1/*
2 * Copyright (C) 2011 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#include "config.h"
27#include "HandleHeap.h"
28
29#include "JSObject.h"
30
31namespace JSC {
32
33WeakHandleOwner::~WeakHandleOwner()
34{
35}
36
37bool WeakHandleOwner::isReachableFromOpaqueRoots(Handle<Unknown>, void*, MarkStack&)
38{
39    return false;
40}
41
42void WeakHandleOwner::finalize(Handle<Unknown>, void*)
43{
44}
45
46HandleHeap::HandleHeap(JSGlobalData* globalData)
47    : m_globalData(globalData)
48    , m_nextToFinalize(0)
49{
50    grow();
51}
52
53void HandleHeap::grow()
54{
55    Node* block = m_blockStack.grow();
56    for (int i = m_blockStack.blockLength - 1; i >= 0; --i) {
57        Node* node = &block[i];
58        new (node) Node(this);
59        m_freeList.push(node);
60    }
61}
62
63void HandleHeap::markStrongHandles(HeapRootMarker& heapRootMarker)
64{
65    Node* end = m_strongList.end();
66    for (Node* node = m_strongList.begin(); node != end; node = node->next())
67        heapRootMarker.mark(node->slot());
68}
69
70void HandleHeap::markWeakHandles(HeapRootMarker& heapRootMarker)
71{
72    MarkStack& markStack = heapRootMarker.markStack();
73
74    Node* end = m_weakList.end();
75    for (Node* node = m_weakList.begin(); node != end; node = node->next()) {
76        ASSERT(isValidWeakNode(node));
77        JSCell* cell = node->slot()->asCell();
78        if (Heap::isMarked(cell))
79            continue;
80
81        WeakHandleOwner* weakOwner = node->weakOwner();
82        if (!weakOwner)
83            continue;
84
85        if (!weakOwner->isReachableFromOpaqueRoots(Handle<Unknown>::wrapSlot(node->slot()), node->weakOwnerContext(), markStack))
86            continue;
87
88        heapRootMarker.mark(node->slot());
89    }
90}
91
92void HandleHeap::finalizeWeakHandles()
93{
94    Node* end = m_weakList.end();
95    for (Node* node = m_weakList.begin(); node != end; node = m_nextToFinalize) {
96        m_nextToFinalize = node->next();
97
98        ASSERT(isValidWeakNode(node));
99        JSCell* cell = node->slot()->asCell();
100        if (Heap::isMarked(cell))
101            continue;
102
103        if (WeakHandleOwner* weakOwner = node->weakOwner()) {
104            weakOwner->finalize(Handle<Unknown>::wrapSlot(node->slot()), node->weakOwnerContext());
105            if (m_nextToFinalize != node->next()) // Owner deallocated node.
106                continue;
107        }
108
109        *node->slot() = JSValue();
110        SentinelLinkedList<Node>::remove(node);
111        m_immediateList.push(node);
112    }
113
114    m_nextToFinalize = 0;
115}
116
117void HandleHeap::writeBarrier(HandleSlot slot, const JSValue& value)
118{
119    ASSERT(!m_nextToFinalize); // Forbid assignment to handles during the finalization phase, since it would violate many GC invariants.
120
121    if (!value == !*slot && slot->isCell() == value.isCell())
122        return;
123
124    Node* node = toNode(slot);
125    SentinelLinkedList<Node>::remove(node);
126    if (!value || !value.isCell()) {
127        m_immediateList.push(node);
128        return;
129    }
130
131    if (node->isWeak()) {
132        m_weakList.push(node);
133        return;
134    }
135
136    m_strongList.push(node);
137}
138
139unsigned HandleHeap::protectedGlobalObjectCount()
140{
141    unsigned count = 0;
142    Node* end = m_strongList.end();
143    for (Node* node = m_strongList.begin(); node != end; node = node->next()) {
144        JSValue value = *node->slot();
145        if (value.isObject() && asObject(value.asCell())->isGlobalObject())
146            count++;
147    }
148    return count;
149}
150
151#if !ASSERT_DISABLED
152bool HandleHeap::isValidWeakNode(Node* node)
153{
154    if (!node->isWeak())
155        return false;
156
157    JSValue value = *node->slot();
158    if (!value || !value.isCell())
159        return false;
160
161    JSCell* cell = value.asCell();
162    if (!cell || !cell->structure())
163        return false;
164
165#if ENABLE(JSC_ZOMBIES)
166    if (cell->isZombie())
167        return false;
168#endif
169
170    return true;
171}
172#endif
173
174} // namespace JSC
175