130 lines
2.7 KiB
C
130 lines
2.7 KiB
C
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/* DEC *MultiplyDecimal(pDst,pSrc1,pSrc2);
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*
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* ARGUMENT
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* DEC *pDst;
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* DEC *pSrc1,pSrc2;
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*
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* DESCRIPTION
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* Multiplies pSrc1 times pSrc2 and puts it into pDst.
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* pSrc1 and pSrc2 remain unchanged.
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* Additionally, if either number is negative, it
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* is temporarily converted a positive for the mult. and a flag is set
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* to convert the answer if unlike signs.
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*
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* SIDE EFFECTS
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* pDst is indeterminate on error.
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*
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* RETURNS
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* Returns pointer to pDst if successful, otherwise a GM_NULL. The
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* type error (GM_OVERFLOW, GM_UNDERFLOW, GM_NOMEMORY) is in wGMError
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* if wGMError didn't contain a previous error on entry.
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*
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* POSSIBLE ERROR CODES
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*
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* GM_NULLPOINTER
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* GM_OVERFLOW
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* GM_UNDERFLOW
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*
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* AUTHOR
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* Andy Anderson 29-JAN-1987 16:30
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* Copyright (C) 1987-1990 Greenleaf Software Inc. All rights reserved.
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*
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* MODIFICATIONS
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*
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*/
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#include <stdio.h>
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#include "gm.h"
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#include "gmsystem.h"
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DEC *MultiplyDecimal(pDst,pSrc1,pSrc2)
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DEC *pDst;
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DEC *pSrc1,*pSrc2;
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{
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register int i,p;
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int r=0,stktmp=0;
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unsigned SHORT dtp[10];
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_MacStart(GM_DMUL);
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_MacInVarD(pSrc1);
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_MacInVarD(pSrc2);
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_MacOutVarD(pDst);
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/* First, if either of the numbers is zero, the result is alway zero */
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if((_MacIsDecZ(pSrc1)) || (_MacIsDecZ(pSrc2))) {
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i = pSrc1->dc.id + pSrc2->dc.id;
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_MacDZero(pDst);
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pDst->dc.id = (i > GM_MAXID) ? GM_MAXID : i;
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_MacRet(pDst);
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}
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/* Find out number of 16-bit int's in each number */
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i = 3;
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while ( pSrc1->dc.sl[i] ==0 && i>=0 )
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i--;
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p = 3;
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while ( pSrc2->dc.sl[p] == 0 && p>=0 )
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p--;
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/* allow user to specify pDst as one of the sources */
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_MulUnsArrByUnsArr(pSrc1->dc.sl, pSrc2->dc.sl, dtp,
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i+1,p+1,stktmp);
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/* squeeze eight digits down to four */
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p=0;
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while ((dtp[4] >= 500) || (dtp[5] != 0) ||
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(dtp[6] != 0) || (dtp[7] != 0)) {
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r = _DivUnsArrByUns(dtp, 10000, 8);
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p+=4;
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}
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if (!dtp[4] && dtp[3]<=32767) {
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if (r>=5000)
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(void) _IncrementUnsArr(dtp);
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}
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else
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if (dtp[4] >= 50) {
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_DivUnsArrByUnsRound(dtp, 1000, 5);
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p+=3;
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}
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else
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if (dtp[4] >= 5) {
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_DivUnsArrByUnsRound(dtp, 100, 5);
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p+=2;
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}
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else {
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_DivUnsArrByUnsRound(dtp, 10, 5);
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p++;
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}
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/* now p is the power of 10 which was divided */
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i = pSrc1->dc.id + pSrc2->dc.id - p;
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if (i < GM_MINID) {
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_MacErr(GM_OVERFLOW);
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_MacRet(GM_NULL);
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}
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pDst->dc.sl[0] = dtp[0];
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pDst->dc.sl[1] = dtp[1];
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pDst->dc.sl[2] = dtp[2];
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pDst->dc.sl[3] = dtp[3];
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pDst->dc.sl[4] = dtp[4];
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/* if the signs of the sources are different, pDst=-pDst */
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pDst->dc.attr = (pSrc1->dc.attr^pSrc2->dc.attr);
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if (i > GM_MAXID) {
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_DivUnsArrByPwrOf10(pDst->dc.sl,
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4, i - GM_MAXID);
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pDst->dc.id = GM_MAXID;
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if (_MacIsDecZ(pDst))
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_MacErr(GM_UNDERFLOW);
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}
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pDst->dc.id = i;
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_MacRet(pDst);
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}
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