musl/src/math/modfl.c

/* origin: FreeBSD /usr/src/lib/msun/src/s_modfl.c */
/*-
 * Copyright (c) 2007 David Schultz <[email protected]>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Derived from s_modf.c, which has the following Copyright:
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double modfl(long double x, long double *iptr)
{
	return modf(x, (double *)iptr);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384

#if LDBL_MANL_SIZE > 32
#define MASK    ((uint64_t)-1)
#else
#define MASK    ((uint32_t)-1)
#endif
/* Return the last n bits of a word, representing the fractional part. */
#define GETFRAC(bits, n)        ((bits) & ~(MASK << (n)))
/* The number of fraction bits in manh, not counting the integer bit */
#define HIBITS  (LDBL_MANT_DIG - LDBL_MANL_SIZE)

static const long double zero[] = { 0.0, -0.0 };

long double modfl(long double x, long double *iptr)
{
	union IEEEl2bits ux;
	int e;

	ux.e = x;
	e = ux.bits.exp - LDBL_MAX_EXP + 1;
	if (e < HIBITS) {                       /* Integer part is in manh. */
		if (e < 0) {                    /* |x|<1 */
			*iptr = zero[ux.bits.sign];
			return x;
		}
		if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e)|ux.bits.manl) == 0) {
			/* x is an integer. */
			*iptr = x;
			return zero[ux.bits.sign];
		}
		/* Clear all but the top e+1 bits. */
		ux.bits.manh >>= HIBITS - 1 - e;
		ux.bits.manh <<= HIBITS - 1 - e;
		ux.bits.manl = 0;
		*iptr = ux.e;
		return x - ux.e;
	} else if (e >= LDBL_MANT_DIG - 1) {    /* x has no fraction part. */
		*iptr = x;
		if (e == LDBL_MAX_EXP && ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl)) /* nan */
			return x;
		return zero[ux.bits.sign];
	} else {                                /* Fraction part is in manl. */
		if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) {
			/* x is integral. */
			*iptr = x;
			return zero[ux.bits.sign];
		}
		/* Clear all but the top e+1 bits. */
		ux.bits.manl >>= LDBL_MANT_DIG - 1 - e;
		ux.bits.manl <<= LDBL_MANT_DIG - 1 - e;
		*iptr = ux.e;
		return x - ux.e;
	}
}
#endif