;+
; NAME:	
;	HDFreturnSDS.pro
;
;
; PURPOSE: 
;	Given a .hdf filename and an SDS name within that file, will return that SDS
;
;
; AUTHOR: 
;	Alex Fraser
;
;
; CATEGORY: 
;	HDF utility
;
;
; CALLING SEQUENCE: 
;	see example
;
;
; INPUTS: 
;	filename: a string leading to the hdf file (including path).
;	sdsname: a string representing the name of the SDS within the HDF file. To find out which SDSs exist, 
;	use the free HDF Explorer (http://www.space-research.org/explorer.htm), or use another of my routines, HDFAttribs.pro
;
; KEYWORDS:
;	none
;
;
; OUTPUTS:
;	returns the requested SDS
;
;
; RESTRICTIONS:
;	no error handling included. This program is designed to be a lightweight HDF file reader, 
;	and any other programs which use this can do the error checking.
;
;
; EXAMPLE:
;	the below example would return the 'Cloud_Mask' SDS from within the hdf file c:\test.hdf
;	dataset = HDFreturnSDS('c:\test.hdf', 'Cloud_Mask') 
;
;
; MODIFICATION HISTORY:
;
;	Written by Alex Fraser, 2007.
;-

FUNCTION HDFreturnSDS, filename, sdsname

sdfileid=hdf_sd_start(filename, /read)

; Find the index of the "Gridded Data" SDS.
index = HDF_SD_NAMETOINDEX(sdFileID, sdsname)

; Select the Gridded Data SDS.
thisSdsID = HDF_SD_SELECT(sdFileID, index)

HDF_SD_GETDATA, thisSdsID, sds

hdf_sd_end, sdfileid

return, sds
END