e_scalb.c

来自「This is a resource based on j2me embedde」· C语言 代码 · 共 66 行

/*
 * @(#)e_scalb.c	1.9 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

/*
 * __ieee754_scalb(x, fn) is provide for
 * passing various standard test suite. One
 * should use scalbn() instead.
 */

#include "fdlibm.h"

#ifdef _SCALB_INT
#ifdef __STDC__
	double __ieee754_scalb(double x, int fn)
#else
	double __ieee754_scalb(x,fn)
	double x; int fn;
#endif
#else
#ifdef __STDC__
	double __ieee754_scalb(double x, double fn)
#else
	double __ieee754_scalb(x,fn)
	double x, fn;
#endif
#endif
{
#ifdef _SCALB_INT
	return scalbn(x,fn);
#else
	if (isnan(x)||isnan(fn)) return x*fn;
	if (!finite(fn)) {
	    if(fn>0.0) return x*fn;
	    else       return x/(-fn);
	}
	if (rint(fn)!=fn) return (fn-fn)/(fn-fn);
	if ( fn > 65000.0) return scalbn(x, 65000);
	if (-fn > 65000.0) return scalbn(x,-65000);
	return scalbn(x,(int)fn);
#endif
}