BytesToDigits(byte[] bytes, int bytesI, Digits digits, int bitN)
{
if (bitN == 0)
{
Debug.Assert(false, "untested code"); return;
}
int digitN = (bitN + (Digit.BitN - 1)) / Digit.BitN;
digits._SetAll(0, digitN);
for (int iDigit = 0; iDigit != digitN; iDigit++)
{
int byteNLeft = (bitN + 7) / 8 - 4 * iDigit;
Digit digit = 0;
for (
int iByte = 0;
iByte != (4 > byteNLeft ? byteNLeft : 4);
iByte++
)
{
digit
^= (Digit)bytes[bytesI + byteNLeft - 1 - iByte] << 8 * iByte;
}
digits[iDigit] = digit;
}
digits[digitN - 1] &= Digit.MaxValue >> Digit.BitN * digitN - bitN;
}
Mul(Digits a, int aN, Digits b, int bN, Digits c)
{
Debug.Assert(!c._Overlaps(a) && !c._Overlaps(b)
, "overlapping arguments");
Digits p1, p2;
int i, n1, n2;
if (aN > bN)
{
p1 = a;
p2 = b;
n1 = aN;
n2 = bN;
}
else
{
p2 = a;
p1 = b;
n2 = aN;
n1 = bN;
}
if (n2 == 0)
{
Debug.Assert(false, "untested code");
c._SetAll(0, n1);
return;
}
c[n1] = Mul(p1, p2[0], c, n1);
for (i = 1; i != n2; i++)
{
c[i + n1] = Accumulate(p1, p2[i], c + i, n1);
}
}