usr/src/lib/libm/common/C/floor.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 __floor = floor
  30
  31 /*
  32  * floor(x) returns the biggest integral value less than or equal to x.
  33  * NOTE: floor(x) returns result with the same sign as x's, including 0.
  34  *
  35  * Modified 8/4/04 for performance.
  36  */
  37
  38 #include "libm.h"
  39
  40 static const double
  41         zero = 0.0,
  42         one = 1.0,
  43         two52 = 4503599627370496.0;
  44
  45 double
  46 floor(double x) {
  47         double  t, w;
  48         int     hx, lx, ix;
  49
  50         hx = ((int *)&x)[HIWORD];
  51         lx = ((int *)&x)[LOWORD];
  52         ix = hx & ~0x80000000;
  53         if (ix >= 0x43300000)   /* return x if |x| >= 2^52, or x is NaN */
  54                 return (x * one);
  55         t = (hx >= 0)? two52 : -two52;
  56         w = x + t;
  57         t = w - t;
  58         if (ix < 0x3ff00000) {
  59                 if ((ix | lx) == 0)
  60                         return (x);
  61                 else
  62                         return ((hx < 0)? -one : zero);
  63         }
  64         return ((t <= x)? t : t - one);
  65 }