context: //
  // System.Web.Compilation.AspTokenizer
  //
  // Authors:
  //	Gonzalo Paniagua Javier (gonzalo@ximian.com)
  //      Marek Habersack <mhabersack@novell.com>
  //
  // (C) 2002,2003 Ximian, Inc (http://www.ximian.com)
  // (C) 2003-2009 Novell, Inc (http://novell.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.IO;
  using System.Text;
  using System.Security.Cryptography;
  
  namespace System.Web.Compilation
  {
  	class Token
  	{
  		public const int EOF 		= 0x0200000;
  		public const int IDENTIFIER 	= 0x0200001;
  		public const int DIRECTIVE 	= 0x0200002;
  		public const int ATTVALUE	= 0x0200003;
  		public const int TEXT	    	= 0x0200004;
  		public const int DOUBLEDASH 	= 0x0200005;
  		public const int CLOSING 	= 0x0200006;
  	}
  
  	class AspTokenizer
  	{
  		const int CHECKSUM_BUF_SIZE = 8192;
  
  		class PutBackItem
  		{
  			public readonly string Value;
  			public readonly int Position;
  			public readonly int CurrentToken;
  			public readonly bool InTag;
  			
  			public PutBackItem (string value, int position, int currentToken, bool inTag)
  			{
  				Value = value;
  				Position = position;
  				CurrentToken = currentToken;
  				InTag = inTag;
  			}
  		}
  		
  		static char [] lfcr = new char [] { '\n', '\r' };
  		TextReader sr;
  		int current_token;
  		StringBuilder sb, odds;
  		int col, line;
  		int begcol, begline;
  		int position;
  		bool inTag;
  		bool expectAttrValue;
  		bool alternatingQuotes;
  		bool hasPutBack;
  		bool verbatim;
  		bool have_value;
  		bool have_unget;
  		int unget_value;
  		string val;
  		Stack putBackBuffer;
  		MD5 checksum;
  		char[] checksum_buf = new char [CHECKSUM_BUF_SIZE];
  		int checksum_buf_pos = -1;
  		
  		public MD5 Checksum {
  			get { return checksum; }
  		}
  		
  		public AspTokenizer (TextReader reader)
  		{
  			this.sr = reader;
  			sb = new StringBuilder ();
  			odds= new StringBuilder();
  			col = line = 1;
  			hasPutBack = inTag = false;
  		}
  
  		public bool Verbatim
  		{
  			get { return verbatim; }
  			set { verbatim = value; }
  		}
  
  		public void put_back ()
  		{
  			if (hasPutBack && !inTag)
  				throw new HttpException ("put_back called twice!");
  			
  			hasPutBack = true;
  			if (putBackBuffer == null)
  				putBackBuffer = new Stack ();
  
  			string val = Value;
  			putBackBuffer.Push (new PutBackItem (val, position, current_token, inTag));
  			position -= val.Length;
  		}
  		
  		public int get_token ()
  		{
  			if (hasPutBack) {
  				PutBackItem pbi;
  				if (verbatim) {
  					pbi = putBackBuffer.Pop () as PutBackItem;
  					string value = pbi.Value;
  					switch (value.Length) {
  						case 0:
  							// do nothing, CurrentToken will be used
  							break;
  
  						case 1:
  							pbi = new PutBackItem (String.Empty, pbi.Position, (int)value [0], false);
  							break;
  
  						default:
  							pbi = new PutBackItem (value, pbi.Position, (int)value [0], false);
  							break;
  					}		
  				} else
  					pbi = putBackBuffer.Pop () as PutBackItem;
  				
  				hasPutBack = putBackBuffer.Count > 0;
  				position = pbi.Position;
  				have_value = false;
  				val = null;
  				sb = new StringBuilder (pbi.Value);
  				current_token = pbi.CurrentToken;
  				inTag = pbi.InTag;
  				return current_token;
  			}
  
  			begline = line;
  			begcol = col;
  			have_value = false;
  			current_token = NextToken ();
  			return current_token;
  		}
  
  		bool is_identifier_start_character (char c)
  		{
  			return (Char.IsLetter (c) || c == '_' );
  		}
  
  		bool is_identifier_part_character (char c)
  		{
  			return (Char.IsLetterOrDigit (c) || c == '_' || c == '-');
  		}
  
  		void ungetc (int value)
  		{
  			have_unget = true;
  			unget_value = value;
  
  			// Only '/' passes through here now.
  			// If we ever let \n here, update 'line'
  			position--;
  			col--;
  		}
  
  		void TransformNextBlock (int count, bool final)
  		{
  			byte[] input = Encoding.UTF8.GetBytes (checksum_buf, 0, count);
  
  			if (checksum == null)
  				checksum = MD5.Create ();
  			
  			if (final)
  				checksum.TransformFinalBlock (input, 0, input.Length);
  			else
  				checksum.TransformBlock (input, 0, input.Length, input, 0);
  			input = null;
  			
  			checksum_buf_pos = -1;
  		}
  		
  		void UpdateChecksum (int c)
  		{
  			bool final = c == -1;
  
  			if (!final) {
  				if (checksum_buf_pos + 1 >= CHECKSUM_BUF_SIZE)
  					TransformNextBlock (checksum_buf_pos + 1, false);
  				checksum_buf [++checksum_buf_pos] = (char)c;
  			} else
  				TransformNextBlock (checksum_buf_pos + 1, true);
  		}
  
  		int read_char ()
  		{
  			int c;
  			if (have_unget) {
  				c = unget_value;
  				have_unget = false;
  			} else {
  				c = sr.Read ();
  				UpdateChecksum (c);
  			}
  
  			if (c == '\r' && sr.Peek () == '\n') {
  				c = sr.Read ();
  				UpdateChecksum (c);
  				position++;
  			}
  
  			if (c == '\n'){
  				col = -1;
  				line++;
  			}
  
  			if (c != -1) {
  				col++;
  				position++;
  			}
  
  			return c;
  		}
  
  		int ReadAttValue (int start)
  		{
  			int quoteChar = 0;
  			bool quoted = false;
  
  			if (start == '"' || start == '\'') {
  				quoteChar = start;
  				quoted = true;
  			} else {
  				sb.Append ((char) start);
  			}
  
  			int c;
  			int last = 0;
  			bool inServerTag = false;
  			alternatingQuotes = true;
  			
  			while ((c = sr.Peek ()) != -1) {
  				if (c == '%' && last == '<') {
  					inServerTag = true;
  				} else if (inServerTag && c == '>' && last == '%') {
  					inServerTag = false;
  				} else if (!inServerTag) {
  					if (!quoted && c == '/') {
  						read_char ();
  						c = sr.Peek ();
  						if (c == -1) {
  							c = '/';
  						} else if (c == '>') {
  							ungetc ('/');
  							break;
  						}
  					} else if (!quoted && (c == '>' || Char.IsWhiteSpace ((char) c))) {
  						break;
  					} else if (quoted && c == quoteChar && last != '\\') {
  						read_char ();
  						break;
  					}
  				} else if (quoted && c == quoteChar) {
  					alternatingQuotes = false;
  				}
  
  				sb.Append ((char) c);
  				read_char ();
  				last = c;
  			}
  
  			return Token.ATTVALUE;
  		}
  
  		int NextToken ()
  		{
  			int c;
  			
  			sb.Length = 0;
  			odds.Length=0;
  			while ((c = read_char ()) != -1){
  				if (verbatim){
  					inTag = false;
  					sb.Append  ((char) c);
  					return c;
  				}
  
  				if (inTag && expectAttrValue && (c == '"' || c == '\''))
  					return ReadAttValue (c);
  				
  				if (c == '<'){
  					inTag = true;
  					sb.Append ((char) c);
  					return c;
  				}
  
  				if (c == '>'){
  					inTag = false;
  					sb.Append ((char) c);
  					return c;
  				}
  
  				if (current_token == '<' && "%/!".IndexOf ((char) c) != -1){
  					sb.Append ((char) c);
  					return c;
  				}
  
  				if (inTag && current_token == '%' && "@#=".IndexOf ((char) c) != -1){
  					if (odds.Length == 0 || odds.ToString ().IndexOfAny (lfcr) < 0) {
  						sb.Append ((char) c);
  						return c;
  					}
  					sb.Append ((char) c);
  					continue;
  				}
  
  				if (inTag && c == '-' && sr.Peek () == '-'){
  					sb.Append ("--");
  					read_char ();
  					return Token.DOUBLEDASH;
  				}
  
  				if (!inTag){
  					sb.Append ((char) c);
  					while ((c = sr.Peek ()) != -1 && c != '<')
  						sb.Append ((char) read_char ());
  
  					return (c != -1 || sb.Length > 0) ? Token.TEXT : Token.EOF;
  				}
  
  				if (inTag && current_token == '=' && !Char.IsWhiteSpace ((char) c))
  					return ReadAttValue (c);
  
  				if (inTag && is_identifier_start_character ((char) c)){
  					sb.Append ((char) c);
  					while ((c = sr.Peek ()) != -1) {
  						if (!is_identifier_part_character ((char) c) && c != ':')
  							break;
  						sb.Append ((char) read_char ());
  					}
  
  					if (current_token == '@' && Directive.IsDirective (sb.ToString ()))
  						return Token.DIRECTIVE;
  					
  					return Token.IDENTIFIER;
  				}
  
  				if (!Char.IsWhiteSpace ((char) c)) {
  					sb.Append  ((char) c);
  					return c;
  				}
  				// keep otherwise discarded characters in case we need.
  				odds.Append((char) c);
  			}
  
  			return Token.EOF;
  		}
  
  		public string Value {
  			get {
  				if (have_value)
  					return val;
  
  				have_value = true;
  				val = sb.ToString ();
  				return val;
  			}
  		}
  
  		public string Odds {
  			get {
  				return odds.ToString();
  			}
  		}
  
  		public bool InTag {
  			get { return inTag; }
  			set { inTag = value; }
  		}
  
  		// Hack for preventing confusion with VB comments (see bug #63451)
  		public bool ExpectAttrValue {
  			get { return expectAttrValue; }
  			set { expectAttrValue = value; }
  		}
  		
  		public bool AlternatingQuotes {
  			get { return alternatingQuotes; }
  		}
  		
  		public int BeginLine {
  			get { return begline; }
  		}
  
  		public int BeginColumn {
  
gt: 			get { return begcol; }