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The ANTLR 4 grammar compiler.
/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.analysis;
import org.antlr.runtime.CommonToken;
import org.antlr.runtime.TokenStream;
import org.antlr.runtime.tree.CommonTreeNodeStream;
import org.antlr.runtime.tree.Tree;
import org.antlr.v4.Tool;
import org.antlr.v4.codegen.CodeGenerator;
import org.antlr.v4.parse.ANTLRParser;
import org.antlr.v4.parse.GrammarASTAdaptor;
import org.antlr.v4.parse.LeftRecursiveRuleWalker;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.runtime.misc.Tuple;
import org.antlr.v4.runtime.misc.Tuple2;
import org.antlr.v4.tool.ErrorType;
import org.antlr.v4.tool.ast.AltAST;
import org.antlr.v4.tool.ast.GrammarAST;
import org.stringtemplate.v4.ST;
import org.stringtemplate.v4.STGroup;
import org.stringtemplate.v4.STGroupFile;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/** Using a tree walker on the rules, determine if a rule is directly left-recursive and if it follows
* our pattern.
*/
public class LeftRecursiveRuleAnalyzer extends LeftRecursiveRuleWalker {
public static enum ASSOC { left, right }
public Tool tool;
public String ruleName;
public LinkedHashMap binaryAlts = new LinkedHashMap();
public LinkedHashMap ternaryAlts = new LinkedHashMap();
public LinkedHashMap suffixAlts = new LinkedHashMap();
public List prefixAlts = new ArrayList();
public List otherAlts = new ArrayList();
/** Pointer to ID node of ^(= ID element) */
public List> leftRecursiveRuleRefLabels =
new ArrayList>();
/** Tokens from which rule AST comes from */
public final TokenStream tokenStream;
public GrammarAST retvals;
public STGroup recRuleTemplates;
public STGroup codegenTemplates;
public String language;
public Map altAssociativity = new HashMap();
public LeftRecursiveRuleAnalyzer(GrammarAST ruleAST,
Tool tool, String ruleName, String language)
{
super(new CommonTreeNodeStream(new GrammarASTAdaptor(ruleAST.token.getInputStream()), ruleAST));
this.tool = tool;
this.ruleName = ruleName;
this.language = language;
this.tokenStream = ruleAST.g.tokenStream;
if (this.tokenStream == null) {
throw new NullPointerException("grammar must have a token stream");
}
loadPrecRuleTemplates();
}
public void loadPrecRuleTemplates() {
String templateGroupFile = "org/antlr/v4/tool/templates/LeftRecursiveRules.stg";
recRuleTemplates = new STGroupFile(templateGroupFile);
if ( !recRuleTemplates.isDefined("recRule") ) {
tool.errMgr.toolError(ErrorType.MISSING_CODE_GEN_TEMPLATES, "LeftRecursiveRules");
}
// use codegen to get correct language templates; that's it though
CodeGenerator gen = new CodeGenerator(tool, null, language);
codegenTemplates = gen.getTemplates();
}
@Override
public void setReturnValues(GrammarAST t) {
retvals = t;
}
@Override
public void setAltAssoc(AltAST t, int alt) {
ASSOC assoc = ASSOC.left;
if ( t.getOptions()!=null ) {
String a = t.getOptionString("assoc");
if ( a!=null ) {
if ( a.equals(ASSOC.right.toString()) ) {
assoc = ASSOC.right;
}
else if ( a.equals(ASSOC.left.toString()) ) {
assoc = ASSOC.left;
}
else {
tool.errMgr.toolError(ErrorType.ILLEGAL_OPTION_VALUE, "assoc", assoc);
}
}
}
if ( altAssociativity.get(alt)!=null && altAssociativity.get(alt)!=assoc ) {
tool.errMgr.toolError(ErrorType.ALL_OPS_NEED_SAME_ASSOC, alt);
}
altAssociativity.put(alt, assoc);
// System.out.println("setAltAssoc: op " + alt + ": " + t.getText()+", assoc="+assoc);
}
@Override
public void binaryAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
GrammarAST lrlabel = stripLeftRecursion(altTree);
String label = lrlabel != null ? lrlabel.getText() : null;
if ( lrlabel!=null ) {
leftRecursiveRuleRefLabels.add(Tuple.create(lrlabel,altLabel));
}
stripAssocOptions(altTree);
stripAltLabel(altTree);
// rewrite e to be e_[rec_arg]
int nextPrec = nextPrecedence(alt);
altTree = addPrecedenceArgToRules(altTree, nextPrec);
stripAltLabel(altTree);
String altText = text(altTree);
altText = altText.trim();
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, label, altLabel, originalAltTree);
a.nextPrec = nextPrec;
binaryAlts.put(alt, a);
//System.out.println("binaryAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void prefixAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
stripAltLabel(altTree);
int nextPrec = precedence(alt);
// rewrite e to be e_[prec]
altTree = addPrecedenceArgToRules(altTree, nextPrec);
String altText = text(altTree);
altText = altText.trim();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, null, altLabel, originalAltTree);
a.nextPrec = nextPrec;
prefixAlts.add(a);
//System.out.println("prefixAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void suffixAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
GrammarAST lrlabel = stripLeftRecursion(altTree);
String label = lrlabel != null ? lrlabel.getText() : null;
if ( lrlabel!=null ) {
leftRecursiveRuleRefLabels.add(Tuple.create(lrlabel,altLabel));
}
stripAltLabel(altTree);
String altText = text(altTree);
altText = altText.trim();
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, label, altLabel, originalAltTree);
suffixAlts.put(alt, a);
// System.out.println("suffixAlt " + alt + ": " + altText + ", rewrite=" + rewriteText);
}
@Override
public void otherAlt(AltAST originalAltTree, int alt) {
AltAST altTree = (AltAST)originalAltTree.dupTree();
stripAltLabel(altTree);
String altText = text(altTree);
String altLabel = altTree.altLabel!=null ? altTree.altLabel.getText() : null;
LeftRecursiveRuleAltInfo a =
new LeftRecursiveRuleAltInfo(alt, altText, null, altLabel, originalAltTree);
otherAlts.add(a);
// System.out.println("otherAlt " + alt + ": " + altText);
}
// --------- get transformed rules ----------------
public String getArtificialOpPrecRule() {
ST ruleST = recRuleTemplates.getInstanceOf("recRule");
ruleST.add("ruleName", ruleName);
ST ruleArgST = codegenTemplates.getInstanceOf("recRuleArg");
ruleST.add("argName", ruleArgST);
ST setResultST = codegenTemplates.getInstanceOf("recRuleSetResultAction");
ruleST.add("setResultAction", setResultST);
ruleST.add("userRetvals", retvals);
LinkedHashMap opPrecRuleAlts = new LinkedHashMap();
opPrecRuleAlts.putAll(binaryAlts);
opPrecRuleAlts.putAll(ternaryAlts);
opPrecRuleAlts.putAll(suffixAlts);
for (int alt : opPrecRuleAlts.keySet()) {
LeftRecursiveRuleAltInfo altInfo = opPrecRuleAlts.get(alt);
ST altST = recRuleTemplates.getInstanceOf("recRuleAlt");
ST predST = codegenTemplates.getInstanceOf("recRuleAltPredicate");
predST.add("opPrec", precedence(alt));
predST.add("ruleName", ruleName);
altST.add("pred", predST);
altST.add("alt", altInfo);
altST.add("precOption", LeftRecursiveRuleTransformer.PRECEDENCE_OPTION_NAME);
altST.add("opPrec", precedence(alt));
ruleST.add("opAlts", altST);
}
ruleST.add("primaryAlts", prefixAlts);
ruleST.add("primaryAlts", otherAlts);
tool.log("left-recursion", ruleST.render());
return ruleST.render();
}
public AltAST addPrecedenceArgToRules(AltAST t, int prec) {
if ( t==null ) return null;
// get all top-level rule refs from ALT
List outerAltRuleRefs = t.getNodesWithTypePreorderDFS(IntervalSet.of(RULE_REF));
for (GrammarAST rref : outerAltRuleRefs) {
boolean recursive = rref.getText().equals(ruleName);
boolean rightmost = rref == outerAltRuleRefs.get(outerAltRuleRefs.size()-1);
if ( recursive && rightmost ) {
rref.setText(ruleName+"<"+LeftRecursiveRuleTransformer.PRECEDENCE_OPTION_NAME+"="+prec+">");
}
}
return t;
}
public void stripAssocOptions(GrammarAST t) {
if ( t==null ) return;
for (GrammarAST options : t.getNodesWithType(ELEMENT_OPTIONS)) {
int i=0;
while ( i label; alter indexes in altAST */
public void stripAltLabel(GrammarAST altAST) {
int start = altAST.getTokenStartIndex();
int stop = altAST.getTokenStopIndex();
// find =>
for (int i=stop; i>=start; i--) {
if ( tokenStream.get(i).getType()==POUND ) {
altAST.setTokenStopIndex(i-1);
return;
}
}
}
public String text(GrammarAST t) {
if ( t==null ) return "";
CommonToken ta = (CommonToken) tokenStream.get(t.getTokenStartIndex());
CommonToken tb = (CommonToken) tokenStream.get(t.getTokenStopIndex());
return tokenStream.toString(ta, tb);
}
public int precedence(int alt) {
return numAlts-alt+1;
}
// Assumes left assoc
public int nextPrecedence(int alt) {
int p = precedence(alt);
if ( altAssociativity.get(alt)==ASSOC.right ) return p;
return p+1;
}
@Override
public String toString() {
return "PrecRuleOperatorCollector{" +
"binaryAlts=" + binaryAlts +
", ternaryAlts=" + ternaryAlts +
", suffixAlts=" + suffixAlts +
", prefixAlts=" + prefixAlts +
", otherAlts=" + otherAlts +
'}';
}
}