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// Copyright 2017 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.android.desugar;
import com.google.common.base.Preconditions;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
/**
* A class scanner to check whether the class has the synthetic method $closeResource(Throwable,
* AutoCloseable).
*/
public class CloseResourceMethodScanner extends ClassVisitor {
private boolean hasCloseResourceMethod;
private String internalName;
private int classFileVersion;
public CloseResourceMethodScanner() {
super(Opcodes.ASM6);
}
@Override
public void visit(
int version,
int access,
String name,
String signature,
String superName,
String[] interfaces) {
Preconditions.checkState(internalName == null, "This scanner has been used.");
this.internalName = name;
this.classFileVersion = version;
super.visit(version, access, name, signature, superName, interfaces);
}
public boolean hasCloseResourceMethod() {
return hasCloseResourceMethod;
}
@Override
public MethodVisitor visitMethod(
int access, String name, String desc, String signature, String[] exceptions) {
if (classFileVersion <= 50) {
// A Java 6 or below class file should not have $closeResource method.
return null;
}
if (!hasCloseResourceMethod) {
hasCloseResourceMethod =
TryWithResourcesRewriter.isSyntheticCloseResourceMethod(access, name, desc);
}
return new StackMapFrameCollector(name, desc);
}
private class StackMapFrameCollector extends MethodVisitor {
private final String methodSignature;
private boolean hasCallToCloseResourceMethod;
private boolean hasJumpInstructions;
private boolean hasStackMapFrame;
public StackMapFrameCollector(String name, String desc) {
super(Opcodes.ASM6);
methodSignature = internalName + '.' + name + desc;
}
@Override
public void visitEnd() {
if (!hasCallToCloseResourceMethod) {
return;
}
if (hasJumpInstructions && !hasStackMapFrame) {
throw new UnsupportedOperationException(
"The method "
+ methodSignature
+ " calls $closeResource(Throwable, AutoCloseable), "
+ "and Desugar thus needs to perform type inference for it "
+ "to rewrite $closeResourceMethod. "
+ "However, this method has jump instructions, but does not have stack map frames. "
+ "Please recompile this class with stack map frames.");
}
}
@Override
public void visitMethodInsn(int opcode, String owner, String name, String desc, boolean itf) {
if (!hasCallToCloseResourceMethod
&& TryWithResourcesRewriter.isCallToSyntheticCloseResource(
internalName, opcode, owner, name, desc)) {
hasCallToCloseResourceMethod = true;
}
}
@Override
public void visitFrame(int type, int nLocal, Object[] local, int nStack, Object[] stack) {
hasStackMapFrame = true;
}
@Override
public void visitJumpInsn(int opcode, Label label) {
hasJumpInstructions = true;
}
}
}
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