comp.lang.idl-pvwave archive: archive » Re: read a C written binary file with IDL

Home » Public Forums » archive » Re: read a C written binary file with IDL

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: read a C written binary file with IDL [message #79232 is a reply to message #79231]

Fri, 10 February 2012 06:09

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

Senior Member

Have you tried ASSOC? It has a PACKED keyword you can play with:

<quote>
PACKED
When ASSOC is applied to structures, the default action is to map the actual definition of the structure for the current
machine, including any holes required to properly align the fields. (IDL uses the same rules for laying out structures
as the C language). If the PACKED keyword is specified, I/O using the resulting variable instead works in the same
manner as READU and WRITEU, and data is moved one field at a time and there are no alignment gaps between the fields.
</quote>

So you might want to experiment with ASSOC and /PACKED, e.g.

mystruct={a:0L, b:0LL, c:0L,d:0.0}
openr, 1, filename, /swap_if_big_endian
a = assoc(1, {a:0L, b:0LL, c:0L,d:0.0})
or
a = assoc(1, {a:0L, b:0LL, c:0L,d:0.0},/packed)
help, a[0]

cheers,

paulv

bing999 wrote:
> Hi,
>
> I am having a problem with reading a C written binary file with IDL.
> It may come from differences of type definitions between C and IDL but
> I could not really figure out from Google...
>
> In C, it writes a structure containing the following variable types:
>
> struct MyStruct
> {
> int a;
> long long b;
> int c;
> float d;
> };
>
> Then, in IDL, I read this with:
>
> MyStruct = {$
> a : 0L, $
> b : 0LL, $
> c : 0L, $
> d : 0.0 $
> }
>
> openr, 1, filename, /SWAP_IF_BIG_ENDIAN
> readu, 1, MyStruct
> close, 1
>
>
> but this gives me wrong values.
>
> Did I miss something about the type conversion??
>
> If someone could please clarify this, it would really help!
> Thanks !
>
>
>
>
>

Report message to a moderator

[Message index]

		Re: read a C written binary file with IDL By: Paul Van Delst[1] on Fri, 10 February 2012 08:02
		Re: read a C written binary file with IDL By: Bill Nel on Fri, 10 February 2012 07:12
		Re: read a C written binary file with IDL By: Paul Van Delst[1] on Fri, 10 February 2012 06:09
		Re: read a C written binary file with IDL By: Thibault Garel on Thu, 09 February 2012 21:08
		Re: read a C written binary file with IDL By: manodeep@gmail.com on Thu, 09 February 2012 20:56
		Re: read a C written binary file with IDL By: Thibault Garel on Mon, 20 February 2012 17:49

Previous Topic:	Re: tracking clusters through multiple timesteps
Next Topic:	Making a html image map?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 11:39:27 PDT 2025

Total time taken to generate the page: 0.64200 seconds