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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* A class that computes and caches the indices used for :nth-* pseudo-class
* matching.
*/
#include "nsNthIndexCache.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/NodeInfoInlines.h"
nsNthIndexCache::nsNthIndexCache()
{
}
nsNthIndexCache::~nsNthIndexCache()
{
}
void
nsNthIndexCache::Reset()
{
mCaches[0][0].clear();
mCaches[0][1].clear();
mCaches[1][0].clear();
mCaches[1][1].clear();
}
inline bool
nsNthIndexCache::SiblingMatchesElement(nsIContent* aSibling, Element* aElement,
bool aIsOfType)
{
return aSibling->IsElement() &&
(!aIsOfType ||
aSibling->NodeInfo()->NameAndNamespaceEquals(aElement->NodeInfo()));
}
inline bool
nsNthIndexCache::IndexDeterminedFromPreviousSibling(nsIContent* aSibling,
Element* aChild,
bool aIsOfType,
bool aIsFromEnd,
const Cache& aCache,
int32_t& aResult)
{
if (SiblingMatchesElement(aSibling, aChild, aIsOfType)) {
Cache::Ptr siblingEntry = aCache.lookup(aSibling);
if (siblingEntry) {
int32_t siblingIndex = siblingEntry->value();
NS_ASSERTION(siblingIndex != 0,
"How can a non-anonymous node have an anonymous sibling?");
if (siblingIndex > 0) {
// At this point, aResult is a count of how many elements matching
// aChild we have seen after aSibling, including aChild itself.
// |siblingIndex| is the index of aSibling.
// So if aIsFromEnd, we want |aResult = siblingIndex - aResult| and
// otherwise we want |aResult = siblingIndex + aResult|.
aResult = siblingIndex + aResult * (1 - 2 * aIsFromEnd);
return true;
}
}
++aResult;
}
return false;
}
int32_t
nsNthIndexCache::GetNthIndex(Element* aChild, bool aIsOfType,
bool aIsFromEnd, bool aCheckEdgeOnly)
{
if (aChild->IsRootOfAnonymousSubtree()) {
return 0;
}
Cache& cache = mCaches[aIsOfType][aIsFromEnd];
if (!cache.initialized() && !cache.init()) {
// Give up and just don't match.
return 0;
}
Cache::AddPtr entry = cache.lookupForAdd(aChild);
// Default the value to -2 when adding
if (!entry && !cache.add(entry, aChild, -2)) {
// No good; don't match.
return 0;
}
int32_t& slot = entry->value();
if (slot != -2 && (slot != -1 || aCheckEdgeOnly)) {
return slot;
}
int32_t result = 1;
if (aCheckEdgeOnly) {
// The caller only cares whether or not the result is 1, so we can
// stop as soon as we see any other elements that match us.
if (aIsFromEnd) {
for (nsIContent *cur = aChild->GetNextSibling();
cur;
cur = cur->GetNextSibling()) {
if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
result = -1;
break;
}
}
} else {
for (nsIContent *cur = aChild->GetPreviousSibling();
cur;
cur = cur->GetPreviousSibling()) {
if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
result = -1;
break;
}
}
}
} else {
// In the common case, we already have a cached index for one of
// our previous siblings, so check that first.
for (nsIContent *cur = aChild->GetPreviousSibling();
cur;
cur = cur->GetPreviousSibling()) {
if (IndexDeterminedFromPreviousSibling(cur, aChild, aIsOfType,
aIsFromEnd, cache, result)) {
slot = result;
return result;
}
}
// Now if aIsFromEnd we lose: need to actually compute our index,
// since looking at previous siblings wouldn't have told us
// anything about it. Note that it doesn't make sense to do cache
// lookups on our following siblings, since chances are the cache
// is not primed for them.
if (aIsFromEnd) {
result = 1;
for (nsIContent *cur = aChild->GetNextSibling();
cur;
cur = cur->GetNextSibling()) {
if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
++result;
}
}
}
}
slot = result;
return result;
}
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