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ProGuardCORE is a free library to read, analyze, modify, and write Java class files.
There is a newer version: 9.1.6
/*
 * ProGuardCORE -- library to process Java bytecode.
 *
 * Copyright (c) 2002-2020 Guardsquare NV
 *
 * 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 proguard.evaluation;

import org.jetbrains.annotations.NotNull;
import proguard.analysis.datastructure.CodeLocation;
import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.evaluation.value.*;
import proguard.evaluation.value.object.AnalyzedObject;

/**
 * This {@link ValueFactory} tags newly created reference values so they can be traced throughout
 * the execution of a method.
 *
 * @see TracedReferenceValue
 * @see InstructionOffsetValue
 * @author Eric Lafortune
 */
public class ReferenceTracingValueFactory implements InstructionVisitor, ValueFactory {
  private final ValueFactory valueFactory;
  private final boolean preserveTraceValueOnCasts;

  private Value traceValue;

  /**
   * Creates a new ReferenceTracingValueFactory that attaches instruction offset values based on
   * being used as an instruction visitor. This instance preserves trace values in the {@link #cast}
   * method.
   *
   * @param valueFactory the value factory that creates the actual values.
   */
  public ReferenceTracingValueFactory(ValueFactory valueFactory) {
    this(valueFactory, true);
  }

  /**
   * Creates a new ReferenceTracingValueFactory that attaches instruction offset values based on
   * being used as an instruction visitor.
   *
   * @param valueFactory the value factory that creates the actual values.
   * @param preserveTraceValueOnCasts specifies whether to preserve the trace value for reference
   *     values that are passed to the {@link #cast} method.
   */
  public ReferenceTracingValueFactory(
      ValueFactory valueFactory, boolean preserveTraceValueOnCasts) {
    this.valueFactory = valueFactory;
    this.preserveTraceValueOnCasts = preserveTraceValueOnCasts;
  }

  public void setTraceValue(Value traceValue) {
    this.traceValue = traceValue;
  }

  /**
   * Casts a given traced reference value to the given type, either keeping its trace value or
   * setting a new one.
   */
  public TracedReferenceValue cast(
      TracedReferenceValue referenceValue, String type, Clazz referencedClass, boolean alwaysCast) {
    // Cast the value.
    ReferenceValue castValue =
        referenceValue.getReferenceValue().cast(type, referencedClass, valueFactory, alwaysCast);

    // Trace it.
    return new TracedReferenceValue(
        castValue, preserveTraceValueOnCasts ? referenceValue.getTraceValue() : traceValue);
  }

  // Implementations for InstructionVisitor.

  public void visitAnyInstruction(
      Clazz clazz,
      Method method,
      CodeAttribute codeAttribute,
      int offset,
      Instruction instruction) {
    traceValue = null;
  }

  public void visitSimpleInstruction(
      Clazz clazz,
      Method method,
      CodeAttribute codeAttribute,
      int offset,
      SimpleInstruction simpleInstruction) {
    switch (simpleInstruction.opcode) {
      case Instruction.OP_ACONST_NULL:
      case Instruction.OP_NEWARRAY:
      case Instruction.OP_ATHROW:
        traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.NEW_INSTANCE);
        break;

      case Instruction.OP_AALOAD:
        traceValue = new InstructionOffsetValue(offset);
        break;

      default:
        traceValue = null;
        break;
    }
  }

  public void visitConstantInstruction(
      Clazz clazz,
      Method method,
      CodeAttribute codeAttribute,
      int offset,
      ConstantInstruction constantInstruction) {
    switch (constantInstruction.opcode) {
      case Instruction.OP_LDC:
      case Instruction.OP_LDC_W:
      case Instruction.OP_NEW:
      case Instruction.OP_ANEWARRAY:
      case Instruction.OP_MULTIANEWARRAY:
        traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.NEW_INSTANCE);
        break;

      case Instruction.OP_GETSTATIC:
      case Instruction.OP_GETFIELD:
        traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.FIELD_VALUE);
        break;

      case Instruction.OP_INVOKEVIRTUAL:
      case Instruction.OP_INVOKESPECIAL:
      case Instruction.OP_INVOKESTATIC:
      case Instruction.OP_INVOKEINTERFACE:
        traceValue =
            new InstructionOffsetValue(offset | InstructionOffsetValue.METHOD_RETURN_VALUE);
        break;

      case Instruction.OP_CHECKCAST:
        traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.CAST);
        break;

      default:
        traceValue = null;
        break;
    }
  }

  // Implementations for BasicValueFactory.

  @Override
  public Value createValue(
      String type, Clazz referencedClass, boolean mayBeExtension, boolean mayBeNull) {
    return trace(valueFactory.createValue(type, referencedClass, mayBeExtension, mayBeNull));
  }

  @Override
  public IntegerValue createIntegerValue() {
    return valueFactory.createIntegerValue();
  }

  @Override
  public IntegerValue createIntegerValue(int value) {
    return valueFactory.createIntegerValue(value);
  }

  @Override
  public IntegerValue createIntegerValue(int min, int max) {
    return valueFactory.createIntegerValue(min, max);
  }

  @Override
  public LongValue createLongValue() {
    return valueFactory.createLongValue();
  }

  @Override
  public LongValue createLongValue(long value) {
    return valueFactory.createLongValue(value);
  }

  @Override
  public FloatValue createFloatValue() {
    return valueFactory.createFloatValue();
  }

  @Override
  public FloatValue createFloatValue(float value) {
    return valueFactory.createFloatValue(value);
  }

  @Override
  public DoubleValue createDoubleValue() {
    return valueFactory.createDoubleValue();
  }

  public DoubleValue createDoubleValue(double value) {
    return valueFactory.createDoubleValue(value);
  }

  @Override
  public ReferenceValue createReferenceValue() {
    return trace(valueFactory.createReferenceValue());
  }

  @Override
  public ReferenceValue createReferenceValueNull() {
    return trace(valueFactory.createReferenceValueNull());
  }

  @Override
  public ReferenceValue createReferenceValue(
      String type, Clazz referencedClass, boolean mayBeExtension, boolean mayBeNull) {
    return trace(
        valueFactory.createReferenceValue(type, referencedClass, mayBeExtension, mayBeNull));
  }

  /**
   * Deprecated, use {@link ReferenceTracingValueFactory#createReferenceValue(Clazz, boolean,
   * boolean, AnalyzedObject)}.
   */
  @Override
  @Deprecated
  public ReferenceValue createReferenceValue(
      String type, Clazz referencedClass, boolean mayBeExtension, boolean mayBeNull, Object value) {
    return trace(
        valueFactory.createReferenceValue(type, referencedClass, mayBeExtension, mayBeNull, value));
  }

  @Override
  public ReferenceValue createReferenceValue(
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      @NotNull AnalyzedObject value) {
    return trace(
        valueFactory.createReferenceValue(referencedClass, mayBeExtension, mayBeNull, value));
  }

  @Override
  public ReferenceValue createReferenceValue(
      String type,
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      Clazz creationClass,
      Method creationMethod,
      int creationOffset) {
    return trace(
        valueFactory.createReferenceValue(type, referencedClass, mayBeExtension, mayBeNull));
  }

  /**
   * Deprecated, use {@link ReferenceTracingValueFactory#createReferenceValue(Clazz, boolean,
   * boolean, CodeLocation, AnalyzedObject)}
   */
  @Override
  @Deprecated
  public ReferenceValue createReferenceValue(
      String type,
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      Clazz creationClass,
      Method creationMethod,
      int creationOffset,
      Object value) {
    return trace(
        valueFactory.createReferenceValue(type, referencedClass, mayBeExtension, mayBeNull, value));
  }

  @Override
  public ReferenceValue createReferenceValue(
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      CodeLocation creationLocation,
      @NotNull AnalyzedObject value) {
    return trace(
        valueFactory.createReferenceValue(referencedClass, mayBeExtension, mayBeNull, value));
  }

  @Override
  public ReferenceValue createReferenceValueForId(
      String type, Clazz referencedClass, boolean mayBeExtension, boolean mayBeNull, Object id) {
    return trace(
        valueFactory.createReferenceValueForId(
            type, referencedClass, mayBeExtension, mayBeNull, id));
  }

  /**
   * Deprecated, use {@link ReferenceTracingValueFactory#createReferenceValueForId(Clazz, boolean,
   * boolean, Object, AnalyzedObject)}.
   */
  @Override
  @Deprecated
  public ReferenceValue createReferenceValueForId(
      String type,
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      Object id,
      Object value) {
    return trace(
        valueFactory.createReferenceValueForId(
            type, referencedClass, mayBeExtension, mayBeNull, id, value));
  }

  @Override
  public ReferenceValue createReferenceValueForId(
      Clazz referencedClass,
      boolean mayBeExtension,
      boolean mayBeNull,
      Object id,
      @NotNull AnalyzedObject value) {
    return trace(
        valueFactory.createReferenceValueForId(
            referencedClass, mayBeExtension, mayBeNull, id, value));
  }

  @Override
  public ReferenceValue createArrayReferenceValue(
      String type, Clazz referencedClass, IntegerValue arrayLength) {
    return trace(valueFactory.createArrayReferenceValue(type, referencedClass, arrayLength));
  }

  /**
   * Creates a new ReferenceValue that represents an array with elements of the given type, with the
   * given length and initial element values.
   */
  @Override
  public ReferenceValue createArrayReferenceValue(
      String type, Clazz referencedClass, IntegerValue arrayLength, Object elementValues) {
    return trace(
        valueFactory.createArrayReferenceValue(type, referencedClass, arrayLength, elementValues));
  }

  // Small utility methods.

  /** Attaches the current trace value to given value, if it is a reference value. */
  public Value trace(Value value) {
    return value.computationalType() == Value.TYPE_REFERENCE
        ? trace(value.referenceValue())
        : value;
  }

  /** Attaches the current trace value to given reference value. */
  public ReferenceValue trace(ReferenceValue referenceValue) {
    return traceValue != null
        ? new TracedReferenceValue(referenceValue, traceValue)
        : referenceValue;
  }
}