1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 
  26 /*
  27  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __nextafter = nextafter
  32 #pragma weak _nextafter = nextafter
  33 
  34 #include "libm.h"
  35 #include <float.h>                        /* DBL_MIN */
  36 
  37 double
  38 nextafter(double x, double y)
  39 {
  40         int hx, hy, k;
  41         double ans;
  42         unsigned lx;
  43         volatile double dummy __unused;
  44 
  45         hx = ((int *)&x)[HIWORD];
  46         lx = ((int *)&x)[LOWORD];
  47         hy = ((int *)&y)[HIWORD];
  48         k = (hx & ~0x80000000) | lx;
  49 
  50         if (x == y)
  51                 return (y);             /* C99 requirement */
  52 
  53         if (x != x || y != y)
  54                 return (x * y);
  55 
  56         if (k == 0) {                   /* x = 0 */
  57                 k = hy & 0x80000000;
  58                 ((int *)&ans)[HIWORD] = k;
  59                 ((int *)&ans)[LOWORD] = 1;
  60         } else if (hx >= 0) {
  61                 if (x > y) {
  62                         ((int *)&ans)[LOWORD] = lx - 1;
  63                         k = (lx == 0) ? hx - 1 : hx;
  64                         ((int *)&ans)[HIWORD] = k;
  65                 } else {
  66                         ((int *)&ans)[LOWORD] = lx + 1;
  67                         k = (lx == 0xffffffff) ? hx + 1 : hx;
  68                         ((int *)&ans)[HIWORD] = k;
  69                 }
  70         } else {
  71                 if (x < y) {
  72                         ((int *)&ans)[LOWORD] = lx - 1;
  73                         k = (lx == 0) ? hx - 1 : hx;
  74                         ((int *)&ans)[HIWORD] = k;
  75                 } else {
  76                         ((int *)&ans)[LOWORD] = lx + 1;
  77                         k = (lx == 0xffffffff) ? hx + 1 : hx;
  78                         ((int *)&ans)[HIWORD] = k;
  79                 }
  80         }
  81 
  82         k = (k >> 20) & 0x7ff;
  83 
  84         if (k == 0x7ff) {
  85                 /* overflow */
  86                 return (_SVID_libm_err(x, y, 46));
  87 #if !defined(__lint)
  88         } else if (k == 0) {
  89                 /* underflow */
  90                 dummy = DBL_MIN * copysign(DBL_MIN, x);
  91 #endif
  92         }
  93 
  94         return (ans);
  95 }