/src/mozilla-central/modules/fdlibm/src/s_rint.cpp
Line | Count | Source (jump to first uncovered line) |
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 | | //#include <sys/cdefs.h> |
14 | | //__FBSDID("$FreeBSD$"); |
15 | | |
16 | | /* |
17 | | * rint(x) |
18 | | * Return x rounded to integral value according to the prevailing |
19 | | * rounding mode. |
20 | | * Method: |
21 | | * Using floating addition. |
22 | | * Exception: |
23 | | * Inexact flag raised if x not equal to rint(x). |
24 | | */ |
25 | | |
26 | | #include <float.h> |
27 | | |
28 | | #include "math_private.h" |
29 | | |
30 | | static const double |
31 | | TWO52[2]={ |
32 | | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
33 | | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
34 | | }; |
35 | | |
36 | | double |
37 | | rint(double x) |
38 | 0 | { |
39 | 0 | int32_t i0,j0,sx; |
40 | 0 | u_int32_t i,i1; |
41 | 0 | double w,t; |
42 | 0 | EXTRACT_WORDS(i0,i1,x); |
43 | 0 | sx = (i0>>31)&1; |
44 | 0 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
45 | 0 | if(j0<20) { |
46 | 0 | if(j0<0) { |
47 | 0 | if(((i0&0x7fffffff)|i1)==0) return x; |
48 | 0 | i1 |= (i0&0x0fffff); |
49 | 0 | i0 &= 0xfffe0000; |
50 | 0 | i0 |= ((i1|-i1)>>12)&0x80000; |
51 | 0 | SET_HIGH_WORD(x,i0); |
52 | 0 | STRICT_ASSIGN(double,w,TWO52[sx]+x); |
53 | 0 | t = w-TWO52[sx]; |
54 | 0 | GET_HIGH_WORD(i0,t); |
55 | 0 | SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); |
56 | 0 | return t; |
57 | 0 | } else { |
58 | 0 | i = (0x000fffff)>>j0; |
59 | 0 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
60 | 0 | i>>=1; |
61 | 0 | if(((i0&i)|i1)!=0) { |
62 | 0 | /* |
63 | 0 | * Some bit is set after the 0.5 bit. To avoid the |
64 | 0 | * possibility of errors from double rounding in |
65 | 0 | * w = TWO52[sx]+x, adjust the 0.25 bit to a lower |
66 | 0 | * guard bit. We do this for all j0<=51. The |
67 | 0 | * adjustment is trickiest for j0==18 and j0==19 |
68 | 0 | * since then it spans the word boundary. |
69 | 0 | */ |
70 | 0 | if(j0==19) i1 = 0x40000000; else |
71 | 0 | if(j0==18) i1 = 0x80000000; else |
72 | 0 | i0 = (i0&(~i))|((0x20000)>>j0); |
73 | 0 | } |
74 | 0 | } |
75 | 0 | } else if (j0>51) { |
76 | 0 | if(j0==0x400) return x+x; /* inf or NaN */ |
77 | 0 | else return x; /* x is integral */ |
78 | 0 | } else { |
79 | 0 | i = ((u_int32_t)(0xffffffff))>>(j0-20); |
80 | 0 | if((i1&i)==0) return x; /* x is integral */ |
81 | 0 | i>>=1; |
82 | 0 | if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); |
83 | 0 | } |
84 | 0 | INSERT_WORDS(x,i0,i1); |
85 | 0 | STRICT_ASSIGN(double,w,TWO52[sx]+x); |
86 | 0 | return w-TWO52[sx]; |
87 | 0 | } |