common/C/nextafter.c

	nextafter.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 nextafter = __nextafter
#pragma weak _nextafter = __nextafter

#include "libm.h"
#include <float.h>      /* DBL_MIN */

double
nextafter(double x, double y) {
    int     hx, hy, k;
    double      ans;
    unsigned    lx;
    volatile double dummy;

    hx = ((int *)&x)[HIWORD];
    lx = ((int *)&x)[LOWORD];
    hy = ((int *)&y)[HIWORD];
    k = (hx & ~0x80000000) | lx;

    if (x == y)
        return (y);     /* C99 requirement */
    if (x != x || y != y)
        return (x * y);
    if (k == 0) {           /* x = 0 */
        k = hy & 0x80000000;
        ((int *)&ans)[HIWORD] = k;
        ((int *)&ans)[LOWORD] = 1;
    } else if (hx >= 0) {
        if (x > y) {
            ((int *)&ans)[LOWORD] = lx - 1;
            k = (lx == 0)? hx - 1 : hx;
            ((int *)&ans)[HIWORD] = k;
        } else {
            ((int *)&ans)[LOWORD] = lx + 1;
            k  = (lx == 0xffffffff)? hx + 1 : hx;
            ((int *)&ans)[HIWORD] = k;
        }
    } else {
        if (x < y) {
            ((int *)&ans)[LOWORD] = lx - 1;
            k = (lx == 0)? hx - 1 : hx;
            ((int *)&ans)[HIWORD] = k;
        } else {
            ((int *)&ans)[LOWORD] = lx + 1;
            k  = (lx == 0xffffffff)? hx + 1 : hx;
            ((int *)&ans)[HIWORD] = k;
        }
    }
    k = (k >> 20) & 0x7ff;
    if (k == 0x7ff) {
        /* overflow */
        return (_SVID_libm_err(x, y, 46));
#if !defined(__lint)
    } else if (k == 0) {
        /* underflow */
        dummy = DBL_MIN * copysign(DBL_MIN, x);
#endif
    }
    return (ans);
}