1/*
2 * Copyright (C) 2007 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 COMPUTER, INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "PageCache.h"
28
29#include "Cache.h"
30#include "CachedPage.h"
31#include "FrameLoader.h"
32#include "HistoryItem.h"
33#include "Logging.h"
34#include "SystemTime.h"
35#include <wtf/CurrentTime.h>
36
37using namespace std;
38
39namespace WebCore {
40
41static const double autoreleaseInterval = 3;
42
43PageCache* pageCache()
44{
45    static PageCache* staticPageCache = new PageCache;
46    return staticPageCache;
47}
48
49PageCache::PageCache()
50    : m_capacity(0)
51    , m_size(0)
52    , m_head(0)
53    , m_tail(0)
54    , m_autoreleaseTimer(this, &PageCache::releaseAutoreleasedPagesNowOrReschedule)
55{
56}
57
58void PageCache::setCapacity(int capacity)
59{
60    ASSERT(capacity >= 0);
61    m_capacity = max(capacity, 0);
62
63    prune();
64}
65
66int PageCache::frameCount() const
67{
68    int frameCount = 0;
69    for (HistoryItem* current = m_head; current; current = current->m_next) {
70        ++frameCount;
71        ASSERT(current->m_cachedPage);
72        frameCount += current->m_cachedPage ? current->m_cachedPage->cachedMainFrame()->descendantFrameCount() : 0;
73    }
74
75    return frameCount;
76}
77
78int PageCache::autoreleasedPageCount() const
79{
80    return m_autoreleaseSet.size();
81}
82
83void PageCache::add(PassRefPtr<HistoryItem> prpItem, PassRefPtr<CachedPage> cachedPage)
84{
85    ASSERT(prpItem);
86    ASSERT(cachedPage);
87
88    HistoryItem* item = prpItem.releaseRef(); // Balanced in remove().
89
90    // Remove stale cache entry if necessary.
91    if (item->m_cachedPage)
92        remove(item);
93
94    item->m_cachedPage = cachedPage;
95    addToLRUList(item);
96    ++m_size;
97
98    prune();
99}
100
101void PageCache::remove(HistoryItem* item)
102{
103    // Safely ignore attempts to remove items not in the cache.
104    if (!item || !item->m_cachedPage)
105        return;
106
107    autorelease(item->m_cachedPage.release());
108    removeFromLRUList(item);
109    --m_size;
110
111    item->deref(); // Balanced in add().
112}
113
114void PageCache::prune()
115{
116    while (m_size > m_capacity) {
117        ASSERT(m_tail && m_tail->m_cachedPage);
118        remove(m_tail);
119    }
120}
121
122void PageCache::addToLRUList(HistoryItem* item)
123{
124    item->m_next = m_head;
125    item->m_prev = 0;
126
127    if (m_head) {
128        ASSERT(m_tail);
129        m_head->m_prev = item;
130    } else {
131        ASSERT(!m_tail);
132        m_tail = item;
133    }
134
135    m_head = item;
136}
137
138void PageCache::removeFromLRUList(HistoryItem* item)
139{
140    if (!item->m_next) {
141        ASSERT(item == m_tail);
142        m_tail = item->m_prev;
143    } else {
144        ASSERT(item != m_tail);
145        item->m_next->m_prev = item->m_prev;
146    }
147
148    if (!item->m_prev) {
149        ASSERT(item == m_head);
150        m_head = item->m_next;
151    } else {
152        ASSERT(item != m_head);
153        item->m_prev->m_next = item->m_next;
154    }
155}
156
157void PageCache::releaseAutoreleasedPagesNowOrReschedule(Timer<PageCache>* timer)
158{
159    double loadDelta = currentTime() - FrameLoader::timeOfLastCompletedLoad();
160    float userDelta = userIdleTime();
161
162    // FIXME: <rdar://problem/5211190> This limit of 42 risks growing the page cache far beyond its nominal capacity.
163    if ((userDelta < 0.5 || loadDelta < 1.25) && m_autoreleaseSet.size() < 42) {
164        LOG(PageCache, "WebCorePageCache: Postponing releaseAutoreleasedPagesNowOrReschedule() - %f since last load, %f since last input, %i objects pending release", loadDelta, userDelta, m_autoreleaseSet.size());
165        timer->startOneShot(autoreleaseInterval);
166        return;
167    }
168
169    LOG(PageCache, "WebCorePageCache: Releasing page caches - %f seconds since last load, %f since last input, %i objects pending release", loadDelta, userDelta, m_autoreleaseSet.size());
170    releaseAutoreleasedPagesNow();
171}
172
173void PageCache::releaseAutoreleasedPagesNow()
174{
175    m_autoreleaseTimer.stop();
176
177    // Postpone dead pruning until all our resources have gone dead.
178    cache()->setPruneEnabled(false);
179
180    CachedPageSet tmp;
181    tmp.swap(m_autoreleaseSet);
182
183    CachedPageSet::iterator end = tmp.end();
184    for (CachedPageSet::iterator it = tmp.begin(); it != end; ++it)
185        (*it)->destroy();
186
187    // Now do the prune.
188    cache()->setPruneEnabled(true);
189    cache()->prune();
190}
191
192void PageCache::autorelease(PassRefPtr<CachedPage> page)
193{
194    ASSERT(page);
195    ASSERT(!m_autoreleaseSet.contains(page.get()));
196    m_autoreleaseSet.add(page);
197    if (!m_autoreleaseTimer.isActive())
198        m_autoreleaseTimer.startOneShot(autoreleaseInterval);
199}
200
201} // namespace WebCore
202