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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "core/dom/NthIndexCache.h"
#include "core/dom/Document.h"
#include "core/dom/ElementTraversal.h"
namespace blink {
NthIndexCache::NthIndexCache(Document& document)
: m_document(&document)
#if DCHECK_IS_ON()
,
m_domTreeVersion(document.domTreeVersion())
#endif
{
document.setNthIndexCache(this);
}
NthIndexCache::~NthIndexCache() {
#if DCHECK_IS_ON()
DCHECK_EQ(m_domTreeVersion, m_document->domTreeVersion());
#endif
m_document->setNthIndexCache(nullptr);
}
namespace {
// Generating the cached nth-index counts when the number of children
// exceeds this count. This number is picked based on testing
// querySelectorAll for :nth-child(3n+2) and :nth-of-type(3n+2) on an
// increasing number of children.
const unsigned kCachedSiblingCountLimit = 32;
unsigned uncachedNthChildIndex(Element& element) {
int index = 1;
for (const Element* sibling = ElementTraversal::previousSibling(element);
sibling; sibling = ElementTraversal::previousSibling(*sibling))
index++;
return index;
}
unsigned uncachedNthLastChildIndex(Element& element) {
int index = 1;
for (const Element* sibling = ElementTraversal::nextSibling(element); sibling;
sibling = ElementTraversal::nextSibling(*sibling))
++index;
return index;
}
unsigned uncachedNthOfTypeIndex(Element& element, unsigned& siblingCount) {
int index = 1;
const QualifiedName& tag = element.tagQName();
for (const Element* sibling = ElementTraversal::previousSibling(element);
sibling; sibling = ElementTraversal::previousSibling(*sibling)) {
if (sibling->tagQName() == tag)
++index;
++siblingCount;
}
return index;
}
unsigned uncachedNthLastOfTypeIndex(Element& element, unsigned& siblingCount) {
int index = 1;
const QualifiedName& tag = element.tagQName();
for (const Element* sibling = ElementTraversal::nextSibling(element); sibling;
sibling = ElementTraversal::nextSibling(*sibling)) {
if (sibling->tagQName() == tag)
++index;
++siblingCount;
}
return index;
}
} // namespace
unsigned NthIndexCache::nthChildIndex(Element& element) {
if (element.isPseudoElement())
return 1;
DCHECK(element.parentNode());
NthIndexCache* nthIndexCache = element.document().nthIndexCache();
NthIndexData* nthIndexData = nullptr;
if (nthIndexCache && nthIndexCache->m_parentMap)
nthIndexData = nthIndexCache->m_parentMap->get(element.parentNode());
if (nthIndexData)
return nthIndexData->nthIndex(element);
unsigned index = uncachedNthChildIndex(element);
if (nthIndexCache && index > kCachedSiblingCountLimit)
nthIndexCache->cacheNthIndexDataForParent(element);
return index;
}
unsigned NthIndexCache::nthLastChildIndex(Element& element) {
if (element.isPseudoElement())
return 1;
DCHECK(element.parentNode());
NthIndexCache* nthIndexCache = element.document().nthIndexCache();
NthIndexData* nthIndexData = nullptr;
if (nthIndexCache && nthIndexCache->m_parentMap)
nthIndexData = nthIndexCache->m_parentMap->get(element.parentNode());
if (nthIndexData)
return nthIndexData->nthLastIndex(element);
unsigned index = uncachedNthLastChildIndex(element);
if (nthIndexCache && index > kCachedSiblingCountLimit)
nthIndexCache->cacheNthIndexDataForParent(element);
return index;
}
NthIndexData* NthIndexCache::nthTypeIndexDataForParent(Element& element) const {
DCHECK(element.parentNode());
if (!m_parentMapForType)
return nullptr;
if (const IndexByType* map = m_parentMapForType->get(element.parentNode()))
return map->get(element.tagName());
return nullptr;
}
unsigned NthIndexCache::nthOfTypeIndex(Element& element) {
if (element.isPseudoElement())
return 1;
NthIndexCache* nthIndexCache = element.document().nthIndexCache();
if (nthIndexCache) {
if (NthIndexData* nthIndexData =
nthIndexCache->nthTypeIndexDataForParent(element))
return nthIndexData->nthOfTypeIndex(element);
}
unsigned siblingCount = 0;
unsigned index = uncachedNthOfTypeIndex(element, siblingCount);
if (nthIndexCache && siblingCount > kCachedSiblingCountLimit)
nthIndexCache->cacheNthOfTypeIndexDataForParent(element);
return index;
}
unsigned NthIndexCache::nthLastOfTypeIndex(Element& element) {
if (element.isPseudoElement())
return 1;
NthIndexCache* nthIndexCache = element.document().nthIndexCache();
if (nthIndexCache) {
if (NthIndexData* nthIndexData =
nthIndexCache->nthTypeIndexDataForParent(element))
return nthIndexData->nthLastOfTypeIndex(element);
}
unsigned siblingCount = 0;
unsigned index = uncachedNthLastOfTypeIndex(element, siblingCount);
if (nthIndexCache && siblingCount > kCachedSiblingCountLimit)
nthIndexCache->cacheNthOfTypeIndexDataForParent(element);
return index;
}
void NthIndexCache::cacheNthIndexDataForParent(Element& element) {
DCHECK(element.parentNode());
if (!m_parentMap)
m_parentMap = new ParentMap();
ParentMap::AddResult addResult =
m_parentMap->add(element.parentNode(), nullptr);
DCHECK(addResult.isNewEntry);
addResult.storedValue->value = new NthIndexData(*element.parentNode());
}
NthIndexCache::IndexByType& NthIndexCache::ensureTypeIndexMap(
ContainerNode& parent) {
if (!m_parentMapForType)
m_parentMapForType = new ParentMapForType();
ParentMapForType::AddResult addResult =
m_parentMapForType->add(&parent, nullptr);
if (addResult.isNewEntry)
addResult.storedValue->value = new IndexByType();
DCHECK(addResult.storedValue->value);
return *addResult.storedValue->value;
}
void NthIndexCache::cacheNthOfTypeIndexDataForParent(Element& element) {
DCHECK(element.parentNode());
IndexByType::AddResult addResult =
ensureTypeIndexMap(*element.parentNode()).add(element.tagName(), nullptr);
DCHECK(addResult.isNewEntry);
addResult.storedValue->value =
new NthIndexData(*element.parentNode(), element.tagQName());
}
unsigned NthIndexData::nthIndex(Element& element) const {
DCHECK(!element.isPseudoElement());
unsigned index = 0;
for (Element *sibling = &element; sibling;
sibling = ElementTraversal::previousSibling(*sibling), index++) {
auto it = m_elementIndexMap.find(sibling);
if (it != m_elementIndexMap.end())
return it->value + index;
}
return index;
}
unsigned NthIndexData::nthOfTypeIndex(Element& element) const {
DCHECK(!element.isPseudoElement());
unsigned index = 0;
for (Element *sibling = &element; sibling;
sibling = ElementTraversal::previousSibling(
*sibling, HasTagName(element.tagQName())),
index++) {
auto it = m_elementIndexMap.find(sibling);
if (it != m_elementIndexMap.end())
return it->value + index;
}
return index;
}
unsigned NthIndexData::nthLastIndex(Element& element) const {
return m_count - nthIndex(element) + 1;
}
unsigned NthIndexData::nthLastOfTypeIndex(Element& element) const {
return m_count - nthOfTypeIndex(element) + 1;
}
NthIndexData::NthIndexData(ContainerNode& parent) {
// The frequency at which we cache the nth-index for a set of siblings. A
// spread value of 3 means every third Element will have its nth-index cached.
// Using a spread value > 1 is done to save memory. Looking up the nth-index
// will still be done in constant time in terms of sibling count, at most
// 'spread' elements will be traversed.
const unsigned spread = 3;
unsigned count = 0;
for (Element* sibling = ElementTraversal::firstChild(parent); sibling;
sibling = ElementTraversal::nextSibling(*sibling)) {
if (!(++count % spread))
m_elementIndexMap.add(sibling, count);
}
DCHECK(count);
m_count = count;
}
NthIndexData::NthIndexData(ContainerNode& parent, const QualifiedName& type) {
// The frequency at which we cache the nth-index of type for a set of
// siblings. A spread value of 3 means every third Element of its type will
// have its nth-index cached. Using a spread value > 1 is done to save
// memory. Looking up the nth-index of its type will still be done in less
// time, as most number of elements traversed will be equal to find 'spread'
// elements in the sibling set.
const unsigned spread = 3;
unsigned count = 0;
for (Element* sibling =
ElementTraversal::firstChild(parent, HasTagName(type));
sibling;
sibling = ElementTraversal::nextSibling(*sibling, HasTagName(type))) {
if (!(++count % spread))
m_elementIndexMap.add(sibling, count);
}
DCHECK(count);
m_count = count;
}
DEFINE_TRACE(NthIndexData) {
visitor->trace(m_elementIndexMap);
}
} // namespace blink
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