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 #include "libm.h"
  32 
  33 static const double invpi = 0.3183098861837906715377675;
  34 
  35 float
  36 atan2pif(float y, float x)
  37 {
  38         int ix, iy, hx, hy;
  39 
  40         ix = *(int *)&x;
  41         iy = *(int *)&y;
  42         hx = ix & ~0x80000000;
  43         hy = iy & ~0x80000000;
  44 
  45         if (hx > 0x7f800000 || hy > 0x7f800000)   /* x or y is nan */
  46                 return (x * y);
  47 
  48         if ((hx | hy) == 0) {
  49                 /* x and y are both zero */
  50                 if (ix == 0)
  51                         return (y);
  52 
  53                 return ((iy == 0) ? 1.0f : -1.0f);
  54         }
  55 
  56         return ((float)(invpi * atan2((double)y, (double)x)));
  57 }