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package com.sun.jdo.api.persistence.enhancer.classfile;

import java.io.PrintStream;

/**
 * Special instruction form for the opc_lookupswitch instruction
 */

public class InsnLookupSwitch extends Insn {
  /* The target for the default case */
  private InsnTarget defaultOp;

  /* The int constants against which to perform the lookup */
  private int[] matchesOp;

  /* The branch targets for the cases corresponding to the entries in
   * the matchesOp array */
  private InsnTarget[] targetsOp;

  /* public accessors */

  public int nStackArgs() {
    return 1;
  }

  public int nStackResults() {
    return 0;
  }

  /**
   * What are the types of the stack operands ?
   */
  public String argTypes() {
      return "I";//NOI18N
  }

  /**
   * What are the types of the stack results?
   */
  public String resultTypes() {
      return "";//NOI18N
  }

  public boolean branches() {
    return true;
  }

  /**
   * Mark possible branch targets
   */
  public void markTargets() {
    defaultOp.setBranchTarget();
    for (int i=0; i<targetsOp.length; i++)
      targetsOp[i].setBranchTarget();
  }


  /**
   * Return the defaultTarget for the switch
   */
  public InsnTarget defaultTarget() {
    return defaultOp;
  }

  /**
   * Return the case values of the switch.
   */
  public int[] switchCases() {
    return matchesOp;
  }

  /**
   * Return the targets for the cases of the switch.
   */
  public InsnTarget[] switchTargets() {
    return targetsOp;
  }

  /**
   * Constructor for opc_lookupswitch
   */
  public InsnLookupSwitch (InsnTarget defaultOp, int[] matchesOp,
			   InsnTarget[] targetsOp) {
    this(defaultOp, matchesOp, targetsOp, NO_OFFSET);
  }


  /* package local methods */

  InsnLookupSwitch (InsnTarget defaultOp, int[] matchesOp,
		    InsnTarget[] targetsOp, int offset) {
    super(opc_lookupswitch, offset);

    this.defaultOp = defaultOp; 
    this.matchesOp = matchesOp;
    this.targetsOp = targetsOp;

    if (defaultOp == null || targetsOp == null || matchesOp == null ||
	targetsOp.length != matchesOp.length)
        throw new InsnError ("attempt to create an opc_lookupswitch" +//NOI18N
                             " with invalid operands");//NOI18N
  }

  void print (PrintStream out, int indent) {
    ClassPrint.spaces(out, indent);
    out.println(offset() + "  opc_lookupswitch  ");//NOI18N
    for (int i=0; i<matchesOp.length; i++) {
      ClassPrint.spaces(out, indent+2);
      out.println(matchesOp[i] + " -> " + targetsOp[i].offset());//NOI18N
    }
    ClassPrint.spaces(out, indent+2);
    out.println("default -> " + defaultOp.offset());//NOI18N
  }

  int store(byte[] buf, int index) {
    buf[index++] = (byte) opcode();
    index = (index + 3) & ~3;
    index = storeInt(buf, index, defaultOp.offset() - offset());
    index = storeInt(buf, index, targetsOp.length);
    for (int i=0; i<targetsOp.length; i++) {
      index = storeInt(buf, index, matchesOp[i]);
      index = storeInt(buf, index, targetsOp[i].offset() - offset());
    }
    return index;
  }

  int size() {
    /* account for the instruction, 0-3 bytes of pad, 2 ints */
    int basic = ((offset() + 4) & ~3) - offset() + 8;
    /* Add 8*number of offsets */
    return basic + targetsOp.length*8;
  }

  static InsnLookupSwitch read (InsnReadEnv insnEnv, int myPC) {
    /* eat up any padding */
    int thisPC = myPC +1;
    for (int pads = ((thisPC + 3) & ~3) - thisPC; pads > 0; pads--)
      insnEnv.getByte();
    InsnTarget defaultTarget = insnEnv.getTarget(insnEnv.getInt() + myPC);
    int npairs = insnEnv.getInt();
    int matches[] = new int[npairs];
    InsnTarget[] offsets = new InsnTarget[npairs];
    for (int i=0; i<npairs; i++) {
      matches[i] = insnEnv.getInt();
      offsets[i] = insnEnv.getTarget(insnEnv.getInt() + myPC);
    }
    return new InsnLookupSwitch(defaultTarget, matches, offsets, myPC);
  }
}