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renamed next to target. factored out to methods, commented code.

This commit is contained in:
Terence Parr 2012-02-21 12:47:34 -08:00
parent 0e23c7e2a3
commit 58ef729be5
1 changed files with 55 additions and 24 deletions
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79
runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
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@ -297,42 +297,47 @@ public class LexerATNSimulator extends ATNSimulator {
traceLookahead1();
int t = input.LA(1);
DFAState s = ds0;
DFAState s = ds0; // s is current/from DFA state
while ( true ) { // while more work
if ( debug ) {
System.out.format("in reach starting closure: %s\n", closure);
}
DFAState next = null;
// As we move src->trg, src->trg, we keep track of the previous trg to
// avoid looking up the DFA state again, which is expensive.
// If the previous target was already part of the DFA, we might
// be able to avoid doing a reach operation upon t. If s!=null,
// it means that semantic predicates didn't prevent us from
// creating a DFA state. Once we know s!=null, we check to see if
// the DFA state has an edge already for t. If so, we can just reuse
// it's configuration set; there's no point in re-computing it.
// This is kind of like doing DFA simulation within the ATN
// simulation because DFA simulation is really just a way to avoid
// computing reach/closure sets. Technically, once we know that
// we have a previously added DFA state, we could jump over to
// the DFA simulator. But, that would mean popping back and forth
// a lot and making things more complicated algorithmically.
// This optimization makes a lot of sense for loops within DFA.
// A character will take us back to an existing DFA state
// that already has lots of edges out of it. e.g., .* in comments.
DFAState target = null;
if (s != null) {
if ( s.edges != null && t < s.edges.length && t > CharStream.EOF ) {
closure = s.configset;
next = s.edges[t];
if (next != null) {
reach = next.configset;
target = s.edges[t];
if (target != null) {
reach = target.configset;
}
}
}
if (next == null) {
for (ATNConfig c : closure) {
if ( debug ) {
System.out.format("testing %s at %s\n", getTokenName(t), c.toString(recog, true));
}
int n = c.state.getNumberOfTransitions();
for (int ti=0; ti<n; ti++) { // for each transition
Transition trans = c.state.transition(ti);
ATNState target = getReachableTarget(trans, t);
if ( target!=null ) {
closure(new ATNConfig(c, target), reach);
}
}
}
if (target == null) { // if we don't find an existing DFA state
// Fill reach starting from closure, following t transitions
getReachableConfigSet(closure, reach, t);
}
if ( reach.isEmpty() ) {
if ( reach.isEmpty() ) { // we got nowhere on t from s
// we reached state associated with closure for sure, so
// make sure it's defined. worst case, we define s0 from
// start state configs.
@ -349,8 +354,9 @@ public class LexerATNSimulator extends ATNSimulator {
processAcceptStates(input, reach);
consume(input);
if (next == null) {
next = addDFAEdge(s, t, reach);
if (target == null) {
// Add an edge from s to target DFA found/created for reach
target = addDFAEdge(s, t, reach);
}
traceLookahead1();
@ -358,10 +364,15 @@ public class LexerATNSimulator extends ATNSimulator {
closure = reach;
reach = new ATNConfigSet();
s = next;
s = target; // flip; current DFA target becomes new src/from state
}
return failOrAccept(atnPrevAccept, input, reach, t);
}
protected int failOrAccept(ATNExecState atnPrevAccept, CharStream input,
ATNConfigSet reach, int t)
{
if ( atnPrevAccept.config==null ) {
// if no accept and EOF is first char, return EOF
if ( t==CharStream.EOF && input.index()==startIndex ) {
@ -376,6 +387,26 @@ public class LexerATNSimulator extends ATNSimulator {
return atn.ruleToTokenType[ruleIndex];
}
/** Given a starting configuration set, figure out all ATN configurations
* we can reach upon input t. Parameter reach is a return parameter.
*/
protected void getReachableConfigSet(ATNConfigSet closure, ATNConfigSet reach, int t) {
for (ATNConfig c : closure) {
if ( debug ) {
System.out.format("testing %s at %s\n", getTokenName(t), c.toString(recog, true));
}
int n = c.state.getNumberOfTransitions();
for (int ti=0; ti<n; ti++) { // for each transition
Transition trans = c.state.transition(ti);
ATNState target = getReachableTarget(trans, t);
if ( target!=null ) {
closure(new ATNConfig(c, target), reach);
}
}
}
}
protected void processAcceptStates(@NotNull CharStream input, @NotNull ATNConfigSet reach) {
for (int ci=0; ci<reach.size(); ci++) {
ATNConfig c = reach.get(ci);