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Re: 10 bytes real [message #22230]

Mon, 30 October 2000 13:46

Peter Mason
Messages: 145
Registered: June 1996

Senior Member

"Karl Schultz" <kschultz@researchsystems.com> wrote:
<...>
> Also, the 80x87 math processors on wintel machines are 80-bit anyway
> and I think that there are instructions that would load 80-bit floats
> into the floating point regs. After you've done that, you can read
> them back out as a double. I don't know if there is any C compiler
> support.
<...>

Apparently the MS visual C compiler knows about "long doubles" - 80-bit
IEEE floating point numbers.
*Provided* that your 10-byte numbers are indeed IEEE FP format, you
should be able to use the following routine (compiled etc) to do the
conversion. On the input side I gues you'd just use a BYTARR or
something, stuffed with the inscrutable 10-byte reals, and for the
output you'd present a DOUBLE array of the right size - hopefully it
will get filled with something useful :-)
I haven't tested the routine below. (In fact I've never used a "long
double" before.) But give it a try.
If you don't have a MS visual C compiler, let me know and I will
compile the routine for you.

Cheers
Peter Mason

/*
10-byte to 8-byte IEEE floating-point converter (untested).
Peter Mason, CSIRO DEM, October 2000
*/
#define STRICT
#define VC_EXTRALEAN
#include <windows.h>

/*********************************************************** ************
******/
BOOL WINAPI DllMain(HINSTANCE hinst, unsigned long reason, void *resvd)
{
hinst=hinst; reason=reason; resvd=resvd;
return 1;
}
/*********************************************************** **********/
/*
This is it.
The call is:
status=call_external('[pathfconv.dll','idlfp10to8',in10,out8 ,n)
. in10[n] is an array of 10-byte IEEE floating-point numbers;
. out8[n] is an array that will be filled with the conversions;
. n is the number of numbers (in all its splendour?)
*/
int WINAPI idlfp10to8(int ac, int *a[])
{
register long double *in10;
register double *out8;
register int n;
if(ac!=3) return 1; //incorrect number of arguments
in10 = (long double *)a[0];
out8 = (double *)a[1];
n = *a[2];
for( ; n; --n, ++in10, ++out8) *out8 = (double)(*in10);
return 0;
}
/*********************************************************** **********/

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[Message index]

		Re: 10 bytes real By: Peter Mason on Mon, 30 October 2000 13:46
		Re: 10 bytes real By: Ed Santiago on Mon, 30 October 2000 05:39
		Re: 10 bytes real By: Craig Markwardt on Fri, 27 October 2000 09:39
		Re: 10 bytes real By: davidf on Fri, 27 October 2000 09:08
		Re: 10 bytes real By: Karl Schultz on Fri, 27 October 2000 08:39
		Re: 10 bytes real By: Thierry Wannier on Thu, 26 October 2000 23:20
		Re: 10 bytes real By: Craig Markwardt on Thu, 26 October 2000 15:40
		Re: 10 bytes real By: promashkin on Thu, 26 October 2000 15:07
		Re: 10 bytes real By: Craig Markwardt on Thu, 26 October 2000 08:31

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