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    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.verifier.structurals;
    18
    19
    20  import java.util.ArrayList;
    21  import org.apache.bcel.generic.InstructionHandle;
    22
    23  /***
    24   * An InstructionContext offers convenient access
    25   * to information like control flow successors and
    26   * such.
    27   *
    28   * @version $Id: InstructionContext.java 382272 2006-03-02 03:31:46Z tcurdt $
    29   * @author Enver Haase
    30   */
    31  public interface InstructionContext{
    32
    33  	/***
    34  	 * The getTag and setTag methods may be used for
    35  	 * temporary flagging, such as graph colouring.
    36  	 * Nothing in the InstructionContext object depends
    37  	 * on the value of the tag. JustIce does not use it.
    38  	 *
    39  	 * @see #setTag(int tag)
    40  	 */
    41  	public int getTag();
    42
    43  	/***
    44  	 * The getTag and setTag methods may be used for
    45  	 * temporary flagging, such as graph colouring.
    46  	 * Nothing in the InstructionContext object depends
    47  	 * on the value of the tag. JustIce does not use it.
    48  	 *
    49  	 * @see #getTag()
    50  	 */
    51  	public void setTag(int tag);
    52
    53  	/***
    54  	 * This method symbolically executes the Instruction
    55  	 * held in the InstructionContext.
    56  	 * It "merges in" the incoming execution frame situation
    57  	 * (see The Java Virtual Machine Specification, 2nd
    58  	 * edition, page 146).
    59  	 * By so doing, the outgoing execution frame situation
    60  	 * is calculated.
    61  	 *
    62  	 * This method is JustIce-specific and is usually of
    63  	 * no sense for users of the ControlFlowGraph class.
    64  	 * They should use getInstruction().accept(Visitor),
    65  	 * possibly in conjunction with the ExecutionVisitor.
    66  	 *
    67  	 *
    68  	 * @see ControlFlowGraph
    69  	 * @see ExecutionVisitor
    70  	 * @see #getOutFrame(ArrayList)
    71  	 * @return true -  if and only if the "outgoing" frame situation
    72  	 * changed from the one before execute()ing.
    73  	 */
    74  	boolean execute(Frame inFrame, ArrayList executionPredecessors, InstConstraintVisitor icv, ExecutionVisitor ev);
    75
    76  	Frame getInFrame();
    77
    78  	/***
    79  	 * This method returns the outgoing execution frame situation;
    80  	 * therefore <B>it has to be calculated by execute(Frame, ArrayList)
    81  	 * first.</B>
    82  	 *
    83  	 * @see #execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor)
    84  	 */
    85  	Frame getOutFrame(ArrayList executionPredecessors);
    86
    87  	/***
    88  	 * Returns the InstructionHandle this InstructionContext is wrapped around.
    89  	 *
    90  	 * @return The InstructionHandle this InstructionContext is wrapped around.
    91  	 */
    92  	InstructionHandle getInstruction();
    93
    94  	/***
    95  	 * Returns the usual control flow successors.
    96  	 * @see #getExceptionHandlers()
    97  	 */
    98  	InstructionContext[] getSuccessors();
    99
    100 	/***
    101 	 * Returns the exception handlers that protect this instruction.
    102 	 * They are special control flow successors.
    103 	 */
    104 	ExceptionHandler[] getExceptionHandlers();
    105 }