com.google.devtools.build.android.desugar.InvokeDynamicLambdaMethodCollector.java Source code

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Here is the source code for com.google.devtools.build.android.desugar.InvokeDynamicLambdaMethodCollector.java

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// Copyright 2016 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.collect.ImmutableSet;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Handle;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * Class visitor to collect all the lambda methods that are used in invokedynamic instructions.
 *
 * <p>Note that this class only collects lambda methods. If the invokedynamic is used for other
 * purposes, the methods used in the instruction are NOT collected.
 */
class InvokeDynamicLambdaMethodCollector extends ClassVisitor {

    private final ImmutableSet.Builder<MethodInfo> lambdaMethodsUsedInInvokeDynamic = ImmutableSet.builder();
    private boolean needOuterClassRewrite = false;

    public InvokeDynamicLambdaMethodCollector() {
        super(Opcodes.ASM5);
    }

    /**
     * Returns whether the visited class is declared in the scope of a lambda.  In that case
     * {@link LambdaDesugaring} will want to rewrite the EnclosingMethod attribute of the class.
     */
    public boolean needOuterClassRewrite() {
        return needOuterClassRewrite;
    }

    /** Returns methods referenced in invokedynamic instructions that use LambdaMetafactory. */
    public ImmutableSet<MethodInfo> getLambdaMethodsUsedInInvokeDynamics() {
        return lambdaMethodsUsedInInvokeDynamic.build();
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
        return new LambdaMethodCollector(mv);
    }

    @Override
    public void visitOuterClass(String owner, String name, String desc) {
        needOuterClassRewrite = needOuterClassRewrite || (name != null && name.startsWith("lambda$"));
        super.visitOuterClass(owner, name, desc);
    }

    private class LambdaMethodCollector extends MethodVisitor {

        public LambdaMethodCollector(MethodVisitor dest) {
            super(Opcodes.ASM5, dest);
        }

        @Override
        public void visitInvokeDynamicInsn(String name, String desc, Handle bsm, Object... bsmArgs) {
            if (!"java/lang/invoke/LambdaMetafactory".equals(bsm.getOwner())) {
                // Not an invokedynamic for a lambda expression
                return;
            }
            Handle handle = (Handle) bsmArgs[1];
            lambdaMethodsUsedInInvokeDynamic
                    .add(MethodInfo.create(handle.getOwner(), handle.getName(), handle.getDesc()));
            super.visitInvokeDynamicInsn(name, desc, bsm, bsmArgs);
        }
    }
}