| The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_rint.c 1.3 95/01/18 */ |
| 3 | /* |
| 4 | * ==================================================== |
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 6 | * |
| 7 | * Developed at SunSoft, 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 | * ieee_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 ieee_rint(x). |
| 22 | */ |
| 23 | |
| 24 | #include "fdlibm.h" |
| 25 | |
| 26 | #ifdef __STDC__ |
| 27 | static const double |
| 28 | #else |
| 29 | static double |
| 30 | #endif |
| 31 | TWO52[2]={ |
| 32 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
| 33 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
| 34 | }; |
| 35 | |
| 36 | #ifdef __STDC__ |
| 37 | double ieee_rint(double x) |
| 38 | #else |
| 39 | double ieee_rint(x) |
| 40 | double x; |
| 41 | #endif |
| 42 | { |
| 43 | int i0,j0,sx; |
| 44 | unsigned i,i1; |
| 45 | double w,t; |
| 46 | i0 = __HI(x); |
| 47 | sx = (i0>>31)&1; |
| 48 | i1 = __LO(x); |
| 49 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
| 50 | if(j0<20) { |
| 51 | if(j0<0) { |
| 52 | if(((i0&0x7fffffff)|i1)==0) return x; |
| 53 | i1 |= (i0&0x0fffff); |
| 54 | i0 &= 0xfffe0000; |
| 55 | i0 |= ((i1|-i1)>>12)&0x80000; |
| 56 | __HI(x)=i0; |
| 57 | w = TWO52[sx]+x; |
| 58 | t = w-TWO52[sx]; |
| 59 | i0 = __HI(t); |
| 60 | __HI(t) = (i0&0x7fffffff)|(sx<<31); |
| 61 | return t; |
| 62 | } else { |
| 63 | i = (0x000fffff)>>j0; |
| 64 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
| 65 | i>>=1; |
| 66 | if(((i0&i)|i1)!=0) { |
| 67 | if(j0==19) i1 = 0x40000000; else |
| 68 | i0 = (i0&(~i))|((0x20000)>>j0); |
| 69 | } |
| 70 | } |
| 71 | } else if (j0>51) { |
| 72 | if(j0==0x400) return x+x; /* inf or NaN */ |
| 73 | else return x; /* x is integral */ |
| 74 | } else { |
| 75 | i = ((unsigned)(0xffffffff))>>(j0-20); |
| 76 | if((i1&i)==0) return x; /* x is integral */ |
| 77 | i>>=1; |
| 78 | if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); |
| 79 | } |
| 80 | __HI(x) = i0; |
| 81 | __LO(x) = i1; |
| 82 | w = TWO52[sx]+x; |
| 83 | return w-TWO52[sx]; |
| 84 | } |