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- /* @(#)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.
- * ====================================================
- */
- #if defined(LIBM_SCCS) && !defined(lint)
- static char rcsid[] = "$NetBSD: s_rint.c,v 1.8 1995/05/10 20:48:04 jtc Exp $";
- #endif
- /*
- * 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 "math.h"
- #include "math_private.h"
- #ifdef __STDC__
- static const double
- #else
- static double
- #endif
- TWO52[2]={
- 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
- -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
- };
- #ifdef __STDC__
- double rint(double x)
- #else
- double rint(x)
- double x;
- #endif
- {
- int32_t i0,j0,sx;
- u_int32_t i,i1;
- double w,t;
- EXTRACT_WORDS(i0,i1,x);
- sx = (i0>>31)&1;
- j0 = ((i0>>20)&0x7ff)-0x3ff;
- if(j0<20) {
- if(j0<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)>>j0;
- if(((i0&i)|i1)==0) return x; /* x is integral */
- i>>=1;
- if(((i0&i)|i1)!=0) {
- if(j0==19) i1 = 0x40000000; else
- i0 = (i0&(~i))|((0x20000)>>j0);
- }
- }
- } else if (j0>51) {
- if(j0==0x400) return x+x; /* inf or NaN */
- else return x; /* x is integral */
- } else {
- i = ((u_int32_t)(0xffffffff))>>(j0-20);
- if((i1&i)==0) return x; /* x is integral */
- i>>=1;
- if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
- }
- INSERT_WORDS(x,i0,i1);
- w = TWO52[sx]+x;
- return w-TWO52[sx];
- }
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