proguard.classfile.editor.InstructionSequencesReplacer Maven / Gradle / Ivy

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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.classfile.editor;

import proguard.classfile.constant.Constant;
import proguard.classfile.instruction.Instruction;
import proguard.classfile.instruction.visitor.*;
import proguard.classfile.util.BranchTargetFinder;

/**
 * This {@link InstructionVisitor} replaces multiple instruction sequences at once.
 *
 * The replacement sequences are optional, defaulting to the empty sequence, to delete the
 * matched pattern sequences.
 *
 * @see InstructionSequenceReplacer
 * @author Eric Lafortune
 */
public class InstructionSequencesReplacer extends MultiInstructionVisitor
    implements InstructionVisitor {
  private static final int PATTERN_INDEX = 0;
  private static final int REPLACEMENT_INDEX = 1;

  private static final Instruction[] EMPTY_INSTRUCTIONS = new Instruction[0];

  /**
   * Creates a new InstructionSequencesReplacer.
   *
   * @param constants any constants referenced by the pattern instructions and replacement
   *     instructions.
   * @param instructionSequences the instruction sequences to be replaced, with subsequently the
   *     sequence pair index, the patten/replacement index (0 or 1), and the instruction index in
   *     the sequence.
   * @param branchTargetFinder a branch target finder that has been initialized to indicate branch
   *     targets in the visited code.
   * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
   */
  public InstructionSequencesReplacer(
      Constant[] constants,
      Instruction[][][] instructionSequences,
      BranchTargetFinder branchTargetFinder,
      CodeAttributeEditor codeAttributeEditor) {
    this(constants, instructionSequences, branchTargetFinder, codeAttributeEditor, null);
  }

  /**
   * Creates a new InstructionSequenceReplacer.
   *
   * @param constants any constants referenced by the pattern instructions and replacement
   *     instructions.
   * @param instructionSequences the instruction sequences to be replaced, with subsequently the
   *     sequence pair index, the patten/replacement index (0 or 1), and the instruction index in
   *     the sequence.
   * @param branchTargetFinder a branch target finder that has been initialized to indicate branch
   *     targets in the visited code.
   * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
   * @param extraInstructionVisitor an optional extra visitor for all deleted load instructions.
   */
  public InstructionSequencesReplacer(
      Constant[] constants,
      Instruction[][][] instructionSequences,
      BranchTargetFinder branchTargetFinder,
      CodeAttributeEditor codeAttributeEditor,
      InstructionVisitor extraInstructionVisitor) {
    super(
        createInstructionSequenceReplacers(
            constants,
            instructionSequences,
            branchTargetFinder,
            codeAttributeEditor,
            extraInstructionVisitor));
  }

  /**
   * Creates an array of InstructionSequenceReplacer instances.
   *
   * @param constants any constants referenced by the pattern instructions and replacement
   *     instructions.
   * @param instructionSequences the instruction sequences to be replaced, with subsequently the
   *     sequence pair index, the from/to index (0 or 1), and the instruction index in the sequence.
   * @param branchTargetFinder a branch target finder that has been initialized to indicate branch
   *     targets in the visited code.
   * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
   * @param extraInstructionVisitor an optional extra visitor for all deleted load instructions.
   */
  private static InstructionVisitor[] createInstructionSequenceReplacers(
      Constant[] constants,
      Instruction[][][] instructionSequences,
      BranchTargetFinder branchTargetFinder,
      CodeAttributeEditor codeAttributeEditor,
      InstructionVisitor extraInstructionVisitor) {
    InstructionVisitor[] instructionSequenceReplacers =
        new InstructionVisitor[instructionSequences.length];

    for (int index = 0; index < instructionSequenceReplacers.length; index++) {
      Instruction[][] instructionSequencePair = instructionSequences[index];

      Instruction[] patternInstructions = instructionSequencePair[PATTERN_INDEX];

      // The replacement sequence is optional.
      Instruction[] replacementInstructions =
          instructionSequencePair.length > REPLACEMENT_INDEX
              ? instructionSequencePair[REPLACEMENT_INDEX]
              : EMPTY_INSTRUCTIONS;

      instructionSequenceReplacers[index] =
          new InstructionSequenceReplacer(
              constants,
              patternInstructions,
              constants,
              replacementInstructions,
              branchTargetFinder,
              codeAttributeEditor,
              extraInstructionVisitor);
    }

    return instructionSequenceReplacers;
  }
}