xref: /titanic_51/usr/src/lib/libbc/libc/gen/common/frexp.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
1*7c478bd9Sstevel@tonic-gate /*
2*7c478bd9Sstevel@tonic-gate  * CDDL HEADER START
3*7c478bd9Sstevel@tonic-gate  *
4*7c478bd9Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
5*7c478bd9Sstevel@tonic-gate  * Common Development and Distribution License, Version 1.0 only
6*7c478bd9Sstevel@tonic-gate  * (the "License").  You may not use this file except in compliance
7*7c478bd9Sstevel@tonic-gate  * with the License.
8*7c478bd9Sstevel@tonic-gate  *
9*7c478bd9Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10*7c478bd9Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
11*7c478bd9Sstevel@tonic-gate  * See the License for the specific language governing permissions
12*7c478bd9Sstevel@tonic-gate  * and limitations under the License.
13*7c478bd9Sstevel@tonic-gate  *
14*7c478bd9Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
15*7c478bd9Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16*7c478bd9Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
17*7c478bd9Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
18*7c478bd9Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
19*7c478bd9Sstevel@tonic-gate  *
20*7c478bd9Sstevel@tonic-gate  * CDDL HEADER END
21*7c478bd9Sstevel@tonic-gate  */
22*7c478bd9Sstevel@tonic-gate #pragma ident	"%Z%%M%	%I%	%E% SMI"  /* from UCB 5.2 3/9/86 */
23*7c478bd9Sstevel@tonic-gate 
24*7c478bd9Sstevel@tonic-gate /*
25*7c478bd9Sstevel@tonic-gate  * the call
26*7c478bd9Sstevel@tonic-gate  *	x = frexp(arg,&exp);
27*7c478bd9Sstevel@tonic-gate  * must return a double fp quantity x which is <1.0
28*7c478bd9Sstevel@tonic-gate  * and the corresponding binary exponent "exp".
29*7c478bd9Sstevel@tonic-gate  * such that
30*7c478bd9Sstevel@tonic-gate  *	arg = x*2^exp
31*7c478bd9Sstevel@tonic-gate  */
32*7c478bd9Sstevel@tonic-gate double
33*7c478bd9Sstevel@tonic-gate frexp(x, i)
34*7c478bd9Sstevel@tonic-gate 	double x;
35*7c478bd9Sstevel@tonic-gate 	int *i;
36*7c478bd9Sstevel@tonic-gate {
37*7c478bd9Sstevel@tonic-gate 	int neg, j;
38*7c478bd9Sstevel@tonic-gate 
39*7c478bd9Sstevel@tonic-gate 	j = 0;
40*7c478bd9Sstevel@tonic-gate 	neg = 0;
41*7c478bd9Sstevel@tonic-gate 	if (x<0) {
42*7c478bd9Sstevel@tonic-gate 		x = -x;
43*7c478bd9Sstevel@tonic-gate 		neg = 1;
44*7c478bd9Sstevel@tonic-gate 	}
45*7c478bd9Sstevel@tonic-gate 	if (x>=1.0)
46*7c478bd9Sstevel@tonic-gate 		while (x>=1.0) {
47*7c478bd9Sstevel@tonic-gate 			j = j+1;
48*7c478bd9Sstevel@tonic-gate 			x = x/2;
49*7c478bd9Sstevel@tonic-gate 		}
50*7c478bd9Sstevel@tonic-gate 	else if (x < 0.5 && x != 0.0)
51*7c478bd9Sstevel@tonic-gate 		while(x<0.5) {
52*7c478bd9Sstevel@tonic-gate 			j = j-1;
53*7c478bd9Sstevel@tonic-gate 			x = 2*x;
54*7c478bd9Sstevel@tonic-gate 		}
55*7c478bd9Sstevel@tonic-gate 	*i = j;
56*7c478bd9Sstevel@tonic-gate 	if(neg)
57*7c478bd9Sstevel@tonic-gate 		x = -x;
58*7c478bd9Sstevel@tonic-gate 	return (x);
59*7c478bd9Sstevel@tonic-gate }
60