1/*
2 * Copyright (C) 2010 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef HandleStack_h
27#define HandleStack_h
28
29#include "Assertions.h"
30#include "BlockStack.h"
31#include "Handle.h"
32
33#include <wtf/UnusedParam.h>
34
35namespace JSC {
36
37class LocalScope;
38class HeapRootMarker;
39
40class HandleStack {
41public:
42    class Frame {
43    public:
44        HandleSlot m_next;
45        HandleSlot m_end;
46    };
47
48    HandleStack();
49
50    void enterScope(Frame&);
51    void leaveScope(Frame&);
52
53    HandleSlot push();
54
55    void mark(HeapRootMarker&);
56
57private:
58    void grow();
59    void zapTo(Frame&);
60    HandleSlot findFirstAfter(HandleSlot);
61
62#ifndef NDEBUG
63    size_t m_scopeDepth;
64#endif
65    BlockStack<JSValue> m_blockStack;
66    Frame m_frame;
67};
68
69inline void HandleStack::enterScope(Frame& lastFrame)
70{
71#ifndef NDEBUG
72    ++m_scopeDepth;
73#endif
74
75    lastFrame = m_frame;
76}
77
78
79
80inline void HandleStack::zapTo(Frame& lastFrame)
81{
82#ifdef NDEBUG
83    UNUSED_PARAM(lastFrame);
84#else
85    const Vector<HandleSlot>& blocks = m_blockStack.blocks();
86
87    if (lastFrame.m_end != m_frame.m_end) { // Zapping to a frame in a different block.
88        int i = blocks.size() - 1;
89        for ( ; blocks[i] + m_blockStack.blockLength != lastFrame.m_end; --i) {
90            for (int j = m_blockStack.blockLength - 1; j >= 0; --j)
91                blocks[i][j] = JSValue();
92        }
93
94        for (HandleSlot it = blocks[i] + m_blockStack.blockLength - 1; it != lastFrame.m_next - 1; --it)
95            *it = JSValue();
96
97        return;
98    }
99
100    for (HandleSlot it = m_frame.m_next - 1; it != lastFrame.m_next - 1; --it)
101        *it = JSValue();
102#endif
103}
104
105inline void HandleStack::leaveScope(Frame& lastFrame)
106{
107#ifndef NDEBUG
108    --m_scopeDepth;
109#endif
110
111    zapTo(lastFrame);
112
113    if (lastFrame.m_end != m_frame.m_end) // Popping to a frame in a different block.
114        m_blockStack.shrink(lastFrame.m_end);
115
116    m_frame = lastFrame;
117}
118
119inline HandleSlot HandleStack::push()
120{
121    ASSERT(m_scopeDepth); // Creating a Local outside of a LocalScope is a memory leak.
122    if (m_frame.m_next == m_frame.m_end)
123        grow();
124    return m_frame.m_next++;
125}
126
127}
128
129#endif
130