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RET.java

package de.fub.bytecode.generic;

import java.io.*;
import de.fub.bytecode.util.ByteSequence;

/** 
 * RET - Return from subroutine
 *
 * <PRE>Stack: ..., -&gt; ..., address</PRE>
 *
 * @version $Id: RET.java,v 1.1.1.1 2002/01/24 03:44:05 pserver Exp $
 * @author  <A HREF="http://www.inf.fu-berlin.de/~dahm">M. Dahm</A>
 */
public class RET extends Instruction {
  private boolean wide;
  private int     index; // index to local variable containg the return address

  /**
   * Empty constructor needed for the Class.newInstance() statement in
   * Instruction.readInstruction(). Not to be used otherwise.
   */
  RET() {}  
  public RET(int index) {
    super(RET, (short)2);
    setIndex(index);   // May set wide as side effect
  }  
  /**
   * Dump instruction as byte code to stream out.
   * @param out Output stream
   */
  public void dump(DataOutputStream out) throws IOException {
    if(wide)
      out.writeByte(WIDE);

    out.writeByte(tag);

    if(wide)
      out.writeShort(index);
    else
      out.writeByte(index);
  }  
  /**
   * @return index of local variable containg the return address
   */
  public final int getIndex() { return index; }  
  /**
   * Read needed data (e.g. index) from file.
   */
  protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException
  {
    this.wide = wide;

    if(wide) {
      index  = bytes.readUnsignedShort();
      length = 4;
    }
    else {
      index = bytes.readUnsignedByte();
      length = 2;
    }
  }  
  /**
   * Set index of local variable containg the return address
   */
  public final void setIndex(int n) { 
    if(n < 0)
      throw new ClassGenException("Negative index value: " + n);

    index = n;
    setWide();
  }  
  private final void setWide() {
    if(wide = index > MAX_BYTE)
      length = 4; // Including the wide byte  
    else
      length = 2;
  }  
  /**
   * @return mnemonic for instruction
   */
  public String toString(boolean verbose) {
    return super.toString(verbose) + " " + index;
  }  
}

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