1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 #include <sys/cdefs.h> 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 25 #include "math.h" 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,j0,sx; 38 u_int32_t i,i1; 39 double w,t; 40 EXTRACT_WORDS(i0,i1,x); 41 sx = (i0>>31)&1; 42 j0 = ((i0>>20)&0x7ff)-0x3ff; 43 if(j0<20) { 44 if(j0<0) { 45 if(((i0&0x7fffffff)|i1)==0) return x; 46 i1 |= (i0&0x0fffff); 47 i0 &= 0xfffe0000; 48 i0 |= ((i1|-i1)>>12)&0x80000; 49 SET_HIGH_WORD(x,i0); 50 STRICT_ASSIGN(double,w,TWO52[sx]+x); 51 t = w-TWO52[sx]; 52 GET_HIGH_WORD(i0,t); 53 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); 54 return t; 55 } else { 56 i = (0x000fffff)>>j0; 57 if(((i0&i)|i1)==0) return x; /* x is integral */ 58 i>>=1; 59 if(((i0&i)|i1)!=0) { 60 /* 61 * Some bit is set after the 0.5 bit. To avoid the 62 * possibility of errors from double rounding in 63 * w = TWO52[sx]+x, adjust the 0.25 bit to a lower 64 * guard bit. We do this for all j0<=51. The 65 * adjustment is trickiest for j0==18 and j0==19 66 * since then it spans the word boundary. 67 */ 68 if(j0==19) i1 = 0x40000000; else 69 if(j0==18) i1 = 0x80000000; else 70 i0 = (i0&(~i))|((0x20000)>>j0); 71 } 72 } 73 } else if (j0>51) { 74 if(j0==0x400) return x+x; /* inf or NaN */ 75 else return x; /* x is integral */ 76 } else { 77 i = ((u_int32_t)(0xffffffff))>>(j0-20); 78 if((i1&i)==0) return x; /* x is integral */ 79 i>>=1; 80 if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); 81 } 82 INSERT_WORDS(x,i0,i1); 83 STRICT_ASSIGN(double,w,TWO52[sx]+x); 84 return w-TWO52[sx]; 85 } 86 87 #if (LDBL_MANT_DIG == 53) 88 __weak_reference(rint, rintl); 89 #endif 90