import Location;
import java.io.PrintWriter;

/**
 * A register for the abstract assembly language.  Each
 * register has a specified name.  You can build new registers
 * (dangerous) or request some of the standard ones, such as
 * the stack pointer.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of April 2001
 */
public class Register
  implements Location
{
  // +--------+------------------------------------------------------------
  // | Fields |
  // +--------+

  /** The name of the register, such as esp. */
  protected String name;

  /** The frame pointer. */
  protected static Register fp = null;

  /** The stack pointer. */
  protected static Register sp = null;

  // +--------------+------------------------------------------------------
  // | Constructors |
  // +--------------+

  /**
   * Build a new register with a specified name.
   */
  public Register(String initialName) {
    this.name = initialName;
  } // Register(String)

  // +------------------+--------------------------------------------------
  // | Location Methods |
  // +------------------+

  /**
   * Print the register.
   */
  public void print(PrintWriter out) {
    out.print("%" + this.name);
  } // print(PrintWriter)

  // +---------------+-----------------------------------------------------
  // | Class Methods |
  // +---------------+

  /**
   * Get the frame pointer.
   */
  public static Register getFramePointer() {
    if (fp == null) {
      fp = new Register("ebp");
    }
    return fp;
  } // getStackPointer()
  /**
   * Get the stack pointer.
   */
  public static Register getStackPointer() {
    if (sp == null) {
      sp = new Register("esp");
    }
    return sp;
  } // getStackPointer()
} // class Register