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