usr/src/lib/libbc/libc/gen/common/modf.c

   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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 #pragma ident   "%Z%%M% %I%     %E% SMI"  /* from ATT S5R3 */
  23
  24 /*      The following is extracted from...      */
  25
  26 /*      Copyright (c) 1984 AT&T */
  27 /*        All Rights Reserved   */
  28
  29
  30 /*
  31  * modf(value, iptr) returns the signed fractional part of value
  32  * and stores the integer part indirectly through iptr.
  33  *
  34  */
  35
  36 #define MAXPOWTWO       4.503599627370496000E+15
  37                         /* doubles >= MAXPOWTWO are already integers */
  38 double
  39 modf(value, iptr)
  40 double value;
  41 register double *iptr;
  42 {
  43         register double absvalue;
  44
  45         if ((absvalue = (value >= 0.0) ? value : -value) >= MAXPOWTWO)
  46                 *iptr = value; /* it must be an integer */
  47         else {
  48                 *iptr = absvalue + MAXPOWTWO; /* shift fraction off right */
  49                 *iptr -= MAXPOWTWO; /* shift back without fraction */
  50                 while (*iptr > absvalue) /* above arithmetic might round */
  51                         *iptr -= 1.0; /* test again just to be sure */
  52                 if (value < 0.0)
  53                         *iptr = -*iptr;
  54         }
  55         return (value - *iptr); /* signed fractional part */
  56 }