static int M_exp_compute_nn(ref int n, BigNumber b, BigNumber a)
{
BigNumber tmp0, tmp1;
String cp = "";
int kk;
n = 0;
tmp0 = new BigNumber();
tmp1 = new BigNumber();
BigNumber.Mul(BN_exp_log2R, a, tmp1);
if (tmp1.signum >= 0)
{
BigNumber.Add(tmp1, BigNumber.BN_OneHalf, tmp0);
BigNumber.Floor(tmp1, tmp0);
}
else
{
BigNumber.Sub(tmp1, BigNumber.BN_OneHalf, tmp0);
BigNumber.Ceil(tmp1, tmp0);
}
kk = tmp1.exponent;
cp = BigNumber.ToIntString(tmp1);
n = Convert.ToInt32(cp);
BigNumber.SetFromLong(b, (long)(n));
kk = BigNumber.Compare(b, tmp1);
return(kk);
}
public static bool operator ==(BigNumber c1, BigNumber c2)
{
return(BigNumber.Compare(c1, c2) == 0);
}
static private void Div(BigNumber aa, BigNumber bb, BigNumber rr, int places)
{
int j, k, m, b0, nexp, indexr, icompare, iterations;
sbyte sign;
long trial_numer;
BigNumber M_div_worka = new BigNumber();
BigNumber M_div_workb = new BigNumber();
BigNumber M_div_tmp7 = new BigNumber();
BigNumber M_div_tmp8 = new BigNumber();
BigNumber M_div_tmp9 = new BigNumber();
sign = (sbyte)(aa.signum * bb.signum);
if (sign == 0) /* one number is zero, result is zero */
{
if (bb.signum == 0)
{
throw new BigNumberException("Division by Zero");
}
BigNumber.SetZero(rr);
return;
}
if (bb.mantissa[0] >= 50)
{
BigNumber.Abs(M_div_worka, aa);
BigNumber.Abs(M_div_workb, bb);
}
else /* 'normal' step D1 */
{
k = 100 / (bb.mantissa[0] + 1);
BigNumber.SetFromLong(M_div_tmp9, (long)k);
BigNumber.Mul(M_div_tmp9, aa, M_div_worka);
BigNumber.Mul(M_div_tmp9, bb, M_div_workb);
M_div_worka.signum = 1;
M_div_workb.signum = 1;
}
b0 = 100 * (int)M_div_workb.mantissa[0];
if (M_div_workb.dataLength >= 3)
{
b0 += M_div_workb.mantissa[1];
}
nexp = M_div_worka.exponent - M_div_workb.exponent;
if (nexp > 0)
{
iterations = nexp + places + 1;
}
else
{
iterations = places + 1;
}
k = (iterations + 1) >> 1; /* required size of result, in bytes */
if (k > rr.mantissa.Length)
{
BigNumber.Expand(rr, k + 32);
}
/* clear the exponent in the working copies */
M_div_worka.exponent = 0;
M_div_workb.exponent = 0;
/* if numbers are equal, ratio == 1.00000... */
if ((icompare = BigNumber.Compare(M_div_worka, M_div_workb)) == 0)
{
iterations = 1;
rr.mantissa[0] = 10;
nexp++;
}
else /* ratio not 1, do the real division */
{
if (icompare == 1) /* numerator > denominator */
{
nexp++; /* to adjust the final exponent */
M_div_worka.exponent += 1; /* multiply numerator by 10 */
}
else /* numerator < denominator */
{
M_div_worka.exponent += 2; /* multiply numerator by 100 */
}
indexr = 0;
m = 0;
while (true)
{
/*
* Knuth step D3. Only use the 3rd -> 6th digits if the number
* actually has that many digits.
*/
trial_numer = 10000L * (long)M_div_worka.mantissa[0];
if (M_div_worka.dataLength >= 5)
{
trial_numer += 100 * M_div_worka.mantissa[1] + M_div_worka.mantissa[2];
}
else
{
if (M_div_worka.dataLength >= 3)
{
trial_numer += 100 * M_div_worka.mantissa[1];
}
}
j = (int)(trial_numer / b0);
/*
* Since the library 'normalizes' all the results, we need
* to look at the exponent of the number to decide if we
* have a lead in 0n or 00.
*/
if ((k = 2 - M_div_worka.exponent) > 0)
{
while (true)
{
j /= 10;
if (--k == 0)
{
break;
}
}
}
if (j == 100) /* qhat == base ?? */
{
j = 99; /* if so, decrease by 1 */
}
BigNumber.SetFromLong(M_div_tmp8, (long)j);
BigNumber.Mul(M_div_tmp8, M_div_workb, M_div_tmp7);
/*
* Compare our q-hat (j) against the desired number.
* j is either correct, 1 too large, or 2 too large
* per Theorem B on pg 272 of Art of Compter Programming,
* Volume 2, 3rd Edition.
*
* The above statement is only true if using the 2 leading
* digits of the numerator and the leading digit of the
* denominator. Since we are using the (3) leading digits
* of the numerator and the (2) leading digits of the
* denominator, we eliminate the case where our q-hat is
* 2 too large, (and q-hat being 1 too large is quite remote).
*/
if (BigNumber.Compare(M_div_tmp7, M_div_worka) == 1)
{
j--;
BigNumber.Sub(M_div_tmp7, M_div_workb, M_div_tmp8);
BigNumber.Copy(M_div_tmp8, M_div_tmp7);
}
/*
* Since we know q-hat is correct, step D6 is unnecessary.
*
* Store q-hat, step D5. Since D6 is unnecessary, we can
* do D5 before D4 and decide if we are done.
*/
rr.mantissa[indexr++] = (byte)j; /* j == 'qhat' */
m += 2;
if (m >= iterations)
{
break;
}
/* step D4 */
BigNumber.Sub(M_div_worka, M_div_tmp7, M_div_tmp9);
/*
* if the subtraction yields zero, the division is exact
* and we are done early.
*/
if (M_div_tmp9.signum == 0)
{
iterations = m;
break;
}
/* multiply by 100 and re-save */
M_div_tmp9.exponent += 2;
BigNumber.Copy(M_div_tmp9, M_div_worka);
}
}
rr.signum = sign;
rr.exponent = nexp;
rr.dataLength = iterations;
BigNumber.Normalize(rr);
}
