

%Get children information. Classes of Vgroups to ignore: cdf0.0, rig0.0
if ~strcmp(lower(class),'cdf0.0') && ~strcmp(lower(class),'rig0.0')
  %Use same tag mapping as NCSA
  for i=1:length(childTags)
    switch childTags(i)
     case {hdfml('tagnum','DFTAG_SD'),hdfml('tagnum','DFTAG_NDG'),hdfml('tagnum','DFTAG_SDG')}
      %Change reference number to index
      index = hdfsd('reftoindex',sdID,childRefs(i));
      hdfwarn(index)
      if index~=-1
	sds = [sds hdfsdsinfo(filename,sdID,anID,index)]; 
      end
     case hdfml('tagnum','DFTAG_RI8')
      raster8 = [raster8 hdfraster8info(filename,anID,childRefs(i))];
     case hdfml('tagnum','DFTAG_RI')
      raster24 = [raster24 hdfraster24info(filename,anID,childRefs(i),anID)];
     case hdfml('tagnum','DFTAG_RIG')
      raster24 = [raster24 hdfraster24info(filename,anID,childRefs(i),anID)];
     case {hdfml('tagnum','DFTAG_VS'),hdfml('tagnum','DFTAG_VH')}
      vdata = [vdata hdfvdatainfo(filename,fileID,anID,childRefs(i))];
     case hdfml('tagnum','DFTAG_VG')
      [vgrouptemp, child] = hdfvgroupinfo(filename,childRefs(i),fileID,sdID,anID);
      vgroup = [vgroup vgrouptemp];
      if ~isempty(child.Tag)
	children.Tag = [children.Tag child.Tag];
	children.Ref = [children.Ref child.Ref];
      end
     otherwise
      warning('MATLAB:hdfvgroupinfo:unknownVgroup', ...
              'Unknown child in Vgroup with Tag number: %d', childTags(i));
    end
  end               
  %Populate output structure
  vginfo.Filename = filename;
  vginfo.Name = name;
  vginfo.Class = class;
  if ~isempty(vgroup)
    vginfo.Vgroup = vgroup;
  end
  if ~isempty(sds)
    vginfo.SDS = sds;
  end
  if ~isempty(vdata)
    vginfo.Vdata = vdata;
  end
  if ~isempty(raster24)
    vginfo.Raster24 = raster24;
  end
  if ~isempty(raster8)
    vginfo.Raster8 = raster8;
  end
  vginfo.Tag = hdfml('tagnum','DFTAG_VG');
  vginfo.Ref = dataset;
  vginfo.Type = 'Vgroup';
end
return;