| /* @(#)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. |
| * ==================================================== |
| */ |
| |
| #include <sys/cdefs.h> |
| |
| /* |
| * 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 "../bsd_private_base.h" |
| |
| static const double |
| TWO52[2]={ |
| 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
| -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
| }; |
| |
| double |
| rint(double x) |
| { |
| 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); |
| STRICT_ASSIGN(double,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) { |
| /* |
| * Some bit is set after the 0.5 bit. To avoid the |
| * possibility of errors from double rounding in |
| * w = TWO52[sx]+x, adjust the 0.25 bit to a lower |
| * guard bit. We do this for all j0<=51. The |
| * adjustment is trickiest for j0==18 and j0==19 |
| * since then it spans the word boundary. |
| */ |
| if(j0==19) i1 = 0x40000000; else |
| if(j0==18) i1 = 0x80000000; 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); |
| STRICT_ASSIGN(double,w,TWO52[sx]+x); |
| return w-TWO52[sx]; |
| } |
