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Re: reading binary files [message #54500 is a reply to message #49280]

Tue, 19 June 2007 07:47

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Vince Oliver wrote:
> we are maybe on the good way. I wrote this
>
>
> OpenR, lun, data, /Get_Lun, /F77_UNFORMATTED
>
> specnr=2
> nlen=7323
> n=2*nlen
> specoff=(n+1)*specnr*4l ; this is letter L not number 1
> spectra = Assoc(lun, Fltarr(n),specoff)

what about something like,

spectra = ASSOC(lun,{RecBegin:0L, Data:FLTARR(2,n), RecEnd:0L})
spectrum = spectra[0]

?

Do the spectrum.data contain the correct info? Additionally, are the values of
spectrum.recbegin and spectrum.recend the same as 2*n*4?

Remember that *each* output record (for Fortran sequential access, unformatted) has a
marker both at the beginning *and* the end specifying the record length (hopefully in
bytes, not "words").

ASSOC is most often used for direct access, unformatted; but there's no reason you can't
use it here also.

>> I assume here that the data is: DWORD|fltarr(n)|DWORD|fltarr(n)...

Nope, it should be

RECLEN1|fltarr(2,n)|RECLEN1|RECLEN2|fltarr(2,n)|RECLEN2....

One of the reasons for the terminating record length marker (what I called "RecEnd" in the
structure above) is so that the Fortran BACKSPACE command works for sequential access files.

cheers,

paulv

--
Paul van Delst Ride lots.
CIMSS @ NOAA/NCEP/EMC Eddy Merckx

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[Message index]

		Reading binary files made by Python By: Liberum on Mon, 10 July 2006 02:45
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 09:10
		Re: reading binary files By: Paul Van Delst[1] on Tue, 19 June 2007 08:28
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 08:06
		Re: reading binary files By: Paul Van Delst[1] on Tue, 19 June 2007 07:47
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 07:16
		Re: reading binary files By: Wox on Tue, 19 June 2007 06:06
		Re: reading binary files By: Wox on Tue, 19 June 2007 06:00

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