1 /* $OpenBSD: s_lround.c,v 1.7 2013/07/03 04:46:36 espie Exp $ */
2 /* $NetBSD: lround.c,v 1.2 2004/10/13 15:18:32 drochner Exp $ */
3
4 /*-
5 * Copyright (c) 2004
6 * Matthias Drochner. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/types.h>
31 #include <sys/limits.h>
32 #include <float.h>
33 #include <math.h>
34 #include <ieeefp.h>
35 #include <machine/ieee.h>
36 #include "math_private.h"
37
38 #ifndef LROUNDNAME
39 #define LROUNDNAME lround
40 #define RESTYPE long int
41 #define RESTYPE_MIN LONG_MIN
42 #define RESTYPE_MAX LONG_MAX
43 #endif
44
45 #define RESTYPE_BITS (int)(sizeof(RESTYPE) * 8)
46
47 RESTYPE
LROUNDNAME(double x)48 LROUNDNAME(double x)
49 {
50 u_int32_t i0, i1;
51 int e, s, shift;
52 RESTYPE res;
53
54 GET_HIGH_WORD(i0, x);
55 e = i0 >> DBL_FRACHBITS;
56 s = e >> DBL_EXPBITS;
57 e = (e & 0x7ff) - DBL_EXP_BIAS;
58
59 /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
60 if (e < -1)
61 return (0);
62 /* 1.0 x 2^31 (or 2^63) is already too large */
63 if (e >= RESTYPE_BITS - 1)
64 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
65
66 /* >= 2^52 is already an exact integer */
67 if (e < DBL_FRACBITS) {
68 /* add 0.5, extraction below will truncate */
69 x += (s ? -0.5 : 0.5);
70 }
71
72 EXTRACT_WORDS(i0, i1, x);
73 e = ((i0 >> DBL_FRACHBITS) & 0x7ff) - DBL_EXP_BIAS;
74 i0 &= 0xfffff;
75 i0 |= (1 << DBL_FRACHBITS);
76
77 shift = e - DBL_FRACBITS;
78 if (shift >=0)
79 res = (shift < RESTYPE_BITS ? (RESTYPE)i1 << shift : 0);
80 else
81 res = (shift > -RESTYPE_BITS ? (RESTYPE)i1 >> -shift : 0);
82 shift += 32;
83 if (shift >=0)
84 res |= (shift < RESTYPE_BITS ? (RESTYPE)i0 << shift : 0);
85 else
86 res |= (shift > -RESTYPE_BITS ? (RESTYPE)i0 >> -shift : 0);
87
88 return (s ? -res : res);
89 }
90
91 #if LDBL_MANT_DIG == DBL_MANT_DIG
92 __strong_alias(lroundl, lround);
93 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
94