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