campo-sirio/gfm/mul10.c

/* int _MulUnsArrByPwrOf10(pa,n,w)
 *
 * ARGUMENT
 *      unsigned        pa[];
 *      int             n;            power of 10 to multiply by
 *      int             w;            number of digits
 *
 * DESCRIPTION
 *      Multiplies the pa[] array by 10^n (0<n<47),
 *
 * SIDE EFFECTS
 *      The value of pa is unchanged on overflow.
 *
 * RETURNS
 *      GM_SUCCES if no overflow, otherwise GM_OVERFLOW
 *
 * AUTHOR
 *      Brugnoli Giugno 1992
 *
 * MODIFICATIONS
 *
 */

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

int Multiply(sr,num,m)
unsigned SHORT  sr[],num;
int       m;
{
  int i;
  unsigned long pdst[10];
  unsigned SHORT carry = 0;

  for (i=0;i<m;i++)
    pdst[i]=(unsigned long)sr[i]*num;

  for (i=0;i<m;i++)
  {
    pdst[i]+=carry;
    if (pdst[i]>MAXUNSINT)
    {
      carry=(unsigned SHORT)(pdst[i]>>BITSPERUI);
      sr[i]=(unsigned SHORT)(pdst[i]&MAXUNSINT);
    }
    else
    {
      carry=0;
      sr[i]=(unsigned SHORT)pdst[i];
    }
  }
  return( (carry)? GM_OVERFLOW : GM_SUCCESS );
}


int    _MulUnsArrByPwrOf10(pa,n,w)
unsigned SHORT        pa[];
int             n,w;
{
  int k=GM_SUCCESS;

  if (n>47)
    return GM_OVERFLOW;

  while (n>4)
  {
    k = Multiply(pa,10000,w);
    if (k != GM_SUCCESS)
      return k;
    n-=4;
  }

  switch (n)
  {
		case 0: k=Multiply(pa,1,w); break;
		case 1: k=Multiply(pa,10,w); break;
		case 2: k=Multiply(pa,100,w); break;
		case 3: k=Multiply(pa,1000,w); break;
		case 4: k=Multiply(pa,10000,w); break;
		default: break;
  }

  return(k);

}