/// <summary>
/// Writes a bigint value to the stream, truncating the value to the given size in bytes.
/// </summary>
public void WriteBigInt(BigInt Value, int Size)
{
for (int t = 0; t < Value.Digits.Length; t++)
{
uint dig = Value.Digits[t];
if (Size >= 4)
{
this.Write((byte)(dig));
this.Write((byte)(dig >> 8));
this.Write((byte)(dig >> 16));
this.Write((byte)(dig >> 24));
Size -= 4;
continue;
}
if (Size == 3)
{
this.Write((byte)(dig));
this.Write((byte)(dig >> 8));
this.Write((byte)(dig >> 16));
break;
}
if (Size == 2)
{
this.Write((byte)(dig));
this.Write((byte)(dig >> 8));
break;
}
if (Size == 1)
{
this.Write((byte)(dig));
break;
}
break;
}
}
/// <summary>
/// Writes a bigint value to the stream.
/// </summary>
public void WriteBigInt(BigInt Value)
{
int bs = Value.ByteSize;
this.WriteInt(bs);
this.WriteBigInt(Value, bs);
}
/// <summary>
/// Subtracts a BigInt in-place from this value. Any carried values will be ignored.
/// </summary>
public void Subtract(BigInt Int)
{
this.Subtract(Int, 0);
}
private static BigInt _PowMod(BigInt Base, BigInt TempExponent, BigInt Modulus)
{
if (TempExponent == 0)
{
return 1;
}
if (TempExponent == 1)
{
return Base % Modulus;
}
if (TempExponent[0])
{
TempExponent[0] = false;
return Multiply(_PowMod(Base, TempExponent, Modulus), Base) % Modulus;
}
else
{
TempExponent.Shift(-1);
BigInt hp = _PowMod(Base, TempExponent, Modulus);
return Multiply(hp, hp) % Modulus;
}
}
/// <summary>
/// Copies a BigInt in-place to this value.
/// </summary>
public void Copy(BigInt Int)
{
this.Copy(Int, 0);
}
/// <summary>
/// Subtracts a BigInt in-place from this value. Any carried values will be ignored.
/// </summary>
/// <param name="Offset">The offset in this BigInt's digits to start adding to. The given Int will, in effect, be multipled
/// by (base ^ Offset) before subtracting.</param>
public void Subtract(BigInt Int, int Offset)
{
int cur = 0;
uint carry = 0;
while (Offset < this.Size)
{
if (cur < Int.Size)
{
uint ncarry;
Subtract(this.Digits[Offset], carry, out this.Digits[Offset], out ncarry);
Subtract(this.Digits[Offset], Int.Digits[cur], out this.Digits[Offset], out carry);
carry += ncarry;
cur++; Offset++;
}
else
{
Subtract(this.Digits[Offset], carry, out this.Digits[Offset], out carry);
if (carry == 0)
{
return;
}
Offset++;
}
}
}
/// <summary>
/// Adds a BigInt in-place to this value. Any carried values will be ignored.
/// </summary>
public void Add(BigInt Int)
{
this.Add(Int, 0);
}
/// <summary>
/// Copies a BigInt in-place to this value, starting at the given offset in this value's digits. Note that if this integer has a larger
/// size than the given integer, the higher digits of this integer will remain unchanged.
/// </summary>
public void Copy(BigInt Int, int Offset)
{
int cur = 0;
while (Offset < this.Size && cur < Int.Size)
{
this.Digits[Offset] = Int.Digits[cur];
cur++; Offset++;
}
}
/// <summary>
/// Subtracts B from A. If B is greater than A, the result will be the 2's complement form
/// of the negative integer result.
/// </summary>
public static BigInt Subtract(BigInt A, BigInt B)
{
BigInt res = BigInt.Empty(Math.Max(A.Size, B.Size) + 1);
res.Copy(A);
res.Subtract(B);
return res;
}
/// <summary>
/// Performs (Base ^ Exponent) % Modulus in an efficent way.
/// </summary>
public static BigInt PowMod(BigInt Base, BigInt Exponent, BigInt Modulus)
{
BigInt tempexp = BigInt.Empty(Exponent.Size);
tempexp.Copy(Exponent);
return _PowMod(Base, tempexp, Modulus);
}
/// <summary>
/// Multiplies two integers together.
/// </summary>
public static BigInt Multiply(BigInt A, BigInt B)
{
BigInt res = BigInt.Empty(A.Size + B.Size);
BigInt temp = BigInt.Empty(A.Size + 1);
for (int t = 0; t < B.Size; t++)
{
temp.ZeroFill();
temp.Copy(A);
temp.Multiply(B.Digits[t]);
res.Add(temp, t);
}
return res;
}
/// <summary>
/// Gets wether A has a lesser value than B.
/// </summary>
public static bool Lesser(BigInt A, BigInt B)
{
int c = Math.Max(A.Digits.Length, B.Digits.Length);
while (c >= 0)
{
uint a = c < A.Digits.Length ? A.Digits[c] : 0;
uint b = c < B.Digits.Length ? B.Digits[c] : 0;
if (a < b)
{
return true;
}
if (a > b)
{
return false;
}
c--;
}
return false;
}
/// <summary>
/// Finds the quotient and remainder for the division of A by B.
/// </summary>
public static void Divide(BigInt A, BigInt B, out BigInt Quotient, out BigInt Remainder)
{
if (B > A)
{
Remainder = A;
Quotient = Zero;
}
Remainder = BigInt.Empty(A.Size);
Remainder.Copy(A);
BigInt btemp = BigInt.Empty(A.Size);
btemp.Copy(B);
int bitoff = A.Magnitude - B.Magnitude;
btemp.Shift(bitoff);
Quotient = BigInt.Empty(bitoff/ 32 + 1);
while (bitoff >= 0)
{
if (btemp <= Remainder)
{
Remainder.Subtract(btemp);
Quotient[bitoff] = true;
}
btemp.Shift(-1);
bitoff--;
}
}
