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      1 /*
      2  * Copyright (C) 2013 Google 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 are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #include "config.h"
     32 #include "core/dom/PresentationAttributeStyle.h"
     33 
     34 #include "core/css/StylePropertySet.h"
     35 #include "core/dom/Attribute.h"
     36 #include "core/dom/Element.h"
     37 #include "core/html/HTMLInputElement.h"
     38 #include "platform/Timer.h"
     39 #include "wtf/HashFunctions.h"
     40 #include "wtf/HashMap.h"
     41 #include "wtf/text/CString.h"
     42 
     43 namespace blink {
     44 
     45 using namespace HTMLNames;
     46 
     47 struct PresentationAttributeCacheKey {
     48     PresentationAttributeCacheKey() : tagName(0) { }
     49     StringImpl* tagName;
     50     Vector<std::pair<StringImpl*, AtomicString>, 3> attributesAndValues;
     51 };
     52 
     53 static bool operator!=(const PresentationAttributeCacheKey& a, const PresentationAttributeCacheKey& b)
     54 {
     55     if (a.tagName != b.tagName)
     56         return true;
     57     return a.attributesAndValues != b.attributesAndValues;
     58 }
     59 
     60 struct PresentationAttributeCacheEntry FINAL : public NoBaseWillBeGarbageCollectedFinalized<PresentationAttributeCacheEntry> {
     61     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
     62 public:
     63     void trace(Visitor* visitor) { visitor->trace(value); }
     64 
     65     PresentationAttributeCacheKey key;
     66     RefPtrWillBeMember<StylePropertySet> value;
     67 };
     68 
     69 typedef WillBeHeapHashMap<unsigned, OwnPtrWillBeMember<PresentationAttributeCacheEntry>, AlreadyHashed> PresentationAttributeCache;
     70 static PresentationAttributeCache& presentationAttributeCache()
     71 {
     72     DEFINE_STATIC_LOCAL(OwnPtrWillBePersistent<PresentationAttributeCache>, cache, (adoptPtrWillBeNoop(new PresentationAttributeCache())));
     73     return *cache;
     74 }
     75 
     76 class PresentationAttributeCacheCleaner {
     77     WTF_MAKE_NONCOPYABLE(PresentationAttributeCacheCleaner); WTF_MAKE_FAST_ALLOCATED;
     78 public:
     79     PresentationAttributeCacheCleaner()
     80         : m_hitCount(0)
     81         , m_cleanTimer(this, &PresentationAttributeCacheCleaner::cleanCache)
     82     {
     83     }
     84 
     85     void didHitPresentationAttributeCache()
     86     {
     87         if (presentationAttributeCache().size() < minimumPresentationAttributeCacheSizeForCleaning)
     88             return;
     89 
     90         m_hitCount++;
     91 
     92         if (!m_cleanTimer.isActive())
     93             m_cleanTimer.startOneShot(presentationAttributeCacheCleanTimeInSeconds, FROM_HERE);
     94     }
     95 
     96 private:
     97     static const unsigned presentationAttributeCacheCleanTimeInSeconds = 60;
     98     static const unsigned minimumPresentationAttributeCacheSizeForCleaning = 100;
     99     static const unsigned minimumPresentationAttributeCacheHitCountPerMinute = (100 * presentationAttributeCacheCleanTimeInSeconds) / 60;
    100 
    101     void cleanCache(Timer<PresentationAttributeCacheCleaner>* timer)
    102     {
    103         ASSERT_UNUSED(timer, timer == &m_cleanTimer);
    104         unsigned hitCount = m_hitCount;
    105         m_hitCount = 0;
    106         if (hitCount > minimumPresentationAttributeCacheHitCountPerMinute)
    107             return;
    108         presentationAttributeCache().clear();
    109     }
    110 
    111     unsigned m_hitCount;
    112     Timer<PresentationAttributeCacheCleaner> m_cleanTimer;
    113 };
    114 
    115 static bool attributeNameSort(const pair<StringImpl*, AtomicString>& p1, const pair<StringImpl*, AtomicString>& p2)
    116 {
    117     // Sort based on the attribute name pointers. It doesn't matter what the order is as long as it is always the same.
    118     return p1.first < p2.first;
    119 }
    120 
    121 static void makePresentationAttributeCacheKey(Element& element, PresentationAttributeCacheKey& result)
    122 {
    123     // FIXME: Enable for SVG.
    124     if (!element.isHTMLElement())
    125         return;
    126     // Interpretation of the size attributes on <input> depends on the type attribute.
    127     if (isHTMLInputElement(element))
    128         return;
    129     AttributeCollection attributes = element.attributesWithoutUpdate();
    130     AttributeCollection::iterator end = attributes.end();
    131     for (AttributeCollection::iterator it = attributes.begin(); it != end; ++it) {
    132         if (!element.isPresentationAttribute(it->name()))
    133             continue;
    134         if (!it->namespaceURI().isNull())
    135             return;
    136         // FIXME: Background URL may depend on the base URL and can't be shared. Disallow caching.
    137         if (it->name() == backgroundAttr)
    138             return;
    139         result.attributesAndValues.append(std::make_pair(it->localName().impl(), it->value()));
    140     }
    141     if (result.attributesAndValues.isEmpty())
    142         return;
    143     // Attribute order doesn't matter. Sort for easy equality comparison.
    144     std::sort(result.attributesAndValues.begin(), result.attributesAndValues.end(), attributeNameSort);
    145     // The cache key is non-null when the tagName is set.
    146     result.tagName = element.localName().impl();
    147 }
    148 
    149 static unsigned computePresentationAttributeCacheHash(const PresentationAttributeCacheKey& key)
    150 {
    151     if (!key.tagName)
    152         return 0;
    153     ASSERT(key.attributesAndValues.size());
    154     unsigned attributeHash = StringHasher::hashMemory(key.attributesAndValues.data(), key.attributesAndValues.size() * sizeof(key.attributesAndValues[0]));
    155     return WTF::pairIntHash(key.tagName->existingHash(), attributeHash);
    156 }
    157 
    158 PassRefPtrWillBeRawPtr<StylePropertySet> computePresentationAttributeStyle(Element& element)
    159 {
    160     DEFINE_STATIC_LOCAL(PresentationAttributeCacheCleaner, cacheCleaner, ());
    161 
    162     ASSERT(element.isStyledElement());
    163 
    164     PresentationAttributeCacheKey cacheKey;
    165     makePresentationAttributeCacheKey(element, cacheKey);
    166 
    167     unsigned cacheHash = computePresentationAttributeCacheHash(cacheKey);
    168 
    169     PresentationAttributeCache::ValueType* cacheValue;
    170     if (cacheHash) {
    171         cacheValue = presentationAttributeCache().add(cacheHash, nullptr).storedValue;
    172         if (cacheValue->value && cacheValue->value->key != cacheKey)
    173             cacheHash = 0;
    174     } else {
    175         cacheValue = 0;
    176     }
    177 
    178     RefPtrWillBeRawPtr<StylePropertySet> style = nullptr;
    179     if (cacheHash && cacheValue->value) {
    180         style = cacheValue->value->value;
    181         cacheCleaner.didHitPresentationAttributeCache();
    182     } else {
    183         style = MutableStylePropertySet::create(element.isSVGElement() ? SVGAttributeMode : HTMLAttributeMode);
    184         AttributeCollection attributes = element.attributesWithoutUpdate();
    185         AttributeCollection::iterator end = attributes.end();
    186         for (AttributeCollection::iterator it = attributes.begin(); it != end; ++it)
    187             element.collectStyleForPresentationAttribute(it->name(), it->value(), toMutableStylePropertySet(style));
    188     }
    189 
    190     if (!cacheHash || cacheValue->value)
    191         return style.release();
    192 
    193     OwnPtrWillBeRawPtr<PresentationAttributeCacheEntry> newEntry = adoptPtrWillBeNoop(new PresentationAttributeCacheEntry);
    194     newEntry->key = cacheKey;
    195     newEntry->value = style;
    196 
    197     static const unsigned presentationAttributeCacheMaximumSize = 4096;
    198     if (presentationAttributeCache().size() > presentationAttributeCacheMaximumSize) {
    199         // FIXME: Discarding the entire cache when it gets too big is probably bad
    200         // since it creates a perf "cliff". Perhaps we should use an LRU?
    201         presentationAttributeCache().clear();
    202         presentationAttributeCache().set(cacheHash, newEntry.release());
    203     } else {
    204         cacheValue->value = newEntry.release();
    205     }
    206 
    207     return style.release();
    208 }
    209 
    210 } // namespace blink
    211