// 
// System.Web.HttpUtility
//
// Authors:
//   Patrik Torstensson (Patrik.Torstensson@labs2.com)
//   Wictor Wilén (decode/encode functions) (wictor@ibizkit.se)
//   Tim Coleman (tim@timcoleman.com)
//   Gonzalo Paniagua Javier (gonzalo@ximian.com)
//

//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections;
using System.Globalization;
using System.IO;
using System.Text;
// using System.Web.Util;

namespace HtmlHelp.ChmDecoding
{
	public sealed class HttpUtility {

		#region Fields
	
		const string _hex = "0123456789ABCDEF";
		const string _chars = "<>;:.?=&@*+%/\\";
		static Hashtable entities;
		static object lock_ = new object ();
	
		#endregion // Fields
	
		static Hashtable Entities {
			get {
				lock (lock_) {
					if (entities == null)
						InitEntities ();

					return entities;
				}
			}
		}
		
		#region Constructors

		static void InitEntities ()
		{
			// Build the hash table of HTML entity references.  This list comes
			// from the HTML 4.01 W3C recommendation.
			entities = new Hashtable ();
			entities.Add ("nbsp", '\u00A0');
			entities.Add ("iexcl", '\u00A1');
			entities.Add ("cent", '\u00A2');
			entities.Add ("pound", '\u00A3');
			entities.Add ("curren", '\u00A4');
			entities.Add ("yen", '\u00A5');
			entities.Add ("brvbar", '\u00A6');
			entities.Add ("sect", '\u00A7');
			entities.Add ("uml", '\u00A8');
			entities.Add ("copy", '\u00A9');
			entities.Add ("ordf", '\u00AA');
			entities.Add ("laquo", '\u00AB');
			entities.Add ("not", '\u00AC');
			entities.Add ("shy", '\u00AD');
			entities.Add ("reg", '\u00AE');
			entities.Add ("macr", '\u00AF');
			entities.Add ("deg", '\u00B0');
			entities.Add ("plusmn", '\u00B1');
			entities.Add ("sup2", '\u00B2');
			entities.Add ("sup3", '\u00B3');
			entities.Add ("acute", '\u00B4');
			entities.Add ("micro", '\u00B5');
			entities.Add ("para", '\u00B6');
			entities.Add ("middot", '\u00B7');
			entities.Add ("cedil", '\u00B8');
			entities.Add ("sup1", '\u00B9');
			entities.Add ("ordm", '\u00BA');
			entities.Add ("raquo", '\u00BB');
			entities.Add ("frac14", '\u00BC');
			entities.Add ("frac12", '\u00BD');
			entities.Add ("frac34", '\u00BE');
			entities.Add ("iquest", '\u00BF');
			entities.Add ("Agrave", '\u00C0');
			entities.Add ("Aacute", '\u00C1');
			entities.Add ("Acirc", '\u00C2');
			entities.Add ("Atilde", '\u00C3');
			entities.Add ("Auml", '\u00C4');
			entities.Add ("Aring", '\u00C5');
			entities.Add ("AElig", '\u00C6');
			entities.Add ("Ccedil", '\u00C7');
			entities.Add ("Egrave", '\u00C8');
			entities.Add ("Eacute", '\u00C9');
			entities.Add ("Ecirc", '\u00CA');
			entities.Add ("Euml", '\u00CB');
			entities.Add ("Igrave", '\u00CC');
			entities.Add ("Iacute", '\u00CD');
			entities.Add ("Icirc", '\u00CE');
			entities.Add ("Iuml", '\u00CF');
			entities.Add ("ETH", '\u00D0');
			entities.Add ("Ntilde", '\u00D1');
			entities.Add ("Ograve", '\u00D2');
			entities.Add ("Oacute", '\u00D3');
			entities.Add ("Ocirc", '\u00D4');
			entities.Add ("Otilde", '\u00D5');
			entities.Add ("Ouml", '\u00D6');
			entities.Add ("times", '\u00D7');
			entities.Add ("Oslash", '\u00D8');
			entities.Add ("Ugrave", '\u00D9');
			entities.Add ("Uacute", '\u00DA');
			entities.Add ("Ucirc", '\u00DB');
			entities.Add ("Uuml", '\u00DC');
			entities.Add ("Yacute", '\u00DD');
			entities.Add ("THORN", '\u00DE');
			entities.Add ("szlig", '\u00DF');
			entities.Add ("agrave", '\u00E0');
			entities.Add ("aacute", '\u00E1');
			entities.Add ("acirc", '\u00E2');
			entities.Add ("atilde", '\u00E3');
			entities.Add ("auml", '\u00E4');
			entities.Add ("aring", '\u00E5');
			entities.Add ("aelig", '\u00E6');
			entities.Add ("ccedil", '\u00E7');
			entities.Add ("egrave", '\u00E8');
			entities.Add ("eacute", '\u00E9');
			entities.Add ("ecirc", '\u00EA');
			entities.Add ("euml", '\u00EB');
			entities.Add ("igrave", '\u00EC');
			entities.Add ("iacute", '\u00ED');
			entities.Add ("icirc", '\u00EE');
			entities.Add ("iuml", '\u00EF');
			entities.Add ("eth", '\u00F0');
			entities.Add ("ntilde", '\u00F1');
			entities.Add ("ograve", '\u00F2');
			entities.Add ("oacute", '\u00F3');
			entities.Add ("ocirc", '\u00F4');
			entities.Add ("otilde", '\u00F5');
			entities.Add ("ouml", '\u00F6');
			entities.Add ("divide", '\u00F7');
			entities.Add ("oslash", '\u00F8');
			entities.Add ("ugrave", '\u00F9');
			entities.Add ("uacute", '\u00FA');
			entities.Add ("ucirc", '\u00FB');
			entities.Add ("uuml", '\u00FC');
			entities.Add ("yacute", '\u00FD');
			entities.Add ("thorn", '\u00FE');
			entities.Add ("yuml", '\u00FF');
			entities.Add ("fnof", '\u0192');
			entities.Add ("Alpha", '\u0391');
			entities.Add ("Beta", '\u0392');
			entities.Add ("Gamma", '\u0393');
			entities.Add ("Delta", '\u0394');
			entities.Add ("Epsilon", '\u0395');
			entities.Add ("Zeta", '\u0396');
			entities.Add ("Eta", '\u0397');
			entities.Add ("Theta", '\u0398');
			entities.Add ("Iota", '\u0399');
			entities.Add ("Kappa", '\u039A');
			entities.Add ("Lambda", '\u039B');
			entities.Add ("Mu", '\u039C');
			entities.Add ("Nu", '\u039D');
			entities.Add ("Xi", '\u039E');
			entities.Add ("Omicron", '\u039F');
			entities.Add ("Pi", '\u03A0');
			entities.Add ("Rho", '\u03A1');
			entities.Add ("Sigma", '\u03A3');
			entities.Add ("Tau", '\u03A4');
			entities.Add ("Upsilon", '\u03A5');
			entities.Add ("Phi", '\u03A6');
			entities.Add ("Chi", '\u03A7');
			entities.Add ("Psi", '\u03A8');
			entities.Add ("Omega", '\u03A9');
			entities.Add ("alpha", '\u03B1');
			entities.Add ("beta", '\u03B2');
			entities.Add ("gamma", '\u03B3');
			entities.Add ("delta", '\u03B4');
			entities.Add ("epsilon", '\u03B5');
			entities.Add ("zeta", '\u03B6');
			entities.Add ("eta", '\u03B7');
			entities.Add ("theta", '\u03B8');
			entities.Add ("iota", '\u03B9');
			entities.Add ("kappa", '\u03BA');
			entities.Add ("lambda", '\u03BB');
			entities.Add ("mu", '\u03BC');
			entities.Add ("nu", '\u03BD');
			entities.Add ("xi", '\u03BE');
			entities.Add ("omicron", '\u03BF');
			entities.Add ("pi", '\u03C0');
			entities.Add ("rho", '\u03C1');
			entities.Add ("sigmaf", '\u03C2');
			entities.Add ("sigma", '\u03C3');
			entities.Add ("tau", '\u03C4');
			entities.Add ("upsilon", '\u03C5');
			entities.Add ("phi", '\u03C6');
			entities.Add ("chi", '\u03C7');
			entities.Add ("psi", '\u03C8');
			entities.Add ("omega", '\u03C9');
			entities.Add ("thetasym", '\u03D1');
			entities.Add ("upsih", '\u03D2');
			entities.Add ("piv", '\u03D6');
			entities.Add ("bull", '\u2022');
			entities.Add ("hellip", '\u2026');
			entities.Add ("prime", '\u2032');
			entities.Add ("Prime", '\u2033');
			entities.Add ("oline", '\u203E');
			entities.Add ("frasl", '\u2044');
			entities.Add ("weierp", '\u2118');
			entities.Add ("image", '\u2111');
			entities.Add ("real", '\u211C');
			entities.Add ("trade", '\u2122');
			entities.Add ("alefsym", '\u2135');
			entities.Add ("larr", '\u2190');
			entities.Add ("uarr", '\u2191');
			entities.Add ("rarr", '\u2192');
			entities.Add ("darr", '\u2193');
			entities.Add ("harr", '\u2194');
			entities.Add ("crarr", '\u21B5');
			entities.Add ("lArr", '\u21D0');
			entities.Add ("uArr", '\u21D1');
			entities.Add ("rArr", '\u21D2');
			entities.Add ("dArr", '\u21D3');
			entities.Add ("hArr", '\u21D4');
			entities.Add ("forall", '\u2200');
			entities.Add ("part", '\u2202');
			entities.Add ("exist", '\u2203');
			entities.Add ("empty", '\u2205');
			entities.Add ("nabla", '\u2207');
			entities.Add ("isin", '\u2208');
			entities.Add ("notin", '\u2209');
			entities.Add ("ni", '\u220B');
			entities.Add ("prod", '\u220F');
			entities.Add ("sum", '\u2211');
			entities.Add ("minus", '\u2212');
			entities.Add ("lowast", '\u2217');
			entities.Add ("radic", '\u221A');
			entities.Add ("prop", '\u221D');
			entities.Add ("infin", '\u221E');
			entities.Add ("ang", '\u2220');
			entities.Add ("and", '\u2227');
			entities.Add ("or", '\u2228');
			entities.Add ("cap", '\u2229');
			entities.Add ("cup", '\u222A');
			entities.Add ("int", '\u222B');
			entities.Add ("there4", '\u2234');
			entities.Add ("sim", '\u223C');
			entities.Add ("cong", '\u2245');
			entities.Add ("asymp", '\u2248');
			entities.Add ("ne", '\u2260');
			entities.Add ("equiv", '\u2261');
			entities.Add ("le", '\u2264');
			entities.Add ("ge", '\u2265');
			entities.Add ("sub", '\u2282');
			entities.Add ("sup", '\u2283');
			entities.Add ("nsub", '\u2284');
			entities.Add ("sube", '\u2286');
			entities.Add ("supe", '\u2287');
			entities.Add ("oplus", '\u2295');
			entities.Add ("otimes", '\u2297');
			entities.Add ("perp", '\u22A5');
			entities.Add ("sdot", '\u22C5');
			entities.Add ("lceil", '\u2308');
			entities.Add ("rceil", '\u2309');
			entities.Add ("lfloor", '\u230A');
			entities.Add ("rfloor", '\u230B');
			entities.Add ("lang", '\u2329');
			entities.Add ("rang", '\u232A');
			entities.Add ("loz", '\u25CA');
			entities.Add ("spades", '\u2660');
			entities.Add ("clubs", '\u2663');
			entities.Add ("hearts", '\u2665');
			entities.Add ("diams", '\u2666');
			entities.Add ("quot", '\u0022');
			entities.Add ("amp", '\u0026');
			entities.Add ("lt", '\u003C');
			entities.Add ("gt", '\u003E');
			entities.Add ("OElig", '\u0152');
			entities.Add ("oelig", '\u0153');
			entities.Add ("Scaron", '\u0160');
			entities.Add ("scaron", '\u0161');
			entities.Add ("Yuml", '\u0178');
			entities.Add ("circ", '\u02C6');
			entities.Add ("tilde", '\u02DC');
			entities.Add ("ensp", '\u2002');
			entities.Add ("emsp", '\u2003');
			entities.Add ("thinsp", '\u2009');
			entities.Add ("zwnj", '\u200C');
			entities.Add ("zwj", '\u200D');
			entities.Add ("lrm", '\u200E');
			entities.Add ("rlm", '\u200F');
			entities.Add ("ndash", '\u2013');
			entities.Add ("mdash", '\u2014');
			entities.Add ("lsquo", '\u2018');
			entities.Add ("rsquo", '\u2019');
			entities.Add ("sbquo", '\u201A');
			entities.Add ("ldquo", '\u201C');
			entities.Add ("rdquo", '\u201D');
			entities.Add ("bdquo", '\u201E');
			entities.Add ("dagger", '\u2020');
			entities.Add ("Dagger", '\u2021');
			entities.Add ("permil", '\u2030');
			entities.Add ("lsaquo", '\u2039');
			entities.Add ("rsaquo", '\u203A');
			entities.Add ("euro", '\u20AC');
		}
	
		public HttpUtility () 
		{
		}
	
		#endregion // Constructors
	
		#region Methods
	
		public static void HtmlAttributeEncode (string s, TextWriter output) 
		{
			output.Write(HtmlAttributeEncode(s));
		}
	
		public static string HtmlAttributeEncode (string s) 
		{
			if (null == s) 
				return null;
	
			if (s.IndexOf ('&') == -1 && s.IndexOf ('"') == -1)
				return s;

			StringBuilder output = new StringBuilder ();
			foreach (char c in s) 
				switch (c) {
				case '&' : 
					output.Append ("&amp;");
					break;
				case '"' :
					output.Append ("&quot;");
					break;
				default:
					output.Append (c);
					break;
				}
	
			return output.ToString();
		}
	
		public static string UrlDecode (string str) 
		{
			return UrlDecode(str, Encoding.UTF8);
		}
	
		private static char [] GetChars (MemoryStream b, Encoding e)
		{
			return e.GetChars (b.GetBuffer (), 0, (int) b.Length);
		}
		
		public static string UrlDecode (string s, Encoding e)
		{
			if (null == s) 
				return null;

			if (s.IndexOf ('%') == -1 && s.IndexOf ('+') == -1)
				return s;

			if (e == null)
				e = Encoding.UTF8;
	
			StringBuilder output = new StringBuilder ();
			long len = s.Length;
			NumberStyles hexa = NumberStyles.HexNumber;
			MemoryStream bytes = new MemoryStream ();
	
			for (int i = 0; i < len; i++) {
				if (s [i] == '%' && i + 2 < len) {
					if (s [i + 1] == 'u' && i + 5 < len) {
						if (bytes.Length > 0) {
							output.Append (GetChars (bytes, e));
							bytes.SetLength (0);
						}
						output.Append ((char) Int32.Parse (s.Substring (i + 2, 4), hexa));
						i += 5;
					} else {
						bytes.WriteByte ((byte) Int32.Parse (s.Substring (i + 1, 2), hexa));
						i += 2;
					}
					continue;
				}

				if (bytes.Length > 0) {
					output.Append (GetChars (bytes, e));
					bytes.SetLength (0);
				}

				if (s [i] == '+') {
					output.Append (' ');
				} else {
					output.Append (s [i]);
				}
	         	}
	
			if (bytes.Length > 0) {
				output.Append (GetChars (bytes, e));
			}

			bytes = null;
			return output.ToString ();
		}
	
		public static string UrlDecode (byte [] bytes, Encoding e)
		{
			if (bytes == null)
				return null;

			return UrlDecode (bytes, 0, bytes.Length, e);
		}

		private static int GetInt (byte b)
		{
			char c = Char.ToUpper ((char) b);
			if (c >= '0' && c <= '9')
				return c - '0';

			if (c < 'A' || c > 'F')
				return 0;

			return (c - 'A' + 10);
		}

		private static char GetChar (byte [] bytes, int offset, int length)
		{
			int value = 0;
			int end = length + offset;
			for (int i = offset; i < end; i++)
				value = (value << 4) + GetInt (bytes [offset]);

			return (char) value;
		}
		
		public static string UrlDecode (byte [] bytes, int offset, int count, Encoding e)
		{
			if (bytes == null || count == 0)
				return null;

			if (bytes == null)
				throw new ArgumentNullException ("bytes");

			if (offset < 0 || offset > bytes.Length)
				throw new ArgumentOutOfRangeException ("offset");

			if (count < 0 || offset + count > bytes.Length)
				throw new ArgumentOutOfRangeException ("count");

			StringBuilder output = new StringBuilder ();
			MemoryStream acc = new MemoryStream ();

			int end = count + offset;
			for (int i = offset; i < end; i++) {
				if (bytes [i] == '%' && i + 2 < count) {
					if (bytes [i + 1] == (byte) 'u' && i + 5 < end) {
						if (acc.Length > 0) {
							output.Append (GetChars (acc, e));
							acc.SetLength (0);
						}
						output.Append (GetChar (bytes, offset + 2, 4));
						i += 5;
					} else {
						acc.WriteByte ((byte) GetChar (bytes, offset + 1, 2));
						i += 2;
					}
					continue;
				}

				if (acc.Length > 0) {
					output.Append (GetChars (acc, e));
					acc.SetLength (0);
				}

				if (bytes [i] == '+') {
					output.Append (' ');
				} else {
					output.Append ((char) bytes [i]);
				}
			}

			if (acc.Length > 0) {
				output.Append (GetChars (acc, e));
			}
			
			acc = null;
			return output.ToString ();
		}
	
		public static byte [] UrlDecodeToBytes (byte [] bytes)
		{
			if (bytes == null)
				return null;

			return UrlDecodeToBytes (bytes, 0, bytes.Length);
		}

		public static byte [] UrlDecodeToBytes (string str)
		{
			return UrlDecodeToBytes (str, Encoding.UTF8);
		}

		public static byte [] UrlDecodeToBytes (string str, Encoding e)
		{
			if (str == null)
				return null;

			if (e == null)
				throw new ArgumentNullException ("e");

			return UrlDecodeToBytes (e.GetBytes (str));
		}

		public static byte [] UrlDecodeToBytes (byte [] bytes, int offset, int count)
		{
			if (bytes == null)
				return null;

			int len = bytes.Length;
			if (offset < 0 || offset >= len)
				throw new ArgumentOutOfRangeException("offset");

			if (count < 0 || offset > len - count)
				throw new ArgumentOutOfRangeException("count");

			MemoryStream result = new MemoryStream ();
			int end = offset + count;
			for (int i = offset; i < end; i++){
				char c = (char) bytes [i];
				if (c == '+')
					c = ' ';
				else if (c == '%' && i < end - 2) {
					c = GetChar (bytes, i, 2);
					i += 2;
				}
				result.WriteByte ((byte) c);
			}

			return result.ToArray ();
		}

		public static string UrlEncode(string str) 
		{
			return UrlEncode(str, Encoding.UTF8);
		}
	
		public static string UrlEncode (string s, Encoding Enc) 
		{
			if (s == null)
				return null;

			if (s == "")
				return "";

			byte [] bytes = Enc.GetBytes (s);
			byte [] b =UrlEncodeToBytes (bytes, 0, bytes.Length);
			return Encoding.ASCII.GetString (b,0,b.Length);
		}
	  
		public static string UrlEncode (byte [] bytes)
		{
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return "";

			byte []b=UrlEncodeToBytes(bytes, 0, bytes.Length);
			return Encoding.ASCII.GetString (b,0,b.Length);
		}

		public static string UrlEncode (byte [] bytes, int offset, int count)
		{
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return "";

			byte []b=UrlEncodeToBytes(bytes, offset, count);
			return Encoding.ASCII.GetString (b,0,b.Length);
		}

		public static byte [] UrlEncodeToBytes (string str)
		{
			return UrlEncodeToBytes (str, Encoding.UTF8);
		}

		public static byte [] UrlEncodeToBytes (string str, Encoding e)
		{
			if (str == null)
				return null;

			if (str == "")
				return new byte [0];

			byte [] bytes = e.GetBytes (str);
			return UrlEncodeToBytes (bytes, 0, bytes.Length);
		}

		public static byte [] UrlEncodeToBytes (byte [] bytes)
		{
			if (bytes == null)
				return null;

			if (bytes.Length == 0)
				return new byte [0];

			return UrlEncodeToBytes (bytes, 0, bytes.Length);
		}

		static char [] hexChars = "0123456789abcdef".ToCharArray ();

		public static byte [] UrlEncodeToBytes (byte [] bytes, int offset, int count)
		{
			if (bytes == null)
				return null;

			int len = bytes.Length;
			if (len == 0)
				return new byte [0];

			if (offset < 0 || offset >= len)
				throw new ArgumentOutOfRangeException("offset");

			if (count < 0 || count > len - offset)
				throw new ArgumentOutOfRangeException("count");

			MemoryStream result = new MemoryStream ();
			int end = offset + count;
			for (int i = offset; i < end; i++) {
				char c = (char) bytes [i];
				if ((c == ' ') || (c < '0' && c != '-' && c != '.') ||
				    (c < 'A' && c > '9') ||
				    (c > 'Z' && c < 'a' && c != '_') ||
				    (c > 'z')) {
					result.WriteByte ((byte) '%');
					int idx = ((int) c) >> 4;
					result.WriteByte ((byte) hexChars [idx]);
					idx = ((int) c) & 0x0F;
					result.WriteByte ((byte) hexChars [idx]);
				} else {
					result.WriteByte ((byte) c);
				}
			}

			return result.ToArray ();
		}

		public static string UrlEncodeUnicode (string str)
		{
			if (str == null)
				return null;

			StringBuilder result = new StringBuilder ();
			int end = str.Length;
			for (int i = 0; i < end; i++) {
				int idx;
				char c = str [i];
				if (c > 255) {
					result.Append ("%u");
					idx = ((int) c) >> 24;
					result.Append (hexChars [idx]);
					idx = (((int) c) >> 16) & 0x0F;
					result.Append (hexChars [idx]);
					idx = (((int) c) >> 8) & 0x0F;
					result.Append (hexChars [idx]);
					idx = ((int) c) & 0x0F;
					result.Append (hexChars [idx]);
					continue;
				}
				
				if ((c == ' ') || (c < '0' && c != '-' && c != '.') ||
				    (c < 'A' && c > '9') ||
				    (c > 'Z' && c < 'a' && c != '_') ||
				    (c > 'z')) {
					result.Append ('%');
					idx = ((int) c) >> 4;
					result.Append (hexChars [idx]);
					idx = ((int) c) & 0x0F;
					result.Append (hexChars [idx]);
					continue;
				}

				result.Append (c);
			}

			return result.ToString ();
		}

		public static byte [] UrlEncodeUnicodeToBytes (string str)
		{
			if (str == null)
				return null;

			if (str == "")
				return new byte [0];

			return Encoding.ASCII.GetBytes (UrlEncodeUnicode (str));
		}

		/// <summary>
		/// Decodes an HTML-encoded string and returns the decoded string.
		/// </summary>
		/// <param name="s">The HTML string to decode. </param>
		/// <returns>The decoded text.</returns>
		public static string HtmlDecode (string s) 
		{
			if (s == null)
				throw new ArgumentNullException ("s");

			if (s.IndexOf ('&') == -1)
				return s;

			bool insideEntity = false; // used to indicate that we are in a potential entity
			string entity = String.Empty;
			StringBuilder output = new StringBuilder ();
			int len = s.Length;
	
			for (int i = 0; i < len; i++) {
				char c = s [i];
				switch (c) {
				case '&' :
					output.Append (entity);
					entity = "&";
					insideEntity = true;
					break;
				case ';' :
					if (!insideEntity) {
						output.Append (c);
						break;
					}

					entity += c;
					int length = entity.Length;
					if (length >= 2 && entity[1] == '#' && entity[2] != ';')
						entity = ((char) Int32.Parse (entity.Substring (2, entity.Length - 3))).ToString();
					else if (length > 1 && Entities.ContainsKey (entity.Substring (1, entity.Length - 2)))
						entity = Entities [entity.Substring (1, entity.Length - 2)].ToString ();
					
					output.Append (entity);
					entity = String.Empty;
					insideEntity = false;
					break;
				default :
					if (insideEntity)
						entity += c;
					else
						output.Append (c);
					break;
				}
			}
			output.Append (entity);
			return output.ToString ();
		}
	
		/// <summary>
		/// Decodes an HTML-encoded string and sends the resulting output to a TextWriter output stream.
		/// </summary>
		/// <param name="s">The HTML string to decode</param>
		/// <param name="output">The TextWriter output stream containing the decoded string. </param>
		public static void HtmlDecode(string s, TextWriter output) 
		{
			if (s != null)
				output.Write (HtmlDecode (s));
		}
	
		/// <summary>
		/// HTML-encodes a string and returns the encoded string.
		/// </summary>
		/// <param name="s">The text string to encode. </param>
		/// <returns>The HTML-encoded text.</returns>
		public static string HtmlEncode (string s) 
		{
			if (s == null)
				return null;

			StringBuilder output = new StringBuilder ();
			
			foreach (char c in s) 
				switch (c) {
				case '&' :
					output.Append ("&amp;");
					break;
				case '>' : 
					output.Append ("&gt;");
					break;
				case '<' :
					output.Append ("&lt;");
					break;
				case '"' :
					output.Append ("&quot;");
					break;
				default:
					if ((int) c > 128) {
						output.Append ("&#");
						output.Append (((int) c).ToString ());
						output.Append (";");
					}
					else
						output.Append (c);
					break;
				}
			return output.ToString ();
		}
	
		/// <summary>
		/// HTML-encodes a string and sends the resulting output to a TextWriter output stream.
		/// </summary>
		/// <param name="s">The string to encode. </param>
		/// <param name="output">The TextWriter output stream containing the encoded string. </param>
		public static void HtmlEncode(string s, TextWriter output) 
		{
			if (s != null)
				output.Write (HtmlEncode (s));
		}

#if NET_1_1
		public string UrlPathEncode (string s)
		{
			if (s == null)
				return null;

			int idx = s.IndexOf ("?");
			string s2 = null;
			if (idx != -1) {
				s2 = s.Substring (0, idx-1);
				s2 = UrlEncode (s2) + s.Substring (idx);
			} else {
				s2 = UrlEncode (s);
			}

			return s2;
		}
#endif
		#endregion // Methods
	}
}