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

import java.io.*;

/**
 * Represents a local variable within a LocalVariableTable within
 * a CodeAttribute in a class file.
 */

public class LocalVariable {
  /* The pc at which the variable becomes effecive */
  private InsnTarget varStartPC; /* inclusive */

  /* The pc at which the variable becomes in-effecive */
  private InsnTarget varEndPC;   /* exclusive */

  /* The name of the variable */
  private ConstUtf8 varName;

  /* The type signature of the variable */
  private ConstUtf8 varSig;

  /* The slot to which the variable is assigned */
  private int varSlot;

  /* public accessors */

  /**
   * Constructor for a local variable
   */
  public LocalVariable(InsnTarget startPC, InsnTarget endPC,
                       ConstUtf8 name, ConstUtf8 sig, int slot) {
    varStartPC = startPC;
    varEndPC = endPC;
    varName = name;
    varSig = sig;
    varSlot = slot;
  }

  /* package local methods */

  static LocalVariable read(DataInputStream data, CodeEnv env)
    throws IOException {
    int startPC = data.readUnsignedShort();
    InsnTarget startPCTarget = env.getTarget(startPC);
    int length = data.readUnsignedShort();
    InsnTarget endPCTarget = env.getTarget(startPC+length);
    ConstUtf8 name = 
      (ConstUtf8) env.pool().constantAt(data.readUnsignedShort());
    ConstUtf8 sig = 
      (ConstUtf8) env.pool().constantAt(data.readUnsignedShort());
    int slot = data.readUnsignedShort();
    return new LocalVariable(startPCTarget, endPCTarget, name, sig, slot);
  }

  void write(DataOutputStream out) throws IOException {
    out.writeShort(varStartPC.offset());
    out.writeShort(varEndPC.offset() - varStartPC.offset());
    out.writeShort((varName == null) ? 0 : varName.getIndex());
    out.writeShort((varSig == null) ? 0 : varSig.getIndex());
    out.writeShort(varSlot);
  }

  public void print(PrintStream out, int indent) {
    ClassPrint.spaces(out, indent);
    out.print("'" + ((varName == null) ? "(null)" : varName.asString()) + "'");//NOI18N
    out.print(" sig = " + ((varSig == null) ? "(null)" : varSig.asString()));//NOI18N
    out.print(" start_pc = " + Integer.toString(varStartPC.offset()));//NOI18N
    out.print(" length = " +//NOI18N
	     Integer.toString(varEndPC.offset() - varStartPC.offset()));
    out.println(" slot = " + Integer.toString(varSlot));//NOI18N
  }

}