xref: /illumos-gate/usr/src/lib/libm/common/Q/scalbl.c (revision ddc0e0b5)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma weak __scalbl = scalbl

/*
 * scalbl(x,n): return x * 2^n by manipulating exponent.
 */

#include "libm.h"

#define	n0	0

long double
scalbl(long double x, long double fn) {
	int *py = (int *) &fn, n;
	long double z;

	if (isnanl(x) || isnanl(fn))
		return (x * fn);

	/*
	 * fn is inf or NaN
	 */
	if ((py[n0] & 0x7fff0000) == 0x7fff0000) {
		if ((py[n0] & 0x80000000) != 0)
			return (x / (-fn));
		else
			return (x * fn);
	}
	if (rintl(fn) != fn)
		return ((fn - fn) / (fn - fn));
	if (fn > 65000.0L)
		z = scalbnl(x, 65000);
	else if (-fn > 65000.0L)
		z = scalbnl(x, -65000);
	else {
		n = (int) fn;
		z = scalbnl(x, n);
	}
	return (z);
}