private static void InversionStep(uint[] p, uint[] u, int uLen, uint[] x, ref int xc)
{
int len = p.Length;
int num = 0;
while (u[0] == 0)
{
Nat.ShiftDownWord(uLen, u, 0u);
num += 32;
}
int trailingZeroes = GetTrailingZeroes(u[0]);
if (trailingZeroes > 0)
{
Nat.ShiftDownBits(uLen, u, trailingZeroes, 0u);
num += trailingZeroes;
}
for (int i = 0; i < num; i++)
{
if ((x[0] & 1) != 0)
{
if (xc < 0)
{
xc += (int)Nat.AddTo(len, p, x);
}
else
{
xc += Nat.SubFrom(len, p, x);
}
}
Nat.ShiftDownBit(len, x, (uint)xc);
}
}
private static int Legendre(BigInteger a, BigInteger b)
{
//int r = 0, bits = b.IntValue;
//for (;;)
//{
// int lowestSetBit = a.GetLowestSetBit();
// a = a.ShiftRight(lowestSetBit);
// r ^= (bits ^ (bits >> 1)) & (lowestSetBit << 1);
// int cmp = a.CompareTo(b);
// if (cmp == 0)
// break;
// if (cmp < 0)
// {
// BigInteger t = a; a = b; b = t;
// int oldBits = bits;
// bits = b.IntValue;
// r ^= oldBits & bits;
// }
// a = a.Subtract(b);
//}
//return BigInteger.One.Equals(b) ? (1 - (r & 2)) : 0;
int bitLength = b.BitLength;
uint[] A = Nat.FromBigInteger(bitLength, a);
uint[] B = Nat.FromBigInteger(bitLength, b);
int r = 0;
int len = B.Length;
for (;;)
{
while (A[0] == 0)
{
Nat.ShiftDownWord(len, A, 0);
}
int shift = Integers.NumberOfTrailingZeros((int)A[0]);
if (shift > 0)
{
Nat.ShiftDownBits(len, A, shift, 0);
int bits = (int)B[0];
r ^= (bits ^ (bits >> 1)) & (shift << 1);
}
int cmp = Nat.Compare(len, A, B);
if (cmp == 0)
{
break;
}
if (cmp < 0)
{
r ^= (int)(A[0] & B[0]);
uint[] t = A; A = B; B = t;
}
while (A[len - 1] == 0)
{
len = len - 1;
}
Nat.Sub(len, A, B, A);
}
return(Nat.IsOne(len, B) ? (1 - (r & 2)) : 0);
}
