/*
 * 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 frexp = __frexp

/*
 * frexp(x, exp) returns the normalized significand of x and sets
 * *exp so that x = r*2^(*exp) where r is the return value.  If x
 * is finite and nonzero, 1/2 <= |r| < 1.
 *
 * If x is zero, infinite or NaN, frexp returns x and sets *exp = 0.
 * (The relevant standards do not specify *exp when x is infinite or
 * NaN, but this code sets it anyway.)
 *
 * If x is a signaling NaN, this code returns x without attempting
 * to raise the invalid operation exception.  If x is subnormal,
 * this code treats it as nonzero regardless of nonstandard mode.
 */

#include "libm.h"

double
__frexp(double x, int *exp) {
        union {
                unsigned i[2];
                double d;
        } xx, yy;
        double t;
        unsigned hx;
        int e;

        xx.d = x;
        hx = xx.i[HIWORD] & ~0x80000000;

        if (hx >= 0x7ff00000) { /* x is infinite or NaN */
                *exp = 0;
                return (x);
        }

        e = 0;
        if (hx < 0x00100000) { /* x is subnormal or zero */
                if ((hx | xx.i[LOWORD]) == 0) {
                        *exp = 0;
                        return (x);
                }

                /*
                 * normalize x by regarding it as an integer
                 *
                 * Here we use 32-bit integer arithmetic to avoid trapping
                 * or emulating 64-bit arithmetic.  If 64-bit arithmetic is
                 * available (e.g., in SPARC V9), do this instead:
                 *
                 *  long lx = ((long) hx << 32) | xx.i[LOWORD];
                 *  xx.d = (xx.i[HIWORD] < 0)? -lx : lx;
                 *
                 * If subnormal arithmetic doesn't trap, just multiply x by
                 * a power of two.
                 */
                yy.i[HIWORD] = 0x43300000 | hx;
                yy.i[LOWORD] = xx.i[LOWORD];
                t = yy.d;
                yy.i[HIWORD] = 0x43300000;
                yy.i[LOWORD] = 0;
                t -= yy.d; /* t = |x| scaled */
                xx.d = ((int)xx.i[HIWORD] < 0)? -t : t;
                hx = xx.i[HIWORD] & ~0x80000000;
                e = -1074;
        }

        /* now xx.d is normal */
        xx.i[HIWORD] = (xx.i[HIWORD] & ~0x7ff00000) | 0x3fe00000;
        *exp = e + (hx >> 20) - 0x3fe;
        return (xx.d);
}