/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 1988 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/* Copyright (c) 1984 AT&T */
/* All Rights Reserved */
#pragma ident "%Z%%M% %I% %E% SMI" /* from S5R2 2.7 */
/*LINTLIBRARY*/
/*
* double ldexp (value, exp)
* double value;
* int exp;
*
* Ldexp returns value * 2**exp, if that result is in range.
* If underflow occurs, it returns zero. If overflow occurs,
* it returns a value of appropriate sign and largest single-
* precision magnitude. In case of underflow or overflow,
* the external int "errno" is set to ERANGE. Note that errno is
* not modified if no error occurs, so if you intend to test it
* after you use ldexp, you had better set it to something
* other than ERANGE first (zero is a reasonable value to use).
*/
#include <values.h>
#include <errno.h>
/* Largest signed long int power of 2 */
#define MAXSHIFT (BITSPERBYTE * sizeof(long) - 2)
extern double frexp();
double
ldexp(value, exp)
register double value;
register int exp;
{
int old_exp;
if (exp == 0 || value == 0.0) /* nothing to do for zero */
return (value);
#if !(pdp11 || u3b5) /* pdp11 "cc" can't handle cast of
double to void on pdp11 or 3b5 */
(void)
#endif
frexp(value, &old_exp);
if (exp > 0) {
if (exp + old_exp > MAXBEXP) { /* overflow */
errno = ERANGE;
return ((double)(value < 0 ? MINDOUBLE : MAXDOUBLE));
/*
return ((double)(value < 0 ? -1.0e999 : 1.0e999));
*/
}
for ( ; exp > MAXSHIFT; exp -= MAXSHIFT)
value *= (1L << MAXSHIFT);
return (value * (1L << exp));
}
if (exp + old_exp < MINBEXP) { /* underflow */
errno = ERANGE;
return (0.0);
}
for ( ; exp < -MAXSHIFT; exp += MAXSHIFT)
value *= 1.0/(1L << MAXSHIFT); /* mult faster than div */
return (value / (1L << -exp));
}