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 #if defined(LIBM_SCCS) && !defined(lint) 14 static char rcsid[] = "$NetBSD: s_rint.c,v 1.8 1995/05/10 20:48:04 jtc Exp $"; 15 #endif 16 17 /* 18 * rint(x) 19 * Return x rounded to integral value according to the prevailing 20 * rounding mode. 21 * Method: 22 * Using floating addition. 23 * Exception: 24 * Inexact flag raised if x not equal to rint(x). 25 */ 26 27 #include <sys/cdefs.h> 28 #include <float.h> 29 #include <math.h> 30 31 #include "math_private.h" 32 33 static const double 34 TWO52[2]={ 35 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ 36 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ 37 }; 38 39 double 40 rint(double x) 41 { 42 int32_t i0,jj0,sx; 43 u_int32_t i,i1; 44 double w,t; 45 EXTRACT_WORDS(i0,i1,x); 46 sx = (i0>>31)&1; 47 jj0 = ((i0>>20)&0x7ff)-0x3ff; 48 if(jj0<20) { 49 if(jj0<0) { 50 if(((i0&0x7fffffff)|i1)==0) return x; 51 i1 |= (i0&0x0fffff); 52 i0 &= 0xfffe0000; 53 i0 |= ((i1|-i1)>>12)&0x80000; 54 SET_HIGH_WORD(x,i0); 55 w = TWO52[sx]+x; 56 t = w-TWO52[sx]; 57 GET_HIGH_WORD(i0,t); 58 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 59 return t; 60 } else { 61 i = (0x000fffff)>>jj0; 62 if(((i0&i)|i1)==0) return x; /* x is integral */ 63 i>>=1; 64 if(((i0&i)|i1)!=0) { 65 if(jj0==19) i1 = 0x40000000; else 66 i0 = (i0&(~i))|((0x20000)>>jj0); 67 } 68 } 69 } else if (jj0>51) { 70 if(jj0==0x400) return x+x; /* inf or NaN */ 71 else return x; /* x is integral */ 72 } else { 73 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 74 if((i1&i)==0) return x; /* x is integral */ 75 i>>=1; 76 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20)); 77 } 78 INSERT_WORDS(x,i0,i1); 79 w = TWO52[sx]+x; 80 return w-TWO52[sx]; 81 } 82 83 #if LDBL_MANT_DIG == 53 84 #ifdef __weak_alias 85 __weak_alias(rintl, rint); 86 #endif /* __weak_alias */ 87 #endif /* LDBL_MANT_DIG == 53 */ 88