/* DEC	*MultiplyDecimal(pDst,pSrc1,pSrc2);
 *
 * ARGUMENT
 *	DEC	*pDst;
 *	DEC	*pSrc1,pSrc2;
 *
 * DESCRIPTION
 *	Multiplies pSrc1 times pSrc2 and puts it into pDst.
 *   pSrc1 and pSrc2 remain unchanged.
 *   Additionally, if either number is negative, it
 *   is	temporarily converted a	positive for the mult. and a flag is set
 *   to	convert	the answer if unlike signs.
 *
 * SIDE	EFFECTS
 *	pDst is	indeterminate on error.
 *
 * RETURNS
 *	Returns	pointer	to pDst	if successful, otherwise a GM_NULL. The
 *   type error	(GM_OVERFLOW, GM_UNDERFLOW, GM_NOMEMORY) is in wGMError
 *   if	wGMError didn't	contain	a previous error on entry.
 *
 * POSSIBLE ERROR CODES
 *
 *	GM_NULLPOINTER
 *	GM_OVERFLOW
 *	GM_UNDERFLOW
 *
 * AUTHOR
 *  Andy Anderson   29-JAN-1987	 16:30
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 */

#include <stdio.h>
#include "gm.h"
#include "gmsystem.h"

DEC	*MultiplyDecimal(pDst,pSrc1,pSrc2)
DEC	*pDst;
DEC	*pSrc1,*pSrc2;
{
	register int	i,p;
	int	r=0,stktmp=0;
	unsigned SHORT dtp[10];


	_MacStart(GM_DMUL);
	_MacInVarD(pSrc1);
	_MacInVarD(pSrc2);
	_MacOutVarD(pDst);

/*  First, if either of	the numbers is zero, the result	is alway zero */
	if((_MacIsDecZ(pSrc1)) || (_MacIsDecZ(pSrc2)))	{
		i = pSrc1->dc.id + pSrc2->dc.id;
		_MacDZero(pDst);
		pDst->dc.id = (i > GM_MAXID) ? GM_MAXID	: i;
		_MacRet(pDst);
		}

/*	Find out number	of 16-bit int's	in each	number */
	i = 3;
	while (	pSrc1->dc.sl[i]	==0 && i>=0 )
	    i--;
	p = 3;
	while (	pSrc2->dc.sl[p]	== 0 &&	p>=0 )
	    p--;


	/* allow user to specify pDst as one of	the sources */
	_MulUnsArrByUnsArr(pSrc1->dc.sl, pSrc2->dc.sl, dtp,
		i+1,p+1,stktmp);

	/* squeeze eight digits	down to	four */
	p=0;
	while ((dtp[4] >= 500) || (dtp[5] != 0)	||
		(dtp[6]	!= 0) || (dtp[7] != 0))	 {
		r = _DivUnsArrByUns(dtp, 10000,	8);
		p+=4;
		}

	if (!dtp[4] && dtp[3]<=32767)  {
		if (r>=5000)
			(void) _IncrementUnsArr(dtp);
	}
	else
	if (dtp[4] >= 50)  {
		_DivUnsArrByUnsRound(dtp, 1000,	5);
		p+=3;
		}
	else
	if (dtp[4] >= 5)  {
		_DivUnsArrByUnsRound(dtp, 100, 5);
		p+=2;
		}
	else  {
		_DivUnsArrByUnsRound(dtp, 10, 5);
		p++;
	}
/* now p is the	power of 10 which was divided */

	i = pSrc1->dc.id + pSrc2->dc.id	- p;
	if (i <	GM_MINID)  {
		_MacErr(GM_OVERFLOW);
		_MacRet(GM_NULL);
	}

	pDst->dc.sl[0] = dtp[0];
	pDst->dc.sl[1] = dtp[1];
	pDst->dc.sl[2] = dtp[2];
	pDst->dc.sl[3] = dtp[3];
	pDst->dc.sl[4] = dtp[4];

/*  if the signs of the	sources	are different, pDst=-pDst */
	pDst->dc.attr =	(pSrc1->dc.attr^pSrc2->dc.attr);

	if (i >	GM_MAXID)  {
		_DivUnsArrByPwrOf10(pDst->dc.sl,
			4, i - GM_MAXID);
		pDst->dc.id = GM_MAXID;
		if (_MacIsDecZ(pDst))
			_MacErr(GM_UNDERFLOW);
		}

	pDst->dc.id = i;

	_MacRet(pDst);
}