update

2022-12-13 22:47:31 +08:00
parent 9e7b10c1a5
commit df178687ba
40 changed files with 5401 additions and 15 deletions
@@ -0,0 +1,184 @@
+using System;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace BaseNcoding
+{
+	public abstract class Base
+	{
+		public uint CharsCount { get; }
+
+		public double BitsPerChars => (double)BlockBitsCount / BlockCharsCount;
+
+		public int BlockBitsCount { get; protected set; }
+
+		public int BlockCharsCount { get; protected set; }
+
+		public string Alphabet { get; }
+
+		public char Special { get; }
+
+		public abstract bool HasSpecial { get; }
+
+		public Encoding Encoding { get; set; }
+
+		public bool Parallel { get; set; }
+
+		protected readonly int[] InvAlphabet;
+
+		public Base(uint charsCount, string alphabet, char special, Encoding encoding = null, bool parallel = false)
+		{
+			if (alphabet.Length != charsCount)
+				throw new ArgumentException($"Base string should contain {charsCount} chars");
+
+			for (int i = 0; i < charsCount; i++)
+				for (int j = i + 1; j < charsCount; j++)
+					if (alphabet[i] == alphabet[j])
+						throw new ArgumentException("Base string should contain distinct chars");
+
+			if (alphabet.Contains(special))
+				throw new ArgumentException("Base string should not contain special char");
+
+			CharsCount = charsCount;
+			Alphabet = alphabet;
+			Special = special;
+			int bitsPerChar = LogBase2(charsCount);
+			BlockBitsCount = Lcm(bitsPerChar, 8);
+			BlockCharsCount = BlockBitsCount / bitsPerChar;
+
+			InvAlphabet = new int[Alphabet.Max() + 1];
+
+			for (int i = 0; i < InvAlphabet.Length; i++)
+				InvAlphabet[i] = -1;
+
+			for (int i = 0; i < charsCount; i++)
+				InvAlphabet[Alphabet[i]] = i;
+
+			Encoding = encoding ?? Encoding.UTF8;
+			Parallel = parallel;
+		}
+
+		public virtual string EncodeString(string data)
+		{
+			return Encode(Encoding.GetBytes(data));
+		}
+
+		public abstract string Encode(byte[] data);
+
+		public string DecodeToString(string data)
+		{
+			return Encoding.GetString(Decode(Regex.Replace(data, @"\r\n?|\n", "")));
+		}
+
+		public abstract byte[] Decode(string data);
+
+		/// <summary>
+		/// From: http://stackoverflow.com/a/600306/1046374
+		/// </summary>
+		/// <param name="x"></param>
+		/// <returns></returns>
+		public static bool IsPowerOf2(uint x)
+		{
+			uint xint = x;
+			if (x - xint != 0)
+				return false;
+
+			return (xint & (xint - 1)) == 0;
+		}
+
+		/// <summary>
+		/// From: http://stackoverflow.com/a/13569863/1046374
+		/// </summary>
+		public static int Lcm(int a, int b)
+		{
+			int num1, num2;
+			if (a > b)
+			{
+				num1 = a;
+				num2 = b;
+			}
+			else
+			{
+				num1 = b;
+				num2 = a;
+			}
+
+			for (int i = 1; i <= num2; i++)
+			{
+				int mult = num1 * i;
+				if (mult % num2 == 0)
+					return mult;
+			}
+
+			return num2;
+		}
+
+		private static int LogBase2(uint x)
+		{
+			int r = 0;
+			while ((x >>= 1) != 0)
+				r++;
+			return r;
+		}
+
+		private static int LogBaseN(uint x, uint n)
+		{
+			int r = 0;
+			while ((x /= n) != 0)
+				r++;
+			return r;
+		}
+
+		public static int GetOptimalBitsCount2(uint charsCount, out uint charsCountInBits,
+			uint maxBitsCount = 64, bool base2BitsCount = false)
+		{
+			int result = 0;
+			charsCountInBits = 0;
+			int n1 = LogBase2(charsCount);
+			double charsCountLog = Math.Log(2, charsCount);
+			double maxRatio = 0;
+
+			for (int n = n1; n <= maxBitsCount; n++)
+			{
+				if (base2BitsCount && n % 8 != 0)
+					continue;
+
+				uint l1 = (uint)Math.Ceiling(n * charsCountLog);
+				double ratio = (double)n / l1;
+				if (ratio > maxRatio)
+				{
+					maxRatio = ratio;
+					result = n;
+					charsCountInBits = l1;
+				}
+			}
+
+			return result;
+		}
+
+		protected static int GetOptimalBitsCount(uint charsCount, out uint charsCountInBits,
+			uint maxBitsCount = 64, uint radix = 2)
+		{
+			int result = 0;
+			charsCountInBits = 0;
+			int n0 = LogBaseN(charsCount, radix);
+			double charsCountLog = Math.Log(radix, charsCount);
+			double maxRatio = 0;
+
+			for (int n = n0; n <= maxBitsCount; n++)
+			{
+				uint k = (uint)Math.Ceiling(n * charsCountLog);
+				double ratio = (double)n / k;
+				if (ratio > maxRatio)
+				{
+					maxRatio = ratio;
+					result = n;
+					charsCountInBits = k;
+				}
+			}
+
+			return result;
+		}
+	}
+}