| Re: hexadecimal variables [message #15175 is a reply to message #15093] |
Thu, 22 April 1999 00:00   |
Vapuser
Messages: 63
Registered: November 1998
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Member |
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Pavel Romashkin <promashkin@cmdl.noaa.gov> writes:
> Hi,
> Is there a nice way to convert hexadecimal variables? Here's what I am
> trying to do:
>
> This is received from the outside.
> h_string = '40000FC0DA'
>
> h_long = long(h_string)
> This, obviously, fails to recognize alphabetical hexadecimal part and
> sets h_long to 40,000.
>
> temp = execute("h_long = long(' "+h_string+" 'x)")
> This, naturally, works, setting h_long to the desired 1032410,
This is not what h_long equals; 1032410 = 'fc0da'x. You've only gotten
the first 32 bits. See below.
> but looks
> quite ugly. Besides, it is 3 times slower than without "execute" - not
> really a concern on fast machines, but inefficient code just bugs me.
>
> I am sure I am missing something here. Can anyone suggest a neater way
> to do this? Maybe, there is a way to use Z-formatted READ here?
>
> Thank you,
> Pavel
>
40000FC0DA is larger than 32 bits. Unless you're using idl 5.2,
having access to 64 bit integers, you're out of luck, without kluging
together something having the same flavor as a 'far' pointer in old
MS-DOS.
The general method, however, is to use reads, which works on scalars
and arrays. Here's an example, using IDL 5.2, and 64 bit integers.
IDL> h='40000FC0DA'
IDL> x=0LL
IDL> help,x
X LONG64 = 0
IDL> reads,h,x,form='(Z)'
IDL> print,x,form='(z)'
40000fc0da
IDL> print,x
274878939354
IDL>
If you try this in idl<5.2,(with x=0L) you'll only get the right
most 32 bits, i.e. X = 'fc0da'x. Witness...
IDL> x1=0L
IDL> reads,h,x1,form='(Z)'
IDL> print,x1
1032410
IDL> print,x1,form='(z)'
fc0da
If you really need the > 32 bits, you're going to have to use idl
5.2, or read it, split it, and recombine it as a double?
--
William Daffer
vapuser@catspaw.jpl.nasa.gov
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