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Re: Converting Byte Arrays [message #10176 is a reply to message #10049]

Wed, 08 October 1997 00:00

davis
Messages: 15
Registered: March 1995

Junior Member

On Mon, 06 Oct 1997 16:54:55 -0500, Liam Gumley <liam.gumley@ssec.wisc.edu>
wrote:
> One way to read a data file with mixed variable types (integers, floats) is by
> using an anonymous structure, e.g.
>
> record = { var1:0, var2:0L, var3:0.0 }
> openr, lun, file, /get_lun
> readu, lun, record
> free_lun, lun
> help, record.var1, record.var2, record.var3

This is not really portable because you need to know how the structure
and data are padded. For example, consider the C code:

#include <stdio.h>
typedef struct
{
short s;
long l;
}
Short_Long_Type;

int main (int argc, char **argv)
{
Short_Long_Type sl;
FILE *fp;

sl.s = 1234;
sl.l = 2147483647;

fp = fopen ("sl.dat", "wb");
fwrite ((char *) &sl, sizeof (Short_Long_Type), 1, fp);
fclose (fp);
return 0;
}

In general, the SIZE of data file that this program produces will
vary. Under Linux, it produces an 8 byte file, whereas under DOS the
resulting file is 6 bytes. If you want portable datafiles, never
directly write out the structures.

--John

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[Message index]

		Converting Byte Arrays By: popprice on Mon, 06 October 1997 00:00
		Re: Converting Byte Arrays By: pit on Mon, 13 October 1997 00:00
		Re: Converting Byte Arrays By: popprice on Thu, 09 October 1997 00:00
		Re: Converting Byte Arrays By: David Foster on Wed, 08 October 1997 00:00
		Re: Converting Byte Arrays By: davis on Wed, 08 October 1997 00:00

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