static private void FastMul(BigNumber aa, BigNumber bb, BigNumber rr)
{
int ii, k, nexp, sign;
BigNumber M_ain = new BigNumber();
BigNumber M_bin = new BigNumber();
BigNumber.Copy(aa, M_ain);
BigNumber.Copy(bb, M_bin);
int size_flag = GetSizeofInt();
int bit_limit = 8 * size_flag + 1;
sign = M_ain.signum * M_bin.signum;
nexp = M_ain.exponent + M_bin.exponent;
if (M_ain.dataLength >= M_bin.dataLength)
{
ii = M_ain.dataLength;
}
else
{
ii = M_bin.dataLength;
}
ii = (ii + 1) >> 1;
ii = NextPowerOfTwo(ii);
k = 2 * ii; /* required size of result, in bytes */
BigNumber.Pad(M_ain, k); /* fill out the data so the number of */
BigNumber.Pad(M_bin, k); /* bytes is an exact power of 2 */
if (k > rr.mantissa.Length)
{
BigNumber.Expand(rr, (k + 32));
}
BigNumber.FastMulFFT(rr.mantissa, M_ain.mantissa, M_bin.mantissa, ii);
rr.signum = (sbyte)sign;
rr.exponent = nexp;
rr.dataLength = 4 * ii;
BigNumber.Normalize(rr);
}
/// <summary>
/// normalize number
/// </summary>
/// <param name="atm"></param>
static private void Normalize(BigNumber atm)
{
if (atm.signum == 0)
{
return;
}
int ucp = 0;
int i;
int index;
int datalength = atm.dataLength;
int exponent = atm.exponent;
byte numdiv = 0, numrem = 0, numrem2 = 0;
BigNumber.Pad(atm, datalength + 3);
// remove leading zeroes
while (true)
{
// extract first 2 nibbles
Unpack(atm.mantissa[0], ref numdiv, ref numrem);
// if first digit is greater 1 we are done
if (numdiv >= 1)
{
break;
}
// otherwise we have leading zeroes
index = (datalength + 1) >> 1;
if (numrem == 0) // both nibbles are 0
{
i = 0;
ucp = 0;
while (true)
{
if (atm.mantissa[ucp] != 0)
{
break;
}
ucp++;
i++;
}
byte[] copy = new byte[atm.mantissa.Length];
Array.Copy(atm.mantissa, ucp, copy, 0, (index + 1 - i));
atm.mantissa = copy;
datalength -= 2 * i;
exponent -= 2 * i;
}
else
{
for (i = 0; i < index; i++)
{
Unpack(atm.mantissa[i + 1], ref numdiv, ref numrem2);
atm.mantissa[i] = (byte)(10 * numrem + numdiv);
numrem = numrem2;
}
datalength--;
exponent--;
}
}
// remove trailing zeroes
while (true)
{
index = ((datalength + 1) >> 1) - 1;
if ((datalength & 1) == 0) /* back-up full bytes at a time if the */
{ /* current length is an even number */
ucp = index;
if (atm.mantissa[ucp] == 0)
{
while (true)
{
datalength -= 2;
index--;
ucp--;
if (atm.mantissa[ucp] != 0)
{
break;
}
}
}
}
Unpack(atm.mantissa[index], ref numdiv, ref numrem);
if (numrem != 0) /* last digit non-zero, all done */
{
break;
}
if ((datalength & 1) != 0) /* if odd, then first char must be non-zero */
{
if (numdiv != 0)
{
break;
}
}
if (datalength == 1)
{
atm.signum = 0;
exponent = 0;
break;
}
datalength--;
}
atm.dataLength = datalength;
atm.exponent = exponent;
}