001 // MemAreaStack.java, created by wbeebee
002 // Copyright (C) 2001 Wes Beebee <wbeebee@mit.edu>
003 // Licensed under the terms of the GNU GPL; see COPYING for details.
004 package javax.realtime;
005
006 /** <code>MemAreaStack</code> can be used to create a tree of MemoryArea
007 * references to determine whether a ScopedMemory check fails. This is
008 * the same cactus stack that is used to determine which MemoryArea x
009 * RealtimeThread MemBlock to enter for the constructor of a .newArray'ed
010 * or a newInstance'd object.
011 * @author Wes Beebee <<a href="mailto:wbeebee@mit.edu">wbeebee@mit.edu</a>>
012 */
013
014 class MemAreaStack {
015 /** A MemoryArea on the stack
016 */
017 public MemoryArea entry, original;
018
019 /** The "next" pointer for the stack.
020 */
021 public MemAreaStack next;
022
023 /** Push the MemoryArea on the cactus stack.
024 */
025 public MemAreaStack(MemoryArea entry, MemoryArea original, MemAreaStack next) {
026 this.entry = entry;
027 this.original = original;
028 this.next = next;
029 }
030
031 public static MemAreaStack PUSH(MemoryArea entry, MemoryArea original,
032 MemAreaStack next) {
033 RealtimeThread.checkInit();
034 RefCountArea ref = RefCountArea.refInstance();
035 Object mas = null;
036 if ((next != null) && (next.memoryArea == ref)) ref.INCREF(next);
037 if ((entry != null) && (entry.memoryArea == ref)) ref.INCREF(entry);
038 if ((original != null) && (original.memoryArea == ref)) ref.INCREF(original);
039 try {
040 mas = ref.newInstance(MemAreaStack.class,
041 new Class[] { MemoryArea.class, MemoryArea.class,
042 MemAreaStack.class },
043 new Object[] { entry, original, next});
044 } catch (Exception e) {
045 NoHeapRealtimeThread.print(e.toString());
046 System.exit(-1);
047 }
048 mas.memoryArea = ref;
049 return (MemAreaStack)mas;
050 }
051
052 public static MemAreaStack POP(MemAreaStack top) {
053 MemAreaStack next = top.next;
054 RefCountArea ref = RefCountArea.refInstance();
055 if (top.memoryArea == ref) ref.DECREF(top);
056 return next;
057 }
058
059 /** Get the MemAreaStack of the first occurance of the
060 * MemoryArea mem, or null if it is not found.
061 */
062 public MemAreaStack first(MemoryArea mem) {
063 MemAreaStack current = this;
064
065 while (current != null) {
066 if (current.entry == mem) {
067 return current;
068 }
069 current = current.next;
070 }
071
072 return null;
073 }
074
075 /** Dump a description of each MemoryArea on the stack.
076 */
077 public String toString() {
078 if (next != null) {
079 return entry.toString()+"\n"+next.toString();
080 } else {
081 return entry.toString();
082 }
083 }
084 }