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/*
* Copyright 2008 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.js;
import com.google.gwt.dev.jjs.InternalCompilerException;
import com.google.gwt.dev.js.ast.JsArrayAccess;
import com.google.gwt.dev.js.ast.JsArrayLiteral;
import com.google.gwt.dev.js.ast.JsBinaryOperation;
import com.google.gwt.dev.js.ast.JsBooleanLiteral;
import com.google.gwt.dev.js.ast.JsConditional;
import com.google.gwt.dev.js.ast.JsContext;
import com.google.gwt.dev.js.ast.JsExpression;
import com.google.gwt.dev.js.ast.JsFunction;
import com.google.gwt.dev.js.ast.JsInvocation;
import com.google.gwt.dev.js.ast.JsNameOf;
import com.google.gwt.dev.js.ast.JsNameRef;
import com.google.gwt.dev.js.ast.JsNew;
import com.google.gwt.dev.js.ast.JsNullLiteral;
import com.google.gwt.dev.js.ast.JsNumberLiteral;
import com.google.gwt.dev.js.ast.JsNumericEntry;
import com.google.gwt.dev.js.ast.JsObjectLiteral;
import com.google.gwt.dev.js.ast.JsPostfixOperation;
import com.google.gwt.dev.js.ast.JsPrefixOperation;
import com.google.gwt.dev.js.ast.JsPropertyInitializer;
import com.google.gwt.dev.js.ast.JsRegExp;
import com.google.gwt.dev.js.ast.JsStringLiteral;
import com.google.gwt.dev.js.ast.JsThisRef;
import com.google.gwt.dev.js.ast.JsVisitor;
import com.google.gwt.dev.util.collect.Stack;
import java.util.ArrayList;
import java.util.List;
/**
* A utility class to clone JsExpression AST members. Not all expressions are necessarily
* cloned , only those expressions that are safe to hoist into outer call sites.
*/
public final class JsSafeCloner {
/**
* Implements actual cloning logic. We rely on the JsExpressions to provide
* traversal logic. The {@link #stack} field is used to accumulate
* already-cloned JsExpression instances. One gotcha that falls out of this is
* that argument lists are on the stack in reverse order, so lists should be
* constructed via inserts, rather than appends.
*/
public static class Cloner extends JsVisitor {
protected final Stack stack = new Stack();
private boolean successful = true;
@Override
public void endVisit(JsArrayAccess x, JsContext ctx) {
JsArrayAccess newExpression = new JsArrayAccess(x.getSourceInfo());
newExpression.setIndexExpr(stack.pop());
newExpression.setArrayExpr(stack.pop());
stack.push(newExpression);
}
@Override
public void endVisit(JsArrayLiteral x, JsContext ctx) {
JsArrayLiteral toReturn = new JsArrayLiteral(x.getSourceInfo());
List expressions = toReturn.getExpressions();
int size = x.getExpressions().size();
while (size-- > 0) {
expressions.add(0, stack.pop());
}
stack.push(toReturn);
}
@Override
public void endVisit(JsBinaryOperation x, JsContext ctx) {
JsBinaryOperation toReturn = new JsBinaryOperation(x.getSourceInfo(),
x.getOperator());
toReturn.setArg2(stack.pop());
toReturn.setArg1(stack.pop());
stack.push(toReturn);
}
@Override
public void endVisit(JsBooleanLiteral x, JsContext ctx) {
stack.push(x);
}
@Override
public void endVisit(JsConditional x, JsContext ctx) {
JsConditional toReturn = new JsConditional(x.getSourceInfo());
toReturn.setElseExpression(stack.pop());
toReturn.setThenExpression(stack.pop());
toReturn.setTestExpression(stack.pop());
stack.push(toReturn);
}
/**
* The only functions that would get be visited are those being used as
* first-class objects.
*/
@Override
public void endVisit(JsFunction x, JsContext ctx) {
// Set a flag to indicate that we cannot continue, and push a null so
// we don't run out of elements on the stack.
successful = false;
stack.push(null);
}
/**
* Cloning the invocation allows us to modify it without damaging other call
* sites.
*/
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
JsInvocation toReturn = new JsInvocation(x.getSourceInfo());
List params = toReturn.getArguments();
int size = x.getArguments().size();
while (size-- > 0) {
params.add(0, stack.pop());
}
toReturn.setQualifier(stack.pop());
stack.push(toReturn);
}
@Override
public void endVisit(JsNameOf x, JsContext ctx) {
JsNameOf toReturn = new JsNameOf(x.getSourceInfo(), x.getName());
stack.push(toReturn);
}
/**
* Do a deep clone of a JsNameRef. Because JsNameRef chains are shared
* throughout the AST, you can't just go and change their qualifiers when
* re-writing an invocation.
*/
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
if (x.getQualifier() == null && x.getIdent() == "arguments") {
// References to the arguments object can not be hoisted.
successful = false;
stack.push(null);
}
JsNameRef toReturn = new JsNameRef(x.getSourceInfo(), x.getName());
if (x.getQualifier() != null) {
toReturn.setQualifier(stack.pop());
}
stack.push(toReturn);
}
@Override
public void endVisit(JsNew x, JsContext ctx) {
int size = x.getArguments().size();
List arguments = new ArrayList(size);
while (size-- > 0) {
arguments.add(0, stack.pop());
}
JsNew toReturn = new JsNew(x.getSourceInfo(), stack.pop());
toReturn.getArguments().addAll(arguments);
stack.push(toReturn);
}
@Override
public void endVisit(JsNullLiteral x, JsContext ctx) {
stack.push(x);
}
@Override
public void endVisit(JsNumberLiteral x, JsContext ctx) {
stack.push(x);
}
@Override
public void endVisit(JsNumericEntry x, JsContext ctx) {
stack.push(x);
}
@Override
public boolean visit(JsObjectLiteral x, JsContext ctx) {
JsObjectLiteral.Builder builder = JsObjectLiteral.builder(x.getSourceInfo());
if (x.isInternable()) {
builder.setInternable();
}
for (JsPropertyInitializer propertyInitializer : x.getPropertyInitializers()) {
/*
* JsPropertyInitializers are the only non-JsExpression objects that we
* care about, so we just go ahead and create the objects in the loop,
* rather than expecting it to be on the stack and having to perform
* narrowing casts at all stack.pop() invocations.
*/
accept(propertyInitializer.getLabelExpr());
JsExpression label = stack.pop();
accept(propertyInitializer.getValueExpr());
JsExpression value = stack.pop();
builder.add(propertyInitializer.getSourceInfo(), label, value);
}
stack.push(builder.build());
return false;
}
@Override
public void endVisit(JsPostfixOperation x, JsContext ctx) {
JsPostfixOperation toReturn = new JsPostfixOperation(x.getSourceInfo(),
x.getOperator());
toReturn.setArg(stack.pop());
stack.push(toReturn);
}
@Override
public void endVisit(JsPrefixOperation x, JsContext ctx) {
JsPrefixOperation toReturn = new JsPrefixOperation(x.getSourceInfo(),
x.getOperator());
toReturn.setArg(stack.pop());
stack.push(toReturn);
}
@Override
public void endVisit(JsRegExp x, JsContext ctx) {
stack.push(x);
}
@Override
public void endVisit(JsStringLiteral x, JsContext ctx) {
stack.push(x);
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
stack.push(new JsThisRef(x.getSourceInfo()));
}
public JsExpression getExpression() {
return (successful && checkStack()) ? stack.peek() : null;
}
private boolean checkStack() {
if (stack.size() > 1) {
throw new InternalCompilerException("Too many expressions on stack");
}
return stack.size() == 1;
}
}
/**
* Given a JsStatement, construct an expression to clone into the outer
* caller. This does not perform any name replacement, nor does it verify the
* scope of referenced elements, but simply constructs a mutable copy of the
* expression that can be manipulated at-will.
*
* @return A copy of the original expression, or null if the
* expression cannot be hoisted.
*/
public static JsExpression clone(JsExpression expression) {
if (expression == null) {
return null;
}
Cloner c = new Cloner();
c.accept(expression);
return c.getExpression();
}
private JsSafeCloner() {
}
}
