xref: /titanic_41/usr/src/lib/libbc/libc/gen/common/modf.c (revision 74e20cfe817b82802b16fac8690dadcda76f54f5)
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 }
57