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comparison src/libm/s_floor.c @ 2758:045d9976f285

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Yet more math...
author Sam Lantinga <slouken@libsdl.org>
date Mon, 15 Sep 2008 06:48:41 +0000
parents
children 02aa80d7905f
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2757:0581f49c9294 2758:045d9976f285
1 /* @(#)s_floor.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 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] =
15 "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
16 #endif
17
18 /*
19 * floor(x)
20 * Return x rounded toward -inf to integral value
21 * Method:
22 * Bit twiddling.
23 * Exception:
24 * Inexact flag raised if x not equal to floor(x).
25 */
26
27 #include "math.h"
28 #include "math_private.h"
29
30 #ifdef __STDC__
31 static const double huge = 1.0e300;
32 #else
33 static double huge = 1.0e300;
34 #endif
35
36 libm_hidden_proto(floor)
37 #ifdef __STDC__
38 double floor(double x)
39 #else
40 double floor(x)
41 double x;
42 #endif
43 {
44 int32_t i0, i1, j0;
45 u_int32_t i, j;
46 EXTRACT_WORDS(i0, i1, x);
47 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
48 if (j0 < 20) {
49 if (j0 < 0) { /* raise inexact if x != 0 */
50 if (huge + x > 0.0) { /* return 0*sign(x) if |x|<1 */
51 if (i0 >= 0) {
52 i0 = i1 = 0;
53 } else if (((i0 & 0x7fffffff) | i1) != 0) {
54 i0 = 0xbff00000;
55 i1 = 0;
56 }
57 }
58 } else {
59 i = (0x000fffff) >> j0;
60 if (((i0 & i) | i1) == 0)
61 return x; /* x is integral */
62 if (huge + x > 0.0) { /* raise inexact flag */
63 if (i0 < 0)
64 i0 += (0x00100000) >> j0;
65 i0 &= (~i);
66 i1 = 0;
67 }
68 }
69 } else if (j0 > 51) {
70 if (j0 == 0x400)
71 return x + x; /* inf or NaN */
72 else
73 return x; /* x is integral */
74 } else {
75 i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
76 if ((i1 & i) == 0)
77 return x; /* x is integral */
78 if (huge + x > 0.0) { /* raise inexact flag */
79 if (i0 < 0) {
80 if (j0 == 20)
81 i0 += 1;
82 else {
83 j = i1 + (1 << (52 - j0));
84 if (j < i1)
85 i0 += 1; /* got a carry */
86 i1 = j;
87 }
88 }
89 i1 &= (~i);
90 }
91 }
92 INSERT_WORDS(x, i0, i1);
93 return x;
94 }
95
96 libm_hidden_def(floor)