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Re: Double-Precision Byte Swap [message #11595 is a reply to message #11588]

Tue, 28 April 1998 00:00

Peter Mason
Messages: 145
Registered: June 1996

Senior Member

On 28 Apr 1998, R. Kyle Justice wrote:
> Using PV-Wave in UNIX, is there a way to read
> double-precision floating point data generated
> on a PC?
> I think I need something something similar to
> the BYTEORDER procedure, but I need to (or do I?)
> swap 8 instead of 4 bytes.

Assuming that the data are IEEE double-precision (almost certainly), yes, you
just need to reverse the order of each number's 8 bytes.
(But note that if it's Digital Unix that you're using then you should NOT
re-order.)

I don't use PV-Wave, but here's a little IDL routine for the job:
;==================================
; Reverse the byte order of a whatever
pro byterev,v
j=size(v) &nj=n_elements(j) &t=j(nj-2) &n=j(nj-1)
if (t le 1) or (t ge 7) then return ;undefined, or inappropriate type
case t of
2:byteorder,v,/sswap ;short
3:byteorder,v,/lswap ;long
4:byteorder,v,/lswap ;float
5:begin &for i=0L,n-1L do v(i)=double(rotate(byte(v(i),0,8),2),0) &end ;double
6:byteorder,v,/lswap ;complex (it works, too!)
endcase
return
end
;==================================

Peter Mason

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[Message index]

		Re: Double-Precision Byte Swap By: rkj on Wed, 29 April 1998 00:00
		Re: Double-Precision Byte Swap By: rkj on Wed, 29 April 1998 00:00
		Re: Double-Precision Byte Swap By: Peter Mason on Tue, 28 April 1998 00:00

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