public static int CompareTo(this byte[] leftSide, byte[] rightSide, bool signed)
{
// A method to compare two byte arrays arithmetically. There are 3 possible return values.
// 0: The arrays were equal.
// 1: The left side was greater than the right.
// 3: The right side was greater than the left.
// PadEqual sign/zero extends(depending on $signed) the smallest operand to the greatest length of the two input arrays
// If they are both equal in length, nothing happens.
Bitwise.PadEqual(ref leftSide, ref rightSide, signed);
// The main algorithm will not work on inputs with different signs because it doesn't consider the weight of the MSB in twos compliment.
if (signed)
{
// Get the signs of the inputs
bool LeftSign = leftSide.IsNegative();
bool RightSign = rightSide.IsNegative();
// The following statement will evaluate as true if exactly one of the signs are on. In this case it is immediately clear which is greater.
if ((LeftSign ^ RightSign) == true)
{
// If the left side is negative, return -1, because the right side must have been positive for the XOR to work.
return(LeftSign ? -1 : 1);
}
}
// As little endian is exclusively worked with, work backwards. This means that the bytes in the array are compared in order of magnitude.
// For example,
// When comparing two base 10 numbers, 10 and 21, the 0 and 1 digits can be completely ignored, only the tens column is needed to determine the outcome.
// The numbers could be,
// 1, 2
// 10000, 21000
// The result is the same. This allows the problem to be abstracted. Naturally, the numbers had to be padded to the correct size with their value preserved
// which has already been done.
// -The most significant column difference dictates which value is greater. This can be used instead of subtraction to determine the result, which is more
// performant because no unecessary operations are carried out.
for (int i = leftSide.Length - 1; i >= 0; i--)
{
// If the two indexes are not the same value, the two inputs cannot be equal, the result can be determined here.
if (leftSide[i] != rightSide[i])
{
// Return 1 if the most significant column difference of leftSide is greater than that of rightSide, -1 if it is not.
return(leftSide[i] > rightSide[i] ? 1 : -1);
}
}
// If the method hasn't returned already, the two inputs must be equal
return(0);
}
