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Kotlin multiplatform port of ANTLR
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.kotlinruntime.atn
import com.strumenta.kotlinmultiplatform.assert
import com.strumenta.kotlinmultiplatform.outMessage
import com.strumenta.kotlinmultiplatform.synchronized
import org.antlr.v4.kotlinruntime.*
import org.antlr.v4.kotlinruntime.dfa.DFA
import org.antlr.v4.kotlinruntime.dfa.DFAState
import org.antlr.v4.kotlinruntime.misc.Interval
/** "dup" of ParserInterpreter */
class LexerATNSimulator(protected val recog: Lexer?, atn: ATN,
val decisionToDFA: Array,
sharedContextCache: PredictionContextCache) : ATNSimulator(atn, sharedContextCache) {
/** The current token's starting index into the character stream.
* Shared across DFA to ATN simulation in case the ATN fails and the
* DFA did not have a previous accept state. In this case, we use the
* ATN-generated exception object.
*/
protected var startIndex = -1
/** line number 1..n within the input */
var line = 1
/** The index of the character relative to the beginning of the line 0..n-1 */
var charPositionInLine = 0
protected var mode = Lexer.DEFAULT_MODE
/** Used during DFA/ATN exec to record the most recent accept configuration info */
protected val prevAccept = SimState()
/** When we hit an accept state in either the DFA or the ATN, we
* have to notify the character stream to start buffering characters
* via [IntStream.mark] and record the current state. The current sim state
* includes the current index into the input, the current line,
* and current character position in that line. Note that the Lexer is
* tracking the starting line and characterization of the token. These
* variables track the "state" of the simulator when it hits an accept state.
*
*
* We track these variables separately for the DFA and ATN simulation
* because the DFA simulation often has to fail over to the ATN
* simulation. If the ATN simulation fails, we need the DFA to fall
* back to its previously accepted state, if any. If the ATN succeeds,
* then the ATN does the accept and the DFA simulator that invoked it
* can simply return the predicted token type.
*/
protected class SimState {
var index = -1
var line = 0
var charPos = -1
var dfaState: DFAState? = null
fun reset() {
index = -1
line = 0
charPos = -1
dfaState = null
}
}
constructor(atn: ATN, decisionToDFA: Array,
sharedContextCache: PredictionContextCache) : this(null, atn, decisionToDFA, sharedContextCache) {
}
fun copyState(simulator: LexerATNSimulator) {
this.charPositionInLine = simulator.charPositionInLine
this.line = simulator.line
this.mode = simulator.mode
this.startIndex = simulator.startIndex
}
fun match(input: CharStream, mode: Int): Int {
this.mode = mode
val mark = input.mark()
try {
this.startIndex = input.index()
this.prevAccept.reset()
val dfa = decisionToDFA[mode]
return if (dfa!!.s0 == null) {
matchATN(input)
} else {
execATN(input, dfa!!.s0 as DFAState)
}
} finally {
input.release(mark)
}
}
override fun reset() {
prevAccept.reset()
startIndex = -1
line = 1
charPositionInLine = 0
mode = Lexer.DEFAULT_MODE
}
override fun clearDFA() {
for (d in decisionToDFA.indices) {
decisionToDFA[d] = DFA(atn.getDecisionState(d) as DecisionState, d)
}
}
protected fun matchATN(input: CharStream): Int {
val startState = atn.modeToStartState[mode]
if (debug) {
outMessage("matchATN mode $mode start: $startState\n")
}
val old_mode = mode
val s0_closure = computeStartState(input, startState)
val suppressEdge = s0_closure.hasSemanticContext
s0_closure.hasSemanticContext = false
val next = addDFAState(s0_closure)
if (!suppressEdge) {
decisionToDFA[mode]!!.s0 = next
}
val predict = execATN(input, next)
if (debug) {
outMessage("DFA after matchATN: ${decisionToDFA[old_mode]!!.toLexerString()}\n")
}
return predict
}
protected fun execATN(input: CharStream, ds0: DFAState): Int {
//System.out.println("enter exec index "+input.index()+" from "+ds0.configs);
if (debug) {
outMessage("start state closure=${ds0.configs}\n")
}
if (ds0.isAcceptState) {
// allow zero-length tokens
captureSimState(prevAccept, input, ds0)
}
var t = input.LA(1)
var s: DFAState? = ds0 // s is current/from DFA state
while (true) { // while more work
if (debug) {
outMessage("execATN loop starting closure: ${s!!.configs}\n")
}
// 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.
var target = getExistingTargetState(s, t)
if (target == null) {
target = computeTargetState(input, s, t)
}
if (target === ATNSimulator.ERROR) {
break
}
// If this is a consumable input element, make sure to consume before
// capturing the accept state so the input index, line, and char
// position accurately reflect the state of the interpreter at the
// end of the token.
if (t != IntStream.EOF) {
consume(input)
}
if (target!!.isAcceptState) {
captureSimState(prevAccept, input, target)
if (t == IntStream.EOF) {
break
}
}
t = input.LA(1)
s = target // flip; current DFA target becomes new src/from state
}
return failOrAccept(prevAccept, input, s!!.configs!!, t)
}
/**
* Get an existing target state for an edge in the DFA. If the target state
* for the edge has not yet been computed or is otherwise not available,
* this method returns `null`.
*
* @param s The current DFA state
* @param t The next input symbol
* @return The existing target DFA state for the given input symbol
* `t`, or `null` if the target state for this edge is not
* already cached
*/
fun getExistingTargetState(s: DFAState?, t: Int): DFAState? {
if (s!!.edges == null || t < MIN_DFA_EDGE || t > MAX_DFA_EDGE) {
return null
}
val target = s!!.edges!![t - MIN_DFA_EDGE]
if (debug && target != null) {
outMessage("reuse state " + s!!.stateNumber +
" edge to " + target!!.stateNumber)
}
return target
}
/**
* Compute a target state for an edge in the DFA, and attempt to add the
* computed state and corresponding edge to the DFA.
*
* @param input The input stream
* @param s The current DFA state
* @param t The next input symbol
*
* @return The computed target DFA state for the given input symbol
* `t`. If `t` does not lead to a valid DFA state, this method
* returns [.ERROR].
*/
fun computeTargetState(input: CharStream, s: DFAState?, t: Int): DFAState {
val reach = OrderedATNConfigSet()
// if we don't find an existing DFA state
// Fill reach starting from closure, following t transitions
getReachableConfigSet(input, s!!.configs!!, reach, t)
if (reach.isEmpty()) { // we got nowhere on t from s
if (!reach.hasSemanticContext) {
// we got nowhere on t, don't throw out this knowledge; it'd
// cause a failover from DFA later.
addDFAEdge(s, t, ATNSimulator.ERROR)
}
// stop when we can't match any more char
return ATNSimulator.ERROR
}
// Add an edge from s to target DFA found/created for reach
return addDFAEdge(s, t, reach)
}
protected fun failOrAccept(prevAccept: SimState, input: CharStream,
reach: ATNConfigSet, t: Int): Int {
if (prevAccept.dfaState != null) {
val lexerActionExecutor = prevAccept.dfaState!!.lexerActionExecutor
accept(input, lexerActionExecutor, startIndex,
prevAccept.index, prevAccept.line, prevAccept.charPos)
return prevAccept.dfaState!!.prediction
} else {
// if no accept and EOF is first char, return EOF
if (t == IntStream.EOF && input.index() === startIndex) {
return Token.EOF
}
throw LexerNoViableAltException(recog as Lexer, input, startIndex, reach)
}
}
/**
* Given a starting configuration set, figure out all ATN configurations
* we can reach upon input `t`. Parameter `reach` is a return
* parameter.
*/
protected fun getReachableConfigSet(input: CharStream, closure: ATNConfigSet, reach: ATNConfigSet, t: Int) {
// this is used to skip processing for configs which have a lower priority
// than a config that already reached an accept state for the same rule
var skipAlt = ATN.INVALID_ALT_NUMBER
for (c in closure) {
val currentAltReachedAcceptState = c.alt == skipAlt
if (currentAltReachedAcceptState && (c as LexerATNConfig).hasPassedThroughNonGreedyDecision()) {
continue
}
if (debug) {
outMessage("testing ${getTokenName(t)} at ${c.toString(recog, true)}\n")
}
val n = c.state.numberOfTransitions
for (ti in 0 until n) { // for each transition
val trans = c.state.transition(ti)
val target = getReachableTarget(trans, t)
if (target != null) {
var lexerActionExecutor = (c as LexerATNConfig).lexerActionExecutor
if (lexerActionExecutor != null) {
lexerActionExecutor = lexerActionExecutor!!.fixOffsetBeforeMatch(input.index() - startIndex)
}
val treatEofAsEpsilon = t == CharStream.EOF
if (closure(input, LexerATNConfig(c as LexerATNConfig, target, lexerActionExecutor), reach, currentAltReachedAcceptState, true, treatEofAsEpsilon)) {
// any remaining configs for this alt have a lower priority than
// the one that just reached an accept state.
skipAlt = c.alt
break
}
}
}
}
}
protected fun accept(input: CharStream, lexerActionExecutor: LexerActionExecutor?,
startIndex: Int, index: Int, line: Int, charPos: Int) {
if (debug) {
outMessage("ACTION ${lexerActionExecutor}\n")
}
// seek to after last char in token
input.seek(index)
this.line = line
this.charPositionInLine = charPos
if (lexerActionExecutor != null && recog != null) {
lexerActionExecutor!!.execute(recog, input, startIndex)
}
}
protected fun getReachableTarget(trans: Transition, t: Int): ATNState? {
return if (trans.matches(t, Lexer.MIN_CHAR_VALUE, Lexer.MAX_CHAR_VALUE)) {
trans.target
} else null
}
protected fun computeStartState(input: CharStream,
p: ATNState): ATNConfigSet {
val initialContext = PredictionContext.EMPTY
val configs = OrderedATNConfigSet()
for (i in 0 until p.numberOfTransitions) {
val target = p.transition(i).target
val c = LexerATNConfig(target!!, i + 1, initialContext)
closure(input, c, configs, false, false, false)
}
return configs
}
/**
* Since the alternatives within any lexer decision are ordered by
* preference, this method stops pursuing the closure as soon as an accept
* state is reached. After the first accept state is reached by depth-first
* search from `config`, all other (potentially reachable) states for
* this rule would have a lower priority.
*
* @return `true` if an accept state is reached, otherwise
* `false`.
*/
protected fun closure(input: CharStream, config: LexerATNConfig, configs: ATNConfigSet, currentAltReachedAcceptState: Boolean, speculative: Boolean, treatEofAsEpsilon: Boolean): Boolean {
var currentAltReachedAcceptState = currentAltReachedAcceptState
if (debug) {
println("closure(" + config.toString(recog, true) + ")")
}
if (config.state is RuleStopState) {
if (debug) {
if (recog != null) {
outMessage("closure at ${recog!!.ruleNames!![config.state.ruleIndex]} rule stop $config\n")
} else {
outMessage("closure at rule stop $config\n")
}
}
if (config.context == null || config.context!!.hasEmptyPath()) {
if (config.context == null || config.context!!.isEmpty) {
configs.add(config)
return true
} else {
configs.add(LexerATNConfig(config, config.state, PredictionContext.EMPTY))
currentAltReachedAcceptState = true
}
}
if (config.context != null && !config.context!!.isEmpty) {
for (i in 0 until config.context!!.size()) {
if (config.context!!.getReturnState(i) != PredictionContext.EMPTY_RETURN_STATE) {
val newContext = config.context!!.getParent(i) // "pop" return state
val returnState = atn.states.get(config.context!!.getReturnState(i))
val c = LexerATNConfig(config, returnState!!, newContext!!)
currentAltReachedAcceptState = closure(input, c, configs, currentAltReachedAcceptState, speculative, treatEofAsEpsilon)
}
}
}
return currentAltReachedAcceptState
}
// optimization
if (!config.state.onlyHasEpsilonTransitions()) {
if (!currentAltReachedAcceptState || !config.hasPassedThroughNonGreedyDecision()) {
configs.add(config)
}
}
val p = config.state
for (i in 0 until p.numberOfTransitions) {
val t = p.transition(i)
val c = getEpsilonTarget(input, config, t, configs, speculative, treatEofAsEpsilon)
if (c != null) {
currentAltReachedAcceptState = closure(input, c, configs, currentAltReachedAcceptState, speculative, treatEofAsEpsilon)
}
}
return currentAltReachedAcceptState
}
// side-effect: can alter configs.hasSemanticContext
protected fun getEpsilonTarget(input: CharStream,
config: LexerATNConfig,
t: Transition,
configs: ATNConfigSet,
speculative: Boolean,
treatEofAsEpsilon: Boolean): LexerATNConfig? {
var c: LexerATNConfig? = null
when (t.serializationType) {
Transition.RULE -> {
val ruleTransition = t as RuleTransition
val newContext = SingletonPredictionContext.create(config.context, ruleTransition.followState.stateNumber)
c = LexerATNConfig(config, t.target!!, newContext)
}
Transition.PRECEDENCE -> throw UnsupportedOperationException("Precedence predicates are not supported in lexers.")
Transition.PREDICATE -> {
/* Track traversing semantic predicates. If we traverse,
we cannot add a DFA state for this "reach" computation
because the DFA would not test the predicate again in the
future. Rather than creating collections of semantic predicates
like v3 and testing them on prediction, v4 will test them on the
fly all the time using the ATN not the DFA. This is slower but
semantically it's not used that often. One of the key elements to
this predicate mechanism is not adding DFA states that see
predicates immediately afterwards in the ATN. For example,
a : ID {p1}? | ID {p2}? ;
should create the start state for rule 'a' (to save start state
competition), but should not create target of ID state. The
collection of ATN states the following ID references includes
states reached by traversing predicates. Since this is when we
test them, we cannot cash the DFA state target of ID.
*/
val pt = t as PredicateTransition
if (debug) {
println("EVAL rule " + pt.ruleIndex + ":" + pt.predIndex)
}
configs.hasSemanticContext = true
if (evaluatePredicate(input, pt.ruleIndex, pt.predIndex, speculative)) {
c = LexerATNConfig(config, t.target!!)
}
}
Transition.ACTION -> if (config.context == null || config.context!!.hasEmptyPath()) {
// execute actions anywhere in the start rule for a token.
//
// TODO: if the entry rule is invoked recursively, some
// actions may be executed during the recursive call. The
// problem can appear when hasEmptyPath() is true but
// isEmpty() is false. In this case, the config needs to be
// split into two contexts - one with just the empty path
// and another with everything but the empty path.
// Unfortunately, the current algorithm does not allow
// getEpsilonTarget to return two configurations, so
// additional modifications are needed before we can support
// the split operation.
val lexerActionExecutor = LexerActionExecutor.append(config.lexerActionExecutor, atn.lexerActions!![(t as ActionTransition).actionIndex]!!)
c = LexerATNConfig(config, t.target!!, lexerActionExecutor)
} else {
// ignore actions in referenced rules
c = LexerATNConfig(config, t.target!!)
}
Transition.EPSILON -> c = LexerATNConfig(config, t.target!!)
Transition.ATOM, Transition.RANGE, Transition.SET -> if (treatEofAsEpsilon) {
if (t.matches(CharStream.EOF, Lexer.MIN_CHAR_VALUE, Lexer.MAX_CHAR_VALUE)) {
c = LexerATNConfig(config, t.target!!)
}
}
}
return c
}
/**
* Evaluate a predicate specified in the lexer.
*
*
* If `speculative` is `true`, this method was called before
* [.consume] for the matched character. This method should call
* [.consume] before evaluating the predicate to ensure position
* sensitive values, including [Lexer.getText], [Lexer.getLine],
* and [Lexer.getCharPositionInLine], properly reflect the current
* lexer state. This method should restore `input` and the simulator
* to the original state before returning (i.e. undo the actions made by the
* call to [.consume].
*
* @param input The input stream.
* @param ruleIndex The rule containing the predicate.
* @param predIndex The index of the predicate within the rule.
* @param speculative `true` if the current index in `input` is
* one character before the predicate's location.
*
* @return `true` if the specified predicate evaluates to
* `true`.
*/
protected fun evaluatePredicate(input: CharStream, ruleIndex: Int, predIndex: Int, speculative: Boolean): Boolean {
// assume true if no recognizer was provided
if (recog == null) {
return true
}
if (!speculative) {
return recog!!.sempred(null, ruleIndex, predIndex)
}
val savedCharPositionInLine = charPositionInLine
val savedLine = line
val index = input.index()
val marker = input.mark()
try {
consume(input)
return recog!!.sempred(null, ruleIndex, predIndex)
} finally {
charPositionInLine = savedCharPositionInLine
line = savedLine
input.seek(index)
input.release(marker)
}
}
protected fun captureSimState(settings: SimState,
input: CharStream,
dfaState: DFAState) {
settings.index = input.index()
settings.line = line
settings.charPos = charPositionInLine
settings.dfaState = dfaState
}
protected fun addDFAEdge(from: DFAState?,
t: Int,
q: ATNConfigSet): DFAState {
/* leading to this call, ATNConfigSet.hasSemanticContext is used as a
* marker indicating dynamic predicate evaluation makes this edge
* dependent on the specific input sequence, so the static edge in the
* DFA should be omitted. The target DFAState is still created since
* execATN has the ability to resynchronize with the DFA state cache
* following the predicate evaluation step.
*
* TJP notes: next time through the DFA, we see a pred again and eval.
* If that gets us to a previously created (but dangling) DFA
* state, we can continue in pure DFA mode from there.
*/
val suppressEdge = q.hasSemanticContext
q.hasSemanticContext = false
val to = addDFAState(q)
if (suppressEdge) {
return to
}
addDFAEdge(from, t, to)
return to
}
protected fun addDFAEdge(p: DFAState?, t: Int, q: DFAState) {
if (t < MIN_DFA_EDGE || t > MAX_DFA_EDGE) {
// Only track edges within the DFA bounds
return
}
if (debug) {
println("EDGE " + p + " -> " + q + " upon " + t.toChar())
}
synchronized(p!!) {
if (p!!.edges == null) {
// make room for tokens 1..n and -1 masquerading as index 0
p!!.edges = arrayOfNulls(MAX_DFA_EDGE - MIN_DFA_EDGE + 1)
}
p!!.edges!![t - MIN_DFA_EDGE] = q // connect
}
}
/** Add a new DFA state if there isn't one with this set of
* configurations already. This method also detects the first
* configuration containing an ATN rule stop state. Later, when
* traversing the DFA, we will know which rule to accept.
*/
protected fun addDFAState(configs: ATNConfigSet): DFAState {
/* the lexer evaluates predicates on-the-fly; by this point configs
* should not contain any configurations with unevaluated predicates.
*/
assert(!configs.hasSemanticContext)
val proposed = DFAState(configs)
var firstConfigWithRuleStopState: ATNConfig? = null
for (c in configs) {
if (c.state is RuleStopState) {
firstConfigWithRuleStopState = c
break
}
}
if (firstConfigWithRuleStopState != null) {
proposed.isAcceptState = true
proposed.lexerActionExecutor = (firstConfigWithRuleStopState as LexerATNConfig).lexerActionExecutor
proposed.prediction = atn.ruleToTokenType!![firstConfigWithRuleStopState!!.state.ruleIndex]
}
val dfa = decisionToDFA[mode]
synchronized(dfa!!.states) {
val existing = dfa.states.get(proposed)
if (existing != null) return existing
proposed.stateNumber = dfa!!.states!!.size
configs.isReadonly = true
proposed.configs = configs
dfa.states.put(proposed, proposed)
return proposed
}
}
fun getDFA(mode: Int): DFA {
return decisionToDFA[mode]!!
}
/** Get the text matched so far for the current token.
*/
fun getText(input: CharStream): String {
// index is first lookahead char, don't include.
return input.getText(Interval.of(startIndex, input.index() - 1))
}
fun consume(input: CharStream) {
val curChar = input.LA(1)
if (curChar.toChar() == '\n') {
line++
charPositionInLine = 0
} else {
charPositionInLine++
}
input.consume()
}
fun getTokenName(t: Int): String {
return if (t == -1) "EOF" else "'" + t.toChar() + "'"
//if ( atn.g!=null ) return atn.g.getTokenDisplayName(t);
}
companion object {
val debug = false
val dfa_debug = false
val MIN_DFA_EDGE = 0
val MAX_DFA_EDGE = 127 // forces unicode to stay in ATN
}
}