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nsNthIndexCache.cpp
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nsNthIndexCache.cpp
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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla.org code.
*
* The Initial Developer of the Original Code is
* Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Boris Zbarsky <bzbarsky@mit.edu> (original author)
* L. David Baron <dbaron@dbaron.org>
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
* A class that computes and caches the indices used for :nth-* pseudo-class
* matching.
*/
#include "nsNthIndexCache.h"
#include "nsIContent.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,
PRInt32& aResult)
{
if (SiblingMatchesElement(aSibling, aChild, aIsOfType)) {
Cache::Ptr siblingEntry = aCache.lookup(aSibling);
if (siblingEntry) {
PRInt32 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|.
NS_ABORT_IF_FALSE(aIsFromEnd == 0 || aIsFromEnd == 1,
"Bogus bool value");
aResult = siblingIndex + aResult * (1 - 2 * aIsFromEnd);
return true;
}
}
++aResult;
}
return false;
}
PRInt32
nsNthIndexCache::GetNthIndex(Element* aChild, bool aIsOfType,
bool aIsFromEnd, bool aCheckEdgeOnly)
{
NS_ASSERTION(aChild->GetParent(), "caller should check GetParent()");
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;
}
PRInt32 &slot = entry->value;
if (slot != -2 && (slot != -1 || aCheckEdgeOnly)) {
return slot;
}
PRInt32 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;
}