InstructionComparator xref

View Javadoc

    1   /*
    2    * Copyright  2000-2004 The Apache Software Foundation
    3    *
    4    *  Licensed under the Apache License, Version 2.0 (the "License");
    5    *  you may not use this file except in compliance with the License.
    6    *  You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   *  Unless required by applicable law or agreed to in writing, software
    11   *  distributed under the License is distributed on an "AS IS" BASIS,
    12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   *  See the License for the specific language governing permissions and
    14   *  limitations under the License.
    15   *
    16   */
    17  package org.apache.bcel.generic;
    18
    19  /***
    20   * Equality of instructions isn't clearly to be defined. You might
    21   * wish, for example, to compare whether instructions have the same
    22   * meaning. E.g., whether two INVOKEVIRTUALs describe the same
    23   * call.<br>The DEFAULT comparator however, considers two instructions
    24   * to be equal if they have same opcode and point to the same indexes
    25   * (if any) in the constant pool or the same local variable index. Branch
    26   * instructions must have the same target.
    27   *
    28   * @see Instruction
    29   * @version $Id: InstructionComparator.java 386056 2006-03-15 11:31:56Z tcurdt $
    30   * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
    31   */
    32  public interface InstructionComparator {
    33
    34      public static final InstructionComparator DEFAULT = new InstructionComparator() {
    35
    36          public boolean equals( Instruction i1, Instruction i2 ) {
    37              if (i1.opcode == i2.opcode) {
    38                  if (i1 instanceof Select) {
    39                      InstructionHandle[] t1 = ((Select) i1).getTargets();
    40                      InstructionHandle[] t2 = ((Select) i2).getTargets();
    41                      if (t1.length == t2.length) {
    42                          for (int i = 0; i < t1.length; i++) {
    43                              if (t1[i] != t2[i]) {
    44                                  return false;
    45                              }
    46                          }
    47                          return true;
    48                      }
    49                  } else if (i1 instanceof BranchInstruction) {
    50                      return ((BranchInstruction) i1).target == ((BranchInstruction) i2).target;
    51                  } else if (i1 instanceof ConstantPushInstruction) {
    52                      return ((ConstantPushInstruction) i1).getValue().equals(
    53                              ((ConstantPushInstruction) i2).getValue());
    54                  } else if (i1 instanceof IndexedInstruction) {
    55                      return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2)
    56                              .getIndex();
    57                  } else if (i1 instanceof NEWARRAY) {
    58                      return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
    59                  } else {
    60                      return true;
    61                  }
    62              }
    63              return false;
    64          }
    65      };
    66
    67
    68      public boolean equals( Instruction i1, Instruction i2 );
    69  }