/*

 * Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package sun.jvm.hotspot.utilities;

import java.io.*;

import java.util.*;

import sun.jvm.hotspot.oops.*;

/** Describes a path from an object back to the root which is keeping

    it alive. Elements of the path are (object, field) pairs, where

    the object is expressed as a @link{sun.jvm.hotspot.oops.Oop}, and

    where the field is expressed as a

    @link{sun.jvm.hotspot.oops.FieldIdentifier}. If the element

    reflects a root, the Oop will be null. If the element is the end

    of the path, the FieldIdentifier will be null. */

public class LivenessPath {

  LivenessPath() {

    stack = new Stack();

  }

  /** Number of elements in the path */

  public int size() {

    return stack.size();

  }

  /** Fetch the element at the given index; 0-based */

  public LivenessPathElement get(int index) throws ArrayIndexOutOfBoundsException {

    return (LivenessPathElement) stack.get(index);

  }

  public void printOn(PrintStream tty) {

    for (int j = 0; j < size(); j++) {

      LivenessPathElement el = get(j);

      tty.print("  - ");

      if (el.getObj() != null) {

        Oop.printOopValueOn(el.getObj(), tty);

      }

      if (el.getField() != null) {

        if (el.getObj() != null) {

          tty.print(", field ");

        }

        tty.print(el.getField().getName());

      }

      tty.println();

    }

  }

  /** Indicates whether this path is "complete", i.e., whether the

      last element is a root. Convenience routine for LivenessAnalysis. */

  boolean isComplete() {

    if (size() == 0)

      return false;

    return peek().isRoot();

  }

  // Convenience routine for LivenessAnalysis

  LivenessPathElement peek() {

    return (LivenessPathElement) stack.peek();

  }

  // Convenience routine for LivenessAnalysis

  void push(LivenessPathElement el) {

    stack.push(el);

  }

  // Convenience routine for LivenessAnalysis

  void pop() {

    stack.pop();

  }

  // Make a copy of the contents of the path -- the

  // LivenessPathElements are not duplicated, only the containing path

  LivenessPath copy() {

    LivenessPath dup = new LivenessPath();

    for (int i = 0; i < stack.size(); i++) {

      dup.stack.push(stack.get(i));

    }

    return dup;

  }

  //---------------------------------------------------------------------------

  // Internals only below this point

  //

  private Stack stack;

}