1 /* $NetBSD: lrint.c,v 1.5 2015/07/09 06:17:13 nat Exp $ */
2
3 /*-
4 * Copyright (c) 2004
5 * Matthias Drochner. 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
29 #include <math.h>
30 #include <sys/ieee754.h>
31 #include <machine/limits.h>
32 #include "math_private.h"
33
34 #ifndef LRINTNAME
35 #define LRINTNAME lrint
36 #define RESTYPE long int
37 #define RESTYPE_MIN LONG_MIN
38 #define RESTYPE_MAX LONG_MAX
39 #endif
40
41 #define RESTYPE_BITS (sizeof(RESTYPE) * 8)
42
43 static const double
44 TWO52[2]={
45 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
46 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
47 };
48
49 RESTYPE
LRINTNAME(double x)50 LRINTNAME(double x)
51 {
52 u_int32_t i0, i1;
53 int e, s, shift;
54 RESTYPE res;
55
56 GET_HIGH_WORD(i0, x);
57 e = i0 >> 20;
58 s = (uint32_t)e >> DBL_EXPBITS;
59 e = (e & 0x7ff) - DBL_EXP_BIAS;
60
61 /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
62 if (e < -1)
63 return (0);
64 /* 1.0 x 2^31 (or 2^63) is already too large */
65 if (e >= (int)RESTYPE_BITS - 1)
66 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
67
68 /* >= 2^52 is already an exact integer */
69 if (e < DBL_FRACBITS) {
70 /* round, using current direction */
71 x += TWO52[s];
72 x -= TWO52[s];
73 } else
74 return x;
75
76 EXTRACT_WORDS(i0, i1, x);
77 e = ((i0 >> 20) & 0x7ff) - DBL_EXP_BIAS;
78 i0 &= 0xfffff;
79 i0 |= (1 << 20);
80
81 shift = e - DBL_FRACBITS;
82 if (shift >=0)
83 res = (shift < 32 ? (RESTYPE)i1 << shift : 0);
84 else
85 res = (shift > -32 ? i1 >> -shift : 0);
86 shift += 32;
87 if (shift >=0)
88 res |= (shift < 32 ? (RESTYPE)i0 << shift : 0);
89 else
90 res |= (shift > -32 ? i0 >> -shift : 0);
91
92 return (s ? -res : res);
93 }
94