package de.fub.bytecode.generic;

import de.fub.bytecode.Constants;
import de.fub.bytecode.classfile.*;

/** 
 * This class represents an exception handler, i.e., specifies the  region where
 * a handler is active and an instruction where the actual handling is done.
 * pool as parameters. Opposed to the JVM specification the end of the handled
 * region is set to be inclusive, i.e. all instructions between start and end
 * are protected including the start and end instructions (handles) themselves.
 * The end of the region is automatically mapped to be exclusive when calling
 * getCodeException(), i.e., there is no difference semantically.
 *
 * @version $Id: CodeExceptionGen.java,v 1.6 2001/07/02 12:08:17 dahm Exp $
 * @author  <A HREF="http://www.berlin.de/~markus.dahm/">M. Dahm</A>
 * @see     MethodGen
 * @see     CodeException
 * @see     InstructionHandle
 */
public final class CodeExceptionGen implements InstructionTargeter, Cloneable {
  private InstructionHandle start_pc;
  private InstructionHandle end_pc;
  private InstructionHandle handler_pc;
  private ObjectType        catch_type;
  
  /**
   * Add an exception handler, i.e., specify region where a handler is active and an
   * instruction where the actual handling is done.
   *
   * @param start_pc Start of handled region (inclusive)
   * @param end_pc End of handled region (inclusive)
   * @param handler_pc Where handling is done
   * @param catch_type which exception is handled, null for ANY
   */
  public CodeExceptionGen(InstructionHandle start_pc, InstructionHandle end_pc,
			  InstructionHandle handler_pc, ObjectType catch_type) {
    setStartPC(start_pc);
    setEndPC(end_pc);
    setHandlerPC(handler_pc);
    this.catch_type = catch_type;
  }

  /**
   * Get CodeException object.<BR>
   *
   * This relies on that the instruction list has already been dumped
   * to byte code or or that the `setPositions' methods has been
   * called for the instruction list.
   *
   * @param cp constant pool
   */
  public CodeException getCodeException(ConstantPoolGen cp) {
    return new CodeException(start_pc.getPosition(),
			     end_pc.getPosition() + end_pc.getInstruction().getLength(),
			     handler_pc.getPosition(),
			     (catch_type == null)? 0 : cp.addClass(catch_type));
  }

  /* Set start of handler 
   * @param start_pc Start of handled region (inclusive)
   */
  public void setStartPC(InstructionHandle start_pc) {
    BranchInstruction.notifyTarget(this.start_pc, start_pc, this);
    this.start_pc = start_pc; 
  }

  /* Set end of handler 
   * @param end_pc End of handled region (inclusive)
   */
  public void setEndPC(InstructionHandle end_pc) {
    BranchInstruction.notifyTarget(this.end_pc, end_pc, this);
    this.end_pc = end_pc;
  }

  /* Set handler code
   * @param handler_pc Start of handler
   */
  public void setHandlerPC(InstructionHandle handler_pc) {
    BranchInstruction.notifyTarget(this.handler_pc, handler_pc, this);
    this.handler_pc = handler_pc;
  }

  /**
   * @param old_ih old target, either start or end
   * @param new_ih new target
   */
  public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
    boolean targeted = false;

    if(start_pc == old_ih) {
      targeted = true;
      setStartPC(new_ih);
    }

    if(end_pc == old_ih) {
      targeted = true;
      setEndPC(new_ih);
    }

    if(handler_pc == old_ih) {
      targeted = true;
      setHandlerPC(new_ih);
    }

    if(!targeted)
      throw new ClassGenException("Not targeting " + old_ih + ", but {" + start_pc + ", " +
				  end_pc + ", " + handler_pc + "}");
  }

  /**
   * @return true, if ih is target of this handler
   */
  public boolean containsTarget(InstructionHandle ih) {
    return (start_pc == ih) || (end_pc == ih) || (handler_pc == ih);
  }

  /** Sets the type of the Exception to catch. Set 'null' for ANY. */
  public void              setCatchType(ObjectType catch_type)        { this.catch_type = catch_type; }
  /** Gets the type of the Exception to catch, 'null' for ANY. */
  public ObjectType        getCatchType()                             { return catch_type; }

  /** @return start of handled region (inclusive)
   */
  public InstructionHandle getStartPC()                               { return start_pc; }

  /** @return end of handled region (inclusive)
   */
  public InstructionHandle getEndPC()                                 { return end_pc; }

  /** @return start of handler
   */
  public InstructionHandle getHandlerPC()                             { return handler_pc; }

  public String toString() {
    return "CodeExceptionGen(" + start_pc + ", " + end_pc + ", " + handler_pc + ")";
  }

  public Object clone() {
    try {
      return super.clone();
    } catch(CloneNotSupportedException e) {
      System.err.println(e);
      return null;
    }
  }
}