LZString.cs

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

namespace LZString
{
	public class LZString
	{
		static string keyStrBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
		static string keyStrUriSafe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-$";
		static Dictionary<string, Dictionary<char, int>> baseReverseDic = new Dictionary<string, Dictionary<char, int>>();
		private delegate char GetCharFromInt(int a);
		private static GetCharFromInt f = (a) => Convert.ToChar(a);
		private delegate int GetNextValue(int index);

		private static int getBaseValue(string alphabet, char character)
		{
			if (!baseReverseDic.ContainsKey(alphabet))
			{
				baseReverseDic[alphabet] = new Dictionary<char, int>();
				for (int i = 0; i < alphabet.Length; i++)
				{
					baseReverseDic[alphabet][alphabet[i]] = i;
				}
			}
			return baseReverseDic[alphabet][character];
		}

		public static string compressToBase64(string input)
		{
			if (input == null) return "";
			string res = _compress(input, 6, (a) => keyStrBase64[a]);
			switch (res.Length % 4)
			{
				case 0: return res;
				case 1: return res + "===";
				case 2: return res + "==";
				case 3: return res + "=";
			}
			return null;
		}

		public static string decompressFromBase64(string input)
		{
			if (input == null) return "";
			if (input == "") return null;
			return _decompress(input.Length, 32, (index) => getBaseValue(keyStrBase64, input[index]));
		}

		public static string compressToUTF16(string input)
		{
			if (input == null) return "";
			return _compress(input, 15, (a) => f(a + 32)) + " ";
		}

		public static string decompressFromUTF16(string compressed)
		{
			if (compressed == null) return "";
			if (compressed == "") return null;
			return _decompress(compressed.Length, 16384, index => Convert.ToInt32(compressed[index]) - 32);
		}

		public static byte[] compressToUint8Array(string uncompressed)
		{
			string compressed = compress(uncompressed);
			byte[] buf = new byte[compressed.Length * 2];

			for (int i = 0, TotalLen = compressed.Length; i < TotalLen; i++)
			{
				int current_value = Convert.ToInt32(compressed[i]);
				buf[i * 2] = (byte)(((uint)current_value) >> 8);
				buf[i * 2 + 1] = (byte)(current_value % 256);
			}
			return buf;
		}

		public static string decompressFromUint8Array(byte[] compressed)
		{
			if (compressed == null) return "";
			else
			{
				int[] buf = new int[compressed.Length / 2];
				for (int i = 0, TotalLen = buf.Length; i < TotalLen; i++)
				{
					buf[i] = ((int)compressed[i * 2]) * 256 + ((int)compressed[i * 2 + 1]);
				}
				char[] result = new char[buf.Length];
				for (int i = 0; i < buf.Length; i++)
				{
					result[i] = f(buf[i]);
				}
				return decompress(new string(result));
			}
		}

		public static string compressToEncodedURIComponent(string input)
		{
			if (input == null) return "";
			return _compress(input, 6, (a) => keyStrUriSafe[a]);
		}

		public static string decompressFromEncodedURIComponent(string input)
		{
			if (input == null) return "";
			if (input == "") return null;
			input = input.Replace(' ', '+');
			return _decompress(input.Length, 32, (index) => getBaseValue(keyStrUriSafe, input[index]));
		}

		public static string compress(string uncompressed)
		{
			return _compress(uncompressed, 16, f);
		}

		private static string _compress(string uncompressed, int bitsPerChar, GetCharFromInt getCharFromInt)
		{
			if (uncompressed == null) return "";
			int i, value, ii, context_enlargeIn = 2, context_dictSize = 3, context_numBits = 2, context_data_val = 0, context_data_position = 0;
			Dictionary<string, bool> context_dictionaryToCreate = new Dictionary<string, bool>();
			Dictionary<string, int> context_dictionary = new Dictionary<string, int>();
			StringBuilder context_data = new StringBuilder();
			string context_c = "";
			string context_wc = "", context_w = "";

			for (ii = 0; ii < uncompressed.Length; ii++)
			{
				context_c = uncompressed[ii].ToString();
				if (!context_dictionary.ContainsKey(context_c))
				{
					context_dictionary[context_c] = context_dictSize++;
					context_dictionaryToCreate[context_c] = true;
				}
				context_wc = context_w + context_c;
				if (context_dictionary.ContainsKey(context_wc))
				{
					context_w = context_wc;
				}
				else
				{
					if (context_dictionaryToCreate.ContainsKey(context_w))
					{
						if (Convert.ToInt32(context_w[0]) < 256)
						{
							for (i = 0; i < context_numBits; i++)
							{
								context_data_val = (context_data_val << 1);
								if (context_data_position == bitsPerChar - 1)
								{
									context_data_position = 0;
									context_data.Append(getCharFromInt(context_data_val));
									context_data_val = 0;
								}
								else
								{
									context_data_position++;
								}
							}
							value = Convert.ToInt32(context_w[0]);
							for (i = 0; i < 8; i++)
							{
								context_data_val = (context_data_val << 1) | (value & 1);
								if (context_data_position == bitsPerChar - 1)
								{
									context_data_position = 0;
									context_data.Append(getCharFromInt(context_data_val));
									context_data_val = 0;
								}
								else
								{
									context_data_position++;
								}
								value = value >> 1;
							}
						}
						else
						{
							value = 1;
							for (i = 0; i < context_numBits; i++)
							{
								context_data_val = (context_data_val << 1) | value;
								if (context_data_position == bitsPerChar - 1)
								{
									context_data_position = 0;
									context_data.Append(getCharFromInt(context_data_val));
									context_data_val = 0;
								}
								else
								{
									context_data_position++;
								}
								value = 0;
							}
							value = Convert.ToInt32(context_w[0]);
							for (i = 0; i < 16; i++)
							{
								context_data_val = (context_data_val << 1) | (value & 1);
								if (context_data_position == bitsPerChar - 1)
								{
									context_data_position = 0;
									context_data.Append(getCharFromInt(context_data_val));
									context_data_val = 0;
								}
								else
								{
									context_data_position++;
								}
								value = value >> 1;
							}
						}
						context_enlargeIn--;
						if (context_enlargeIn == 0)
						{
							context_enlargeIn = (int)Math.Pow(2, context_numBits);
							context_numBits++;
						}
						context_dictionaryToCreate.Remove(context_w);
					}
					else
					{
						value = context_dictionary[context_w];
						for (i = 0; i < context_numBits; i++)
						{
							context_data_val = (context_data_val << 1) | (value & 1);
							if (context_data_position == bitsPerChar - 1)
							{
								context_data_position = 0;
								context_data.Append(getCharFromInt(context_data_val));
								context_data_val = 0;
							}
							else
							{
								context_data_position++;
							}
							value = value >> 1;
						}
					}
					context_enlargeIn--;
					if (context_enlargeIn == 0)
					{
						context_enlargeIn = (int)Math.Pow(2, context_numBits);
						context_numBits++;
					}
					//Add wc to the dictionary
					context_dictionary[context_wc] = context_dictSize++;
					context_w = context_c;
				}
			}
			//Output the code for w
			if (context_w != "")
			{
				if (context_dictionaryToCreate.ContainsKey(context_w))
				{
					if (Convert.ToInt32(context_w[0]) < 256)
					{
						for (i = 0; i < context_numBits; i++)
						{
							context_data_val = (context_data_val << 1);
							if (context_data_position == bitsPerChar - 1)
							{
								context_data_position = 0;
								context_data.Append(getCharFromInt(context_data_val));
								context_data_val = 0;
							}
							else
							{
								context_data_position++;
							}
						}
						value = Convert.ToInt32(context_w[0]);
						for (i = 0; i < 8; i++)
						{
							context_data_val = (context_data_val << 1) | (value & 1);
							if (context_data_position == bitsPerChar - 1)
							{
								context_data_position = 0;
								context_data.Append(getCharFromInt(context_data_val));
								context_data_val = 0;
							}
							else
							{
								context_data_position++;
							}
							value = value >> 1;
						}
					}
					else
					{
						value = 1;
						for (i = 0; i < context_numBits; i++)
						{
							context_data_val = (context_data_val << 1) | value;
							if (context_data_position == bitsPerChar - 1)
							{
								context_data_position = 0;
								context_data.Append(getCharFromInt(context_data_val));
								context_data_val = 0;
							}
							else
							{
								context_data_position++;
							}
							value = 0;
						}
						value = Convert.ToInt32(context_w[0]);
						for (i = 0; i < 16; i++)
						{
							context_data_val = (context_data_val << 1) | (value & 1);
							if (context_data_position == bitsPerChar - 1)
							{
								context_data_position = 0;
								context_data.Append(getCharFromInt(context_data_val));
								context_data_val = 0;
							}
							else
							{
								context_data_position++;
							}
							value = value >> 1;
						}
					}
					context_enlargeIn--;
					if (context_enlargeIn == 0)
					{
						context_enlargeIn = (int)Math.Pow(2, context_numBits);
						context_numBits++;
					}
					context_dictionaryToCreate.Remove(context_w);
				}
				else
				{
					value = context_dictionary[context_w];
					for (i = 0; i < context_numBits; i++)
					{
						context_data_val = (context_data_val << 1) | (value & 1);
						if (context_data_position == bitsPerChar - 1)
						{
							context_data_position = 0;
							context_data.Append(getCharFromInt(context_data_val));
							context_data_val = 0;
						}
						else
						{
							context_data_position++;
						}
						value = value >> 1;
					}
				}
				context_enlargeIn--;
				if (context_enlargeIn == 0)
				{
					context_enlargeIn = (int)Math.Pow(2, context_numBits);
					context_numBits++;
				}
			}
			//Mark the end of the stream
			value = 2;
			for (i = 0; i < context_numBits; i++)
			{
				context_data_val = (context_data_val << 1) | (value & 1);
				if (context_data_position == bitsPerChar - 1)
				{
					context_data_position = 0;
					context_data.Append(getCharFromInt(context_data_val));
					context_data_val = 0;
				}
				else
				{
					context_data_position++;
				}
				value = value >> 1;
			}

			//Flush the last char
			while (true)
			{
				context_data_val = (context_data_val << 1);
				if (context_data_position == bitsPerChar - 1)
				{
					context_data.Append(getCharFromInt(context_data_val));
					break;
				}
				else context_data_position++;
			}
			return context_data.ToString();
		}

		public static string decompress(string compressed)
		{
			if (compressed == null) return "";
			if (compressed == "") return null;
			return _decompress(compressed.Length, 32768, (index) => Convert.ToInt32(compressed[index]));
		}


		private struct dataStruct
		{
			public int val, position, index;
		}
		private static string _decompress(int length, int resetValue, GetNextValue getNextValue)
		{
			Dictionary<int, string> dictionary = new Dictionary<int, string>();
			int next, enlargeIn = 4, dictSize = 4, numBits = 3, i, bits, resb, maxpower, power;
			int c = 0;
			string entry = "", w;
			StringBuilder result = new StringBuilder();
			var data = new dataStruct() { val = getNextValue(0), position = resetValue, index = 1 };

			for (i = 0; i < 3; i++)
			{
				dictionary[i] = Convert.ToChar(i).ToString();
			}

			bits = 0;
			maxpower = (int)Math.Pow(2, 2);
			power = 1;
			while (power != maxpower)
			{
				resb = data.val & data.position;
				data.position >>= 1;
				if (data.position == 0)
				{
					data.position = resetValue;
					data.val = getNextValue(data.index++);
				}
				bits |= (resb > 0 ? 1 : 0) * power;
				power <<= 1;
			}

			switch (next = bits)
			{
				case 0:
					bits = 0;
					maxpower = (int)Math.Pow(2, 8);
					power = 1;
					while (power != maxpower)
					{
						resb = data.val & data.position;
						data.position >>= 1;
						if (data.position == 0)
						{
							data.position = resetValue;
							data.val = getNextValue(data.index++);
						}
						bits |= (resb > 0 ? 1 : 0) * power;
						power <<= 1;
					}
					c = Convert.ToInt32(f(bits));
					break;
				case 1:
					bits = 0;
					maxpower = (int)Math.Pow(2, 16);
					power = 1;
					while (power != maxpower)
					{
						resb = data.val & data.position;
						data.position >>= 1;
						if (data.position == 0)
						{
							data.position = resetValue;
							data.val = getNextValue(data.index++);
						}
						bits |= (resb > 0 ? 1 : 0) * power;
						power <<= 1;
					}
					c = Convert.ToInt32(f(bits));
					break;
				case 2:
					return "";
			}
			dictionary[3] = Convert.ToChar(c).ToString();
			w = Convert.ToChar(c).ToString();
			result.Append(Convert.ToChar(c));
			while (true)
			{
				if (data.index > length)
				{
					return "";
				}

				bits = 0;
				maxpower = (int)Math.Pow(2, numBits);
				power = 1;
				while (power != maxpower)
				{
					resb = data.val & data.position;
					data.position >>= 1;
					if (data.position == 0)
					{
						data.position = resetValue;
						data.val = getNextValue(data.index++);
					}
					bits |= (resb > 0 ? 1 : 0) * power;
					power <<= 1;
				}

				switch (c = bits)
				{
					case 0:
						bits = 0;
						maxpower = (int)Math.Pow(2, 8);
						power = 1;
						while (power != maxpower)
						{
							resb = data.val & data.position;
							data.position >>= 1;
							if (data.position == 0)
							{
								data.position = resetValue;
								data.val = getNextValue(data.index++);
							}
							bits |= (resb > 0 ? 1 : 0) * power;
							power <<= 1;
						}

						dictionary[dictSize++] = f(bits).ToString();
						c = dictSize - 1;
						enlargeIn--;
						break;
					case 1:
						bits = 0;
						maxpower = (int)Math.Pow(2, 16);
						power = 1;
						while (power != maxpower)
						{
							resb = data.val & data.position;
							data.position >>= 1;
							if (data.position == 0)
							{
								data.position = resetValue;
								data.val = getNextValue(data.index++);
							}
							bits |= (resb > 0 ? 1 : 0) * power;
							power <<= 1;
						}
						dictionary[dictSize++] = f(bits).ToString();
						c = dictSize - 1;
						enlargeIn--;
						break;
					case 2:
						return result.ToString();
				}

				if (enlargeIn == 0)
				{
					enlargeIn = (int)Math.Pow(2, numBits);
					numBits++;
				}

				if (dictionary.ContainsKey(c))
				{
					entry = dictionary[c];
				}
				else
				{
					if (c == dictSize)
					{
						entry = w + w[0].ToString();
					}
					else
					{
						return null;
					}
				}
				result.Append(entry);

				//Add w+entry[0] to the dictionary.
				dictionary[dictSize++] = w + entry[0].ToString();
				enlargeIn--;
				w = entry;
				if (enlargeIn == 0)
				{
					enlargeIn = (int)Math.Pow(2, numBits);
					numBits++;
				}
			}
		}
	}
}