;
; BITVHEAD
;
;   Accepts a set of records and prints a header to the output
;
;   FORMAT - bit packed format, as described in BITSTRACT
;
;   ITEMS - desired items.  Pass FORMAT.ITEM if all columns are
;           desired.  Must be same as passed to BITVREAD.
;
;   OUTUNIT - output file unit where header is written.
;
;
;  $Id: bitvhead.pro,v 1.2 2002/02/06 21:39:02 craigm Exp $
;
;  C. Markwardt 03 Feb 2002
;
pro bitvhead, format, items, outunit
              
  tname = strarr(n_elements(items))
  tform = tname

  for i = 0, n_elements(items)-1 do begin
      item = items(i)
      wh = where(format.item EQ item, ct)
      if ct GT 0 then begin
          fm = format(wh)

          tname(i) = fm.name
          tform(i) = fm.type
      endif else begin
          message, 'ERROR: could not find item '+strtrim(item,2)
      endelse
  endfor

  ntags = n_tags(template)
  nrec = n_elements(records)

  for i = 0, n_elements(items)-1 do begin
      item = items(i)
      printf, outunit, items(i), tname(i), tform(i), $
        format='("; ",I3," - ",A0," (",A0,")")'
  endfor

  return
end