Simple CSS Parser

using System;
using System.IO;
using System.Collections.Generic;

namespace BoneSoft.CSS {

	public class Token {
		public int kind;    // token kind
		public int pos;     // token position in the source text (starting at 0)
		public int col;     // token column (starting at 1)
		public int line;    // token line (starting at 1)
		public string val;  // token value
		public Token next;  // ML 2005-03-11 Tokens are kept in linked list
	}

	//-----------------------------------------------------------------------------------
	// Buffer
	//-----------------------------------------------------------------------------------
	public class Buffer {
		public const int EOF = char.MaxValue + 1;
		const int MAX_BUFFER_LENGTH = 64 * 1024; // 64KB
		byte[] buf;         // input buffer
		int bufStart;       // position of first byte in buffer relative to input stream
		int bufLen;         // length of buffer
		int fileLen;        // length of input stream
		int pos;            // current position in buffer
		Stream stream;      // input stream (seekable)
		bool isUserStream;  // was the stream opened by the user?

		public Buffer(Stream s, bool isUserStream) {
			stream = s; this.isUserStream = isUserStream;
			fileLen = bufLen = (int)s.Length;
			if (stream.CanSeek && bufLen > MAX_BUFFER_LENGTH) bufLen = MAX_BUFFER_LENGTH;
			buf = new byte[bufLen];
			bufStart = Int32.MaxValue; // nothing in the buffer so far
			Pos = 0; // setup buffer to position 0 (start)
			if (bufLen == fileLen) Close();
		}

		protected Buffer(Buffer b) { // called in UTF8Buffer constructor
			buf = b.buf;
			bufStart = b.bufStart;
			bufLen = b.bufLen;
			fileLen = b.fileLen;
			pos = b.pos;
			stream = b.stream;
			b.stream = null;
			isUserStream = b.isUserStream;
		}

		~Buffer() { Close(); }

		protected void Close() {
			if (!isUserStream && stream != null) {
				stream.Close();
				stream = null;
			}
		}

		public virtual int Read() {
			if (pos < bufLen) {
				return buf[pos++];
			} else if (Pos < fileLen) {
				Pos = Pos; // shift buffer start to Pos
				return buf[pos++];
			} else {
				return EOF;
			}
		}

		public int Peek() {
			int curPos = Pos;
			int ch = Read();
			Pos = curPos;
			return ch;
		}

		public string GetString(int beg, int end) {
			int len = end - beg;
			char[] buf = new char[len];
			int oldPos = Pos;
			Pos = beg;
			for (int i = 0; i < len; i++) buf[i] = (char)Read();
			Pos = oldPos;
			return new String(buf);
		}

		public int Pos {
			get { return pos + bufStart; }
			set {
				if (value < 0) value = 0;
				else if (value > fileLen) value = fileLen;
				if (value >= bufStart && value < bufStart + bufLen) { // already in buffer
					pos = value - bufStart;
				} else if (stream != null) { // must be swapped in
					stream.Seek(value, SeekOrigin.Begin);
					bufLen = stream.Read(buf, 0, buf.Length);
					bufStart = value; pos = 0;
				} else {
					pos = fileLen - bufStart; // make Pos return fileLen
				}
			}
		}
	}

	//-----------------------------------------------------------------------------------
	// UTF8Buffer
	//-----------------------------------------------------------------------------------
	public class UTF8Buffer : Buffer {
		public UTF8Buffer(Buffer b) : base(b) { }

		public override int Read() {
			int ch;
			do {
				ch = base.Read();
				// until we find a uft8 start (0xxxxxxx or 11xxxxxx)
			} while ((ch >= 128) && ((ch & 0xC0) != 0xC0) && (ch != EOF));
			if (ch < 128 || ch == EOF) {
				// nothing to do, first 127 chars are the same in ascii and utf8
				// 0xxxxxxx or end of file character
			} else if ((ch & 0xF0) == 0xF0) {
				// 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
				int c1 = ch & 0x07; ch = base.Read();
				int c2 = ch & 0x3F; ch = base.Read();
				int c3 = ch & 0x3F; ch = base.Read();
				int c4 = ch & 0x3F;
				ch = (((((c1 << 6) | c2) << 6) | c3) << 6) | c4;
			} else if ((ch & 0xE0) == 0xE0) {
				// 1110xxxx 10xxxxxx 10xxxxxx
				int c1 = ch & 0x0F; ch = base.Read();
				int c2 = ch & 0x3F; ch = base.Read();
				int c3 = ch & 0x3F;
				ch = (((c1 << 6) | c2) << 6) | c3;
			} else if ((ch & 0xC0) == 0xC0) {
				// 110xxxxx 10xxxxxx
				int c1 = ch & 0x1F; ch = base.Read();
				int c2 = ch & 0x3F;
				ch = (c1 << 6) | c2;
			}
			return ch;
		}
	}

	//-----------------------------------------------------------------------------------
	// Scanner
	//-----------------------------------------------------------------------------------
	public class Scanner {
		const char EOL = '\n';
		const int eofSym = 0; /* pdt */
		const int maxT = 49;
		const int noSym = 49;


		public Buffer buffer; // scanner buffer

		Token t;          // current token
		int ch;           // current input character
		int pos;          // byte position of current character
		int col;          // column number of current character
		int line;         // line number of current character
		int oldEols;      // EOLs that appeared in a comment;
		Dictionary<int, int> start; // maps first token character to start state

		Token tokens;     // list of tokens already peeked (first token is a dummy)
		Token pt;         // current peek token

		char[] tval = new char[128]; // text of current token
		int tlen;         // length of current token

		public Scanner(string fileName) {
			try {
				Stream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
				buffer = new Buffer(stream, false);
				Init();
			} catch (IOException) {
				throw new FatalError("Cannot open file " + fileName);
			}
		}

		public Scanner(Stream s) {
			buffer = new Buffer(s, true);
			Init();
		}

		void Init() {
			pos = -1; line = 1; col = 0;
			oldEols = 0;
			NextCh();
			if (ch == 0xEF) { // check optional byte order mark for UTF-8
				NextCh(); int ch1 = ch;
				NextCh(); int ch2 = ch;
				if (ch1 != 0xBB || ch2 != 0xBF) {
					throw new FatalError(String.Format("illegal byte order mark: EF {0,2:X} {1,2:X}", ch1, ch2));
				}
				buffer = new UTF8Buffer(buffer); col = 0;
				NextCh();
			}
			start = new Dictionary<int, int>(128);
			for (int i = 65; i <= 84; ++i) start[i] = 1;
			for (int i = 86; i <= 90; ++i) start[i] = 1;
			for (int i = 95; i <= 95; ++i) start[i] = 1;
			for (int i = 97; i <= 122; ++i) start[i] = 1;
			for (int i = 10; i <= 10; ++i) start[i] = 2;
			for (int i = 13; i <= 13; ++i) start[i] = 2;
			for (int i = 48; i <= 57; ++i) start[i] = 3;
			for (int i = 9; i <= 9; ++i) start[i] = 4;
			for (int i = 11; i <= 12; ++i) start[i] = 4;
			for (int i = 32; i <= 32; ++i) start[i] = 4;
			start[60] = 5;
			start[45] = 40;
			start[39] = 11;
			start[34] = 12;
			start[40] = 13;
			start[41] = 14;
			start[64] = 15;
			start[44] = 16;
			start[123] = 17;
			start[59] = 18;
			start[125] = 19;
			start[43] = 20;
			start[62] = 21;
			start[126] = 41;
			start[42] = 42;
			start[35] = 22;
			start[46] = 23;
			start[91] = 24;
			start[61] = 25;
			start[124] = 27;
			start[36] = 29;
			start[94] = 31;
			start[93] = 34;
			start[58] = 35;
			start[33] = 36;
			start[47] = 37;
			start[85] = 43;
			start[37] = 39;
			start[Buffer.EOF] = -1;

			pt = tokens = new Token();  // first token is a dummy
		}

		void NextCh() {
			if (oldEols > 0) { ch = EOL; oldEols--; } else {
				pos = buffer.Pos;
				ch = buffer.Read(); col++;
				// replace isolated '\r' by '\n' in order to make
				// eol handling uniform across Windows, Unix and Mac
				if (ch == '\r' && buffer.Peek() != '\n') ch = EOL;
				if (ch == EOL) { line++; col = 0; }
			}

		}

		void AddCh() {
			if (tlen >= tval.Length) {
				char[] newBuf = new char[2 * tval.Length];
				Array.Copy(tval, 0, newBuf, 0, tval.Length);
				tval = newBuf;
			}
			tval[tlen++] = (char)ch;
			NextCh();
		}



		bool Comment0() {
			int level = 1, pos0 = pos, line0 = line, col0 = col;
			NextCh();
			if (ch == '*') {
				NextCh();
				for (; ; ) {
					if (ch == '*') {
						NextCh();
						if (ch == '/') {
							level--;
							if (level == 0) { oldEols = line - line0; NextCh(); return true; }
							NextCh();
						}
					} else if (ch == Buffer.EOF) return false;
					else NextCh();
				}
			} else {
				buffer.Pos = pos0; NextCh(); line = line0; col = col0;
			}
			return false;
		}


		void CheckLiteral() {
			switch (t.val) {
				case "url": t.kind = 9; break;
				case "all": t.kind = 12; break;
				case "aural": t.kind = 13; break;
				case "braille": t.kind = 14; break;
				case "embossed": t.kind = 15; break;
				case "handheld": t.kind = 16; break;
				case "print": t.kind = 17; break;
				case "projection": t.kind = 18; break;
				case "screen": t.kind = 19; break;
				case "tty": t.kind = 20; break;
				case "tv": t.kind = 21; break;
				case "n": t.kind = 22; break;
				case "important": t.kind = 45; break;
				default: break;
			}
		}

		Token NextToken() {
			while (ch == 10 || ch == 13) NextCh();
			if (ch == '/' && Comment0()) return NextToken();
			t = new Token();
			t.pos = pos; t.col = col; t.line = line;
			int state;
			try { state = start[ch]; } catch (KeyNotFoundException) { state = 0; }
			tlen = 0; AddCh();

			switch (state) {
				case -1: { t.kind = eofSym; break; } // NextCh already done
				case 0: { t.kind = noSym; break; }   // NextCh already done
				case 1:
					if (ch == '-' || ch >= '0' && ch <= '9' || ch >= 'A' && ch <= 'Z' || ch == '_' || ch >= 'a' && ch <= 'z') { AddCh(); goto case 1; } else { t.kind = 1; t.val = new String(tval, 0, tlen); CheckLiteral(); return t; }
				case 2: { t.kind = 2; break; }
				case 3: { t.kind = 3; break; }
				case 4: { t.kind = 4; break; }
				case 5:
					if (ch == '!') { AddCh(); goto case 6; } else { t.kind = noSym; break; }
				case 6:
					if (ch == '-') { AddCh(); goto case 7; } else { t.kind = noSym; break; }
				case 7:
					if (ch == '-') { AddCh(); goto case 8; } else { t.kind = noSym; break; }
				case 8: { t.kind = 5; break; }
				case 9:
					if (ch == '>') { AddCh(); goto case 10; } else { t.kind = noSym; break; }
				case 10: { t.kind = 6; break; }
				case 11: { t.kind = 7; break; }
				case 12: { t.kind = 8; break; }
				case 13: { t.kind = 10; break; }
				case 14: { t.kind = 11; break; }
				case 15: { t.kind = 23; break; }
				case 16: { t.kind = 25; break; }
				case 17: { t.kind = 26; break; }
				case 18: { t.kind = 27; break; }
				case 19: { t.kind = 28; break; }
				case 20: { t.kind = 29; break; }
				case 21: { t.kind = 30; break; }
				case 22: { t.kind = 33; break; }
				case 23: { t.kind = 34; break; }
				case 24: { t.kind = 35; break; }
				case 25: { t.kind = 36; break; }
				case 26: { t.kind = 37; break; }
				case 27:
					if (ch == '=') { AddCh(); goto case 28; } else { t.kind = noSym; break; }
				case 28: { t.kind = 38; break; }
				case 29:
					if (ch == '=') { AddCh(); goto case 30; } else { t.kind = noSym; break; }
				case 30: { t.kind = 39; break; }
				case 31:
					if (ch == '=') { AddCh(); goto case 32; } else { t.kind = noSym; break; }
				case 32: { t.kind = 40; break; }
				case 33: { t.kind = 41; break; }
				case 34: { t.kind = 42; break; }
				case 35: { t.kind = 43; break; }
				case 36: { t.kind = 44; break; }
				case 37: { t.kind = 46; break; }
				case 38: { t.kind = 47; break; }
				case 39: { t.kind = 48; break; }
				case 40:
					if (ch == '-') { AddCh(); goto case 9; } else { t.kind = 24; break; }
				case 41:
					if (ch == '=') { AddCh(); goto case 26; } else { t.kind = 31; break; }
				case 42:
					if (ch == '=') { AddCh(); goto case 33; } else { t.kind = 32; break; }
				case 43:
					if (ch == '-' || ch >= '0' && ch <= '9' || ch >= 'A' && ch <= 'Z' || ch == '_' || ch >= 'a' && ch <= 'z') { AddCh(); goto case 1; } else if (ch == 92) { AddCh(); goto case 38; } else { t.kind = 1; t.val = new String(tval, 0, tlen); CheckLiteral(); return t; }

			}
			t.val = new String(tval, 0, tlen);
			return t;
		}

		// get the next token (possibly a token already seen during peeking)
		public Token Scan() {
			if (tokens.next == null) {
				return NextToken();
			} else {
				pt = tokens = tokens.next;
				return tokens;
			}
		}

		// peek for the next token, ignore pragmas
		public Token Peek() {
			if (pt.next == null) {
				do {
					pt = pt.next = NextToken();
				} while (pt.kind > maxT); // skip pragmas
			} else {
				do {
					pt = pt.next;
				} while (pt.kind > maxT);
			}
			return pt;
		}

		// make sure that peeking starts at the current scan position
		public void ResetPeek() { pt = tokens; }

	} // end Scanner

}