/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================

 * The Apache Software License, Version 1.1

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 * reserved.

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 * Redistribution and use in source and binary forms, with or without

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 *        Apache Software Foundation (http://www.apache.org/)."

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 *    if and wherever such third-party acknowledgments normally appear.

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 *

 * This software consists of voluntary contributions made by many

 * individuals on behalf of the Apache Software Foundation.  For more

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 */

import java.io.*;

import com.sun.org.apache.bcel.internal.util.ByteSequence;

import com.sun.org.apache.bcel.internal.classfile.Utility;

import com.sun.org.apache.bcel.internal.Constants;

/**

 * Abstract super class for instructions dealing with local variables.

 *

 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>

 */

public abstract class LocalVariableInstruction extends Instruction

  implements TypedInstruction, IndexedInstruction {

  protected int     n         = -1; // index of referenced variable

  private short     c_tag     = -1; // compact version, such as ILOAD_0

  private short     canon_tag = -1; // canonical tag such as ILOAD

  private final boolean wide() { return n > Constants.MAX_BYTE; }

  /**

   * Empty constructor needed for the Class.newInstance() statement in

   * Instruction.readInstruction(). Not to be used otherwise.

   * tag and length are defined in readInstruction and initFromFile, respectively.

   */

  LocalVariableInstruction(short canon_tag, short c_tag) {

    super();

    this.canon_tag = canon_tag;

    this.c_tag     = c_tag;

  }

  /**

   * Empty constructor needed for the Class.newInstance() statement in

   * Instruction.readInstruction(). Also used by IINC()!

   */

  LocalVariableInstruction() {

  }

  /**

   * @param opcode Instruction opcode

   * @param c_tag Instruction number for compact version, ALOAD_0, e.g.

   * @param n local variable index (unsigned short)

   */

  protected LocalVariableInstruction(short opcode, short c_tag, int n) {

    super(opcode, (short)2);

    this.c_tag = c_tag;

    canon_tag  = opcode;

    setIndex(n);

  }

  /**

   * Dump instruction as byte code to stream out.

   * @param out Output stream

   */

  public void dump(DataOutputStream out) throws IOException {

    if(wide()) // Need WIDE prefix ?

      out.writeByte(Constants.WIDE);

    out.writeByte(opcode);

    if(length > 1) { // Otherwise ILOAD_n, instruction, e.g.

      if(wide())

        out.writeShort(n);

      else

        out.writeByte(n);

    }

  }

  /**

   * Long output format:

   *

   * <name of opcode> "["<opcode number>"]"

   * "("<length of instruction>")" "<"< local variable index>">"

   *

   * @param verbose long/short format switch

   * @return mnemonic for instruction

   */

  public String toString(boolean verbose) {

    if(((opcode >= Constants.ILOAD_0) &&

        (opcode <= Constants.ALOAD_3)) ||

       ((opcode >= Constants.ISTORE_0) &&

        (opcode <= Constants.ASTORE_3)))

      return super.toString(verbose);

    else

      return super.toString(verbose) + " " + n;

  }

  /**

   * Read needed data (e.g. index) from file.

   * PRE: (ILOAD <= tag <= ALOAD_3) || (ISTORE <= tag <= ASTORE_3)

   */

  protected void initFromFile(ByteSequence bytes, boolean wide)

    throws IOException

  {

    if(wide) {

      n         = bytes.readUnsignedShort();

      length    = 4;

    } else if(((opcode >= Constants.ILOAD) &&

               (opcode <= Constants.ALOAD)) ||

              ((opcode >= Constants.ISTORE) &&

               (opcode <= Constants.ASTORE))) {

      n      = bytes.readUnsignedByte();

      length = 2;

    } else if(opcode <= Constants.ALOAD_3) { // compact load instruction such as ILOAD_2

      n      = (opcode - Constants.ILOAD_0) % 4;

      length = 1;

    } else { // Assert ISTORE_0 <= tag <= ASTORE_3

      n      = (opcode - Constants.ISTORE_0) % 4;

      length = 1;

    }

 }

  /**

   * @return local variable index  referred by this instruction.

   */

  public final int getIndex() { return n; }

  /**

   * Set the local variable index

   */

  public void setIndex(int n) {

    if((n < 0) || (n > Constants.MAX_SHORT))

      throw new ClassGenException("Illegal value: " + n);

    this.n = n;

    if(n >= 0 && n <= 3) { // Use more compact instruction xLOAD_n

      opcode = (short)(c_tag + n);

      length = 1;

    } else {

      opcode = canon_tag;

      if(wide()) // Need WIDE prefix ?

        length = 4;

      else

        length = 2;

    }

  }

  /** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0

   */

  public short getCanonicalTag() {

    return canon_tag;

  }

  /**

   * Returns the type associated with the instruction -

   * in case of ALOAD or ASTORE Type.OBJECT is returned.

   * This is just a bit incorrect, because ALOAD and ASTORE

   * may work on every ReferenceType (including Type.NULL) and

   * ASTORE may even work on a ReturnaddressType .

   * @return type associated with the instruction

   */

  public Type getType(ConstantPoolGen cp) {

    switch(canon_tag) {

    case Constants.ILOAD: case Constants.ISTORE:

      return Type.INT;

    case Constants.LLOAD: case Constants.LSTORE:

      return Type.LONG;

    case Constants.DLOAD: case Constants.DSTORE:

      return Type.DOUBLE;

    case Constants.FLOAD: case Constants.FSTORE:

      return Type.FLOAT;

    case Constants.ALOAD: case Constants.ASTORE:

      return Type.OBJECT;

    default: throw new ClassGenException("Oops: unknown case in switch" + canon_tag);

    }

  }

}