/*
* Copyright 2007 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.jjs.impl;
import com.google.gwt.dev.jjs.SourceInfo;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JBlock;
import com.google.gwt.dev.jjs.ast.JDeclarationStatement;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JIfStatement;
import com.google.gwt.dev.jjs.ast.JInstanceOf;
import com.google.gwt.dev.jjs.ast.JLocal;
import com.google.gwt.dev.jjs.ast.JLocalRef;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JMethodBody;
import com.google.gwt.dev.jjs.ast.JMethodCall;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JReferenceType;
import com.google.gwt.dev.jjs.ast.JStatement;
import com.google.gwt.dev.jjs.ast.JThrowStatement;
import com.google.gwt.dev.jjs.ast.JTryStatement;
import java.util.ArrayList;
import java.util.List;
/**
* Merge multi-catch blocks into a single catch block that uses instanceof tests
* to determine which user block to run.
*/
public class CatchBlockNormalizer {
/**
* Collapses all multi-catch blocks into a single catch block.
*/
private class CollapseCatchBlocks extends JModVisitor {
// @Override
@Override
public void endVisit(JMethodBody x, Context ctx) {
clearLocals();
currentMethodBody = null;
}
// @Override
@Override
public void endVisit(JTryStatement x, Context ctx) {
if (x.getCatchBlocks().isEmpty()) {
return;
}
SourceInfo catchInfo = x.getCatchBlocks().get(0).getSourceInfo();
JLocal exVar = popTempLocal();
JBlock newCatchBlock = new JBlock(catchInfo);
{
// $e = Exceptions.caught($e)
JMethod caughtMethod = program.getIndexedMethod("Exceptions.caught");
JMethodCall call = new JMethodCall(catchInfo, null, caughtMethod);
call.addArg(new JLocalRef(catchInfo, exVar));
newCatchBlock.addStmt(program.createAssignmentStmt(catchInfo,
new JLocalRef(catchInfo, exVar), call));
}
/*
* Build up a series of if, else if statements to test the type of the
* exception object against the type of the user's catch block.
*
* Go backwards so we can nest the else statements in the correct order!
*/
// rethrow the current exception if no one caught it
JStatement cur = new JThrowStatement(catchInfo, new JLocalRef(catchInfo,
exVar));
for (int i = x.getCatchBlocks().size() - 1; i >= 0; --i) {
JBlock block = x.getCatchBlocks().get(i);
JLocalRef arg = x.getCatchArgs().get(i);
catchInfo = block.getSourceInfo();
JReferenceType argType = (JReferenceType) arg.getType();
// if ($e instanceof ArgType) { var userVar = $e; <user code> }
JExpression ifTest = new JInstanceOf(catchInfo, argType, new JLocalRef(
catchInfo, exVar));
JDeclarationStatement declaration = new JDeclarationStatement(
catchInfo, arg, new JLocalRef(catchInfo, exVar));
if (!block.getStatements().isEmpty()) {
// Only bother adding the assignment if the block is non-empty
block.addStmt(0, declaration);
}
// nest the previous as an else for me
cur = new JIfStatement(catchInfo, ifTest, block, cur);
}
newCatchBlock.addStmt(cur);
x.getCatchArgs().clear();
x.getCatchArgs().add(new JLocalRef(newCatchBlock.getSourceInfo(), exVar));
x.getCatchBlocks().clear();
x.getCatchBlocks().add(newCatchBlock);
}
// @Override
@Override
public boolean visit(JMethodBody x, Context ctx) {
currentMethodBody = x;
clearLocals();
return true;
}
// @Override
@Override
public boolean visit(JTryStatement x, Context ctx) {
if (!x.getCatchBlocks().isEmpty()) {
pushTempLocal(x.getSourceInfo());
}
return true;
}
}
public static void exec(JProgram program) {
new CatchBlockNormalizer(program).execImpl();
}
private JMethodBody currentMethodBody;
private int localIndex;
private final JProgram program;
private final List<JLocal> tempLocals = new ArrayList<JLocal>();
private CatchBlockNormalizer(JProgram program) {
this.program = program;
}
private void clearLocals() {
tempLocals.clear();
localIndex = 0;
}
private void execImpl() {
CollapseCatchBlocks collapser = new CollapseCatchBlocks();
collapser.accept(program);
}
private JLocal popTempLocal() {
return tempLocals.get(--localIndex);
}
private void pushTempLocal(SourceInfo sourceInfo) {
if (localIndex == tempLocals.size()) {
JLocal newTemp = program.createLocal(sourceInfo,
("$e" + localIndex).toCharArray(), program.getTypeJavaLangObject(),
false, currentMethodBody);
tempLocals.add(newTemp);
}
++localIndex;
}
}