/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)support.c	5.6 (Berkeley) 10/9/90";
#endif /* not lint */

/* 
 * Some IEEE standard 754 recommended functions and remainder and sqrt for 
 * supporting the C elementary functions.
 ******************************************************************************
 * WARNING:
 *      These codes are developed (in double) to support the C elementary
 * functions temporarily. They are not universal, and some of them are very
 * slow (in particular, drem and sqrt is extremely inefficient). Each 
 * computer system should have its implementation of these functions using 
 * its own assembler.
 ******************************************************************************
 *
 * IEEE 754 required operations:
 *     drem(x,p) 
 *              returns  x REM y  =  x - [x/y]*y , where [x/y] is the integer
 *              nearest x/y; in half way case, choose the even one.
 *     sqrt(x) 
 *              returns the square root of x correctly rounded according to 
 *		the rounding mod.
 *
 * IEEE 754 recommended functions:
 * (a) copysign(x,y) 
 *              returns x with the sign of y. 
 * (b) scalb(x,N) 
 *              returns  x * (2**N), for integer values N.
 * (c) logb(x) 
 *              returns the unbiased exponent of x, a signed integer in 
 *              double precision, except that logb(0) is -INF, logb(INF) 
 *              is +INF, and logb(NAN) is that NAN.
 * (d) finite(x) 
 *              returns the value TRUE if -INF < x < +INF and returns 
 *              FALSE otherwise.
 *
 *
 * CODED IN C BY K.C. NG, 11/25/84;
 * REVISED BY K.C. NG on 1/22/85, 2/13/85, 3/24/85.
 */

#include "mathimpl.h"

#if defined(vax)||defined(tahoe)      /* VAX D format */
#include <errno.h>
    static const unsigned short msign=0x7fff , mexp =0x7f80 ;
    static const short  prep1=57, gap=7, bias=129           ;   
    static const double novf=1.7E38, nunf=3.0E-39, zero=0.0 ;
#else	/* defined(vax)||defined(tahoe) */
    static const unsigned short msign=0x7fff, mexp =0x7ff0  ;
    static const short prep1=54, gap=4, bias=1023           ;
    static const double novf=1.7E308, nunf=3.0E-308,zero=0.0;
#endif	/* defined(vax)||defined(tahoe) */

int finite(x)
double x;    
{
#if defined(vax)||defined(tahoe)
        return(1);
#else	/* defined(vax)||defined(tahoe) */
#ifdef national
        return( (*((short *) &x+3 ) & mexp ) != mexp );
#else	/* national */
        return( (*((short *) &x ) & mexp ) != mexp );
#endif	/* national */
#endif	/* defined(vax)||defined(tahoe) */
}
