간단하게 만들어본 BitNumber Class

BigNumber.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RyuaNerin
{
	public class BigNumber
	{
		public BigNumber()
			: this("0")
		{
		}
		public BigNumber(string value)
			: this(NumToArray(value))
		{
		}
		public BigNumber(int[] array)
		{
			this.arr = array;
		}

		internal int[] arr;

		public string Value
		{
			get
			{
				return ArrayToNum(this.arr);
			}
			set
			{
				this.arr = NumToArray(value);
			}
		}
		public string CutValue()
		{
			string v = this.Value;

			StringBuilder sb = new StringBuilder();

			for (int i = 0; i < v.Length; ++i)
			{
				sb.Append(v[i]);

				if ((i + 1) % 5 == 0)
					sb.Append(' ');

				if ((i + 1) % 100 == 0)
					sb.Append('\n');
			}

			return sb.ToString();
		}

		//////////////////////////////////////////////////////////////////////////
		// Static Functions

		private static int[] NumToArray(string num)
		{
			int[] buff = new int[num.Length];
			int index = 0;
			int multip = 1;

			for (int i = num.Length - 1; i >= 0; --i)
			{
				buff[index] += ((char)num[i] - '0') * multip;
				multip *= 10;

				if (multip >= 10000)
				{
					multip = 1;
					index++;
				}
			}

			return buff;
		}
		private static string ArrayToNum(int[] buff)
		{
			StringBuilder sb = new StringBuilder();
			for (int i = 0; i < buff.Length; i++)
				sb.Insert(0, String.Format("{0:0000}", buff[i]));

			while (sb.Length > 1 && sb[0] == '0')
				sb.Remove(0, 1);

			return sb.ToString();
		}

		public static BigNumber AddNumber(BigNumber num1, BigNumber num2)
		{
			return new BigNumber(AddNumber(num1.arr, num2.arr));
		}
		public static BigNumber SubNumber(BigNumber num1, BigNumber num2)
		{
			return new BigNumber(SubNumber(num1.arr, num2.arr));
		}
		public static BigNumber MultiNumber(BigNumber num1, BigNumber num2)
		{
			return new BigNumber(MultiNumber(num1.arr, num2.arr));
		}
		public static BigNumber MultiNumber(BigNumber num1, int num2)
		{
			return new BigNumber(MultiNumber(num1.arr, num2));
		}

		private static int[] CutInt(int[] num1)
		{
			int len = num1.Length;

			while (len > 0)
			{
				if (num1[len - 1] > 0)
					break;

				len--;
			}

			if (len >= num1.Length - 20)
				return num1;

			int[] arr = new int[len];
			for (int i = 0; i < len; ++i)
				arr[i] = num1[i];

			return arr;
		}

		private static int[] AddNumber(int[] num1, int[] num2)
		{
			int[] arr = new int[Math.Max(num1.Length, num2.Length)];

			for (int i = 0; i < num1.Length; ++i)
			{
				if (i < num2.Length)
					arr[i] += num1[i] + num2[i];

				if (arr[i] >= 10000)
				{
					if (i + 1 >= num1.Length)
						arr = ExpandArray(arr);

					arr[i + 1]++;
					arr[i] -= 10000;
				}
			}

			return arr;
		}
		private static int[] SubNumber(int[] num1, int[] num2)
		{
			int[] arr = new int[Math.Max(num1.Length, num2.Length)];

			for (int i = num1.Length - 1; i >= 0; --i)
			{
				arr[i] = num1[i] - num2[i];

				if (arr[i] < 0)
				{
					arr[i + 1]--;
					arr[i] += 10000;
				}
			}

			return arr;
		}
		private static int[] MultiNumber(int[] num1, int[] num2)
		{
			int[] arr = new int[Math.Max(num1.Length, num2.Length)];
			int[] arrm;

			for (int i = 0; i < num1.Length && i < num2.Length; ++i)
			{
				if (num2[i] > 0)
				{
					arrm = MultiNumber(num1, ((num2[i] / 1) % 10) * 1);
					arrm = Multi10000(arrm, i);

					arr = AddNumber(arr, arrm);
				}
				if (num2[i] > 10)
				{
					arrm = MultiNumber(num1, ((num2[i] / 10) % 10) * 10);
					arrm = Multi10000(arrm, i);

					arr = AddNumber(arr, arrm);
				}
				if (num2[i] > 100)
				{
					arrm = MultiNumber(num1, ((num2[i] / 100) % 10) * 100);
					arrm = Multi10000(arrm, i);

					arr = AddNumber(arr, arrm);
				}
				if (num2[i] > 1000)
				{
					arrm = MultiNumber(num1, ((num2[i] / 1000) % 10) * 1000);
					arrm = Multi10000(arrm, i);

					arr = AddNumber(arr, arrm);
				}
			}

			return CutInt(arr);
		}
		private static int[] MultiNumber(int[] num1, int num2)
		{
			int[] arr = new int[num1.Length];

			for (int i = 0; i < num1.Length; ++i)
			{
				arr[i] += num1[i] * num2;

				if (arr[i] > 10000)
				{
					if (i + 1 >= num1.Length)
						arr = ExpandArray(arr);

					arr[i + 1] += arr[i] / 10000;
					arr[i] = arr[i] % 10000;
				}
			}

			return arr;
		}
		private static int[] Multi10000(int[] num1, int num2)
		{
			if (num2 == 0)
				return num1;

			int[] arr = new int[num1.Length + 1];
			int i;

			for (i = 0; i < num2; ++i)
				arr[i] = 0;

			for (i = 0; i < num1.Length - num2; ++i)
				arr[i + num2] = num1[i];

			return arr;
		}
		private static int[] ExpandArray(int[] num)
		{
			int[] arr = new int[num.Length + 10000];
			Buffer.BlockCopy(num, 0, arr, 0, num.Length * sizeof(int));
			return arr;
		}
	}
}