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Re: structure length in files [message #84911 is a reply to message #84907]

Tue, 18 June 2013 09:20

Bill Nel
Messages: 31
Registered: October 2010

Member

On Tuesday, June 18, 2013 11:20:10 AM UTC-4, Helder wrote:

> [Short summary: When IDL writes structures in unformatted binary data files, what size will the resulting file have, that described by n_tags(Example1,/LENGTH) or n_tags(Example1,/DATA_LENGTH)?]

I don't believe it is documented, but empirically (on my Windows 7 system -- and several years ago on a Unix system), writeu, struct writes the structure unpadded to a file, n_tags(struct, /data_length). You can check yourself using
openw, unit, filename, /get_lun,
writeu, unit, struct
point_lun, -unit, fileOffset

There is one important exception. If the struct contains strings, then n_tags(... , /data_length) isn't the size of the unpadded structure. (This is documented.)

--Wayne

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[Message index]

		structure length in files By: Helder Marchetto on Tue, 18 June 2013 08:20
		Re: structure length in files By: David Fanning on Tue, 18 June 2013 08:31
		Re: structure length in files By: Bill Nel on Tue, 18 June 2013 09:20
		Re: structure length in files By: Helder Marchetto on Tue, 18 June 2013 11:13
		Re: structure length in files By: David Fanning on Tue, 18 June 2013 11:26
		Re: structure length in files By: lecacheux.alain on Tue, 18 June 2013 12:05
		Re: structure length in files By: David Fanning on Tue, 18 June 2013 12:14

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