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 2006 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28 
  29 #pragma weak __remainder = remainder
  30 
  31 /*
  32  * remainder(x,p)
  33  * Code originated from 4.3bsd.
  34  * Modified by K.C. Ng for SUN 4.0 libm.
  35  * Return :
  36  *      returns  x REM p  =  x - [x/p]*p as if in infinite precise arithmetic,
  37  *      where [x/p] is the (inifinite bit) integer nearest x/p (in half way
  38  *      case choose the even one).
  39  * Method :
  40  *      Based on fmod() return x-[x/p]chopped*p exactly.
  41  */
  42 
  43 #include "libm.h"
  44 
  45 static const double zero = 0.0, half = 0.5;
  46 
  47 double
  48 remainder(double x, double p) {
  49         double  halfp;
  50         int     ix, hx, hp;
  51 
  52         ix = ((int *)&x)[HIWORD];
  53         hx = ix & ~0x80000000;
  54         hp = ((int *)&p)[HIWORD] & ~0x80000000;
  55 
  56         if (hp > 0x7ff00000 || (hp == 0x7ff00000 && ((int *)&p)[LOWORD] != 0))
  57                 return (x * p);
  58         if (hx > 0x7ff00000 || (hx == 0x7ff00000 && ((int *)&x)[LOWORD] != 0))
  59                 return (x * p);
  60 
  61         if ((hp | ((int *)&p)[LOWORD]) == 0 || hx == 0x7ff00000)
  62                 return (_SVID_libm_err(x, p, 28));
  63 
  64         p = fabs(p);
  65         if (hp < 0x7fe00000)
  66                 x = fmod(x, p + p);
  67         x = fabs(x);
  68         if (hp < 0x00200000) {
  69                 if (x + x > p) {
  70                         if (x == p)     /* avoid x-x=-0 in RM mode */
  71                                 return ((ix < 0)? -zero : zero);
  72                         x -= p;
  73                         if (x + x >= p)
  74                                 x -= p;
  75                 }
  76         } else {
  77                 halfp = half * p;
  78                 if (x > halfp) {
  79                         if (x == p)     /* avoid x-x=-0 in RM mode */
  80                                 return ((ix < 0)? -zero : zero);
  81                         x -= p;
  82                         if (x >= halfp)
  83                                 x -= p;
  84                 }
  85         }
  86         return ((ix < 0)? -x : x);
  87 }