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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) 2002-2021 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.analysis.datastructure;

import static proguard.classfile.util.ClassUtil.externalClassName;

import java.util.Objects;
import proguard.classfile.Clazz;
import proguard.classfile.Member;
import proguard.classfile.Signature;

/**
 * Represents a unique location in the bytecode. It comprises the {@link Clazz} and {@link Member}
 * where it is contained, the offset therein and the corresponding line number in the source file
 * ({@link Location#UNKNOWN_LINE} if it is unknown). Consider the following pseudo-bytecode example
 * which contains code location comments:
 *
 * {@code
 * public class Test
 * {
 *     // class "Test", member "field", line 3, offset 0
 *     public String field;
 *
 *     public String toString()
 *     {
 *         // class "Test", member "toString", line 6, offset 0
 *         aload_0
 *         // class "Test", member "toString", line 6, offset 1
 *         getfield #1 <Test.field : Ljava/lang/String;>
 *         // class "Test", member "toString", line 6, offset 4
 *         areturn
 *     }
 * }
 *
 * }
 *
 * 
 *   Inside methods: Like each location, instructions inside methods have a line number.
 *       But as there may be several expressions on the same line, to correctly identify each
 *       instruction we also need their bytecode offset. E.g. the {@code getfield} instruction
 *       inside {@code toString()} has the offset 1.
 *   
Fields: In this case {@code Test#field}. A field location has a line number (3 in
 *       this example) but no offset, as this concept is only applicable to methods.
 * 
 */
public class CodeLocation extends Location {

  public final Clazz clazz;
  public final Member member;
  public final int offset;
  public final Signature signature;

  /** Create a code location with an unknown ({@link Location#UNKNOWN_LINE}) line number. */
  public CodeLocation(Clazz clazz, Member member, int offset) {
    this(clazz, member, offset, UNKNOWN_LINE);
  }

  public CodeLocation(Clazz clazz, Member member, int offset, int line) {
    super(line);
    this.clazz = clazz;
    this.member = member;
    this.offset = offset;
    this.signature = Signature.of(clazz, member);
  }

  public String getExternalClassName() {
    return externalClassName(clazz.getName());
  }

  public String getMemberName() {
    return member == null ? null : member.getName(clazz);
  }

  @Override
  public String getName() {
    return signature.getFqn();
  }

  @Override
  public String toString() {
    return signature + "+" + String.format("%04d", offset) + " (line " + line + ")";
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (!(o instanceof CodeLocation)) {
      return false;
    }
    CodeLocation codeLocation = (CodeLocation) o;
    return Objects.equals(signature, codeLocation.signature) && offset == codeLocation.offset;
  }

  @Override
  public int hashCode() {
    return Objects.hash(signature, offset);
  }

  @Override
  public int compareTo(Location o) {
    if (!o.getClass().equals(getClass())) {
      return -1;
    }
    CodeLocation other = (CodeLocation) o;
    // Locations are ordered first by member name (lexicographically
    // increasing), then increasing line number and lastly increasing offset
    if (signature.equals(other.signature)) {
      if (line == other.line) {
        return offset - other.offset;
      }
      return line - other.line;
    }
    return signature.compareTo(other.signature);
  }
}