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 1.10 1999/07/02 15:37:43 simonb 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 #ifdef __STDC__ 32 static const double 33 #else 34 static double 35 #endif 36 TWO52[2]={ 37 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 38 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 39 }; 40 41 #ifdef __STDC__ 42 double rint(double x) 43 #else 44 double rint(x) 45 double x; 46 #endif 47 { 48 int32_t i0,j0,sx; 49 u_int32_t i,i1; 50 double w,t; 51 EXTRACT_WORDS(i0,i1,x); 52 sx = (i0>>31)&1; 53 j0 = ((i0>>20)&0x7ff)-0x3ff; 54 if(j0<20) { 55 if(j0<0) { 56 if(((i0&0x7fffffff)|i1)==0) return x; 57 i1 |= (i0&0x0fffff); 58 i0 &= 0xfffe0000; 59 i0 |= ((i1|-i1)>>12)&0x80000; 60 SET_HIGH_WORD(x,i0); 61 w = TWO52[sx]+x; 62 t = w-TWO52[sx]; 63 GET_HIGH_WORD(i0,t); 64 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 65 return t; 66 } else { 67 i = (0x000fffff)>>j0; 68 if(((i0&i)|i1)==0) return x; /* x is integral */ 69 i>>=1; 70 if(((i0&i)|i1)!=0) { 71 if(j0==19) i1 = 0x40000000; else 72 i0 = (i0&(~i))|((0x20000)>>j0); 73 } 74 } 75 } else if (j0>51) { 76 if(j0==0x400) return x+x; /* inf or NaN */ 77 else return x; /* x is integral */ 78 } else { 79 i = ((u_int32_t)(0xffffffff))>>(j0-20); 80 if((i1&i)==0) return x; /* x is integral */ 81 i>>=1; 82 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); 83 } 84 INSERT_WORDS(x,i0,i1); 85 w = TWO52[sx]+x; 86 return w-TWO52[sx]; 87 } 88