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// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.syntax.compiler;
import net.bytebuddy.description.method.MethodDescription.ForLoadedConstructor;
import net.bytebuddy.implementation.Implementation.Context;
import net.bytebuddy.implementation.bytecode.Duplication;
import net.bytebuddy.implementation.bytecode.StackManipulation;
import net.bytebuddy.implementation.bytecode.member.MethodInvocation;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import java.util.List;
/**
* Builds byte code for new object creation from constructor calls.
*
* <p>Java byte code for new object creation looks like the following pseudo code:
* <pre>
* NEW
* DUP
* ...load constructor parameters...
* INVOKESPECIAL constructor
* </pre>
* This is because a constructor is actually called on the reference to the object itself, which
* is left on the stack by NEW.
*
* This class helps with wrapping the parameter loading with this structure.
*/
public class NewObject implements StackManipulation {
private final ForLoadedConstructor constructor;
private final StackManipulation arguments;
/**
* Intermediate state builder for new object construction with missing constructor argument
* loading.
*/
public static final class NewObjectBuilder {
private final ForLoadedConstructor constructor;
private NewObjectBuilder(ForLoadedConstructor constructor) {
this.constructor = constructor;
}
/**
* Adds the argument loading in the correct for new object construction.
*/
public NewObject arguments(StackManipulation... arguments) {
return new NewObject(constructor, new StackManipulation.Compound(arguments));
}
/**
* Adds the argument loading in the correct for new object construction.
*/
public NewObject arguments(List<StackManipulation> arguments) {
return new NewObject(constructor, new StackManipulation.Compound(arguments));
}
}
private NewObject(ForLoadedConstructor constructor, StackManipulation arguments) {
this.constructor = constructor;
this.arguments = arguments;
}
/**
* Looks for a constructor in the class with the given parameter types and returns an
* intermediate builder.
*/
public static NewObjectBuilder fromConstructor(Class<?> clazz, Class<?>... parameterTypes) {
return new NewObjectBuilder(ReflectionUtils.getConstructor(clazz, parameterTypes));
}
@Override
public boolean isValid() {
return true;
}
@Override
public Size apply(MethodVisitor methodVisitor, Context implementationContext) {
methodVisitor.visitTypeInsn(Opcodes.NEW, constructor.getDeclaringType().getInternalName());
return new StackManipulation.Compound(
Duplication.SINGLE, arguments, MethodInvocation.invoke(constructor))
.apply(methodVisitor, implementationContext);
}
@Override
public String toString() {
return "NewObject(" + constructor + ", " + arguments + ")";
}
}
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