LocalVariableTable 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.classfile;
    18
    19  import java.io.DataInputStream;
    20  import java.io.DataOutputStream;
    21  import java.io.IOException;
    22  import org.apache.bcel.Constants;
    23
    24  /***
    25   * This class represents colection of local variables in a
    26   * method. This attribute is contained in the <em>Code</em> attribute.
    27   *
    28   * @version $Id: LocalVariableTable.java 386056 2006-03-15 11:31:56Z tcurdt $
    29   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
    30   * @see     Code
    31   * @see LocalVariable
    32   */
    33  public class LocalVariableTable extends Attribute {
    34
    35      private int local_variable_table_length; // Table of local
    36      private LocalVariable[] local_variable_table; // variables
    37
    38
    39      /***
    40       * Initialize from another object. Note that both objects use the same
    41       * references (shallow copy). Use copy() for a physical copy.
    42       */
    43      public LocalVariableTable(LocalVariableTable c) {
    44          this(c.getNameIndex(), c.getLength(), c.getLocalVariableTable(), c.getConstantPool());
    45      }
    46
    47
    48      /***
    49       * @param name_index Index in constant pool to `LocalVariableTable'
    50       * @param length Content length in bytes
    51       * @param local_variable_table Table of local variables
    52       * @param constant_pool Array of constants
    53       */
    54      public LocalVariableTable(int name_index, int length, LocalVariable[] local_variable_table,
    55              ConstantPool constant_pool) {
    56          super(Constants.ATTR_LOCAL_VARIABLE_TABLE, name_index, length, constant_pool);
    57          setLocalVariableTable(local_variable_table);
    58      }
    59
    60
    61      /***
    62       * Construct object from file stream.
    63       * @param name_index Index in constant pool
    64       * @param length Content length in bytes
    65       * @param file Input stream
    66       * @param constant_pool Array of constants
    67       * @throws IOException
    68       */
    69      LocalVariableTable(int name_index, int length, DataInputStream file, ConstantPool constant_pool)
    70              throws IOException {
    71          this(name_index, length, (LocalVariable[]) null, constant_pool);
    72          local_variable_table_length = (file.readUnsignedShort());
    73          local_variable_table = new LocalVariable[local_variable_table_length];
    74          for (int i = 0; i < local_variable_table_length; i++) {
    75              local_variable_table[i] = new LocalVariable(file, constant_pool);
    76          }
    77      }
    78
    79
    80      /***
    81       * Called by objects that are traversing the nodes of the tree implicitely
    82       * defined by the contents of a Java class. I.e., the hierarchy of methods,
    83       * fields, attributes, etc. spawns a tree of objects.
    84       *
    85       * @param v Visitor object
    86       */
    87      public void accept( Visitor v ) {
    88          v.visitLocalVariableTable(this);
    89      }
    90
    91
    92      /***
    93       * Dump local variable table attribute to file stream in binary format.
    94       *
    95       * @param file Output file stream
    96       * @throws IOException
    97       */
    98      public final void dump( DataOutputStream file ) throws IOException {
    99          super.dump(file);
    100         file.writeShort(local_variable_table_length);
    101         for (int i = 0; i < local_variable_table_length; i++) {
    102             local_variable_table[i].dump(file);
    103         }
    104     }
    105
    106
    107     /***
    108      * @return Array of local variables of method.
    109      */
    110     public final LocalVariable[] getLocalVariableTable() {
    111         return local_variable_table;
    112     }
    113
    114
    115     /***
    116      * @return first matching variable using index
    117      *
    118      * @param index the variable slot
    119      *
    120      * @return the first LocalVariable that matches the slot or null if not found
    121      *
    122      * @deprecated since 5.2 because multiple variables can share the
    123      *             same slot, use getLocalVariable(int index, int pc) instead.
    124      */
    125     public final LocalVariable getLocalVariable( int index ) {
    126         for (int i = 0; i < local_variable_table_length; i++) {
    127             if (local_variable_table[i].getIndex() == index) {
    128                 return local_variable_table[i];
    129             }
    130         }
    131         return null;
    132     }
    133
    134
    135     /***
    136      * @return matching variable using index when variable is used at supplied pc
    137      *
    138      * @param index the variable slot
    139      * @param pc the current pc that this variable is alive
    140      *
    141      * @return the LocalVariable that matches or null if not found
    142      */
    143     public final LocalVariable getLocalVariable( int index, int pc ) {
    144         for (int i = 0; i < local_variable_table_length; i++) {
    145             if (local_variable_table[i].getIndex() == index) {
    146                 int start_pc = local_variable_table[i].getStartPC();
    147                 int end_pc = start_pc + local_variable_table[i].getLength();
    148                 if ((pc >= start_pc) && (pc < end_pc)) {
    149                     return local_variable_table[i];
    150                 }
    151             }
    152         }
    153         return null;
    154     }
    155
    156
    157     public final void setLocalVariableTable( LocalVariable[] local_variable_table ) {
    158         this.local_variable_table = local_variable_table;
    159         local_variable_table_length = (local_variable_table == null)
    160                 ? 0
    161                 : local_variable_table.length;
    162     }
    163
    164
    165     /***
    166      * @return String representation.
    167      */
    168     public final String toString() {
    169         StringBuffer buf = new StringBuffer("");
    170         for (int i = 0; i < local_variable_table_length; i++) {
    171             buf.append(local_variable_table[i].toString());
    172             if (i < local_variable_table_length - 1) {
    173                 buf.append('\n');
    174             }
    175         }
    176         return buf.toString();
    177     }
    178
    179
    180     /***
    181      * @return deep copy of this attribute
    182      */
    183     public Attribute copy( ConstantPool _constant_pool ) {
    184         LocalVariableTable c = (LocalVariableTable) clone();
    185         c.local_variable_table = new LocalVariable[local_variable_table_length];
    186         for (int i = 0; i < local_variable_table_length; i++) {
    187             c.local_variable_table[i] = local_variable_table[i].copy();
    188         }
    189         c.constant_pool = _constant_pool;
    190         return c;
    191     }
    192
    193
    194     public final int getTableLength() {
    195         return local_variable_table_length;
    196     }
    197 }