80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/* @(#)s_rint.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.
|
|
* ====================================================
|
|
*/
|
|
|
|
/*
|
|
* rint(x)
|
|
* Return x rounded to integral value according to the prevailing
|
|
* rounding mode.
|
|
* Method:
|
|
* Using floating addition.
|
|
* Exception:
|
|
* Inexact flag raised if x not equal to rint(x).
|
|
*/
|
|
|
|
#include <float.h>
|
|
#include <math.h>
|
|
|
|
#include "math_private.h"
|
|
|
|
static const double
|
|
TWO52[2]={
|
|
4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
|
|
-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
|
|
};
|
|
|
|
double
|
|
rint(double x)
|
|
{
|
|
int32_t i0,jj0,sx;
|
|
u_int32_t i,i1;
|
|
double t;
|
|
volatile double w; /* clip extra precision */
|
|
EXTRACT_WORDS(i0,i1,x);
|
|
sx = (i0>>31)&1;
|
|
jj0 = ((i0>>20)&0x7ff)-0x3ff;
|
|
if(jj0<20) {
|
|
if(jj0<0) {
|
|
if(((i0&0x7fffffff)|i1)==0) return x;
|
|
i1 |= (i0&0x0fffff);
|
|
i0 &= 0xfffe0000;
|
|
i0 |= ((i1|-i1)>>12)&0x80000;
|
|
SET_HIGH_WORD(x,i0);
|
|
w = TWO52[sx]+x;
|
|
t = w-TWO52[sx];
|
|
GET_HIGH_WORD(i0,t);
|
|
SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
|
|
return t;
|
|
} else {
|
|
i = (0x000fffff)>>jj0;
|
|
if(((i0&i)|i1)==0) return x; /* x is integral */
|
|
i>>=1;
|
|
if(((i0&i)|i1)!=0) {
|
|
if(jj0==19) i1 = 0x40000000; else
|
|
i0 = (i0&(~i))|((0x20000)>>jj0);
|
|
}
|
|
}
|
|
} 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 */
|
|
i>>=1;
|
|
if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20));
|
|
}
|
|
INSERT_WORDS(x,i0,i1);
|
|
w = TWO52[sx]+x;
|
|
return w-TWO52[sx];
|
|
}
|
|
DEF_STD(rint);
|
|
LDBL_MAYBE_NONSTD_CLONE(rint);
|