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  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29 
  30 #if defined(ELFOBJ)
  31 #pragma weak modf = __modf
  32 #pragma weak _modf = __modf
  33 #endif
  34 
  35 /*
  36  * modf(x, iptr) decomposes x into an integral part and a fractional
  37  * part both having the same sign as x.  It stores the integral part
  38  * in *iptr and returns the fractional part.
  39  *
  40  * If x is infinite, modf sets *iptr to x and returns copysign(0.0,x).
  41  * If x is NaN, modf sets *iptr to x and returns x.
  42  *
  43  * If x is a signaling NaN, this code does not attempt to raise the
  44  * invalid operation exception.
  45  */
  46 
  47 #include "libm.h"
  48 
  49 double
  50 __modf(double x, double *iptr) {
  51         union {
  52                 unsigned i[2];
  53                 double d;
  54         } xx, yy;
  55         unsigned hx, s;
  56 
  57         xx.d = x;
  58         hx = xx.i[HIWORD] & ~0x80000000;
  59 
  60         if (hx >= 0x43300000) {      /* x is NaN, infinite, or integral */
  61                 *iptr = x;
  62                 if (hx < 0x7ff00000 || (hx == 0x7ff00000 &&
  63                         xx.i[LOWORD] == 0)) {
  64                         xx.i[HIWORD] &= 0x80000000;
  65                         xx.i[LOWORD] = 0;
  66                 }
  67                 return (xx.d);
  68         }
  69 
  70         if (hx < 0x3ff00000) {       /* |x| < 1 */
  71                 xx.i[HIWORD] &= 0x80000000;
  72                 xx.i[LOWORD] = 0;
  73                 *iptr = xx.d;
  74                 return (x);
  75         }
  76 
  77         /* split x at the binary point */
  78         s = xx.i[HIWORD] & 0x80000000;
  79         if (hx < 0x41400000) {
  80                 yy.i[HIWORD] = xx.i[HIWORD] & ~((1 << (0x413 - (hx >> 20))) -
  81                         1);
  82                 yy.i[LOWORD] = 0;
  83         } else {
  84                 yy.i[HIWORD] = xx.i[HIWORD];
  85                 yy.i[LOWORD] = xx.i[LOWORD] & ~((1 << (0x433 - (hx >> 20))) -
  86                         1);
  87         }
  88         *iptr = yy.d;
  89         xx.d -= yy.d;
  90         xx.i[HIWORD] = (xx.i[HIWORD] & ~0x80000000) | s;
  91                                                         /* keep sign of x */
  92         return (xx.d);
  93 }