/* $OpenBSD: floatdidf.c,v 1.6 2005/08/08 08:05:35 espie Exp $ */
/*-
 * Copyright (c) 1992, 1993
 * The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include "quad.h"

/*
 * Convert (signed) quad to double.
 */
double __floatdidf(quad_t x)
{
    double d;
    union uu u;
    int neg;

    /*
     * Get an unsigned number first, by negating if necessary.
     */
    if (x < 0) {
        u.q = -x;
        neg = 1;
    }
    else {
        u.q = x;
        neg = 0;
    }

    /*
     * Now u.ul[H] has the factor of 2^32 (or whatever) and u.ul[L]
     * has the units.  Ideally we could just set d, add INT_BITS to
     * its exponent, and then add the units, but this is portable
     * code and does not know how to get at an exponent.  Machine-
     * specific code may be able to do this more efficiently.
     */
    d = (double) u.ul[H] * (((int) 1 << (INT_BITS - 2)) * 4.0);
    d += u.ul[L];

    return neg ? -d : d;
}