| [1] | 1 | |
|---|
| 2 | /* @(#)s_rint.c 5.1 93/09/24 */ |
|---|
| 3 | /* |
|---|
| 4 | * ==================================================== |
|---|
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
|---|
| 6 | * |
|---|
| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
|---|
| 8 | * Permission to use, copy, modify, and distribute this |
|---|
| 9 | * software is freely granted, provided that this notice |
|---|
| 10 | * is preserved. |
|---|
| 11 | * ==================================================== |
|---|
| 12 | */ |
|---|
| 13 | |
|---|
| 14 | /* |
|---|
| 15 | * rint(x) |
|---|
| 16 | * Return x rounded to integral value according to the prevailing |
|---|
| 17 | * rounding mode. |
|---|
| 18 | * Method: |
|---|
| 19 | * Using floating addition. |
|---|
| 20 | * Exception: |
|---|
| 21 | * Inexact flag raised if x not equal to rint(x). |
|---|
| 22 | */ |
|---|
| 23 | |
|---|
| 24 | #include <libm/fdlibm.h> |
|---|
| 25 | |
|---|
| 26 | #ifdef __STDC__ |
|---|
| 27 | static const double |
|---|
| 28 | #else |
|---|
| 29 | static double |
|---|
| 30 | #endif |
|---|
| 31 | one = 1.0, |
|---|
| 32 | TWO52[2]={ |
|---|
| 33 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
|---|
| 34 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
|---|
| 35 | }; |
|---|
| 36 | |
|---|
| 37 | #ifdef __STDC__ |
|---|
| 38 | double rint(double x) |
|---|
| 39 | #else |
|---|
| 40 | double rint(x) |
|---|
| 41 | double x; |
|---|
| 42 | #endif |
|---|
| 43 | { |
|---|
| 44 | int i0,n0,j0,sx; |
|---|
| 45 | unsigned i,i1; |
|---|
| 46 | double w,t; |
|---|
| 47 | n0 = (*((int *)&one)>>29)^1; |
|---|
| 48 | i0 = *(n0+(int*)&x); |
|---|
| 49 | sx = (i0>>31)&1; |
|---|
| 50 | i1 = *(1-n0+(int*)&x); |
|---|
| 51 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
|---|
| 52 | if(j0<20) { |
|---|
| 53 | if(j0<0) { |
|---|
| 54 | if(((i0&0x7fffffff)|i1)==0) return x; |
|---|
| 55 | i1 |= (i0&0x0fffff); |
|---|
| 56 | i0 &= 0xfffe0000; |
|---|
| 57 | i0 |= ((i1|-i1)>>12)&0x80000; |
|---|
| 58 | *(n0+(int*)&x)=i0; |
|---|
| 59 | w = TWO52[sx]+x; |
|---|
| 60 | t = w-TWO52[sx]; |
|---|
| 61 | i0 = *(n0+(int*)&t); |
|---|
| 62 | *(n0+(int*)&t) = (i0&0x7fffffff)|(sx<<31); |
|---|
| 63 | return t; |
|---|
| 64 | } else { |
|---|
| 65 | i = (0x000fffff)>>j0; |
|---|
| 66 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
|---|
| 67 | i>>=1; |
|---|
| 68 | if(((i0&i)|i1)!=0) { |
|---|
| 69 | if(j0==19) i1 = 0x40000000; 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 = ((unsigned)(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 | *(n0+(int*)&x) = i0; |
|---|
| 83 | *(1-n0+(int*)&x) = i1; |
|---|
| 84 | w = TWO52[sx]+x; |
|---|
| 85 | return w-TWO52[sx]; |
|---|
| 86 | } |
|---|
