ContainsTokenUnroll.cs

public static bool ContainsTokenUnroll(string value, string token, char delimiter = ';')
{
    if (string.IsNullOrEmpty(token)) return false;
    if (string.IsNullOrEmpty(value)) return false;

    var valueLength = value.Length;
    var tokenLength = token.Length;

    if (tokenLength > valueLength) return false;

    unsafe
    {
        fixed (char* valuePtr = value, tokenPtr = token)
        {
            char currentChar;
            var curValuePtr = valuePtr;
            var endValuePtr = valuePtr + valueLength - tokenLength;

            do
            {
                var curTokenPtr = tokenPtr;
                var count = tokenLength;

                // Match token against the current position in value
                while (count >= 2)
                {
                    if (*(int*)curValuePtr != *(int*)curTokenPtr)
                    {
                        goto advanceToNextDelimiter;
                    }

                    count -= 2;
                    curValuePtr += 2;
                    curTokenPtr += 2;
                }

                if (count == 1)
                {
                    if (*curValuePtr != *curTokenPtr)
                    {
                        goto advanceToNextDelimiter;
                    }

                    curValuePtr++;
                }

                // Token has been matched, check if the _next_ char
                //    in value is a delimiter or the end of value
                if (*curValuePtr == delimiter || *curValuePtr == '\0')
                {
                    return true;
                }

                curValuePtr++;

                advanceToNextDelimiter:
                // Find the next delimiter in value or the end of the string
                // Unroll the loop by 2
                while (true)
                {
                    currentChar = *curValuePtr;
                    curValuePtr++;

                    if (currentChar == delimiter || currentChar == '\0')
                    {
                        break;
                    }

                    currentChar = *curValuePtr;
                    curValuePtr++;

                    if (currentChar == delimiter || currentChar == '\0')
                    {
                        break;
                    }
                }

            } while (curValuePtr <= endValuePtr);
        }

        return false;
    }
}