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DFA.cs

// DFA.cs   Scaner automaton gnerated by Coco/R  H.Moessenboeck, Univ. of Linz
//----------------------------------------------------------------------------
using System;
using System.IO;
using System.Collections;
using System.Text;

namespace at.jku.ssw.Coco {

//-----------------------------------------------------------------------------
//  State
//-----------------------------------------------------------------------------

public class State {                      // state of finite automaton
      public static int lastNr;     // highest state number
      public int nr;                                  // state number
      public Action firstAction;// to first action of this state
      public Symbol endOf;                // recognized token if state is final
      public bool ctx;                          // true if state is reached via contextTrans
      public State next;
      
      public State() {
            nr = ++lastNr;
      }
      
      public void AddAction(Action act) {
            Action lasta = null, a = firstAction;
            while (a != null && act.typ >= a.typ) {lasta = a; a = a.next;}
            // collecting classes at the beginning gives better performance
            act.next = a;
            if (a==firstAction) firstAction = act; else lasta.next = act;
      }
      
      public void DetachAction(Action act) {
            Action lasta = null, a = firstAction;
            while (a != null && a != act) {lasta = a; a = a.next;}
            if (a != null)
                  if (a == firstAction) firstAction = a.next; else lasta.next = a.next;
      }
      
      public Action TheAction(char ch) {
            BitArray s;
            for (Action a = firstAction; a != null; a = a.next)
                  if (a.typ == Node.chr && ch == a.sym) return a;
                  else if (a.typ == Node.clas) {
                        s = CharClass.Set(a.sym);
                        if (s[ch]) return a;
                  }
            return null;
      }
      
      public void MeltWith(State s) { // copy actions of s to state
            Action a;
            for (Action action = s.firstAction; action != null; action = action.next) {
                  a = new Action(action.typ, action.sym, action.tc);
                  a.AddTargets(action);
                  AddAction(a);
            }
      }
      
}

//-----------------------------------------------------------------------------
//  Action
//-----------------------------------------------------------------------------

public class Action {               // action of finite automaton
      public int typ;                           // type of action symbol: clas, chr
      public int sym;                           // action symbol
      public int tc;                            // transition code: normalTrans, contextTrans
      public Target target;         // states reached from this action
      public Action next;
      
      public Action(int typ, int sym, int tc) {
            this.typ = typ; this.sym = sym; this.tc = tc;
      }
      
      public void AddTarget(Target t) { // add t to the action.targets
            Target last = null;
            Target p = target;
            while (p != null && t.state.nr >= p.state.nr) {
                  if (t.state == p.state) return;
                  last = p; p = p.next;
            }
            t.next = p;
            if (p == target) target = t; else last.next = t;
      }

      public void AddTargets(Action a) { // add copy of a.targets to action.targets
            for (Target p = a.target; p != null; p = p.next) {
                  Target t = new Target(p.state);
                  AddTarget(t);
            }
            if (a.tc == Node.contextTrans) tc = Node.contextTrans;
      }
      
      public BitArray Symbols() {
            BitArray s;
            if (typ == Node.clas)
                  s = (BitArray) CharClass.Set(sym).Clone();
            else {
                  s = new BitArray(CharClass.charSetSize); s[sym] = true;
            }
            return s;
      }
      
      public void ShiftWith(BitArray s) {
            if (Sets.Elements(s) == 1) {
                  typ = Node.chr; sym = Sets.First(s);
            } else {
                  CharClass c = CharClass.Find(s);
                  if (c == null) c = new CharClass("#", s); // class with dummy name
                  typ = Node.clas; sym = c.n;
            }
      }
      
      public void GetTargetStates(out BitArray targets, out Symbol endOf, out bool ctx) { 
            // compute the set of target states
            targets = new BitArray(DFA.maxStates); endOf = null;
            ctx = false;
            for (Target t = target; t != null; t = t.next) {
                  int stateNr = t.state.nr;
                  if (stateNr <= DFA.lastSimState) targets[stateNr] = true;
                  else targets.Or(Melted.Set(stateNr));
                  if (t.state.endOf != null)
                        if (endOf == null || endOf == t.state.endOf)
                              endOf = t.state.endOf;
                        else {
                              Console.WriteLine("Tokens {0} and {1} cannot be distinguished", endOf.name, t.state.endOf.name);
                              Errors.count++;
                        }
                  if (t.state.ctx) {
                        ctx = true;
                        // The following check seems to be unnecessary. It reported an error
                        // if a symbol + context was the prefix of another symbol, e.g.
                        //   s1 = "a" "b" "c".
                        //   s2 = "a" CONTEXT("b").
                        // But this is ok.
                        // if (t.state.endOf != null) {
                        //   Console.WriteLine("Ambiguous context clause");
                        //     Errors.count++;
                        // }
                  }
            }
      }
      
}

//-----------------------------------------------------------------------------
//  Target
//-----------------------------------------------------------------------------

public class Target {                     // set of states that are reached by an action
      public State state;                       // target state
      public Target next;
      
      public Target (State s) {
            state = s;
      }
}

//-----------------------------------------------------------------------------
//  Melted
//-----------------------------------------------------------------------------

public class Melted {                           // info about melted states
      public static Melted first;   // head of melted state list
      public BitArray set;                      // set of old states
      public State state;                             // new state
      public Melted next;
      
      public Melted(BitArray set, State state) {
            this.set = set; this.state = state;
            this.next = first; first = this;
      }

      public static BitArray Set(int nr) {
            Melted m = first;
            while (m != null) {
                  if (m.state.nr == nr) return m.set; else m = m.next;
            }
            throw new Exception("-- compiler error in Melted.Set");
      }
      
      public static Melted StateWithSet(BitArray s) {
            for (Melted m = first; m != null; m = m.next)
                  if (Sets.Equals(s, m.set)) return m;
            return null;
      }
      
}

//-----------------------------------------------------------------------------
//  Comment
//-----------------------------------------------------------------------------

public class Comment {                          // info about comment syntax
      public static Comment first;  // list of comments
      public string start;
      public string stop;
      public bool nested;
      public Comment next;
      
      static string Str(Node p) {
            StringBuilder s = new StringBuilder();
            while (p != null) {
                  if (p.typ == Node.chr) {
                        s.Append((char)p.val);
                  } else if (p.typ == Node.clas) {
                        BitArray set = CharClass.Set(p.val);
                        if (Sets.Elements(set) != 1) Parser.SemErr("character set contains more than 1 character");
                        s.Append((char)Sets.First(set));
                  } else Parser.SemErr("comment delimiters may not be structured");
                  p = p.next;
            }
            if (s.Length == 0 || s.Length > 2) {
                  Parser.SemErr("comment delimiters must be 1 or 2 characters long");
                  s = new StringBuilder("?");
            }
            return s.ToString();
      }
      
      public Comment(Node from, Node to, bool nested) {
            start = Str(from);
            stop = Str(to);
            this.nested = nested;
            this.next = first; first = this;
      }
      
}

//-----------------------------------------------------------------------------
//  DFA
//-----------------------------------------------------------------------------

public class DFA {
      public static int maxStates;
      public const int  EOF = -1;
      public const char CR  = '\r';
      public const char LF  = '\n';
      
      public static State firstState;
      public static State lastState;            // last allocated state
      public static int lastSimState;           // last non melted state
      public static FileStream fram;            // scanner frame input
      public static StreamWriter gen;           // generated scanner file
             static string srcDir;      // directory of attributed grammar file
      public static Symbol curSy;                     // current token to be recognized (in FindTrans)
      public static Node curGraph;              // start of graph for current token (in FindTrans)
      public static bool dirtyDFA;              // DFA may become nondeterministic in MatchedDFA
      public static bool hasCtxMoves;           // DFA has context transitions
      
      //---------- Output primitives
      private static string Ch(char ch) {
            if (ch < ' ' || ch >= 127 || ch == '\'' || ch == '\\') return Convert.ToString((int)ch);
            else return String.Format("'{0}'", ch);
      }
      
      private static string ChCond(char ch) {
            return String.Format("ch == {0}", Ch(ch));
      }
      
      private static void PutRange(BitArray s) {
            int[] lo = new int[32];
            int[] hi = new int[32];
            // fill lo and hi
            int max = CharClass.charSetSize;
            int top = -1;
            int i = 0;
            while (i < max) {
                  if (s[i]) {
                        top++; lo[top] = i; i++;
                        while (i < max && s[i]) i++;
                        hi[top] = i-1;
                  } else i++;
            }
            // print ranges
            if (top == 1 && lo[0] == 0 && hi[1] == max-1 && hi[0]+2 == lo[1]) {
                  BitArray s1 = new BitArray(max); s1[hi[0]+1] = true;
                  gen.Write("!"); PutRange(s1);
            } else {
                  gen.Write("(");
                  for (i = 0; i <= top; i++) {
                        if (hi[i] == lo[i]) gen.Write("ch == {0}", Ch((char)lo[i]));
                        else if (lo[i] == 0) gen.Write("ch <= {0}", Ch((char)hi[i]));
                        else if (hi[i] == max-1) gen.Write("ch >= {0}", Ch((char)lo[i]));
                        else gen.Write("ch >= {0} && ch <= {1}", Ch((char)lo[i]), Ch((char)hi[i]));
                        if (i < top) gen.Write(" || ");
                  }
                  gen.Write(")");
            }
      }
      
      //---------- String handling
      static char Hex2Char(string s) {
            int val = 0;
            for (int i = 0; i < s.Length; i++) {
                  char ch = s[i];
                  if ('0' <= ch && ch <= '9') val = 16 * val + (ch - '0');
                  else if ('a' <= ch && ch <= 'f') val = 16 * val + (10 + ch - 'a');
                  else if ('A' <= ch && ch <= 'Z') val = 16 * val + (10 + ch - 'A');
                  else Parser.SemErr("bad escape sequence in string or character");
            }
            return (char)val;
      }
      
      static string Char2Hex(char ch) {
            StringWriter w = new StringWriter();
            w.Write("\\u{0:x4}", (int)ch);
            return w.ToString();
      }
            
      public static string Unescape (string s) {
            /* replaces escape sequences in s by their Unicode values. */
            StringBuilder buf = new StringBuilder();
            int i = 0;
            while (i < s.Length) {
                  if (s[i] == '\\') {
                        switch (s[i+1]) {
                              case '\\': buf.Append('\\'); i += 2; break;
                              case '\'': buf.Append('\''); i += 2; break;
                              case '\"': buf.Append('\"'); i += 2; break;
                              case 'r': buf.Append('\r'); i += 2; break;
                              case 'n': buf.Append('\n'); i += 2; break;
                              case 't': buf.Append('\t'); i += 2; break;
                              case '0': buf.Append('\0'); i += 2; break;
                              case 'a': buf.Append('\a'); i += 2; break;
                              case 'b': buf.Append('\b'); i += 2; break;
                              case 'f': buf.Append('\f'); i += 2; break;
                              case 'v': buf.Append('\v'); i += 2; break;
                              case 'u': case 'x':
                                    if (i + 6 <= s.Length) {
                                          buf.Append(Hex2Char(s.Substring(i+2, 4))); i += 6; break;
                                    } else {
                                          Parser.SemErr("bad escape sequence in string or character"); i = s.Length; break;
                                    }
                              default: Parser.SemErr("bad escape sequence in string or character"); i += 2; break;
                        }
                  } else {
                        buf.Append(s[i]);
                        i++;
                  }
            }
            return buf.ToString();
      }
      
      public static string Escape (string s) {
            StringBuilder buf = new StringBuilder();
            foreach (char ch in s) {
                  if (ch == '\\') buf.Append("\\\\");
                  else if (ch == '"') buf.Append("\\\"");
                  else if (ch < ' ' || ch > '\u007f') buf.Append(Char2Hex(ch));
                  else buf.Append(ch);
            }
            return buf.ToString();
      }
            
      //---------- State handling
      static State NewState() {
            State s = new State();
            if (firstState == null) firstState = s; else lastState.next = s;
            lastState = s;
            return s;
      }
      
      static void NewTransition(State from, State to, int typ, int sym, int tc) {
            if (to == firstState) Parser.SemErr("token must not start with an iteration");
            Target t = new Target(to);
            Action a = new Action(typ, sym, tc); a.target = t;
            from.AddAction(a);
      }
      
      static void CombineShifts() {
            State state;
            Action a, b, c;
            BitArray seta, setb;
            for (state = firstState; state != null; state = state.next) {
                  for (a = state.firstAction; a != null; a = a.next) {
                        b = a.next;
                        while (b != null)
                              if (a.target.state == b.target.state && a.tc == b.tc) {
                                    seta = a.Symbols(); setb = b.Symbols();
                                    seta.Or(setb);
                                    a.ShiftWith(seta);
                                    c = b; b = b.next; state.DetachAction(c);
                              } else b = b.next;
                  }
            }
      }
      
      static void FindUsedStates(State state, BitArray used) {
            if (used[state.nr]) return;
            used[state.nr] = true;
            for (Action a = state.firstAction; a != null; a = a.next)
                  FindUsedStates(a.target.state, used);
      }
      
      static void DeleteRedundantStates() {
            State[] newState = new State[State.lastNr + 1];
            BitArray used = new BitArray(State.lastNr + 1);
            FindUsedStates(firstState, used);
            // combine equal final states
            for (State s1 = firstState.next; s1 != null; s1 = s1.next) // firstState cannot be final
                  if (used[s1.nr] && s1.endOf != null && s1.firstAction == null && !s1.ctx)
                        for (State s2 = s1.next; s2 != null; s2 = s2.next)
                              if (used[s2.nr] && s1.endOf == s2.endOf && s2.firstAction == null & !s2.ctx) {
                                    used[s2.nr] = false; newState[s2.nr] = s1;
                              }
            for (State state = firstState; state != null; state = state.next)
                  if (used[state.nr])
                        for (Action a = state.firstAction; a != null; a = a.next)
                              if (!used[a.target.state.nr])
                                    a.target.state = newState[a.target.state.nr];
            // delete unused states
            lastState = firstState; State.lastNr = 0; // firstState has number 0
            for (State state = firstState.next; state != null; state = state.next)
                  if (used[state.nr]) {state.nr = ++State.lastNr; lastState = state;}
                  else lastState.next = state.next;
      }
      
      static State TheState(Node p) {
            State state;
            if (p == null) {state = NewState(); state.endOf = curSy; return state;}
            else return p.state;
      }
      
      static void Step(State from, Node p, BitArray stepped) {
            if (p == null) return;
            stepped[p.n] = true;
            switch (p.typ) {
                  case Node.clas: case Node.chr: {
                        NewTransition(from, TheState(p.next), p.typ, p.val, p.code);
                        break;
                  }
                  case Node.alt: {
                        Step(from, p.sub, stepped); Step(from, p.down, stepped);
                        break;
                  }
                  case Node.iter: case Node.opt: {
                        if (p.next != null && !stepped[p.next.n]) Step(from, p.next, stepped);
                        Step(from, p.sub, stepped);
                        break;
                  }
            }
      }
      
      static void NumberNodes(Node p, State state) {
            /* Assigns a state n.state to every node n. There will be a transition from
               n.state to n.next.state triggered by n.val. All nodes in an alternative
               chain are represented by the same state.
            */
            if (p == null) return;
            if (p.state != null) return; // already visited;
            if (state == null) state = NewState();
            p.state = state;
            if (Node.DelGraph(p)) state.endOf = curSy;
            switch (p.typ) {
                  case Node.clas: case Node.chr: {
                        NumberNodes(p.next, null);
                        break;
                  }
                  case Node.opt: {
                        NumberNodes(p.next, null); NumberNodes(p.sub, state);
                        break;
                  }
                  case Node.iter: {
                        NumberNodes(p.next, state); NumberNodes(p.sub, state);
                        break;
                  }
                  case Node.alt: {
                        NumberNodes(p.sub, state); NumberNodes(p.down, state);
                        break;
                  }
            }
      }
      
      static void FindTrans (Node p, bool start, BitArray marked) {
            if (p == null || marked[p.n]) return;
            marked[p.n] = true;
            if (start) Step(p.state, p, new BitArray(Node.nodes.Count)); // start of group of equally numbered nodes
            switch (p.typ) {
                  case Node.clas: case Node.chr: {
                        FindTrans(p.next, true, marked);
                        break;
                  }
                  case Node.opt: {
                        FindTrans(p.next, true, marked); FindTrans(p.sub, false, marked);
                        break;
                  }
                  case Node.iter: {
                        FindTrans(p.next, false, marked); FindTrans(p.sub, false, marked);
                        break;
                  }
                  case Node.alt: {
                        FindTrans(p.sub, false, marked); FindTrans(p.down, false, marked);
                        break;
                  }
            }
      }
      
      public static void ConvertToStates(Node p, Symbol sym) {
            curGraph = p; curSy = sym;
            if (Node.DelGraph(curGraph)) Parser.SemErr("token might be empty");
            NumberNodes(curGraph, firstState);
            FindTrans(curGraph, true, new BitArray(Node.nodes.Count));
      }
      
      static Symbol MatchedDFA(string s, Symbol sym) {
            int i, len = s.Length;
            bool weakMatch = false;
            // s has no quotes
            State state = firstState;
            for (i = 0; i < len; i++) { // try to match s against existing DFA
                  Action a = state.TheAction(s[i]);
                  if (a == null) break;
                  if (a.typ == Node.clas) weakMatch = true;
                  state = a.target.state;
            }
            // don't execute the following block if s was totally consumed and the DFA is in a final state
            if (weakMatch && (i != len || state.endOf == null)) {
                  state = firstState; i = 0;
                  dirtyDFA = true;
            }
            for (; i < len; i++) { // make new DFA for s[i..len-1]
                  State to = NewState();
                  NewTransition(state, to, Node.chr, s[i], Node.normalTrans);
                  state = to;
            }
            Symbol matchedSym = state.endOf;
            if (state.endOf == null) state.endOf = sym;
            return matchedSym;
      }
      
      public static void MatchLiteral(Symbol sym) { // store string either as token or as literal
            string name = Unescape(sym.name.Substring(1, sym.name.Length-2));
            if (name.IndexOf('\0') >= 0) Parser.SemErr("\\0 not allowed here. Used as eof character");
        Symbol matchedSym = MatchedDFA(name, sym);
        if (matchedSym == null)
          sym.tokenKind = Symbol.classToken;
        else {
          matchedSym.tokenKind = Symbol.classLitToken;
          sym.tokenKind = Symbol.litToken;
        }
      }
      
      static void SplitActions(State state, Action a, Action b) {
            Action c; BitArray seta, setb, setc;
            seta = a.Symbols(); setb = b.Symbols();
            if (Sets.Equals(seta, setb)) {
                  a.AddTargets(b);
                  state.DetachAction(b);
            } else if (Sets.Includes(seta, setb)) {
                  setc = (BitArray)seta.Clone(); Sets.Subtract(setc, setb);
                  b.AddTargets(a);
                  a.ShiftWith(setc);
            } else if (Sets.Includes(setb, seta)) {
                  setc = (BitArray)setb.Clone(); Sets.Subtract(setc, seta);
                  a.AddTargets(b);
                  b.ShiftWith(setc);
            } else {
                  setc = (BitArray)seta.Clone(); setc.And(setb);
                  Sets.Subtract(seta, setc);
                  Sets.Subtract(setb, setc);
                  a.ShiftWith(seta);
                  b.ShiftWith(setb);
                  c = new Action(0, 0, Node.normalTrans);  // typ and sym are set in ShiftWith
                  c.AddTargets(a);
                  c.AddTargets(b);
                  c.ShiftWith(setc);
                  state.AddAction(c);
            }
      }
      
      private static bool Overlap(Action a, Action b) {
            BitArray seta, setb;
            if (a.typ == Node.chr)
                  if (b.typ == Node.chr) return a.sym == b.sym;
                  else {setb = CharClass.Set(b.sym); return setb[a.sym];}
            else {
                  seta = CharClass.Set(a.sym);
                  if (b.typ ==Node.chr) return seta[b.sym];
                  else {setb = CharClass.Set(b.sym); return Sets.Intersect(seta, setb);}
            }
      }
      
      static bool MakeUnique(State state) { // return true if actions were split
            bool changed = false;
            for (Action a = state.firstAction; a != null; a = a.next)
                  for (Action b = a.next; b != null; b = b.next)
                        if (Overlap(a, b)) {SplitActions(state, a, b); changed = true;}
            return changed;
      }
      
      static void MeltStates(State state) {
            bool changed, ctx;
            BitArray targets;
            Symbol endOf;
            for (Action action = state.firstAction; action != null; action = action.next) {
                  if (action.target.next != null) {
                        action.GetTargetStates(out targets, out endOf, out ctx);
                        Melted melt = Melted.StateWithSet(targets);
                        if (melt == null) {
                              State s = NewState(); s.endOf = endOf; s.ctx = ctx;
                              for (Target targ = action.target; targ != null; targ = targ.next)
                                    s.MeltWith(targ.state);
                              do {changed = MakeUnique(s);} while (changed);
                              melt = new Melted(targets, s);
                        }
                        action.target.next = null;
                        action.target.state = melt.state;
                  }
            }
      }
      
      static void FindCtxStates() {
            for (State state = firstState; state != null; state = state.next)
                  for (Action a = state.firstAction; a != null; a = a.next)
                        if (a.tc == Node.contextTrans) a.target.state.ctx = true;
      }
      
      public static void MakeDeterministic() {
            State state;
            bool changed;
            lastSimState = lastState.nr;
            maxStates = 2 * lastSimState; // heuristic for set size in Melted.set
            FindCtxStates();
            for (state = firstState; state != null; state = state.next)
                  do {changed = MakeUnique(state);} while (changed);
            for (state = firstState; state != null; state = state.next)
                  MeltStates(state);
            DeleteRedundantStates();
            CombineShifts();
      }
      
      public static void PrintStates() {
            Trace.WriteLine("\n---------- states ----------");
            for (State state = firstState; state != null; state = state.next) {
                  bool first = true;
                  if (state.endOf == null) Trace.Write("               ");
                  else Trace.Write("E({0,12})", Node.Name(state.endOf.name));
                  Trace.Write("{0,3}:", state.nr);
                  if (state.firstAction == null) Trace.WriteLine();
                  for (Action action = state.firstAction; action != null; action = action.next) {
                        if (first) {Trace.Write(" "); first = false;} else Trace.Write("                    ");
                        if (action.typ == Node.clas) Trace.Write(((CharClass)CharClass.classes[action.sym]).name);
                        else Trace.Write("{0, 3}", Ch((char)action.sym));
                        for (Target targ = action.target; targ != null; targ = targ.next)
                              Trace.Write(" {0, 3}", targ.state.nr);
                        if (action.tc == Node.contextTrans) Trace.WriteLine(" context"); else Trace.WriteLine();
                  }
            }
            Trace.WriteLine("\n---------- character classes ----------");
            CharClass.WriteClasses();
      }
      
      static void GenComBody(Comment com) {
            gen.WriteLine(  "\t\t\tfor(;;) {");
            gen.Write    (  "\t\t\t\tif ({0}) ", ChCond(com.stop[0])); gen.WriteLine("{");
            if (com.stop.Length == 1) {
                  gen.WriteLine("\t\t\t\t\tlevel--;");
                  gen.WriteLine("\t\t\t\t\tif (level == 0) { oldEols = line - line0; NextCh(); return true; }");
                  gen.WriteLine("\t\t\t\t\tNextCh();");
            } else {
                  gen.WriteLine("\t\t\t\t\tNextCh();");
                  gen.WriteLine("\t\t\t\t\tif ({0}) {{", ChCond(com.stop[1]));
                  gen.WriteLine("\t\t\t\t\t\tlevel--;");
                  gen.WriteLine("\t\t\t\t\t\tif (level == 0) { oldEols = line - line0; NextCh(); return true; }");
                  gen.WriteLine("\t\t\t\t\t\tNextCh();");
                  gen.WriteLine("\t\t\t\t\t}");
            }
            if (com.nested) {
                  gen.Write    ("\t\t\t\t}"); gen.Write(" else if ({0}) ", ChCond(com.start[0])); gen.WriteLine("{");
                  if (com.start.Length == 1)
                        gen.WriteLine("\t\t\t\t\tlevel++; NextCh();");
                  else {
                        gen.WriteLine("\t\t\t\t\tNextCh();");
                        gen.Write    ("\t\t\t\t\tif ({0}) ", ChCond(com.start[1])); gen.WriteLine("{");
                        gen.WriteLine("\t\t\t\t\t\tlevel++; NextCh();");
                        gen.WriteLine("\t\t\t\t\t}");
                  }
            }
            gen.WriteLine(    "\t\t\t\t} else if (ch == EOF) return false;");
            gen.WriteLine(    "\t\t\t\telse NextCh();");
            gen.WriteLine(    "\t\t\t}");
      }
      
      static void GenComment(Comment com, int i) {
            gen.Write    ("\n\tstatic bool Comment{0}() ", i); gen.WriteLine("{");
            gen.WriteLine("\t\tint level = 1, line0 = line, lineStart0 = lineStart;");
            if (com.start.Length == 1) {
                  gen.WriteLine("\t\tNextCh();");
                  GenComBody(com);
            } else {
                  gen.WriteLine("\t\tNextCh();");
                  gen.Write    ("\t\tif ({0}) ", ChCond(com.start[1])); gen.WriteLine("{");
                  gen.WriteLine("\t\t\tNextCh();");
                  GenComBody(com);
                  gen.WriteLine("\t\t} else {");
                  gen.WriteLine("\t\t\tif (ch==EOL) {line--; lineStart = lineStart0;}");
                  gen.WriteLine("\t\t\tpos = pos - 2; Buffer.Pos = pos+1; NextCh();");
                  gen.WriteLine("\t\t}");
                  gen.WriteLine("\t\treturn false;");
            }
            gen.WriteLine("\t}");
      }
      
      static void CopyFramePart(string stop) {
            char startCh = stop[0];
            int endOfStopString = stop.Length-1;
            int ch = fram.ReadByte();
            while (ch != EOF)
                  if (ch == startCh) {
                        int i = 0;
                        do {
                              if (i == endOfStopString) return; // stop[0..i] found
                              ch = fram.ReadByte(); i++;
                        } while (ch == stop[i]);
                        // stop[0..i-1] found; continue with last read character
                        gen.Write(stop.Substring(0, i));
                  } else {
                        gen.Write((char)ch); ch = fram.ReadByte();
                  }
            Errors.Exception(" -- incomplete or corrupt scanner frame file");
      }
      
      static void GenLiterals () {
            foreach (Symbol sym in Symbol.terminals) {
                  if (sym.tokenKind == Symbol.litToken) {
                        // sym.name stores literals with quotes, e.g. "\"Literal\"",
                        // therefore do NOT place any quotes around {0} after the case
                        // or you'll get: case ""Literal"": t.kind = ..., which causes an error
                        gen.WriteLine("\t\t\tcase {0}: t.kind = {1}; break;", sym.name, sym.n);
                  }
            }
            gen.WriteLine("\t\t\tdefault: break;");
      }
      
      static void WriteState(State state) {
            Symbol endOf = state.endOf;
            gen.WriteLine("\t\t\tcase {0}:", state.nr);
            bool ctxEnd = state.ctx;
            for (Action action = state.firstAction; action != null; action = action.next) {
                  if (action == state.firstAction) gen.Write("\t\t\t\tif (");
                  else gen.Write("\t\t\t\telse if (");
                  if (action.typ == Node.chr) gen.Write(ChCond((char)action.sym));
                  else PutRange(CharClass.Set(action.sym));
                  gen.Write(") {");
                  if (action.tc == Node.contextTrans) {
                        gen.Write("apx++; "); ctxEnd = false;
                  } else if (state.ctx)
                        gen.Write("apx = 0; ");
                  gen.Write("buf.Append(ch); NextCh(); goto case {0};", action.target.state.nr);
                  gen.WriteLine("}");
            }
            if (state.firstAction == null)
                  gen.Write("\t\t\t\t{");
            else
                  gen.Write("\t\t\t\telse {");
            if (ctxEnd) { // final context state: cut appendix
                  gen.WriteLine();
                  gen.WriteLine("\t\t\t\t\tbuf.Length = buf.Length - apx;");
                  gen.WriteLine("\t\t\t\t\tpos = pos - apx - 1; line = t.line;");
                  gen.WriteLine("\t\t\t\t\tBuffer.Pos = pos+1; NextCh();");
                  gen.Write(        "\t\t\t\t\t");
            }
            if (endOf == null) {
                  gen.WriteLine("t.kind = noSym; goto done;}");
            } else {
                  gen.Write("t.kind = {0}; ", endOf.n);
                  if (endOf.tokenKind == Symbol.classLitToken) {
                        gen.WriteLine("t.val = buf.ToString(); CheckLiteral(); return t;}");
                  } else {
                        gen.WriteLine("goto done;}");
                  }
            }
      }
      
      static void FillStartTab(int[] startTab) {
            startTab[0] = State.lastNr + 1; // eof
            for (Action action = firstState.firstAction; action != null; action = action.next) {
                  int targetState = action.target.state.nr;
                  if (action.typ == Node.chr) startTab[action.sym] = targetState;
                  else {
                        BitArray s = CharClass.Set(action.sym);
                        for (int i = 0; i < s.Count; i++)
                              if (s[i]) startTab[i] = targetState;
                  }
            }
      }
      
      public static void WriteScanner() {
            int i, j;
            int[] startTab = new int[CharClass.charSetSize];
            string dir = System.Environment.CurrentDirectory;
            string fr = Path.Combine (dir, "Scanner.frame");
            if (!File.Exists(fr)) {
                  string frameDir = Environment.GetEnvironmentVariable("crframes");
                  if (frameDir != null) fr = Path.Combine (frameDir.Trim(), "Scanner.frame");
                  if (!File.Exists(fr)) Errors.Exception("-- Cannot find Scanner.frame");
            }
            try {
                  fram = new FileStream(fr, FileMode.Open, FileAccess.Read, FileShare.Read);
            } catch (FileNotFoundException) {
                  Errors.Exception("-- Cannot open Scanner.frame.");
            }
            try {
                  string fn = dir + "\\Scanner.cs";
                  if (File.Exists(fn)) File.Copy(fn, fn+".old", true);
                  FileStream s = new FileStream(fn, FileMode.Create);
                  gen = new StreamWriter(s);
            } catch (IOException) {
                  Errors.Exception("-- Cannot generate scanner file.");
            }
            if (dirtyDFA) MakeDeterministic();
            FillStartTab(startTab);

            CopyFramePart("-->namespace");
            /* AW add namespace, if it exists */
            if (Tab.nsName != null && Tab.nsName.Length > 0) {
                  gen.Write("namespace ");
                  gen.Write(Tab.nsName);
                  gen.Write(" {");
            }
            CopyFramePart("-->constants");
            gen.WriteLine("\tconst int maxT = {0};", Symbol.terminals.Count - 1);
            CopyFramePart("-->declarations");
            gen.WriteLine("\tconst int noSym = {0};", Tab.noSym.n);
            gen.WriteLine("\tstatic short[] start = {");
            for (i = 0; i < CharClass.charSetSize / 16; i++) {
                  gen.Write("\t");
                  for (j = 0; j < 16; j++)
                        gen.Write("{0,3},", startTab[16*i+j]);
                  gen.WriteLine();
            }
            gen.WriteLine("\t  0};");
            CopyFramePart("-->initialization");
            gen.WriteLine("\t\tignore = new BitArray({0});", CharClass.charSetSize);
            gen.Write("\t\t");
            if (Tab.ignored == null) gen.Write("ignore[' '] = true;");
            else {
                  j = 0;
                  for (i = 0; i < Tab.ignored.Count; i++)
                        if (Tab.ignored[i]) {
                              gen.Write("ignore[{0}] = true; ", i);
                              if (++j % 4 == 0) { gen.WriteLine(); gen.Write("\t\t"); }
                        }
            } 
            CopyFramePart("-->comment");
            Comment com = Comment.first; i = 0;
            while (com != null) {
                  GenComment(com, i);
                  com = com.next; i++;
            }
            CopyFramePart("-->literals"); GenLiterals();
            CopyFramePart("-->scan1");
            if (Comment.first!=null) {
                  gen.Write("\t\tif (");
                  com = Comment.first; i = 0;
                  while (com != null) {
                        gen.Write(ChCond(com.start[0]));
                        gen.Write(" && Comment{0}()", i);
                        if (com.next != null) gen.Write(" ||");
                        com = com.next; i++;
                  }
                  gen.Write(") return NextToken();");
            }
            if (hasCtxMoves) gen.WriteLine("\t\tint apx = 0;");
            CopyFramePart("-->scan2");
            for (State state = firstState.next; state != null; state = state.next)
                  WriteState(state);
            gen.Write("\t\t\tcase "+(State.lastNr+1)+": {t.kind = 0; goto done;}");
            CopyFramePart("$$$");
            /* AW 12-20-02 close namespace, if it exists */
            if (Tab.nsName != null && Tab.nsName.Length > 0) gen.Write("}");
            gen.Close();
      }
      
      public static void Init (string dir) {
            srcDir = dir;
            firstState = null; lastState = null; State.lastNr = -1;
            firstState = NewState();
            Melted.first = null; Comment.first = null;
            dirtyDFA = false;
            hasCtxMoves = false;
      }
      
} // end DFA

} // end namespace

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