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 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __remainder = remainder
  32 
  33 /*
  34  * remainder(x,p)
  35  * Code originated from 4.3bsd.
  36  * Modified by K.C. Ng for SUN 4.0 libm.
  37  * Return :
  38  *      returns  x REM p  =  x - [x/p]*p as if in infinite precise arithmetic,
  39  *      where [x/p] is the (inifinite bit) integer nearest x/p (in half way
  40  *      case choose the even one).
  41  * Method :
  42  *      Based on fmod() return x-[x/p]chopped*p exactly.
  43  */
  44 
  45 #include "libm.h"
  46 
  47 static const double zero = 0.0, half = 0.5;
  48 
  49 double
  50 remainder(double x, double p)
  51 {
  52         double halfp;
  53         int ix, hx, hp;
  54 
  55         ix = ((int *)&x)[HIWORD];
  56         hx = ix & ~0x80000000;
  57         hp = ((int *)&p)[HIWORD] & ~0x80000000;
  58 
  59         if (hp > 0x7ff00000 || (hp == 0x7ff00000 && ((int *)&p)[LOWORD] != 0))
  60                 return (x * p);
  61 
  62         if (hx > 0x7ff00000 || (hx == 0x7ff00000 && ((int *)&x)[LOWORD] != 0))
  63                 return (x * p);
  64 
  65         if ((hp | ((int *)&p)[LOWORD]) == 0 || hx == 0x7ff00000)
  66                 return (_SVID_libm_err(x, p, 28));
  67 
  68         p = fabs(p);
  69 
  70         if (hp < 0x7fe00000)
  71                 x = fmod(x, p + p);
  72 
  73         x = fabs(x);
  74 
  75         if (hp < 0x00200000) {
  76                 if (x + x > p) {
  77                         if (x == p)     /* avoid x-x=-0 in RM mode */
  78                                 return ((ix < 0) ? -zero : zero);
  79 
  80                         x -= p;
  81 
  82                         if (x + x >= p)
  83                                 x -= p;
  84                 }
  85         } else {
  86                 halfp = half * p;
  87 
  88                 if (x > halfp) {
  89                         if (x == p)     /* avoid x-x=-0 in RM mode */
  90                                 return ((ix < 0) ? -zero : zero);
  91 
  92                         x -= p;
  93 
  94                         if (x >= halfp)
  95                                 x -= p;
  96                 }
  97         }
  98 
  99         return ((ix < 0) ? -x : x);
 100 }