;------------------------------------------------------------
;------------------------------------------------------------
;------------------------------------------------------------
;+
; NAME:write_oasis
;
; PURPOSE:write an Oasis file (version < 2.5)
;
; CATEGORY:
;
; CALLING SEQUENCE:write_oasis, filename, varname, z2d
; 
; INPUTS:
;        filename:the filename
;        varname: the name of the variable to be written
;        z2d: the variable (2D array) to be written
;
; KEYWORD PARAMETERS:
;        /I2, /I4, /I8, /R4: to change the defaut format (R8) of the data to 
;        be written.
;
;        /APPEND: to open the file with the file pointer at the end of
;        the file, ready for data to be appended.
;
; OUTPUTS:
;
; COMMON BLOCKS:
;
; SIDE EFFECTS:varname is automatically written as a "charactere*8"
;              by defaut z2d is written as an R8 array
;
; RESTRICTIONS:
;
; EXAMPLE:
;
; MODIFICATION HISTORY:Sebastien Masson (smasson@lodyc.jussieu.fr)
;                      July 01, 2002
;-
;------------------------------------------------------------
;------------------------------------------------------------
;------------------------------------------------------------


PRO write_oasis, filename, varname, z2d, I2, I4 = i4, I8 = i8, R4 = r4, APPEND = append
   openw, unit, filename , /F77_UNFORMATTED, /GET_LUN, /SWAP_IF_LITTLE_ENDIAN $
    , error=err, APPEND = append
   if err ne 0 then begin
      print,!err_string
      return
   endif
   
   writeu, unit, string(varname, format='(a8)')
   case 1 of
      keyword_set(i2):writeu, unit, fix(z2d)
      keyword_set(i4):writeu, unit, long(z2d)
      keyword_set(i8):writeu, unit, long64(z2d)
      keyword_set(r4):writeu, unit, float(z2d)
      ELSE:writeu, unit, double(z2d)
   endcase

   free_lun,unit
   return
end