org.antlr.v4.runtime.RuleContext Maven / Gradle / Ivy
Show all versions of antlr4-runtime Show documentation
/*
* Copyright (c) 2012 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.runtime;
import org.antlr.v4.runtime.atn.ATN;
import org.antlr.v4.runtime.misc.Interval;
import org.antlr.v4.runtime.misc.Nullable;
import org.antlr.v4.runtime.tree.ParseTree;
import org.antlr.v4.runtime.tree.ParseTreeVisitor;
import org.antlr.v4.runtime.tree.RuleNode;
import org.antlr.v4.runtime.tree.Trees;
import java.util.Arrays;
import java.util.List;
/** A rule context is a record of a single rule invocation.
*
* We form a stack of these context objects using the parent
* pointer. A parent pointer of null indicates that the current
* context is the bottom of the stack. The ParserRuleContext subclass
* as a children list so that we can turn this data structure into a
* tree.
*
* The root node always has a null pointer and invokingState of -1.
*
* Upon entry to parsing, the first invoked rule function creates a
* context object (a subclass specialized for that rule such as
* SContext) and makes it the root of a parse tree, recorded by field
* Parser._ctx.
*
* public final SContext s() throws RecognitionException {
* SContext _localctx = new SContext(_ctx, getState()); <-- create new node
* enterRule(_localctx, 0, RULE_s); <-- push it
* ...
* exitRule(); <-- pop back to _localctx
* return _localctx;
* }
*
* A subsequent rule invocation of r from the start rule s pushes a
* new context object for r whose parent points at s and use invoking
* state is the state with r emanating as edge label.
*
* The invokingState fields from a context object to the root
* together form a stack of rule indication states where the root
* (bottom of the stack) has a -1 sentinel value. If we invoke start
* symbol s then call r1, which calls r2, the would look like
* this:
*
* SContext[-1] <- root node (bottom of the stack)
* R1Context[p] <- p in rule s called r1
* R2Context[q] <- q in rule r1 called r2
*
* So the top of the stack, _ctx, represents a call to the current
* rule and it holds the return address from another rule that invoke
* to this rule. To invoke a rule, we must always have a current context.
*
* The parent contexts are useful for computing lookahead sets and
* getting error information.
*
* These objects are used during parsing and prediction.
* For the special case of parsers, we use the subclass
* ParserRuleContext.
*
* @see ParserRuleContext
*/
public class RuleContext implements RuleNode {
/** What context invoked this rule? */
public RuleContext parent;
/** What state invoked the rule associated with this context?
* The "return address" is the followState of invokingState
* If parent is null, this should be -1 this context object represents
* the start rule.
*/
public int invokingState = -1;
public RuleContext() {}
public RuleContext(RuleContext parent, int invokingState) {
this.parent = parent;
//if ( parent!=null ) System.out.println("invoke "+stateNumber+" from "+parent);
this.invokingState = invokingState;
}
public static RuleContext getChildContext(RuleContext parent, int invokingState) {
return new RuleContext(parent, invokingState);
}
public int depth() {
int n = 0;
RuleContext p = this;
while ( p!=null ) {
p = p.parent;
n++;
}
return n;
}
/** A context is empty if there is no invoking state; meaning nobody called
* current context.
*/
public boolean isEmpty() {
return invokingState == -1;
}
// satisfy the ParseTree / SyntaxTree interface
@Override
public Interval getSourceInterval() {
return Interval.INVALID;
}
@Override
public RuleContext getRuleContext() { return this; }
@Override
public RuleContext getParent() { return parent; }
@Override
public RuleContext getPayload() { return this; }
/** Return the combined text of all child nodes. This method only considers
* tokens which have been added to the parse tree.
*
* Since tokens on hidden channels (e.g. whitespace or comments) are not
* added to the parse trees, they will not appear in the output of this
* method.
*/
@Override
public String getText() {
if (getChildCount() == 0) {
return "";
}
StringBuilder builder = new StringBuilder();
for (int i = 0; i < getChildCount(); i++) {
builder.append(getChild(i).getText());
}
return builder.toString();
}
public int getRuleIndex() { return -1; }
/** For rule associated with this parse tree internal node, return
* the outer alternative number used to match the input. Default
* implementation does not compute nor store this alt num. Create
* a subclass of ParserRuleContext with backing field and set
* option contextSuperClass.
* to set it.
*
* @since 4.5.3
*/
public int getAltNumber() { return ATN.INVALID_ALT_NUMBER; }
/** Set the outer alternative number for this context node. Default
* implementation does nothing to avoid backing field overhead for
* trees that don't need it. Create
* a subclass of ParserRuleContext with backing field and set
* option contextSuperClass.
*
* @since 4.5.3
*/
public void setAltNumber(int altNumber) { }
/** @since 4.7. */
public void setParent(RuleContext parent) {
this.parent = parent;
}
@Override
public ParseTree getChild(int i) {
return null;
}
@Override
public int getChildCount() {
return 0;
}
@Override
public T accept(ParseTreeVisitor visitor) {
return visitor.visitChildren(this);
}
/** Print out a whole tree, not just a node, in LISP format
* (root child1 .. childN). Print just a node if this is a leaf.
* We have to know the recognizer so we can get rule names.
*/
@Override
public String toStringTree(@Nullable Parser recog) {
return Trees.toStringTree(this, recog);
}
/** Print out a whole tree, not just a node, in LISP format
* (root child1 .. childN). Print just a node if this is a leaf.
*/
public String toStringTree(@Nullable List ruleNames) {
return Trees.toStringTree(this, ruleNames);
}
@Override
public String toStringTree() {
return toStringTree((List)null);
}
@Override
public String toString() {
return toString((List)null, (RuleContext)null);
}
public final String toString(@Nullable Recognizer recog) {
return toString(recog, ParserRuleContext.emptyContext());
}
public final String toString(@Nullable List ruleNames) {
return toString(ruleNames, null);
}
// recog null unless ParserRuleContext, in which case we use subclass toString(...)
public String toString(@Nullable Recognizer recog, @Nullable RuleContext stop) {
String[] ruleNames = recog != null ? recog.getRuleNames() : null;
List ruleNamesList = ruleNames != null ? Arrays.asList(ruleNames) : null;
return toString(ruleNamesList, stop);
}
public String toString(@Nullable List ruleNames, @Nullable RuleContext stop) {
StringBuilder buf = new StringBuilder();
RuleContext p = this;
buf.append("[");
while (p != null && p != stop) {
if (ruleNames == null) {
if (!p.isEmpty()) {
buf.append(p.invokingState);
}
}
else {
int ruleIndex = p.getRuleIndex();
String ruleName = ruleIndex >= 0 && ruleIndex < ruleNames.size() ? ruleNames.get(ruleIndex) : Integer.toString(ruleIndex);
buf.append(ruleName);
}
if (p.parent != null && (ruleNames != null || !p.parent.isEmpty())) {
buf.append(" ");
}
p = p.parent;
}
buf.append("]");
return buf.toString();
}
}