1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2007 David Schultz <das@FreeBSD.ORG>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * Derived from s_modf.c, which has the following Copyright:
29 * ====================================================
30 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
31 *
32 * Developed at SunPro, a Sun Microsystems, Inc. business.
33 * Permission to use, copy, modify, and distribute this
34 * software is freely granted, provided that this notice
35 * is preserved.
36 * ====================================================
37 */
38
39 #include <float.h>
40 #include <math.h>
41 #include <sys/types.h>
42
43 #include "fpmath.h"
44
45 #if LDBL_MANL_SIZE > 32
46 #define MASK ((uint64_t)-1)
47 #else
48 #define MASK ((uint32_t)-1)
49 #endif
50 /* Return the last n bits of a word, representing the fractional part. */
51 #define GETFRAC(bits, n) ((bits) & ~(MASK << (n)))
52 /* The number of fraction bits in manh, not counting the integer bit */
53 #define HIBITS (LDBL_MANT_DIG - LDBL_MANL_SIZE)
54
55 static const long double zero[] = { 0.0L, -0.0L };
56
57 long double
modfl(long double x,long double * iptr)58 modfl(long double x, long double *iptr)
59 {
60 union IEEEl2bits ux;
61 int e;
62
63 ux.e = x;
64 e = ux.bits.exp - LDBL_MAX_EXP + 1;
65 if (e < HIBITS) { /* Integer part is in manh. */
66 if (e < 0) { /* |x|<1 */
67 *iptr = zero[ux.bits.sign];
68 return (x);
69 } else {
70 if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e) |
71 ux.bits.manl) == 0) { /* X is an integer. */
72 *iptr = x;
73 return (zero[ux.bits.sign]);
74 } else {
75 /* Clear all but the top e+1 bits. */
76 ux.bits.manh >>= HIBITS - 1 - e;
77 ux.bits.manh <<= HIBITS - 1 - e;
78 ux.bits.manl = 0;
79 *iptr = ux.e;
80 return (x - ux.e);
81 }
82 }
83 } else if (e >= LDBL_MANT_DIG - 1) { /* x has no fraction part. */
84 *iptr = x;
85 if (x != x) /* Handle NaNs. */
86 return (x);
87 return (zero[ux.bits.sign]);
88 } else { /* Fraction part is in manl. */
89 if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) {
90 /* x is integral. */
91 *iptr = x;
92 return (zero[ux.bits.sign]);
93 } else {
94 /* Clear all but the top e+1 bits. */
95 ux.bits.manl >>= LDBL_MANT_DIG - 1 - e;
96 ux.bits.manl <<= LDBL_MANT_DIG - 1 - e;
97 *iptr = ux.e;
98 return (x - ux.e);
99 }
100 }
101 }
102