core/src/core/org/jnode/vm/memmgr/generational/GenGCStack.java - new-gc-algorithms in JNode

/*
 * $Id$
 *
 * Copyright (C) 2003-2009 JNode.org
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.vm.memmgr.generational;

import org.jnode.vm.VmSystemObject;
import org.jnode.annotation.Inline;
import org.vmmagic.pragma.Uninterruptible;

/**
 * @author epr
 */
final class GenGCStack extends VmSystemObject implements Uninterruptible {

    /**
     * The default size of a stack
     */
    public static final int DEFAULT_STACK_SIZE = 4096;
    /**
     * The actual stack
     */
    private final Object[] stack;
    /**
     * The size of the stack (in objects)
     */
    private final int size;
    /**
     * The stackpointer
     */
    private int stackPtr;
    /**
     * Has the stack occurred an overflow?
     */
    private boolean overflow;

    /**
     * Create a new instance
     */
    public GenGCStack() {
        this.stack = new Object[DEFAULT_STACK_SIZE];
        this.size = stack.length;
    }

    /**
     * Push a given object on the stack. If an overflow occurs, mark
     * the overflow and do not push the object.
     *
     * @param object
     */
    @Inline
    public final void push(Object object) {
        if (object == null) {
            throw new IllegalArgumentException("Cannot push null object");
        }
        if (stackPtr == size) {
            overflow = true;
        } else {
            stack[stackPtr++] = object;
        }
    }

    /**
     * Gets the last pushed object of the stack and remove it from the stack.
     *
     * @return The object
     */
    @Inline
    public final Object pop() {
        if (stackPtr == 0) {
            return null;
        } else {
            stackPtr--;
            Object result = stack[stackPtr];
            if (result == null) {
                throw new IllegalStateException("Null object found on GCStack");
            }
            stack[stackPtr] = null;
            return result;
        }
    }

    /**
     * Is this stack empty?
     *
     * @return boolean
     */
    public boolean isEmpty() {
        return (stackPtr == 0);
    }

    /**
     * Has a stackoverflow occurred?
     *
     * @return boolean
     */
    @Inline
    public final boolean isOverflow() {
        return overflow;
    }

    /**
     * Reset the contents of this stack to its original state
     */
    public void reset() {
        stackPtr = 0;
        overflow = false;
    }
}

1	/*
2	* $Id$
3	*
4	* Copyright (C) 2003-2009 JNode.org
5	*
6	* This library is free software; you can redistribute it and/or modify it
7	* under the terms of the GNU Lesser General Public License as published
8	* by the Free Software Foundation; either version 2.1 of the License, or
9	* (at your option) any later version.
10	*
11	* This library is distributed in the hope that it will be useful, but
12	* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13	* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
14	* License for more details.
15	*
16	* You should have received a copy of the GNU Lesser General Public License
17	* along with this library; If not, write to the Free Software Foundation, Inc.,
18	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
19	*/
20
21	package org.jnode.vm.memmgr.generational;
22
23	import org.jnode.vm.VmSystemObject;
24	import org.jnode.annotation.Inline;
25	import org.vmmagic.pragma.Uninterruptible;
26
27	/**
28	* @author epr
29	*/
30	final class GenGCStack extends VmSystemObject implements Uninterruptible {
31
32	/**
33	* The default size of a stack
34	*/
35	public static final int DEFAULT_STACK_SIZE = 4096;
36	/**
37	* The actual stack
38	*/
39	private final Object[] stack;
40	/**
41	* The size of the stack (in objects)
42	*/
43	private final int size;
44	/**
45	* The stackpointer
46	*/
47	private int stackPtr;
48	/**
49	* Has the stack occurred an overflow?
50	*/
51	private boolean overflow;
52
53	/**
54	* Create a new instance
55	*/
56	public GenGCStack() {
57	this.stack = new Object[DEFAULT_STACK_SIZE];
58	this.size = stack.length;
59	}
60
61	/**
62	* Push a given object on the stack. If an overflow occurs, mark
63	* the overflow and do not push the object.
64	*
65	* @param object
66	*/
67	@Inline
68	public final void push(Object object) {
69	if (object == null) {
70	throw new IllegalArgumentException("Cannot push null object");
71	}
72	if (stackPtr == size) {
73	overflow = true;
74	} else {
75	stack[stackPtr++] = object;
76	}
77	}
78
79	/**
80	* Gets the last pushed object of the stack and remove it from the stack.
81	*
82	* @return The object
83	*/
84	@Inline
85	public final Object pop() {
86	if (stackPtr == 0) {
87	return null;
88	} else {
89	stackPtr--;
90	Object result = stack[stackPtr];
91	if (result == null) {
92	throw new IllegalStateException("Null object found on GCStack");
93	}
94	stack[stackPtr] = null;
95	return result;
96	}
97	}
98
99	/**
100	* Is this stack empty?
101	*
102	* @return boolean
103	*/
104	public boolean isEmpty() {
105	return (stackPtr == 0);
106	}
107
108	/**
109	* Has a stackoverflow occurred?
110	*
111	* @return boolean
112	*/
113	@Inline
114	public final boolean isOverflow() {
115	return overflow;
116	}
117
118	/**
119	* Reset the contents of this stack to its original state
120	*/
121	public void reset() {
122	stackPtr = 0;
123	overflow = false;
124	}
125	}

Gitorious