cfmul.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 103 行

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*                            Open Watcom Project
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*    This file contains Original Code and/or Modifications of Original
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#include "cfloat.h"

extern  cfloat  *       CFAlloc(int);
extern  int             CFAccess(cfloat*,int);
extern  cfloat  *       CFAdd(cfloat*,cfloat*);
extern  void            CFFree(cfloat*);
extern  void            CFDeposit(cfloat*,int,int);
extern  void            CFClean(cfloat*);

static  cfloat  *SDMul( cfloat *op1, int plyer, int op1left,
                        int op1exp, int byexp ) {
/*******************************************************************/

    int         sum;
    int         exp;
    cfloat      *result;
    int         resexp;
    int         respos;

    sum = 0;
    exp = op1exp;
    resexp = op1exp + byexp - 1;
    respos = op1left - op1exp + 1;
    result = CFAlloc( respos + 1 );
    result->len = respos + 1;
    result->exp = op1left + byexp;
    while( exp <= op1left ) {
        sum += CFAccess( op1, op1->exp - exp++ ) * plyer;
        CFDeposit( result, respos--, sum % 10 );
        sum /= 10;
        resexp++;
    }
    CFDeposit( result, respos, sum % 10 );
    result->sign = op1->sign;          /* by convention*/
    CFClean( result );
    return( result );
}

extern  cfloat  *CFMul( cfloat *op1, cfloat *op2 ) {
/**************************************************/

    cfloat      *result;
    cfloat      *temp;
    cfloat      *sum;
    int         op1left;
    int         op1exp;
    int         op2exp;
    int         op2ptr;
    int         sgn;

    sgn = op1->sign * op2->sign;
    result = CFAlloc( 1 );
    if( sgn != 0 ) {
        op1left = op1->exp;
        op1exp = op1left - op1->len + 1;
        op2exp = op2->exp - op2->len + 1;
        op2ptr = op2->len - 1;
        while( op2ptr >= 0 ) {
            temp = SDMul( op1, CFAccess( op2, op2ptr-- ),
                op1left, op1exp, op2exp++ );
            sum = CFAdd( result, temp );
            CFFree( temp );
            CFFree( result );
            result = sum;
        }
        result->sign = sgn;
    }
    return( result );
}