/// <summary>
/// Modifies result array as multiple of two input arrays without overflow
/// Method uses Booth's multiplication algorithm
/// </summary>
/// <param name="m">Left array must have the same length as right array</param>
/// <param name="r">Right array must have the same length as left array</param>
/// <returns>New array with same length as parents have</returns>
public static bool[] Multiply(bool[] m, bool[] r)
{
if ((m == null) || (r == null))
{
throw new ArgumentNullException("Array is null");
}
bool[] extendedM = new bool[m.Length + 1];
bool[] extendedR = new bool[r.Length + 1];
for (int i = 0; i < m.Length; i++)
{
extendedM[i + 1] = m[i];
}
for (int i = 0; i < r.Length; i++)
{
extendedR[i + 1] = r[i];
}
bool[] a = new bool[extendedM.Length + extendedR.Length + 1];
bool[] s = new bool[extendedM.Length + extendedR.Length + 1];
bool[] result = new bool[extendedM.Length + extendedR.Length + 1];
bool[] actualResult = new bool[result.Length - 1];
bool[] minusM = BitwiseOperation.UnaryMinus(extendedM);
for (int i = 0; i < extendedM.Length; i++)
{
a[i] = extendedM[i];
s[i] = minusM[i];
}
for (int i = 0; i < extendedR.Length; i++)
{
result[extendedM.Length + i] = extendedR[i];
}
result[result.Length - 1] = false;
//00 -> no sum
//11 -> no sum
//01 -> result + a
//10 -> result + s
for (int i = 0; i < extendedR.Length; i++)
{
if (result[result.Length - 1])
{
if (!result[result.Length - 2])
{
result = BitwiseOperation.Add(result, a);
}
}
else
{
if (result[result.Length - 2])
{
result = BitwiseOperation.Add(result, s);
}
}
result = BitwiseOperation.ArithmeticRightShift(result, 1);
}
for (int i = 0; i < actualResult.Length; i++)
{
actualResult[i] = result[i];
}
return(actualResult);
}
/// <summary>
/// Returns new array as difference of two arrays without overflow.
/// </summary>
/// <param name="lhs">Left array must have the same length as right array</param>
/// <param name="rhs">Right array must have the same length as left array</param>
/// <returns>New array with same length as parents have</returns>
public static bool[] Subtract(bool[] lhs, bool[] rhs)
{
rhs = BitwiseOperation.UnaryMinus(rhs);
return(BitwiseOperation.Add(lhs, rhs));
}