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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 "HTMLNames.h"
     35 #include "core/css/StylePropertySet.h"
     36 #include "core/dom/Attribute.h"
     37 #include "core/dom/Element.h"
     38 #include "wtf/HashFunctions.h"
     39 #include "wtf/HashMap.h"
     40 #include "wtf/text/CString.h"
     41 
     42 namespace WebCore {
     43 
     44 using namespace HTMLNames;
     45 
     46 struct PresentationAttributeCacheKey {
     47     PresentationAttributeCacheKey() : tagName(0) { }
     48     StringImpl* tagName;
     49     Vector<std::pair<StringImpl*, AtomicString>, 3> attributesAndValues;
     50 };
     51 
     52 static bool operator!=(const PresentationAttributeCacheKey& a, const PresentationAttributeCacheKey& b)
     53 {
     54     if (a.tagName != b.tagName)
     55         return true;
     56     return a.attributesAndValues != b.attributesAndValues;
     57 }
     58 
     59 struct PresentationAttributeCacheEntry {
     60     WTF_MAKE_FAST_ALLOCATED;
     61 public:
     62     PresentationAttributeCacheKey key;
     63     RefPtr<StylePropertySet> value;
     64 };
     65 
     66 typedef HashMap<unsigned, OwnPtr<PresentationAttributeCacheEntry>, AlreadyHashed> PresentationAttributeCache;
     67 static PresentationAttributeCache& presentationAttributeCache()
     68 {
     69     DEFINE_STATIC_LOCAL(PresentationAttributeCache, cache, ());
     70     return cache;
     71 }
     72 
     73 class PresentationAttributeCacheCleaner {
     74     WTF_MAKE_NONCOPYABLE(PresentationAttributeCacheCleaner); WTF_MAKE_FAST_ALLOCATED;
     75 public:
     76     PresentationAttributeCacheCleaner()
     77         : m_hitCount(0)
     78         , m_cleanTimer(this, &PresentationAttributeCacheCleaner::cleanCache)
     79     {
     80     }
     81 
     82     void didHitPresentationAttributeCache()
     83     {
     84         if (presentationAttributeCache().size() < minimumPresentationAttributeCacheSizeForCleaning)
     85             return;
     86 
     87         m_hitCount++;
     88 
     89         if (!m_cleanTimer.isActive())
     90             m_cleanTimer.startOneShot(presentationAttributeCacheCleanTimeInSeconds);
     91     }
     92 
     93 private:
     94     static const unsigned presentationAttributeCacheCleanTimeInSeconds = 60;
     95     static const unsigned minimumPresentationAttributeCacheSizeForCleaning = 100;
     96     static const unsigned minimumPresentationAttributeCacheHitCountPerMinute = (100 * presentationAttributeCacheCleanTimeInSeconds) / 60;
     97 
     98     void cleanCache(Timer<PresentationAttributeCacheCleaner>* timer)
     99     {
    100         ASSERT_UNUSED(timer, timer == &m_cleanTimer);
    101         unsigned hitCount = m_hitCount;
    102         m_hitCount = 0;
    103         if (hitCount > minimumPresentationAttributeCacheHitCountPerMinute)
    104             return;
    105         presentationAttributeCache().clear();
    106     }
    107 
    108     unsigned m_hitCount;
    109     Timer<PresentationAttributeCacheCleaner> m_cleanTimer;
    110 };
    111 
    112 static bool attributeNameSort(const pair<StringImpl*, AtomicString>& p1, const pair<StringImpl*, AtomicString>& p2)
    113 {
    114     // Sort based on the attribute name pointers. It doesn't matter what the order is as long as it is always the same.
    115     return p1.first < p2.first;
    116 }
    117 
    118 static void makePresentationAttributeCacheKey(Element& element, PresentationAttributeCacheKey& result)
    119 {
    120     // FIXME: Enable for SVG.
    121     if (!element.isHTMLElement())
    122         return;
    123     // Interpretation of the size attributes on <input> depends on the type attribute.
    124     if (element.hasTagName(inputTag))
    125         return;
    126     unsigned size = element.attributeCount();
    127     for (unsigned i = 0; i < size; ++i) {
    128         const Attribute* attribute = element.attributeItem(i);
    129         if (!element.isPresentationAttribute(attribute->name()))
    130             continue;
    131         if (!attribute->namespaceURI().isNull())
    132             return;
    133         // FIXME: Background URL may depend on the base URL and can't be shared. Disallow caching.
    134         if (attribute->name() == backgroundAttr)
    135             return;
    136         result.attributesAndValues.append(std::make_pair(attribute->localName().impl(), attribute->value()));
    137     }
    138     if (result.attributesAndValues.isEmpty())
    139         return;
    140     // Attribute order doesn't matter. Sort for easy equality comparison.
    141     std::sort(result.attributesAndValues.begin(), result.attributesAndValues.end(), attributeNameSort);
    142     // The cache key is non-null when the tagName is set.
    143     result.tagName = element.localName().impl();
    144 }
    145 
    146 static unsigned computePresentationAttributeCacheHash(const PresentationAttributeCacheKey& key)
    147 {
    148     if (!key.tagName)
    149         return 0;
    150     ASSERT(key.attributesAndValues.size());
    151     unsigned attributeHash = StringHasher::hashMemory(key.attributesAndValues.data(), key.attributesAndValues.size() * sizeof(key.attributesAndValues[0]));
    152     return WTF::pairIntHash(key.tagName->existingHash(), attributeHash);
    153 }
    154 
    155 PassRefPtr<StylePropertySet> computePresentationAttributeStyle(Element& element)
    156 {
    157     DEFINE_STATIC_LOCAL(PresentationAttributeCacheCleaner, cacheCleaner, ());
    158 
    159     ASSERT(element.isStyledElement());
    160 
    161     PresentationAttributeCacheKey cacheKey;
    162     makePresentationAttributeCacheKey(element, cacheKey);
    163 
    164     unsigned cacheHash = computePresentationAttributeCacheHash(cacheKey);
    165 
    166     PresentationAttributeCache::iterator cacheIterator;
    167     if (cacheHash) {
    168         cacheIterator = presentationAttributeCache().add(cacheHash, nullptr).iterator;
    169         if (cacheIterator->value && cacheIterator->value->key != cacheKey)
    170             cacheHash = 0;
    171     } else {
    172         cacheIterator = presentationAttributeCache().end();
    173     }
    174 
    175     RefPtr<StylePropertySet> style;
    176     if (cacheHash && cacheIterator->value) {
    177         style = cacheIterator->value->value;
    178         cacheCleaner.didHitPresentationAttributeCache();
    179     } else {
    180         style = MutableStylePropertySet::create(element.isSVGElement() ? SVGAttributeMode : HTMLAttributeMode);
    181         unsigned size = element.attributeCount();
    182         for (unsigned i = 0; i < size; ++i) {
    183             const Attribute* attribute = element.attributeItem(i);
    184             element.collectStyleForPresentationAttribute(attribute->name(), attribute->value(), toMutableStylePropertySet(style));
    185         }
    186     }
    187 
    188     if (!cacheHash || cacheIterator->value)
    189         return style.release();
    190 
    191     OwnPtr<PresentationAttributeCacheEntry> newEntry = adoptPtr(new PresentationAttributeCacheEntry);
    192     newEntry->key = cacheKey;
    193     newEntry->value = style;
    194 
    195     static const unsigned presentationAttributeCacheMaximumSize = 4096;
    196     if (presentationAttributeCache().size() > presentationAttributeCacheMaximumSize) {
    197         // FIXME: Discarding the entire cache when it gets too big is probably bad
    198         // since it creates a perf "cliff". Perhaps we should use an LRU?
    199         presentationAttributeCache().clear();
    200         presentationAttributeCache().set(cacheHash, newEntry.release());
    201     } else {
    202         cacheIterator->value = newEntry.release();
    203     }
    204 
    205     return style.release();
    206 }
    207 
    208 } // namespace WebCore
    209