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 __remainderl = remainderl
  32 
  33 #include "libm.h"
  34 #include "longdouble.h"
  35 
  36 /*
  37  * remainderl(x,p)
  38  *      returns  x REM p  =  x - [x/p]*p as if in infinite
  39  *      precise arithmetic, where [x/p] is the (inifinite bit)
  40  *      integer nearest x/p (in half way case choose the even one).
  41  * Method :
  42  *      Based on fmodl() return x-[x/p]chopped*p exactly.
  43  */
  44 
  45 #define HFMAX           5.948657476786158825428796633140035080982e+4931L
  46 #define DBMIN           6.724206286224187012525355634643505205196e-4932L
  47 
  48 static const long double 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 {
  56         long double hp;
  57         int sx;
  58 
  59         if (isnanl(p))
  60                 return (x + p);
  61 
  62         if (!finitel(x))
  63                 return (x - x);
  64 
  65         p = fabsl(p);
  66 
  67         if (p <= hfmax)
  68                 x = fmodl(x, p + p);
  69 
  70         sx = signbitl(x);
  71         x = fabsl(x);
  72 
  73         if (p < dbmin) {
  74                 if (x + x > p) {
  75                         if (x == p)
  76                                 x = zero;
  77                         else
  78                                 x -= p;         /* avoid x-x=-0 in RM mode */
  79 
  80                         if (x + x >= p)
  81                                 x -= p;
  82                 }
  83         } else {
  84                 hp = half * p;
  85 
  86                 if (x > hp) {
  87                         if (x == p)
  88                                 x = zero;
  89                         else
  90                                 x -= p;         /* avoid x-x=-0 in RM mode */
  91 
  92                         if (x >= hp)
  93                                 x -= p;
  94                 }
  95         }
  96 
  97         return (sx == 0 ? x : -x);
  98 }