1 /* @(#)s_rint.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 #include <sys/cdefs.h> 14 #if defined(LIBM_SCCS) && !defined(lint) 15 __RCSID("$NetBSD: s_rint.c,v 1.12 2008/04/25 22:21:53 christos Exp $"); 16 #endif 17 18 /* 19 * rint(x) 20 * Return x rounded to integral value according to the prevailing 21 * rounding mode. 22 * Method: 23 * Using floating addition. 24 * Exception: 25 * Inexact flag raised if x not equal to rint(x). 26 */ 27 28 #include "math.h" 29 #include "math_private.h" 30 31 static const double 32 TWO52[2]={ 33 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 34 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 35 }; 36 37 double 38 rint(double x) 39 { 40 int32_t i0,jj0,sx; 41 u_int32_t i,i1; 42 double w,t; 43 EXTRACT_WORDS(i0,i1,x); 44 sx = (i0>>31)&1; 45 jj0 = ((i0>>20)&0x7ff)-0x3ff; 46 if(jj0<20) { 47 if(jj0<0) { 48 if(((i0&0x7fffffff)|i1)==0) return x; 49 i1 |= (i0&0x0fffff); 50 i0 &= 0xfffe0000; 51 i0 |= ((i1|-i1)>>12)&0x80000; 52 SET_HIGH_WORD(x,i0); 53 w = TWO52[sx]+x; 54 t = w-TWO52[sx]; 55 GET_HIGH_WORD(i0,t); 56 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 57 return t; 58 } else { 59 i = (0x000fffff)>>jj0; 60 if(((i0&i)|i1)==0) return x; /* x is integral */ 61 i>>=1; 62 if(((i0&i)|i1)!=0) { 63 if(jj0==19) i1 = 0x40000000; else 64 i0 = (i0&(~i))|((0x20000)>>jj0); 65 } 66 } 67 } else if (jj0>51) { 68 if(jj0==0x400) return x+x; /* inf or NaN */ 69 else return x; /* x is integral */ 70 } else { 71 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 72 if((i1&i)==0) return x; /* x is integral */ 73 i>>=1; 74 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20)); 75 } 76 INSERT_WORDS(x,i0,i1); 77 w = TWO52[sx]+x; 78 return w-TWO52[sx]; 79 } 80