common/C/scalb.c

	scalb.c revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
/*
 * 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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma weak scalb = __scalb
#pragma weak _scalb = __scalb

#include "libm.h"

double
scalb(double x, double fn) {
    int hn, in, n;
    double  z;

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

    in = ((int *)&fn)[HIWORD];
    hn = in & ~0x80000000;
    if (hn == 0x7ff00000)   /* fn is inf */
        return (_SVID_libm_err(x, fn, 47));

    /* see if fn is an integer without raising inexact */
    if (hn >= 0x43300000) {
        /* |fn| >= 2^52, so it must be an integer */
        n = (in < 0)? -65000 : 65000;
    } else if (hn < 0x3ff00000) {
        /* |fn| < 1, so it must be zero or non-integer */
        return ((fn == 0.0)? x : (x - x) / (x - x));
    } else if (hn < 0x41400000) {
        /* |fn| < 2^21 */
        if ((hn & ((1 << (0x413 - (hn >> 20))) - 1))
            | ((int *)&fn)[LOWORD])
            return ((x - x) / (x - x));
        n = (int)fn;
    } else {
        if (((int *)&fn)[LOWORD] & ((1 << (0x433 - (hn >> 20))) - 1))
            return ((x - x) / (x - x));
        n = (in < 0)? -65000 : 65000;
    }
    z = scalbn(x, n);
    if (z != x) {
        if (z == 0.0)
            return (_SVID_libm_err(x, fn, 33));
        if (!finite(z))
            return (_SVID_libm_err(x, fn, 32));
    }
    return (z);
}