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

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import java.io.*;

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

/**

 * Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions.

 *

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

 * @see LOOKUPSWITCH

 * @see TABLESWITCH

 * @see InstructionList

 */

public abstract class Select extends BranchInstruction

  implements VariableLengthInstruction, StackProducer

{

  protected int[]               match;        // matches, i.e., case 1: ...

  protected int[]               indices;      // target offsets

  protected InstructionHandle[] targets;      // target objects in instruction list

  protected int                 fixed_length; // fixed length defined by subclasses

  protected int                 match_length; // number of cases

  protected int                 padding = 0;  // number of pad bytes for alignment

  /**

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

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

   */

  Select() {}

  /**

   * (Match, target) pairs for switch.

   * `Match' and `targets' must have the same length of course.

   *

   * @param match array of matching values

   * @param targets instruction targets

   * @param target default instruction target

   */

  Select(short opcode, int[] match, InstructionHandle[] targets,

         InstructionHandle target) {

    super(opcode, target);

    this.targets = targets;

    for(int i=0; i < targets.length; i++) {

      BranchInstruction.notifyTargetChanged(targets[i], this);

    }

    this.match = match;

    if((match_length = match.length) != targets.length)

      throw new ClassGenException("Match and target array have not the same length");

    indices = new int[match_length];

  }

  /**

   * Since this is a variable length instruction, it may shift the following

   * instructions which then need to update their position.

   *

   * Called by InstructionList.setPositions when setting the position for every

   * instruction. In the presence of variable length instructions `setPositions'

   * performs multiple passes over the instruction list to calculate the

   * correct (byte) positions and offsets by calling this function.

   *

   * @param offset additional offset caused by preceding (variable length) instructions

   * @param max_offset the maximum offset that may be caused by these instructions

   * @return additional offset caused by possible change of this instruction's length

   */

  @Override

  protected int updatePosition(int offset, int max_offset) {

    position += offset; // Additional offset caused by preceding SWITCHs, GOTOs, etc.

    short old_length = length;

    /* Alignment on 4-byte-boundary, + 1, because of tag byte.

     */

    padding = (4 - ((position + 1) % 4)) % 4;

    length  = (short)(fixed_length + padding); // Update length

    return length - old_length;

  }

  /**

   * Dump instruction as byte code to stream out.

   * @param out Output stream

   */

  @Override

  public void dump(DataOutputStream out) throws IOException {

    out.writeByte(opcode);

    for(int i=0; i < padding; i++) // Padding bytes

      out.writeByte(0);

    index = getTargetOffset();     // Write default target offset

    out.writeInt(index);

  }

  /**

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

   */

  @Override

  protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException

  {

    padding = (4 - (bytes.getIndex() % 4)) % 4; // Compute number of pad bytes

    for(int i=0; i < padding; i++) {

      bytes.readByte();

    }

    // Default branch target common for both cases (TABLESWITCH, LOOKUPSWITCH)

    index = bytes.readInt();

  }

  /**

   * @return mnemonic for instruction

   */

  @Override

  public String toString(boolean verbose) {

    final StringBuilder buf = new StringBuilder(super.toString(verbose));

    if(verbose) {

      for(int i=0; i < match_length; i++) {

        String s = "null";

        if(targets[i] != null)

          s = targets[i].getInstruction().toString();

          buf.append("(").append(match[i]).append(", ")

             .append(s).append(" = {").append(indices[i]).append("})");

      }

    }

    else

      buf.append(" ...");

    return buf.toString();

  }

  /**

   * Set branch target for `i'th case

   */

  public final void setTarget(int i, InstructionHandle target) {

    notifyTargetChanging(targets[i], this);

    targets[i] = target;

    notifyTargetChanged(targets[i], this);

  }

  /**

   * @param old_ih old target

   * @param new_ih new target

   */

  @Override

  public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {

    boolean targeted = false;

    if(target == old_ih) {

      targeted = true;

      setTarget(new_ih);

    }

    for(int i=0; i < targets.length; i++) {

      if(targets[i] == old_ih) {

        targeted = true;

        setTarget(i, new_ih);

      }

    }

    if(!targeted)

      throw new ClassGenException("Not targeting " + old_ih);

  }

  /**

   * @return true, if ih is target of this instruction

   */

  @Override

  public boolean containsTarget(InstructionHandle ih) {

    if(target == ih)

      return true;

    for(int i=0; i < targets.length; i++)

      if(targets[i] == ih)

        return true;

    return false;

  }

  /**

   * Inform targets that they're not targeted anymore.

   */

  @Override

  void dispose() {

    super.dispose();

    for(int i=0; i < targets.length; i++)

      targets[i].removeTargeter(this);

  }

  /**

   * @return array of match indices

   */

  public int[] getMatchs() { return match; }

  /**

   * @return array of match target offsets

   */

  public int[] getIndices() { return indices; }

  /**

   * @return array of match targets

   */

  public InstructionHandle[] getTargets() { return targets; }

}