LocalVariableGen xref

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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.generic;
    18
    19  import org.apache.bcel.Constants;
    20  import org.apache.bcel.classfile.LocalVariable;
    21
    22  /***
    23   * This class represents a local variable within a method. It contains its
    24   * scope, name and type. The generated LocalVariable object can be obtained
    25   * with getLocalVariable which needs the instruction list and the constant
    26   * pool as parameters.
    27   *
    28   * @version $Id: LocalVariableGen.java 386056 2006-03-15 11:31:56Z tcurdt $
    29   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
    30   * @see     LocalVariable
    31   * @see     MethodGen
    32   */
    33  public class LocalVariableGen implements InstructionTargeter, NamedAndTyped, Cloneable,
    34          java.io.Serializable {
    35
    36      private int index;
    37      private String name;
    38      private Type type;
    39      private InstructionHandle start, end;
    40
    41
    42      /***
    43       * Generate a local variable that with index `index'. Note that double and long
    44       * variables need two indexs. Index indices have to be provided by the user.
    45       *
    46       * @param index index of local variable
    47       * @param name its name
    48       * @param type its type
    49       * @param start from where the instruction is valid (null means from the start)
    50       * @param end until where the instruction is valid (null means to the end)
    51       */
    52      public LocalVariableGen(int index, String name, Type type, InstructionHandle start,
    53              InstructionHandle end) {
    54          if ((index < 0) || (index > Constants.MAX_SHORT)) {
    55              throw new ClassGenException("Invalid index index: " + index);
    56          }
    57          this.name = name;
    58          this.type = type;
    59          this.index = index;
    60          setStart(start);
    61          setEnd(end);
    62      }
    63
    64
    65      /***
    66       * Get LocalVariable object.
    67       *
    68       * This relies on that the instruction list has already been dumped to byte code or
    69       * or that the `setPositions' methods has been called for the instruction list.
    70       *
    71       * Note that for local variables whose scope end at the last
    72       * instruction of the method's code, the JVM specification is ambiguous:
    73       * both a start_pc+length ending at the last instruction and
    74       * start_pc+length ending at first index beyond the end of the code are
    75       * valid.
    76       *
    77       * @param cp constant pool
    78       */
    79      public LocalVariable getLocalVariable( ConstantPoolGen cp ) {
    80          int start_pc = start.getPosition();
    81          int length = end.getPosition() - start_pc;
    82          if (length > 0) {
    83              length += end.getInstruction().getLength();
    84          }
    85          int name_index = cp.addUtf8(name);
    86          int signature_index = cp.addUtf8(type.getSignature());
    87          return new LocalVariable(start_pc, length, name_index, signature_index, index, cp
    88                  .getConstantPool());
    89      }
    90
    91
    92      public void setIndex( int index ) {
    93          this.index = index;
    94      }
    95
    96
    97      public int getIndex() {
    98          return index;
    99      }
    100
    101
    102     public void setName( String name ) {
    103         this.name = name;
    104     }
    105
    106
    107     public String getName() {
    108         return name;
    109     }
    110
    111
    112     public void setType( Type type ) {
    113         this.type = type;
    114     }
    115
    116
    117     public Type getType() {
    118         return type;
    119     }
    120
    121
    122     public InstructionHandle getStart() {
    123         return start;
    124     }
    125
    126
    127     public InstructionHandle getEnd() {
    128         return end;
    129     }
    130
    131
    132     public void setStart( InstructionHandle start ) {
    133         BranchInstruction.notifyTarget(this.start, start, this);
    134         this.start = start;
    135     }
    136
    137
    138     public void setEnd( InstructionHandle end ) {
    139         BranchInstruction.notifyTarget(this.end, end, this);
    140         this.end = end;
    141     }
    142
    143
    144     /***
    145      * @param old_ih old target, either start or end
    146      * @param new_ih new target
    147      */
    148     public void updateTarget( InstructionHandle old_ih, InstructionHandle new_ih ) {
    149         boolean targeted = false;
    150         if (start == old_ih) {
    151             targeted = true;
    152             setStart(new_ih);
    153         }
    154         if (end == old_ih) {
    155             targeted = true;
    156             setEnd(new_ih);
    157         }
    158         if (!targeted) {
    159             throw new ClassGenException("Not targeting " + old_ih + ", but {" + start + ", " + end
    160                     + "}");
    161         }
    162     }
    163
    164
    165     /***
    166      * @return true, if ih is target of this variable
    167      */
    168     public boolean containsTarget( InstructionHandle ih ) {
    169         return (start == ih) || (end == ih);
    170     }
    171
    172
    173     /*** @return a hash code value for the object.
    174      */
    175     public int hashCode() {
    176         //If the user changes the name or type, problems with the targeter hashmap will occur
    177         int hc = index ^ name.hashCode() ^ type.hashCode();
    178         return hc;
    179     }
    180
    181
    182     /***
    183      * We consider to local variables to be equal, if the use the same index and
    184      * are valid in the same range.
    185      */
    186     public boolean equals( Object o ) {
    187         if (!(o instanceof LocalVariableGen)) {
    188             return false;
    189         }
    190         LocalVariableGen l = (LocalVariableGen) o;
    191         return (l.index == index) && (l.start == start) && (l.end == end);
    192     }
    193
    194
    195     public String toString() {
    196         return "LocalVariableGen(" + name + ", " + type + ", " + start + ", " + end + ")";
    197     }
    198
    199
    200     public Object clone() {
    201         try {
    202             return super.clone();
    203         } catch (CloneNotSupportedException e) {
    204             System.err.println(e);
    205             return null;
    206         }
    207     }
    208 }