1 /* $NetBSD: modf.c,v 1.1 1995/02/10 17:50:25 cgd Exp $ */
2 /* $FreeBSD: src/lib/libc/alpha/gen/modf.c,v 1.1.1.1.6.1 2000/08/21 21:09:29 jhb Exp $ */
5 * Copyright (c) 1994, 1995 Carnegie-Mellon University.
8 * Author: Chris G. Demetriou
10 * Permission to use, copy, modify and distribute this software and
11 * its documentation is hereby granted, provided that both the copyright
12 * notice and this permission notice appear in all copies of the
13 * software, derivative works or modified versions, and any portions
14 * thereof, and that both notices appear in supporting documentation.
16 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
17 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
18 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
20 * Carnegie Mellon requests users of this software to return to
22 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
23 * School of Computer Science
24 * Carnegie Mellon University
25 * Pittsburgh PA 15213-3890
27 * any improvements or extensions that they make and grant Carnegie the
28 * rights to redistribute these changes.
31 #include <sys/types.h>
32 #include <machine/ieee.h>
37 * double modf(double val, double *iptr)
38 * returns: f and i such that |f| < 1.0, (f + i) = val, and
39 * sign(f) == sign(i) == sign(val).
41 * Beware signedness when doing subtraction, and also operand size!
54 * If input is Inf or NaN, return it and leave i alone.
57 if (u.s.dbl_exp == DBL_EXP_INFNAN)
61 * If input can't have a fractional part, return
62 * (appropriately signed) zero, and make i be the input.
64 if ((int)u.s.dbl_exp - DBL_EXP_BIAS > DBL_FRACBITS - 1) {
67 v.s.dbl_sign = u.s.dbl_sign;
72 * If |input| < 1.0, return it, and set i to the appropriately
75 if (u.s.dbl_exp < DBL_EXP_BIAS) {
77 v.s.dbl_sign = u.s.dbl_sign;
83 * There can be a fractional part of the input.
84 * If you look at the math involved for a few seconds, it's
85 * plain to see that the integral part is the input, with the
86 * low (DBL_FRACBITS - (exponent - DBL_EXP_BIAS)) bits zeroed,
87 * the the fractional part is the part with the rest of the
88 * bits zeroed. Just zeroing the high bits to get the
89 * fractional part would yield a fraction in need of
90 * normalization. Therefore, we take the easy way out, and
91 * just use subtraction to get the fractional part.
94 /* Zero the low bits of the fraction, the sleazy way. */
95 frac = ((u_int64_t)v.s.dbl_frach << 32) + v.s.dbl_fracl;
96 frac >>= DBL_FRACBITS - (u.s.dbl_exp - DBL_EXP_BIAS);
97 frac <<= DBL_FRACBITS - (u.s.dbl_exp - DBL_EXP_BIAS);
98 v.s.dbl_fracl = frac & 0xffffffff;
99 v.s.dbl_frach = frac >> 32;
103 u.s.dbl_sign = v.s.dbl_sign;