| Re: Size of variables in bytes? [message #9840] |
Wed, 03 September 1997 00:00 |
pete
Messages: 4
Registered: March 1997
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Junior Member |
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Christian Soeller wrote:
>
> Christian Salow <csalow@chaos.bwl.uni-mainz.de> writes:
>
>>
>> Is the following true and is it machine independent?
>>
>> byte 1b
>> integer 2b
>> long int 4b
>> floating 4b
>> double 8b
>> string ???
>> structure n_tags(var, /length)
>>
>
> A related question would be why one has to know? If all you
You may need/want to know what the sizes are because you are giving a
data set generated outside of pvwave/idl. On Dec Alpha workstations the
long int maps to 8 bytes leaving no 4 byte integer. I am interfacing
with a c++ routine that writes out 4 byte integers, to force the c++
code to reengineer and waste 4*1465*15500 (this size is one of the
smaller file size) bytes of disk space per file (appx 40-50 files
generated daily) is absurd --- beside does it hurt to understand how
something is defined --- don't want to start an argument here *l*
> are interested in is cross platform data exchange you are better
> off using an appropriate (IDL supported) data format. Otherwise
> you have to take care of endianess youself, etc. And C programmers
> can use sizeof with the appropriate IDL C-type.
>
> Christian Soeller
--
------------------------------------------------------------ ------
"Madness takes it's toll. Please have exact change."
------------------------------------------------------------ ------
KYSOTI :P
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| Re: Size of variables in bytes? [message #9847 is a reply to message #9840] |
Tue, 02 September 1997 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Christian Salow writes:
> is it true that there is no function in IDL 5.0.2 to get the size of a
> variable in bytes (except structures)?
True.
> An integer variable seams to be 2 bytes indpendent from the system
> architecture but a string seams to be 1 byte per character on a Win32
> machine and 2 bytes on a SunOS-machine. I wrote a string to an
> unformatted output file and looked at the filepointer to get the size in
> bytes.
I think it would be less trouble to use the StrLen function to
find the length of the string. This is its size in bytes. Even
on a SunOS machine, I should think.
> Is the following true and is it machine independent?
> byte 1b
> integer 2b
> long int 4b
> floating 4b
> double 8b
> string ???
> structure n_tags(var, /length)
Yes, this is true and it is machine independent.
Strings are always ??? (variable length) in IDL.
> What about:
> complex floating
8 bytes.
> double-precision complex
16 bytes.
> pointer
4 bytes
> object reference
Don't know.
Cheers,
David
----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
Customizable IDL Programming Courses
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com
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