usr/src/lib/libm/common/C/scalb.c

   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  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  23  */
  24 /*
  25  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28
  29 #pragma weak __scalb = scalb
  30 #pragma weak _scalb = scalb
  31
  32 #include "libm.h"
  33
  34 double
  35 scalb(double x, double fn) {
  36         int     hn, in, n;
  37         double  z;
  38
  39         if (isnan(x) || isnan(fn))
  40                 return (x * fn);
  41
  42         in = ((int *)&fn)[HIWORD];
  43         hn = in & ~0x80000000;
  44         if (hn == 0x7ff00000)   /* fn is inf */
  45                 return (_SVID_libm_err(x, fn, 47));
  46
  47         /* see if fn is an integer without raising inexact */
  48         if (hn >= 0x43300000) {
  49                 /* |fn| >= 2^52, so it must be an integer */
  50                 n = (in < 0)? -65000 : 65000;
  51         } else if (hn < 0x3ff00000) {
  52                 /* |fn| < 1, so it must be zero or non-integer */
  53                 return ((fn == 0.0)? x : (x - x) / (x - x));
  54         } else if (hn < 0x41400000) {
  55                 /* |fn| < 2^21 */
  56                 if ((hn & ((1 << (0x413 - (hn >> 20))) - 1))
  57                     | ((int *)&fn)[LOWORD])
  58                         return ((x - x) / (x - x));
  59                 n = (int)fn;
  60         } else {
  61                 if (((int *)&fn)[LOWORD] & ((1 << (0x433 - (hn >> 20))) - 1))
  62                         return ((x - x) / (x - x));
  63                 n = (in < 0)? -65000 : 65000;
  64         }
  65         z = scalbn(x, n);
  66         if (z != x) {
  67                 if (z == 0.0)
  68                         return (_SVID_libm_err(x, fn, 33));
  69                 if (!finite(z))
  70                         return (_SVID_libm_err(x, fn, 32));
  71         }
  72         return (z);
  73 }