s_trunc.c
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/* @(#)s_floor.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#if 0
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
#endif
/*
* trunc(x)
* Return x rounded toward 0 to integral value
* Method:
* Bit twiddling.
* Exception:
* Inexact flag raised if x not equal to trunc(x).
*/
#include "math.h"
#include "math_private.h"
static const double huge = 1.0e300;
double
trunc(double x)
{
int32_t i0,i1,jj0;
u_int32_t i;
EXTRACT_WORDS(i0,i1,x);
jj0 = ((i0>>20)&0x7ff)-0x3ff;
if(jj0<20) {
if(jj0<0) { /* raise inexact if x != 0 */
if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
i0 &= 0x80000000U;
i1 = 0;
}
} else {
i = (0x000fffff)>>jj0;
if(((i0&i)|i1)==0) return x; /* x is integral */
if(huge+x>0.0) { /* raise inexact flag */
i0 &= (~i); i1=0;
}
}
} else if (jj0>51) {
if(jj0==0x400) return x+x; /* inf or NaN */
else return x; /* x is integral */
} else {
i = ((u_int32_t)(0xffffffff))>>(jj0-20);
if((i1&i)==0) return x; /* x is integral */
if(huge+x>0.0) /* raise inexact flag */
i1 &= (~i);
}
INSERT_WORDS(x,i0,i1);
return x;
}