/* $OpenBSD: fixunssfdi.c,v 1.5 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"

#define ONE_FOURTH  ((int)1 << (INT_BITS - 2))
#define ONE_HALF    (ONE_FOURTH * 2.0)
#define ONE     (ONE_FOURTH * 4.0)

/*
 * Convert float to (unsigned) quad.  We do most of our work in double,
 * out of sheer paranoia.
 *
 * Not sure what to do with negative numbers---for now, anything out
 * of range becomes UQUAD_MAX.
 *
 * N.B.: must use new ANSI syntax (sorry).
 */
u_quad_t __fixunssfdi(float f)
{
    double x, toppart;
    union uu t;

    if (f < 0) {
        return (UQUAD_MAX); /* ??? should be 0?  ERANGE??? */
    }

#ifdef notdef               /* this falls afoul of a GCC bug */
    if (f >= UQUAD_MAX) {
        return UQUAD_MAX;
    }
#else                   /* so we wire in 2^64-1 instead */
    if (f >= 18446744073709551615.0) {    /* XXX */
        return (UQUAD_MAX);
    }

#endif

    x = f;
    /*
     * Get the upper part of the result.  Note that the divide
     * may round up; we want to avoid this if possible, so we
     * subtract `1/2' first.
     */
    toppart = (x - ONE_HALF) / ONE;
    /*
     * Now build a u_quad_t out of the top part.  The difference
     * between x and this is the bottom part (this may introduce
     * a few fuzzy bits, but what the heck).  With any luck this
     * difference will be nonnegative: x should wind up in the
     * range [0..UINT_MAX].  For paranoia, we assume [INT_MIN..
     * 2*UINT_MAX] instead.
     */
    t.ul[H] = (unsigned int) toppart;
    t.ul[L] = 0;
    x -= (double) t.uq;

    if (x < 0) {
        t.ul[H]--;
        x += UINT_MAX;
    }

    if (x > UINT_MAX) {
        t.ul[H]++;
        x -= UINT_MAX;
    }

    t.ul[L] = (u_int)x;
    return t.uq;
}