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    1   package org.apache.bcel.generic;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache BCEL" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    "Apache BCEL", nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56  import java.io.*;
    57  import org.apache.bcel.util.ByteSequence;
    58  import org.apache.bcel.classfile.Utility;
    59  import org.apache.bcel.Constants;
    60
    61  /***
    62   * Abstract super class for instructions dealing with local variables.
    63   *
    64   * @version $Id: LocalVariableInstruction.java,v 1.2 2002/08/07 18:01:32 mdahm Exp $
    65   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
    66   */
    67  public abstract class LocalVariableInstruction extends Instruction
    68    implements TypedInstruction, IndexedInstruction {
    69    protected int     n         = -1; // index of referenced variable
    70    private short     c_tag     = -1; // compact version, such as ILOAD_0
    71    private short     canon_tag = -1; // canonical tag such as ILOAD
    72
    73    private final boolean wide() { return n > Constants.MAX_BYTE; }
    74
    75    /***
    76     * Empty constructor needed for the Class.newInstance() statement in
    77     * Instruction.readInstruction(). Not to be used otherwise.
    78     * tag and length are defined in readInstruction and initFromFile, respectively.
    79     */
    80    LocalVariableInstruction(short canon_tag, short c_tag) {
    81      super();
    82      this.canon_tag = canon_tag;
    83      this.c_tag     = c_tag;
    84    }
    85
    86    /***
    87     * Empty constructor needed for the Class.newInstance() statement in
    88     * Instruction.readInstruction(). Also used by IINC()!
    89     */
    90    LocalVariableInstruction() {
    91    }
    92
    93    /***
    94     * @param opcode Instruction opcode
    95     * @param c_tag Instruction number for compact version, ALOAD_0, e.g.
    96     * @param n local variable index (unsigned short)
    97     */
    98    protected LocalVariableInstruction(short opcode, short c_tag, int n) {
    99      super(opcode, (short)2);
    100
    101     this.c_tag = c_tag;
    102     canon_tag  = opcode;
    103
    104     setIndex(n);
    105   }
    106
    107   /***
    108    * Dump instruction as byte code to stream out.
    109    * @param out Output stream
    110    */
    111   public void dump(DataOutputStream out) throws IOException {
    112     if(wide()) // Need WIDE prefix ?
    113       out.writeByte(Constants.WIDE);
    114
    115     out.writeByte(opcode);
    116
    117     if(length > 1) { // Otherwise ILOAD_n, instruction, e.g.
    118       if(wide())
    119 	out.writeShort(n);
    120       else
    121 	out.writeByte(n);
    122     }
    123   }
    124
    125   /***
    126    * Long output format:
    127    *
    128    * <name of opcode> "["<opcode number>"]"
    129    * "("<length of instruction>")" "<"< local variable index>">"
    130    *
    131    * @param verbose long/short format switch
    132    * @return mnemonic for instruction
    133    */
    134   public String toString(boolean verbose) {
    135     if(((opcode >= Constants.ILOAD_0) &&
    136 	(opcode <= Constants.ALOAD_3)) ||
    137        ((opcode >= Constants.ISTORE_0) &&
    138 	(opcode <= Constants.ASTORE_3)))
    139       return super.toString(verbose);
    140     else
    141       return super.toString(verbose) + " " + n;
    142   }
    143
    144   /***
    145    * Read needed data (e.g. index) from file.
    146    * PRE: (ILOAD <= tag <= ALOAD_3) || (ISTORE <= tag <= ASTORE_3)
    147    */
    148   protected void initFromFile(ByteSequence bytes, boolean wide)
    149     throws IOException
    150   {
    151     if(wide) {
    152       n         = bytes.readUnsignedShort();
    153       length    = 4;
    154     } else if(((opcode >= Constants.ILOAD) &&
    155 	       (opcode <= Constants.ALOAD)) ||
    156 	      ((opcode >= Constants.ISTORE) &&
    157 	       (opcode <= Constants.ASTORE))) {
    158       n      = bytes.readUnsignedByte();
    159       length = 2;
    160     } else if(opcode <= Constants.ALOAD_3) { // compact load instruction such as ILOAD_2
    161       n      = (opcode - Constants.ILOAD_0) % 4;
    162       length = 1;
    163     } else { // Assert ISTORE_0 <= tag <= ASTORE_3
    164       n      = (opcode - Constants.ISTORE_0) % 4;
    165       length = 1;
    166     }
    167  }
    168
    169   /***
    170    * @return local variable index  referred by this instruction.
    171    */
    172   public final int getIndex() { return n; }
    173
    174   /***
    175    * Set the local variable index
    176    */
    177   public void setIndex(int n) {
    178     if((n < 0) || (n > Constants.MAX_SHORT))
    179       throw new ClassGenException("Illegal value: " + n);
    180
    181     this.n = n;
    182
    183     if(n >= 0 && n <= 3) { // Use more compact instruction xLOAD_n
    184       opcode = (short)(c_tag + n);
    185       length = 1;
    186     } else {
    187       opcode = canon_tag;
    188
    189       if(wide()) // Need WIDE prefix ?
    190 	length = 4;
    191       else
    192 	length = 2;
    193     }
    194   }
    195
    196   /*** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
    197    */
    198   public short getCanonicalTag() {
    199     return canon_tag;
    200   }
    201
    202   /***
    203    * Returns the type associated with the instruction -
    204    * in case of ALOAD or ASTORE Type.OBJECT is returned.
    205    * This is just a bit incorrect, because ALOAD and ASTORE
    206    * may work on every ReferenceType (including Type.NULL) and
    207    * ASTORE may even work on a ReturnaddressType .
    208    * @return type associated with the instruction
    209    */
    210   public Type getType(ConstantPoolGen cp) {
    211     switch(canon_tag) {
    212     case Constants.ILOAD: case Constants.ISTORE:
    213       return Type.INT;
    214     case Constants.LLOAD: case Constants.LSTORE:
    215       return Type.LONG;
    216     case Constants.DLOAD: case Constants.DSTORE:
    217       return Type.DOUBLE;
    218     case Constants.FLOAD: case Constants.FSTORE:
    219       return Type.FLOAT;
    220     case Constants.ALOAD: case Constants.ASTORE:
    221       return Type.OBJECT;
    222
    223     default: throw new ClassGenException("Oops: unknown case in switch" + canon_tag);
    224     }
    225   }
    226 }

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