/*
* Function: rule
* Description: Recursive descent regular expression parser.
*/
private static Nfa rule()
{
NfaPair pair;
Nfa start = null;
Nfa end = null;
int anchor = Spec.NONE;
#if DESCENT_DEBUG
Utility.enter("rule", spec.lexeme, spec.current_token);
#endif
pair = Alloc.NewNfaPair();
if (Gen.AT_BOL == spec.current_token)
{
anchor = anchor | Spec.START;
gen.Advance();
expr(pair);
start = Alloc.NewNfa(spec);
start.SetEdge(spec.BOL);
start.SetNext(pair.start);
end = pair.end;
}
else
{
expr(pair);
start = pair.start;
end = pair.end;
}
if (Gen.AT_EOL == spec.current_token)
{
gen.Advance();
NfaPair nlpair = Alloc.NewNLPair(spec);
end.SetNext(Alloc.NewNfa(spec));
Nfa enext = end.GetNext();
enext.SetNext(nlpair.start);
enext.SetSib(Alloc.NewNfa(spec));
enext.GetSib().SetEdge(spec.EOF);
enext.GetSib().SetNext(nlpair.end);
end = nlpair.end;
anchor = anchor | Spec.END;
}
/* check for null rules */
if (end == null)
{
Error.parse_error(Error.E_ZERO, input.line_number);
}
/* Handle end of regular expression */
end.SetAccept(gen.packAccept());
end.SetAnchor(anchor);
#if DESCENT_DEBUG
Utility.leave("rule", spec.lexeme, spec.current_token);
#endif
return(start);
}
/*
* Function: e_closure
* Description: Alters input set.
*/
public void e_closure()
{
Nfa state = null;
/*
* Debug checks
*/
#if DEBUG
Utility.assert(null != nfa_set);
Utility.assert(null != nfa_bit);
#endif
accept = null;
anchor = Spec.NONE;
accept_index = Utility.INT_MAX;
/*
* Create initial stack.
*/
Stack nfa_stack = new Stack();
int size = nfa_set.Count;
for (int i = 0; i < size; i++)
{
state = (Nfa)nfa_set[i];
#if DEBUG
Utility.assert(nfa_bit.Get(state.GetLabel()));
#endif
nfa_stack.Push(state);
}
/*
* Main loop.
*/
while (nfa_stack.Count > 0)
{
Object o = nfa_stack.Pop();
if (o == null)
{
break;
}
state = (Nfa)o;
#if OLD_DUMP_DEBUG
if (null != state.GetAccept())
{
Console.WriteLine("Looking at accepting state "
+ Int32.ToString(state.GetLabel())
+ " with <"
+ state.GetAccept().action
+ ">");
}
#endif
if (null != state.GetAccept() && state.GetLabel() < accept_index)
{
accept_index = state.GetLabel();
accept = state.GetAccept();
anchor = state.GetAnchor();
#if OLD_DUMP_DEBUG
Console.WriteLine("Found accepting state "
+ Int32.ToString(state.GetLabel())
+ " with <"
+ state.GetAccept().action
+ ">");
#endif
#if DEBUG
Utility.assert(null != accept);
Utility.assert(Spec.NONE == anchor ||
0 != (anchor & Spec.END) ||
0 != (anchor & Spec.START));
#endif
}
if (Nfa.EPSILON == state.GetEdge())
{
if (state.GetNext() != null)
{
if (false == nfa_set.Contains(state.GetNext()))
{
#if DEBUG
Utility.assert(false == nfa_bit.Get(state.GetNext().GetLabel()));
#endif
nfa_bit.Set(state.GetNext().GetLabel(), true);
nfa_set.Add(state.GetNext());
nfa_stack.Push(state.GetNext());
}
}
if (null != state.GetSib())
{
if (false == nfa_set.Contains(state.GetSib()))
{
#if DEBUG
Utility.assert(false == nfa_bit.Get(state.GetSib().GetLabel()));
#endif
nfa_bit.Set(state.GetSib().GetLabel(), true);
nfa_set.Add(state.GetSib());
nfa_stack.Push(state.GetSib());
}
}
}
}
if (null != nfa_set)
{
sort_states();
}
}
