cpinstruction.java

该开源工具主要用于class文件的操作

package org.apache.bcel.generic;

/* ====================================================================
 * 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. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.io.*;
import org.apache.bcel.util.ByteSequence;
import org.apache.bcel.Constants;
import org.apache.bcel.classfile.*;

/** 
 * Abstract super class for instructions that use an index into the 
 * constant pool such as LDC, INVOKEVIRTUAL, etc.
 *
 * @see ConstantPoolGen
 * @see LDC
 * @see INVOKEVIRTUAL
 *
 * @version $Id: CPInstruction.java,v 1.1.1.1 2001/10/29 20:00:07 jvanzyl Exp $
 * @author  <A HREF="mailto:[e-mail]">M. Dahm</A>
 */
public abstract class CPInstruction extends Instruction
  implements TypedInstruction, IndexedInstruction
{
  protected int index; // index to constant pool

  /**
   * Empty constructor needed for the Class.newInstance() statement in
   * Instruction.readInstruction(). Not to be used otherwise.
   */
  CPInstruction() {}

  /**
   * @param index to constant pool
   */
  protected CPInstruction(short opcode, int index) {
    super(opcode, (short)3);
    setIndex(index);
  }

  /**
   * Dump instruction as byte code to stream out.
   * @param out Output stream
   */
  public void dump(DataOutputStream out) throws IOException {
    out.writeByte(opcode);
    out.writeShort(index);
  }

  /**
   * Long output format:
   *
   * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]" 
   * "("&lt;length of instruction&gt;")" "&lt;"&lt; constant pool index&gt;"&gt;"
   *
   * @param verbose long/short format switch
   * @return mnemonic for instruction
   */
  public String toString(boolean verbose) {
    return super.toString(verbose) + " " + index;
  }

  /**
   * @return mnemonic for instruction with symbolic references resolved
   */
  public String toString(ConstantPool cp) {
    Constant c   = cp.getConstant(index);
    String   str = cp.constantToString(c);

    if(c instanceof ConstantClass)
      str = str.replace('.', '/');

    return org.apache.bcel.Constants.OPCODE_NAMES[opcode] + " " + str;
  }

  /**
   * Read needed data (i.e., index) from file.
   * @param bytes input stream
   * @param wide wide prefix?
   */
  protected void initFromFile(ByteSequence bytes, boolean wide)
       throws IOException
  {
    setIndex(bytes.readUnsignedShort());
    length = 3;
  }

  /**
   * @return index in constant pool referred by this instruction.
   */
  public final int getIndex() { return index; }

  /**
   * Set the index to constant pool.
   * @param index in  constant pool.
   */
  public void setIndex(int index) { 
    if(index < 0)
      throw new ClassGenException("Negative index value: " + index);

    this.index = index;
  }

  /** @return type related with this instruction.
   */
  public Type getType(ConstantPoolGen cpg) {
    ConstantPool cp   = cpg.getConstantPool();
    String       name = cp.getConstantString(index, org.apache.bcel.Constants.CONSTANT_Class);

    if(!name.startsWith("["))
      name = "L" + name + ";";

    return Type.getType(name);
  }
}