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Diffstat (limited to 'lib/libc/mips/gen/modf.c')
| -rw-r--r-- | lib/libc/mips/gen/modf.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/lib/libc/mips/gen/modf.c b/lib/libc/mips/gen/modf.c new file mode 100644 index 000000000000..347090cf1fe7 --- /dev/null +++ b/lib/libc/mips/gen/modf.c @@ -0,0 +1,107 @@ +/* + * Copyright (c) 1994, 1995 Carnegie-Mellon University. + * All rights reserved. + * + * Author: Chris G. Demetriou + * + * Permission to use, copy, modify and distribute this software and + * its documentation is hereby granted, provided that both the copyright + * notice and this permission notice appear in all copies of the + * software, derivative works or modified versions, and any portions + * thereof, and that both notices appear in supporting documentation. + * + * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" + * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND + * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * Carnegie Mellon requests users of this software to return to + * + * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU + * School of Computer Science + * Carnegie Mellon University + * Pittsburgh PA 15213-3890 + * + * any improvements or extensions that they make and grant Carnegie the + * rights to redistribute these changes. + * + * $NetBSD: modf.c,v 1.1 1995/02/10 17:50:25 cgd Exp $ + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/types.h> +#include <errno.h> +#include <math.h> +#include <machine/ieee.h> + +/* + * double modf(double val, double *iptr) + * returns: f and i such that |f| < 1.0, (f + i) = val, and + * sign(f) == sign(i) == sign(val). + * + * Beware signedness when doing subtraction, and also operand size! + */ +double +modf(val, iptr) + double val, *iptr; +{ + union doub { + double v; + struct ieee_double s; + } u, v; + u_int64_t frac; + + /* + * If input is Inf or NaN, return it and leave i alone. + */ + u.v = val; + if (u.s.dbl_exp == DBL_EXP_INFNAN) + return (u.v); + + /* + * If input can't have a fractional part, return + * (appropriately signed) zero, and make i be the input. + */ + if ((int)u.s.dbl_exp - DBL_EXP_BIAS > DBL_FRACBITS - 1) { + *iptr = u.v; + v.v = 0.0; + v.s.dbl_sign = u.s.dbl_sign; + return (v.v); + } + + /* + * If |input| < 1.0, return it, and set i to the appropriately + * signed zero. + */ + if (u.s.dbl_exp < DBL_EXP_BIAS) { + v.v = 0.0; + v.s.dbl_sign = u.s.dbl_sign; + *iptr = v.v; + return (u.v); + } + + /* + * There can be a fractional part of the input. + * If you look at the math involved for a few seconds, it's + * plain to see that the integral part is the input, with the + * low (DBL_FRACBITS - (exponent - DBL_EXP_BIAS)) bits zeroed, + * the the fractional part is the part with the rest of the + * bits zeroed. Just zeroing the high bits to get the + * fractional part would yield a fraction in need of + * normalization. Therefore, we take the easy way out, and + * just use subtraction to get the fractional part. + */ + v.v = u.v; + /* Zero the low bits of the fraction, the sleazy way. */ + frac = ((u_int64_t)v.s.dbl_frach << 32) + v.s.dbl_fracl; + frac >>= DBL_FRACBITS - (u.s.dbl_exp - DBL_EXP_BIAS); + frac <<= DBL_FRACBITS - (u.s.dbl_exp - DBL_EXP_BIAS); + v.s.dbl_fracl = frac & 0xffffffff; + v.s.dbl_frach = frac >> 32; + *iptr = v.v; + + u.v -= v.v; + u.s.dbl_sign = v.s.dbl_sign; + return (u.v); +} |