src/main/java/com/android/tools/r8/shaking/AnnotationRemover.java

// Copyright (c) 2017, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
package com.android.tools.r8.shaking;

import com.android.tools.r8.errors.Unreachable;
import com.android.tools.r8.graph.DexAnnotation;
import com.android.tools.r8.graph.DexAnnotationSet;
import com.android.tools.r8.graph.DexAnnotationSetRefList;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.shaking.Enqueuer.AppInfoWithLiveness;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.InternalOptions.AttributeRemovalOptions;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.function.Predicate;

public class AnnotationRemover {

  private final AppInfoWithLiveness appInfo;
  private final boolean minificationEnabled;
  private final AttributeRemovalOptions keep;

  public AnnotationRemover(AppInfoWithLiveness appInfo, InternalOptions options) {
    this(appInfo, !options.skipMinification, options.attributeRemoval);
  }

  public AnnotationRemover(AppInfoWithLiveness appInfo, boolean minificationEnabled,
      AttributeRemovalOptions keep) {
    this.appInfo = appInfo;
    this.minificationEnabled = minificationEnabled;
    this.keep = keep;
  }

  /**
   * Used to filter annotations on classes, methods and fields.
   */
  private boolean filterAnnotations(DexAnnotation annotation) {
    switch (annotation.visibility) {
      case DexAnnotation.VISIBILITY_SYSTEM:
        // EnclosingClass and InnerClass are used in Dalvik to represent the InnerClasses
        // attribute section from class files.
        DexItemFactory factory = appInfo.dexItemFactory;
        if (keep.innerClasses
            && (DexAnnotation.isInnerClassesAnnotation(annotation, factory) ||
                DexAnnotation.isEnclosingClassAnnotation(annotation, factory))) {
          return true;
        }
        if (keep.enclosingMethod
            && DexAnnotation.isEnclosingMethodAnnotation(annotation, factory)) {
          return true;
        }
        if (keep.exceptions && DexAnnotation.isThrowingAnnotation(annotation, factory)) {
          return true;
        }
        if (keep.signature && DexAnnotation.isSignatureAnnotation(annotation, factory)) {
          return true;
        }
        if (keep.sourceDebugExtension
            && DexAnnotation.isSourceDebugExtension(annotation, factory)) {
          return true;
        }
        return false;
      case DexAnnotation.VISIBILITY_RUNTIME:
        if (!keep.runtimeVisibleAnnotations) {
          return false;
        }
        break;
      case DexAnnotation.VISIBILITY_BUILD:
        if (!keep.runtimeInvisibleAnnotations) {
          return false;
        }
        break;
      default:
        throw new Unreachable("Unexpected annotation visiility.");
    }
    return appInfo.liveTypes.contains(annotation.annotation.type);
  }

  /**
   * Used to filter annotations on parameters.
   */
  private boolean filterParameterAnnotations(DexAnnotation annotation) {
    switch (annotation.visibility) {
      case DexAnnotation.VISIBILITY_SYSTEM:
        return false;
      case DexAnnotation.VISIBILITY_RUNTIME:
        if (!keep.runtimeVisibleParameterAnnotations) {
          return false;
        }
        break;
      case DexAnnotation.VISIBILITY_BUILD:
        if (!keep.runtimeInvisibleParamterAnnotations) {
          return false;
        }
        break;
      default:
        throw new Unreachable("Unexpected annotation visibility.");
    }
    return appInfo.liveTypes.contains(annotation.annotation.type);
  }

  public void run() {
    keep.ensureValid(minificationEnabled);
    for (DexProgramClass clazz : appInfo.classes()) {
      clazz.annotations = stripAnnotations(clazz.annotations, this::filterAnnotations);
      processMethods(clazz.virtualMethods());
      processMethods(clazz.directMethods());
      processFields(clazz.staticFields());
      processFields(clazz.instanceFields());
    }
  }

  private void processMethods(DexEncodedMethod[] methods) {
    for (DexEncodedMethod method : methods) {
      method.annotations = stripAnnotations(method.annotations, this::filterAnnotations);
      method.parameterAnnotations = stripAnnotations(method.parameterAnnotations,
          this::filterParameterAnnotations);
    }
  }

  private void processFields(DexEncodedField[] fields) {
    for (DexEncodedField field : fields) {
      field.annotations = stripAnnotations(field.annotations, this::filterAnnotations);
    }
  }

  private DexAnnotationSetRefList stripAnnotations(DexAnnotationSetRefList annotations,
      Predicate<DexAnnotation> filter) {
    DexAnnotationSet[] filtered = null;
    for (int i = 0; i < annotations.values.length; i++) {
      DexAnnotationSet updated = stripAnnotations(annotations.values[i], filter);
      if (updated != annotations.values[i]) {
        if (filtered == null) {
          filtered = annotations.values.clone();
          filtered[i] = updated;
        }
      }
    }
    if (filtered == null) {
      return annotations;
    } else {
      if (Arrays.stream(filtered).allMatch(DexAnnotationSet::isEmpty)) {
        return DexAnnotationSetRefList.empty();
      }
      return new DexAnnotationSetRefList(filtered);
    }
  }

  private DexAnnotationSet stripAnnotations(DexAnnotationSet annotations,
      Predicate<DexAnnotation> filter) {
    ArrayList<DexAnnotation> filtered = null;
    for (int i = 0; i < annotations.annotations.length; i++) {
      DexAnnotation annotation = annotations.annotations[i];
      if (filter.test(annotation)) {
        if (filtered != null) {
          filtered.add(annotation);
        }
      } else {
        if (filtered == null) {
          filtered = new ArrayList<>(annotations.annotations.length);
          for (int j = 0; j < i; j++) {
            filtered.add(annotations.annotations[j]);
          }
        }
      }
    }
    if (filtered == null) {
      return annotations;
    } else if (filtered.isEmpty()) {
      return DexAnnotationSet.empty();
    } else {
      return new DexAnnotationSet(filtered.toArray(new DexAnnotation[filtered.size()]));
    }
  }
}