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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.shell.rewrite;
import com.google.gwt.dev.shell.rewrite.HostedModeClassRewriter.InstanceMethodOracle;
import com.google.gwt.dev.shell.rewrite.HostedModeClassRewriter.SingleJsoImplData;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.commons.Method;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
/**
* Writes the implementation classes for JSO and its subtypes.
*
* Changes made by the base class:
*
*
The new type has the same name as the old type with a '$' appended.
*
All instance methods in the original type become static methods taking an
* explicit this parameter. Such methods have the same stack
* behavior as the original.
*
*/
abstract class WriteJsoImpl extends ClassVisitor {
/**
* This type implements JavaScriptObject.
*
*
*
JavaScriptObject itself gets a new synthetic field to store the
* underlying hosted mode reference.
*
Instance methods are added so that JavaScriptObject implements all
* SingleJsoImpl interfaces.
*
*
*/
private static class ForJsoDollar extends WriteJsoImpl {
/**
* An unmodifiable set of descriptors containing
* JavaScriptObject and all subclasses.
*/
private final Set jsoDescriptors;
private final SingleJsoImplData jsoData;
public ForJsoDollar(ClassVisitor cv, Set jsoDescriptors,
InstanceMethodOracle mapper, SingleJsoImplData jsoData) {
super(cv, mapper);
this.jsoDescriptors = jsoDescriptors;
this.jsoData = jsoData;
}
@Override
public void visit(int version, int access, String name, String signature,
String superName, String[] interfaces) {
ArrayList jsoDescList = new ArrayList();
jsoDescList.addAll(jsoDescriptors);
interfaces = jsoDescList.toArray(new String[jsoDescList.size()]);
super.visit(version, access, name, signature, superName, interfaces);
/*
* Generate the synthetic "hostedModeReferece" field to contain the
* underlying real reference to the JavaScript object.
*/
FieldVisitor fv = visitField(Opcodes.ACC_PUBLIC | Opcodes.ACC_SYNTHETIC,
HostedModeClassRewriter.REFERENCE_FIELD, "Ljava/lang/Object;", null,
null);
if (fv != null) {
fv.visitEnd();
}
// Implement the trampoline methods
for (String mangledName : jsoData.getMangledNames()) {
List declarations = jsoData.getDeclarations(mangledName);
List implementations = jsoData.getImplementations(mangledName);
assert declarations.size() == implementations.size() : "Declaration / implementation size mismatch";
Iterator declIterator = declarations.iterator();
Iterator implIterator = implementations.iterator();
while (declIterator.hasNext()) {
assert implIterator.hasNext();
writeTrampoline(mangledName, declIterator.next(), implIterator.next());
}
}
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc,
String signature, String[] exceptions) {
if (isCtor(name)) {
// make the JavaScriptObject$ constructor public
access &= ~(Opcodes.ACC_PRIVATE | Opcodes.ACC_PROTECTED);
access |= Opcodes.ACC_PUBLIC;
}
return super.visitMethod(access, name, desc, signature, exceptions);
}
/**
* JSO methods are implemented as flyweight style, with the instance being
* passed as the first parameter. This loop create instance methods on JSO$
* for all of the mangled SingleJsoImpl interface method names. These
* instance methods simply turn around and call the static-dispatch methods.
* In Java, it might look like:
*
*
* interface Interface {
* String someMethod(int a, double b);
* }
*
* class J extends JSO implements I {
* public String com_google_Interface_someMethod(int a, double b) {
* return com.google.MyJso$.someMethod$(this, a, b);
* }
* }
*
*
* @param mangledName {@code com_google_gwt_sample_hello_client_Interface_a}
* @param interfaceMethod {@code java.lang.String a(int, double)}
* @param implementingMethod {@code static final java.lang.String
* a$(com.google.gwt.sample.hello.client.Jso, ...);}
*/
private void writeTrampoline(String mangledName, Method interfaceMethod,
Method implementingMethod) {
assert implementingMethod.getArgumentTypes().length > 0;
/*
* The local descriptor is the same as the descriptor from the abstract
* method in the interface.
*/
String localDescriptor = interfaceMethod.getDescriptor();
Method localMethod = new Method(mangledName, localDescriptor);
/*
* We also use the first argument to know which type to statically
* dispatch to.
*/
Type implementingType = Type.getType("L"
+ implementingMethod.getArgumentTypes()[0].getInternalName() + "$;");
// Maybe create the method. This is marked final as a sanity check
MethodVisitor mv = visitMethodNoRewrite(Opcodes.ACC_PUBLIC
| Opcodes.ACC_FINAL | Opcodes.ACC_SYNTHETIC, localMethod.getName(),
localMethod.getDescriptor(), null, null);
if (mv != null) {
mv.visitCode();
/*
* It just so happens that the stack and local variable sizes are the
* same, but they're kept distinct to aid in clarity should the dispatch
* logic change.
*/
int var = 0;
int size = 0;
for (Type t : implementingMethod.getArgumentTypes()) {
size += t.getSize();
mv.visitVarInsn(t.getOpcode(Opcodes.ILOAD), var);
var += t.getSize();
}
// Make sure there's enough room for the return value
size = Math.max(size, implementingMethod.getReturnType().getSize());
mv.visitMethodInsn(Opcodes.INVOKESTATIC,
implementingType.getInternalName(), implementingMethod.getName(),
implementingMethod.getDescriptor(), false);
mv.visitInsn(localMethod.getReturnType().getOpcode(Opcodes.IRETURN));
mv.visitMaxs(size, var);
mv.visitEnd();
}
}
}
/**
* This type is used to implement subtypes of JSO.
*
*
*
The new type's superclass is mangled by adding $.
*
Constructors are deleted.
*
*/
private static class ForJsoInterface extends WriteJsoImpl {
public ForJsoInterface(ClassVisitor cv, InstanceMethodOracle mapper) {
super(cv, mapper);
}
@Override
public void visit(int version, int access, String name, String signature,
String superName, String[] interfaces) {
// Reference the old superclass's implementation class.
superName += '$';
interfaces = null;
super.visit(version, access, name, signature, superName, interfaces);
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc,
String signature, String[] exceptions) {
boolean isCtor = isCtor(name);
if (isCtor) {
// Don't copy over constructors except for JavaScriptObject itself.
return null;
}
return super.visitMethod(access, name, desc, signature, exceptions);
}
}
/**
* Creates a ClassVisitor to implement a JavaScriptObject subtype. This will
* select between a simple implementation for user-defined JSO subtypes and
* the complex implementation for implementing JavaScriptObject$.
*/
public static ClassVisitor create(ClassVisitor cv, String classDescriptor,
Set jsoDescriptors, InstanceMethodOracle mapper,
SingleJsoImplData singleJsoImplData) {
if (classDescriptor.equals(HostedModeClassRewriter.JAVASCRIPTOBJECT_IMPL_DESC)) {
return new ForJsoDollar(cv, jsoDescriptors, mapper, singleJsoImplData);
} else {
return new ForJsoInterface(cv, mapper);
}
}
/**
* Maps methods to the class in which they are declared.
*/
private final InstanceMethodOracle mapper;
/**
* The original name of the class being visited.
*/
private String originalName;
/**
* Construct a new rewriter instance.
*
* @param cv the visitor to chain to
* @param jsoDescriptors an unmodifiable set of descriptors containing
* JavaScriptObject and all subclasses
* @param mapper maps methods to the class in which they are declared
*/
private WriteJsoImpl(ClassVisitor cv, InstanceMethodOracle mapper) {
super(Opcodes.ASM5, cv);
this.mapper = mapper;
}
/**
* Records the original name and resets access opcodes.
*/
@Override
public void visit(int version, int access, String name, String signature,
String superName, String[] interfaces) {
originalName = name;
super.visit(version, Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC
| Opcodes.ACC_SYNTHETIC, name + '$', signature, superName, interfaces);
}
/**
* Mangle all instance methods declared in JavaScriptObject types.
*/
@Override
public MethodVisitor visitMethod(int access, String name, String desc,
String signature, String[] exceptions) {
boolean isCtor = isCtor(name);
if (!isCtor && !isStatic(access) && !isObjectMethod(name + desc)) {
access |= Opcodes.ACC_STATIC;
desc = HostedModeClassRewriter.addSyntheticThisParam(getOriginalName(),
desc);
name = name + "$";
}
return super.visitMethod(access, name, desc, signature, exceptions);
}
protected String getOriginalName() {
return originalName;
}
protected boolean isCtor(String name) {
return "".equals(name);
}
protected boolean isObjectMethod(String signature) {
return "java/lang/Object".equals(mapper.findOriginalDeclaringClass(
originalName, signature));
}
protected boolean isStatic(int access) {
return (access & Opcodes.ACC_STATIC) != 0;
}
/**
* Allows access to an unmodified visitMethod call.
*/
protected MethodVisitor visitMethodNoRewrite(int access, String name,
String desc, String signature, String[] exceptions) {
return super.visitMethod(access, name, desc, signature, exceptions);
}
}
