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 #pragma weak remainderl = __remainderl
  31 
  32 #include "libm.h"
  33 #include "longdouble.h"
  34 
  35 /*
  36  * remainderl(x,p)
  37  *      returns  x REM p  =  x - [x/p]*p as if in infinite
  38  *      precise arithmetic, where [x/p] is the (inifinite bit)
  39  *      integer nearest x/p (in half way case choose the even one).
  40  * Method :
  41  *      Based on fmodl() return x-[x/p]chopped*p exactly.
  42  */
  43 
  44 #define HFMAX   5.948657476786158825428796633140035080982e+4931L
  45 #define DBMIN   6.724206286224187012525355634643505205196e-4932L
  46 
  47 static const long double
  48         zero = 0.0L,
  49         half = 0.5L,
  50         hfmax = HFMAX,  /* half of the maximum number */
  51         dbmin = DBMIN;  /* double of the minimum (normal) number */
  52 
  53 long double
  54 remainderl(long double x, long double p) {
  55         long double hp;
  56         int sx;
  57 
  58         if (isnanl(p))
  59                 return (x + p);
  60         if (!finitel(x))
  61                 return (x - x);
  62         p = fabsl(p);
  63         if (p <= hfmax)
  64                 x = fmodl(x, p + p);
  65         sx = signbitl(x);
  66         x = fabsl(x);
  67         if (p < dbmin) {
  68                 if (x + x > p) {
  69                         if (x == p)
  70                                 x = zero;
  71                         else
  72                                 x -= p; /* avoid x-x=-0 in RM mode */
  73                         if (x + x >= p)
  74                                 x -= p;
  75                 }
  76         } else {
  77                 hp = half * p;
  78                 if (x > hp) {
  79                         if (x == p)
  80                                 x = zero;
  81                         else
  82                                 x -= p; /* avoid x-x=-0 in RM mode */
  83                         if (x >= hp)
  84                                 x -= p;
  85                 }
  86         }
  87         return (sx == 0 ? x : -x);
  88 }