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 /* LINTLIBRARY */ 24 25 #include <sys/cdefs.h> 26 #include <float.h> 27 #include <math.h> 28 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 t; 43 volatile double w; /* clip extra precision */ 44 EXTRACT_WORDS(i0,i1,x); 45 sx = (i0>>31)&1; 46 jj0 = ((i0>>20)&0x7ff)-0x3ff; 47 if(jj0<20) { 48 if(jj0<0) { 49 if(((i0&0x7fffffff)|i1)==0) return x; 50 i1 |= (i0&0x0fffff); 51 i0 &= 0xfffe0000; 52 i0 |= ((i1|-i1)>>12)&0x80000; 53 SET_HIGH_WORD(x,i0); 54 w = TWO52[sx]+x; 55 t = w-TWO52[sx]; 56 GET_HIGH_WORD(i0,t); 57 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 58 return t; 59 } else { 60 i = (0x000fffff)>>jj0; 61 if(((i0&i)|i1)==0) return x; /* x is integral */ 62 i>>=1; 63 if(((i0&i)|i1)!=0) { 64 if(jj0==19) i1 = 0x40000000; else 65 i0 = (i0&(~i))|((0x20000)>>jj0); 66 } 67 } 68 } else if (jj0>51) { 69 if(jj0==0x400) return x+x; /* inf or NaN */ 70 else return x; /* x is integral */ 71 } else { 72 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 73 if((i1&i)==0) return x; /* x is integral */ 74 i>>=1; 75 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20)); 76 } 77 INSERT_WORDS(x,i0,i1); 78 w = TWO52[sx]+x; 79 return w-TWO52[sx]; 80 } 81 82 #if LDBL_MANT_DIG == 53 83 #ifdef lint 84 /* PROTOLIB1 */ 85 long double rintl(long double); 86 #else /* lint */ 87 __weak_alias(rintl, rint); 88 #endif /* lint */ 89 #endif /* LDBL_MANT_DIG == 53 */ 90