;+
;
; @file_comments
; read the f77 unformatted files used in Oasis (version < 2.5)
;
; @categories
; Reading
;
; @param FILENAME {in}{required}
; the filename
;
; @param VARNAME {in}{required}
; the name of the variable to be read
;
; @param JPI {in}{required}
;
; @param jpj {in}{required}
; the size of the 2d array to be read
;
; @keyword I2
; @keyword I4
; @keyword I8
; @keyword R4
; to change the default format (R8) of the data to be read.
;
; @returns
; a 2d array
;
; @examples
; IDL> a=read_oasis('grids_orca_t106','a106.lon',320,160)
; IDL> m=read_oasis('masks_orca_t106','or1t.msk',182,149,/i4)
;
; see also IDL> scanoasis,'grids_orca_t106'
;
; @history
; Sebastien Masson (smasson\@lodyc.jussieu.fr)
;                      July 01, 2002
; @version
; $Id$
;
;-
;
FUNCTION read_oasis, filename, varname, jpi, jpj, I2 = I2, I4 = i4, I8 = i8, R4 = r4
;
  compile_opt idl2, strictarrsubs
;

   openr, unit, filename, /f77_unformatted, /get_lun, /swap_if_little_endian $
    , error=err
   if err ne 0 then begin
      ras = report(!err_string)
      return, -1
   endif

   char8 = '12345678'
   readu, unit, char8
;   print, char8
   found = char8 EQ varname

   WHILE NOT EOF(unit) AND found NE 1 DO BEGIN
      readu, unit
      if EOF(unit) then begin
         ras = report(varname+' not found in '+filename)
         return, -1
      endif
      readu, unit, char8
;      print, char8
      found = char8 EQ varname
   ENDWHILE
   case 1 of
      keyword_set(i2):res = intarr(jpi, jpj)
      keyword_set(i4):res = lonarr(jpi, jpj)
      keyword_set(i8):res = lon64arr(jpi, jpj)
      keyword_set(r4):res = fltarr(jpi, jpj)
      ELSE:res = dblarr(jpi, jpj)
   endcase

   readu, unit, res

   free_lun,unit

   return, res
end