1/*
2 * Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25package sun.jvm.hotspot.utilities;
26
27import java.io.*;
28import java.util.*;
29import sun.jvm.hotspot.oops.*;
30
31/** Describes a path from an object back to the root which is keeping
32    it alive. Elements of the path are (object, field) pairs, where
33    the object is expressed as a @link{sun.jvm.hotspot.oops.Oop}, and
34    where the field is expressed as a
35    @link{sun.jvm.hotspot.oops.FieldIdentifier}. If the element
36    reflects a root, the Oop will be null. If the element is the end
37    of the path, the FieldIdentifier will be null. */
38
39public class LivenessPath {
40  LivenessPath() {
41    stack = new Stack();
42  }
43
44  /** Number of elements in the path */
45  public int size() {
46    return stack.size();
47  }
48
49  /** Fetch the element at the given index; 0-based */
50  public LivenessPathElement get(int index) throws ArrayIndexOutOfBoundsException {
51    return (LivenessPathElement) stack.get(index);
52  }
53
54  public void printOn(PrintStream tty) {
55    for (int j = 0; j < size(); j++) {
56      LivenessPathElement el = get(j);
57      tty.print("  - ");
58      if (el.getObj() != null) {
59        Oop.printOopValueOn(el.getObj(), tty);
60      }
61      if (el.getField() != null) {
62        if (el.getObj() != null) {
63          tty.print(", field ");
64        }
65        tty.print(el.getField().getName());
66      }
67      tty.println();
68    }
69  }
70
71  /** Indicates whether this path is "complete", i.e., whether the
72      last element is a root. Convenience routine for LivenessAnalysis. */
73  boolean isComplete() {
74    if (size() == 0)
75      return false;
76    return peek().isRoot();
77  }
78
79  // Convenience routine for LivenessAnalysis
80  LivenessPathElement peek() {
81    return (LivenessPathElement) stack.peek();
82  }
83
84  // Convenience routine for LivenessAnalysis
85  void push(LivenessPathElement el) {
86    stack.push(el);
87  }
88
89  // Convenience routine for LivenessAnalysis
90  void pop() {
91    stack.pop();
92  }
93
94  // Make a copy of the contents of the path -- the
95  // LivenessPathElements are not duplicated, only the containing path
96  LivenessPath copy() {
97    LivenessPath dup = new LivenessPath();
98    for (int i = 0; i < stack.size(); i++) {
99      dup.stack.push(stack.get(i));
100    }
101    return dup;
102  }
103
104  //---------------------------------------------------------------------------
105  // Internals only below this point
106  //
107  private Stack stack;
108}
109