[WeakMemoryCache] Make references from MemoryCache to Resource Weak

third_party/WebKit/Source/core/fetch/MemoryCache.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
@@ skipping 44 matching lines @@
 {
     memoryCache();
     MemoryCache* oldCache = gMemoryCache->release();
     *gMemoryCache = cache;
     MemoryCacheDumpProvider::instance()->setMemoryCache(cache);
     return oldCache;
 }
 
 DEFINE_TRACE(MemoryCacheEntry)
 {
-    visitor->trace(m_resource);
+    visitor->template registerWeakMembers<MemoryCacheEntry, &MemoryCacheEntry::clearResourceWeak>(this);
     visitor->trace(m_previousInLiveResourcesList);
     visitor->trace(m_nextInLiveResourcesList);
     visitor->trace(m_previousInAllResourcesList);
     visitor->trace(m_nextInAllResourcesList);
 }
 
+void MemoryCacheEntry::clearResourceWeak(Visitor* visitor)
+{
+    if (!m_resource || ThreadHeap::isHeapObjectAlive(m_resource))
+        return;
+    memoryCache()->remove(m_resource.get());
+    m_resource.clear();
+}
+
 void MemoryCacheEntry::dispose()
 {
     m_resource.clear();
 }
 
 Resource* MemoryCacheEntry::resource()
 {
     return m_resource.get();
 }
 
@@ skipping 70 matching lines @@
     }
     return m_resourceMaps.get(cacheIdentifier);
 }
 
 void MemoryCache::add(Resource* resource)
 {
     ASSERT(WTF::isMainThread());
     ASSERT(resource->url().isValid());
     ResourceMap* resources = ensureResourceMap(resource->cacheIdentifier());
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
-    RELEASE_ASSERT(!resources->contains(url));
+    CHECK(!contains(resource));
     resources->set(url, MemoryCacheEntry::create(resource));
     update(resource, 0, resource->size(), true);
 
     RESOURCE_LOADING_DVLOG(1) << "MemoryCache::add Added " << resource->url().getString() << ", resource " << resource;
 }
 
 void MemoryCache::remove(Resource* resource)
 {
     // The resource may have already been removed by someone other than our caller,
     // who needed a fresh copy for a reload.
@@ skipping 26 matching lines @@
         return nullptr;
     return entry->resource();
 }
 
 HeapVector<Member<Resource>> MemoryCache::resourcesForURL(const KURL& resourceURL)
 {
     ASSERT(WTF::isMainThread());
     KURL url = removeFragmentIdentifierIfNeeded(resourceURL);
     HeapVector<Member<Resource>> results;
     for (const auto& resourceMapIter : m_resourceMaps) {
-        if (MemoryCacheEntry* entry = resourceMapIter.value->get(url))
-            results.append(entry->resource());
+        if (MemoryCacheEntry* entry = resourceMapIter.value->get(url)) {
+            Resource* resource = entry->resource();
+            DCHECK(resource);
+            results.append(resource);
+        }
     }
     return results;
 }
 
 size_t MemoryCache::deadCapacity() const
 {
     // Dead resource capacity is whatever space is not occupied by live resources, bounded by an independent minimum and maximum.
     size_t capacity = m_capacity - std::min(m_liveSize, m_capacity); // Start with available capacity.
     capacity = std::max(capacity, m_minDeadCapacity); // Make sure it's above the minimum.
     capacity = std::min(capacity, m_maxDeadCapacity); // Make sure it's below the maximum.
@@ skipping 130 matching lines @@
     m_maxDeferredPruneDeadCapacity = cDeferredPruneDeadCapacityFactor * maxDeadBytes;
     m_capacity = totalBytes;
     prune();
 }
 
 void MemoryCache::evict(MemoryCacheEntry* entry)
 {
     ASSERT(WTF::isMainThread());
 
     Resource* resource = entry->resource();
+    DCHECK(resource);
     RESOURCE_LOADING_DVLOG(1) << "Evicting resource " << resource << " for " << resource->url().getString() << " from cache";
     TRACE_EVENT1("blink", "MemoryCache::evict", "resource", resource->url().getString().utf8());
     // The resource may have already been removed by someone other than our caller,
     // who needed a fresh copy for a reload. See <http://bugs.webkit.org/show_bug.cgi?id=12479#c6>.
     update(resource, resource->size(), 0, false);
     removeFromLiveDecodedResourcesList(entry);
 
     ResourceMap* resources = m_resourceMaps.get(resource->cacheIdentifier());
     ASSERT(resources);
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
     ResourceMap::iterator it = resources->find(url);
     ASSERT(it != resources->end());
 
     MemoryCacheEntry* entryPtr = it->value;
     resources->remove(it);
     if (entryPtr)
         entryPtr->dispose();
 }
 
 MemoryCacheEntry* MemoryCache::getEntryForResource(const Resource* resource) const
 {
-    if (resource->url().isNull() || resource->url().isEmpty())
+    if (!resource || resource->url().isNull() || resource->url().isEmpty())
         return nullptr;
     ResourceMap* resources = m_resourceMaps.get(resource->cacheIdentifier());
     if (!resources)
         return nullptr;
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
     MemoryCacheEntry* entry = resources->get(url);
     if (!entry || entry->resource() != resource)
         return nullptr;
     return entry;
 }
@@ skipping 189 matching lines @@
     encodedSize += o->encodedSize();
     encodedSizeDuplicatedInDataURLs += o->url().protocolIsData() ? o->encodedSize() : 0;
 }
 
 MemoryCache::Statistics MemoryCache::getStatistics()
 {
     Statistics stats;
     for (const auto& resourceMapIter : m_resourceMaps) {
         for (const auto& resourceIter : *resourceMapIter.value) {
             Resource* resource = resourceIter.value->resource();
+            DCHECK(resource);
             switch (resource->getType()) {
             case Resource::Image:
                 stats.images.addResource(resource);
                 break;
             case Resource::CSSStyleSheet:
                 stats.cssStyleSheets.addResource(resource);
                 break;
             case Resource::Script:
                 stats.scripts.addResource(resource);
                 break;
@@ skipping 131 matching lines @@
 bool MemoryCache::isInSameLRUListForTest(const Resource* x, const Resource* y)
 {
     MemoryCacheEntry* ex = getEntryForResource(x);
     MemoryCacheEntry* ey = getEntryForResource(y);
     ASSERT(ex);
     ASSERT(ey);
     return lruListFor(ex->m_accessCount, x->size()) == lruListFor(ey->m_accessCount, y->size());
 }
 
 } // namespace blink