1 /* $NetBSD: lroundf.c,v 1.3 2008/04/26 23:49:50 christos 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 LROUNDNAME
35 #define LROUNDNAME lroundf
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 RESTYPE
LROUNDNAME(float x)44 LROUNDNAME(float x)
45 {
46 u_int32_t i0;
47 int e, s, shift;
48 RESTYPE res;
49
50 GET_FLOAT_WORD(i0, x);
51 e = i0 >> SNG_FRACBITS;
52 s = (uint32_t)e >> SNG_EXPBITS;
53 e = (e & 0xff) - SNG_EXP_BIAS;
54
55 /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
56 if (e < -1)
57 return (0);
58 /* 1.0 x 2^31 (or 2^63) is already too large */
59 if (e >= (int)RESTYPE_BITS - 1)
60 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
61
62 /* >= 2^23 is already an exact integer */
63 if (e < SNG_FRACBITS) {
64 /* add 0.5, extraction below will truncate */
65 x += (s ? -0.5 : 0.5);
66 }
67
68 GET_FLOAT_WORD(i0, x);
69 e = ((i0 >> SNG_FRACBITS) & 0xff) - SNG_EXP_BIAS;
70 i0 &= 0x7fffff;
71 i0 |= (1 << SNG_FRACBITS);
72
73 shift = e - SNG_FRACBITS;
74 if (shift >=0)
75 res = (shift < 32 ? (RESTYPE)i0 << shift : 0);
76 else
77 res = (shift > -32 ? i0 >> -shift : 0);
78
79 return (s ? -res : res);
80 }
81