Java tutorial
package org.aspectj.apache.bcel.classfile; /* ==================================================================== * The Apache Software License, Version 1.1 * * Copyright (c) 2001 The Apache Software Foundation. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. 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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. */ import java.io.ByteArrayInputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import org.aspectj.apache.bcel.Constants; /** * This class represents collection of local variables in a method. This attribute is contained in the <em>Code</em> attribute. * * @version $Id: LocalVariableTable.java,v 1.8 2009/09/15 19:40:12 aclement Exp $ * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> * @see Code * @see LocalVariable Updates: Andy 14Feb06 - Made unpacking of the data lazy, depending on someone actually asking for it. */ public class LocalVariableTable extends Attribute { // if 'isInPackedState' then this data needs unpacking private boolean isInPackedState = false; private byte[] data; private int localVariableTableLength; private LocalVariable[] localVariableTable; /** * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a physical * copy. */ public LocalVariableTable(LocalVariableTable c) { this(c.getNameIndex(), c.getLength(), c.getLocalVariableTable(), c.getConstantPool()); } /** * @param name_index Index in constant pool to `LocalVariableTable' * @param length Content length in bytes * @param local_variable_table Table of local variables * @param constant_pool Array of constants */ public LocalVariableTable(int name_index, int length, LocalVariable[] local_variable_table, ConstantPool constant_pool) { super(Constants.ATTR_LOCAL_VARIABLE_TABLE, name_index, length, constant_pool); setLocalVariableTable(local_variable_table); } /** * Construct object from file stream. * * @param name_index Index in constant pool * @param length Content length in bytes * @param file Input stream * @param constant_pool Array of constants * @throws IOException */ LocalVariableTable(int name_index, int length, DataInputStream file, ConstantPool constant_pool) throws IOException { super(Constants.ATTR_LOCAL_VARIABLE_TABLE, name_index, length, constant_pool); data = new byte[length]; file.readFully(data); isInPackedState = true; // assert(bytesRead==length) } /** * Called by objects that are traversing the nodes of the tree implicitely defined by the contents of a Java class. I.e., the * hierarchy of methods, fields, attributes, etc. spawns a tree of objects. * * @param v Visitor object */ @Override public void accept(ClassVisitor v) { unpack(); v.visitLocalVariableTable(this); } /** * Dump local variable table attribute to file stream in binary format. * * @param file Output file stream * @throws IOException */ @Override public final void dump(DataOutputStream file) throws IOException { super.dump(file); if (isInPackedState) { file.write(data); } else { file.writeShort(localVariableTableLength); for (int i = 0; i < localVariableTableLength; i++) localVariableTable[i].dump(file); } } /** * @return Array of local variables of method. */ public final LocalVariable[] getLocalVariableTable() { unpack(); return localVariableTable; } /** * @return first matching variable using index */ public final LocalVariable getLocalVariable(int index) { unpack(); for (int i = 0; i < localVariableTableLength; i++) { if (localVariableTable[i] != null && localVariableTable[i].getIndex() == index) { return localVariableTable[i]; } } return null; } public final void setLocalVariableTable(LocalVariable[] local_variable_table) { data = null; isInPackedState = false; this.localVariableTable = local_variable_table; localVariableTableLength = (local_variable_table == null) ? 0 : local_variable_table.length; } /** * @return String representation. */ @Override public final String toString() { StringBuffer buf = new StringBuffer(""); unpack(); for (int i = 0; i < localVariableTableLength; i++) { buf.append(localVariableTable[i].toString()); if (i < localVariableTableLength - 1) buf.append('\n'); } return buf.toString(); } /** * @return deep copy of this attribute */ // public Attribute copy(ConstantPool constant_pool) { // unpack(); // LocalVariableTable c = (LocalVariableTable) clone(); // // c.localVariableTable = new LocalVariable[localVariableTableLength]; // for (int i = 0; i < localVariableTableLength; i++) // c.localVariableTable[i] = localVariableTable[i].copy(); // // c.cpool = constant_pool; // return c; // } public final int getTableLength() { unpack(); return localVariableTableLength; } // --- // Unpacks the byte array into the table private void unpack() { if (!isInPackedState) return; try { ByteArrayInputStream bs = new ByteArrayInputStream(data); DataInputStream dis = new DataInputStream(bs); localVariableTableLength = (dis.readUnsignedShort()); localVariableTable = new LocalVariable[localVariableTableLength]; for (int i = 0; i < localVariableTableLength; i++) localVariableTable[i] = new LocalVariable(dis, cpool); dis.close(); data = null; // throw it away now } catch (IOException e) { throw new RuntimeException("Unpacking of LocalVariableTable attribute failed"); } isInPackedState = false; } }