gecko/content/base/src/nsContentList.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 sw=2 et tw=78: */
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 * 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
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
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 * in which case the provisions of the GPL or the LGPL are applicable instead
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/*
 * nsBaseContentList is a basic list of content nodes; nsContentList
 * is a commonly used NodeList implementation (used for
 * getElementsByTagName, some properties on nsIDOMHTMLDocument, etc).
 */

#include "nsContentList.h"
#include "nsIContent.h"
#include "nsIDOMNode.h"
#include "nsIDOM3Node.h"
#include "nsIDocument.h"
#include "nsGenericElement.h"

#include "nsContentUtils.h"

#include "nsGkAtoms.h"

// Form related includes
#include "nsIDOMHTMLFormElement.h"

#include "pldhash.h"

#ifdef DEBUG_CONTENT_LIST
#include "nsIContentIterator.h"
nsresult
NS_NewPreContentIterator(nsIContentIterator** aInstancePtrResult);
#define ASSERT_IN_SYNC AssertInSync()
#else
#define ASSERT_IN_SYNC PR_BEGIN_MACRO PR_END_MACRO
#endif


static nsContentList *gCachedContentList;

nsBaseContentList::nsBaseContentList()
{
}

nsBaseContentList::~nsBaseContentList()
{
}

NS_IMPL_CYCLE_COLLECTION_CLASS(nsBaseContentList)
NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsBaseContentList)
  NS_IMPL_CYCLE_COLLECTION_UNLINK_NSCOMARRAY(mElements)
NS_IMPL_CYCLE_COLLECTION_UNLINK_END
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsBaseContentList)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_NSCOMARRAY(mElements)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

// QueryInterface implementation for nsBaseContentList
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsBaseContentList)
  NS_INTERFACE_MAP_ENTRY(nsINodeList)
  NS_INTERFACE_MAP_ENTRY(nsIDOMNodeList)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMNodeList)
  NS_INTERFACE_MAP_ENTRY_CONTENT_CLASSINFO(NodeList)
NS_INTERFACE_MAP_END


NS_IMPL_CYCLE_COLLECTING_ADDREF(nsBaseContentList)
NS_IMPL_CYCLE_COLLECTING_RELEASE(nsBaseContentList)


NS_IMETHODIMP
nsBaseContentList::GetLength(PRUint32* aLength)
{
  *aLength = mElements.Count();

  return NS_OK;
}

NS_IMETHODIMP
nsBaseContentList::Item(PRUint32 aIndex, nsIDOMNode** aReturn)
{
  nsISupports *tmp = GetNodeAt(aIndex);

  if (!tmp) {
    *aReturn = nsnull;

    return NS_OK;
  }

  return CallQueryInterface(tmp, aReturn);
}

nsINode*
nsBaseContentList::GetNodeAt(PRUint32 aIndex)
{
  return mElements.SafeObjectAt(aIndex);
}

void
nsBaseContentList::AppendElement(nsIContent *aContent)
{
  mElements.AppendObject(aContent);
}

void
nsBaseContentList::RemoveElement(nsIContent *aContent)
{
  mElements.RemoveObject(aContent);
}

PRInt32
nsBaseContentList::IndexOf(nsIContent *aContent, PRBool aDoFlush)
{
  return mElements.IndexOf(aContent);
}

void
nsBaseContentList::Reset()
{
  mElements.Clear();
}

// static
void
nsBaseContentList::Shutdown()
{
  NS_IF_RELEASE(gCachedContentList);
}


// nsFormContentList

nsFormContentList::nsFormContentList(nsIDOMHTMLFormElement *aForm,
                                     nsBaseContentList& aContentList)
  : nsBaseContentList()
{

  // move elements that belong to mForm into this content list

  PRUint32 i, length = 0;
  nsCOMPtr<nsIDOMNode> item;

  aContentList.GetLength(&length);

  for (i = 0; i < length; i++) {
    aContentList.Item(i, getter_AddRefs(item));

    nsCOMPtr<nsIContent> c(do_QueryInterface(item));

    if (c && nsContentUtils::BelongsInForm(aForm, c)) {
      AppendElement(c);
    }
  }
}

// Hashtable for storing nsContentLists
static PLDHashTable gContentListHashTable;

struct ContentListHashEntry : public PLDHashEntryHdr
{
  nsContentList* mContentList;
};

PR_STATIC_CALLBACK(PLDHashNumber)
ContentListHashtableHashKey(PLDHashTable *table, const void *key)
{
  const nsContentListKey* list = static_cast<const nsContentListKey *>(key);
  return list->GetHash();
}

PR_STATIC_CALLBACK(PRBool)
ContentListHashtableMatchEntry(PLDHashTable *table,
                               const PLDHashEntryHdr *entry,
                               const void *key)
{
  const ContentListHashEntry *e =
    static_cast<const ContentListHashEntry *>(entry);
  const nsContentListKey* list1 = e->mContentList->GetKey();
  const nsContentListKey* list2 = static_cast<const nsContentListKey *>(key);

  return list1->Equals(*list2);
}

already_AddRefed<nsContentList>
NS_GetContentList(nsINode* aRootNode, nsIAtom* aMatchAtom,
                  PRInt32 aMatchNameSpaceId)
{
  NS_ASSERTION(aRootNode, "content list has to have a root");

  nsContentList* list = nsnull;

  static PLDHashTableOps hash_table_ops =
  {
    PL_DHashAllocTable,
    PL_DHashFreeTable,
    ContentListHashtableHashKey,
    ContentListHashtableMatchEntry,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub,
    PL_DHashFinalizeStub
  };

  // Initialize the hashtable if needed.
  if (!gContentListHashTable.ops) {
    PRBool success = PL_DHashTableInit(&gContentListHashTable,
                                       &hash_table_ops, nsnull,
                                       sizeof(ContentListHashEntry),
                                       16);

    if (!success) {
      gContentListHashTable.ops = nsnull;
    }
  }
  
  ContentListHashEntry *entry = nsnull;
  // First we look in our hashtable.  Then we create a content list if needed
  if (gContentListHashTable.ops) {
    nsContentListKey hashKey(aRootNode, aMatchAtom,
                             aMatchNameSpaceId);
    
    // A PL_DHASH_ADD is equivalent to a PL_DHASH_LOOKUP for cases
    // when the entry is already in the hashtable.
    entry = static_cast<ContentListHashEntry *>
                       (PL_DHashTableOperate(&gContentListHashTable,
                                                &hashKey,
                                                PL_DHASH_ADD));
    if (entry)
      list = entry->mContentList;
  }

  if (!list) {
    // We need to create a ContentList and add it to our new entry, if
    // we have an entry
    list = new nsContentList(aRootNode, aMatchAtom,
                             aMatchNameSpaceId);
    if (entry) {
      if (list)
        entry->mContentList = list;
      else
        PL_DHashTableRawRemove(&gContentListHashTable, entry);
    }

    NS_ENSURE_TRUE(list, nsnull);
  }

  NS_ADDREF(list);

  // Hold on to the last requested content list to avoid having it be
  // removed from the cache immediately when it's released. Avoid
  // bumping the refcount on the list if the requested list is the one
  // that's already cached.

  if (gCachedContentList != list) {
    NS_IF_RELEASE(gCachedContentList);

    gCachedContentList = list;
    NS_ADDREF(gCachedContentList);
  }

  return list;
}


// nsContentList implementation

nsContentList::nsContentList(nsINode* aRootNode,
                             nsIAtom* aMatchAtom,
                             PRInt32 aMatchNameSpaceId,
                             PRBool aDeep)
  : nsBaseContentList(),
    nsContentListKey(aRootNode, aMatchAtom, aMatchNameSpaceId),
    mFunc(nsnull),
    mDestroyFunc(nsnull),
    mData(nsnull),
    mState(LIST_DIRTY),
    mDeep(aDeep),
    mFuncMayDependOnAttr(PR_FALSE)
{
  NS_ASSERTION(mRootNode, "Must have root");
  if (nsGkAtoms::_asterix == mMatchAtom) {
    mMatchAll = PR_TRUE;
  }
  else {
    mMatchAll = PR_FALSE;
  }
  mRootNode->AddMutationObserver(this);
}

nsContentList::nsContentList(nsINode* aRootNode,
                             nsContentListMatchFunc aFunc,
                             nsContentListDestroyFunc aDestroyFunc,
                             void* aData,
                             PRBool aDeep,
                             nsIAtom* aMatchAtom,
                             PRInt32 aMatchNameSpaceId,
                             PRBool aFuncMayDependOnAttr)
  : nsBaseContentList(),
    nsContentListKey(aRootNode, aMatchAtom, aMatchNameSpaceId),
    mFunc(aFunc),
    mDestroyFunc(aDestroyFunc),
    mData(aData),
    mMatchAll(PR_FALSE),
    mState(LIST_DIRTY),
    mDeep(aDeep),
    mFuncMayDependOnAttr(aFuncMayDependOnAttr)
{
  NS_ASSERTION(mRootNode, "Must have root");
  mRootNode->AddMutationObserver(this);
}

nsContentList::~nsContentList()
{
  RemoveFromHashtable();
  if (mRootNode) {
    mRootNode->RemoveMutationObserver(this);
  }

  if (mDestroyFunc) {
    // Clean up mData
    (*mDestroyFunc)(mData);
  }
}


// QueryInterface implementation for nsContentList
NS_INTERFACE_MAP_BEGIN(nsContentList)
  NS_INTERFACE_MAP_ENTRY(nsIDOMHTMLCollection)
  NS_INTERFACE_MAP_ENTRY(nsIMutationObserver)
  NS_INTERFACE_MAP_ENTRY_CONTENT_CLASSINFO(ContentList)
NS_INTERFACE_MAP_END_INHERITING(nsBaseContentList)


NS_IMPL_ADDREF_INHERITED(nsContentList, nsBaseContentList)
NS_IMPL_RELEASE_INHERITED(nsContentList, nsBaseContentList)


nsISupports *
nsContentList::GetParentObject()
{
  return mRootNode;
}
  
PRUint32
nsContentList::Length(PRBool aDoFlush)
{
  BringSelfUpToDate(aDoFlush);
    
  return mElements.Count();
}

nsIContent *
nsContentList::Item(PRUint32 aIndex, PRBool aDoFlush)
{
  if (mRootNode && aDoFlush) {
    // XXX sXBL/XBL2 issue
    nsIDocument* doc = mRootNode->GetCurrentDoc();
    if (doc) {
      // Flush pending content changes Bug 4891.
      doc->FlushPendingNotifications(Flush_ContentAndNotify);
    }
  }

  if (mState != LIST_UP_TO_DATE)
    PopulateSelf(aIndex+1);

  ASSERT_IN_SYNC;
  NS_ASSERTION(!mRootNode || mState != LIST_DIRTY,
               "PopulateSelf left the list in a dirty (useless) state!");

  return mElements.SafeObjectAt(aIndex);
}

nsIContent *
nsContentList::NamedItem(const nsAString& aName, PRBool aDoFlush)
{
  BringSelfUpToDate(aDoFlush);
    
  PRInt32 i, count = mElements.Count();

  // Typically IDs and names are atomized
  nsCOMPtr<nsIAtom> name = do_GetAtom(aName);
  NS_ENSURE_TRUE(name, nsnull);

  for (i = 0; i < count; i++) {
    nsIContent *content = mElements[i];
    // XXX Should this pass eIgnoreCase?
    if (content &&
        (content->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
                              name, eCaseMatters) ||
         content->AttrValueIs(kNameSpaceID_None, nsGkAtoms::id,
                              name, eCaseMatters))) {
      return content;
    }
  }

  return nsnull;
}

PRInt32
nsContentList::IndexOf(nsIContent *aContent, PRBool aDoFlush)
{
  BringSelfUpToDate(aDoFlush);
    
  return mElements.IndexOf(aContent);
}

void
nsContentList::NodeWillBeDestroyed(const nsINode* aNode)
{
  // We shouldn't do anything useful from now on

  RemoveFromHashtable();
  mRootNode = nsnull;

  // We will get no more updates, so we can never know we're up to
  // date
  SetDirty();
}

// static
void
nsContentList::OnDocumentDestroy(nsIDocument *aDocument)
{
  // If our content list cache holds a list used for a document that's
  // now being destroyed, free the cache to prevent the list from
  // staying around until the next use of content lists ends up
  // replacing what's in the cache.

  if (gCachedContentList && gCachedContentList->mRootNode &&
      gCachedContentList->mRootNode->GetOwnerDoc() == aDocument) {
    NS_RELEASE(gCachedContentList);
  }
}

NS_IMETHODIMP
nsContentList::GetLength(PRUint32* aLength)
{
  *aLength = Length(PR_TRUE);

  return NS_OK;
}

NS_IMETHODIMP
nsContentList::Item(PRUint32 aIndex, nsIDOMNode** aReturn)
{
  nsINode* node = GetNodeAt(aIndex);

  if (node) {
    return CallQueryInterface(node, aReturn);
  }

  *aReturn = nsnull;

  return NS_OK;
}

NS_IMETHODIMP
nsContentList::NamedItem(const nsAString& aName, nsIDOMNode** aReturn)
{
  nsIContent *content = NamedItem(aName, PR_TRUE);

  if (content) {
    return CallQueryInterface(content, aReturn);
  }

  *aReturn = nsnull;

  return NS_OK;
}

nsINode*
nsContentList::GetNodeAt(PRUint32 aIndex)
{
  return Item(aIndex, PR_TRUE);
}

void
nsContentList::AttributeChanged(nsIDocument *aDocument, nsIContent* aContent,
                                PRInt32 aNameSpaceID, nsIAtom* aAttribute,
                                PRInt32 aModType, PRUint32 aStateMask)
{
  NS_PRECONDITION(aContent, "Must have a content node to work with");
  NS_PRECONDITION(aContent->IsNodeOfType(nsINode::eELEMENT),
                  "Should be an element");
  
  if (!mFunc || !mFuncMayDependOnAttr || mState == LIST_DIRTY ||
      !MayContainRelevantNodes(aContent->GetNodeParent()) ||
      !nsContentUtils::IsInSameAnonymousTree(mRootNode, aContent)) {
    // Either we're already dirty or this notification doesn't affect
    // whether we might match aContent.
    return;
  }
  
  if (Match(aContent)) {
    if (mElements.IndexOf(aContent) == -1) {
      // We match aContent now, and it's not in our list already.  Just dirty
      // ourselves; this is simpler than trying to figure out where to insert
      // aContent.
      SetDirty();
    }
  } else {
    // We no longer match aContent.  Remove it from our list.  If it's
    // already not there, this is a no-op (though a potentially
    // expensive one).  Either way, no change of mState is required
    // here.
    mElements.RemoveObject(aContent);
  }
}

void
nsContentList::ContentAppended(nsIDocument *aDocument, nsIContent* aContainer,
                               PRInt32 aNewIndexInContainer)
{
  NS_PRECONDITION(aContainer, "Can't get at the new content if no container!");
  
  /*
   * If the state is LIST_DIRTY then we have no useful information in our list
   * and we want to put off doing work as much as possible.  Also, if
   * aContainer is anonymous from our point of view, we know that we can't
   * possibly be matching any of the kids.
   */
  if (mState == LIST_DIRTY ||
      !nsContentUtils::IsInSameAnonymousTree(mRootNode, aContainer) ||
      !MayContainRelevantNodes(aContainer))
    return;

  /*
   * We want to handle the case of ContentAppended by sometimes
   * appending the content to our list, not just setting state to
   * LIST_DIRTY, since most of our ContentAppended notifications
   * should come during pageload and be at the end of the document.
   * Do a bit of work to see whether we could just append to what we
   * already have.
   */
  
  PRInt32 count = aContainer->GetChildCount();

  if (count > 0) {
    PRInt32 ourCount = mElements.Count();
    PRBool appendToList = PR_FALSE;
    if (ourCount == 0) {
      appendToList = PR_TRUE;
    } else {
      nsIContent* ourLastContent = mElements[ourCount - 1];
      /*
       * We want to append instead of invalidating if the first thing
       * that got appended comes after ourLastContent.
       */
      if (nsContentUtils::PositionIsBefore(ourLastContent,
                                           aContainer->GetChildAt(aNewIndexInContainer))) {
        appendToList = PR_TRUE;
      }
    }
    
    PRInt32 i;
    
    if (!appendToList) {
      // The new stuff is somewhere in the middle of our list; check
      // whether we need to invalidate
      for (i = aNewIndexInContainer; i <= count-1; ++i) {
        if (MatchSelf(aContainer->GetChildAt(i))) {
          // Uh-oh.  We're gonna have to add elements into the middle
          // of our list. That's not worth the effort.
          SetDirty();
          break;
        }
      }
 
      ASSERT_IN_SYNC;
      return;
    }

    /*
     * At this point we know we could append.  If we're not up to
     * date, however, that would be a bad idea -- it could miss some
     * content that we never picked up due to being lazy.  Further, we
     * may never get asked for this content... so don't grab it yet.
     */
    if (mState == LIST_LAZY) // be lazy
      return;

    /*
     * We're up to date.  That means someone's actively using us; we
     * may as well grab this content....
     */
    for (i = aNewIndexInContainer; i <= count-1; ++i) {
      PRUint32 limit = PRUint32(-1);
      nsIContent* newContent = aContainer->GetChildAt(i);
      if (newContent->IsNodeOfType(nsINode::eELEMENT)) {
        PopulateWith(newContent, limit);
      }
    }

    ASSERT_IN_SYNC;
  }
}

void
nsContentList::ContentInserted(nsIDocument *aDocument,
                               nsIContent* aContainer,
                               nsIContent* aChild,
                               PRInt32 aIndexInContainer)
{
  // Note that aContainer can be null here if we are inserting into
  // the document itself; any attempted optimizations to this method
  // should deal with that.
  if (mState != LIST_DIRTY &&
      MayContainRelevantNodes(NODE_FROM(aContainer, aDocument)) &&
      nsContentUtils::IsInSameAnonymousTree(mRootNode, aChild) &&
      MatchSelf(aChild)) {
    SetDirty();
  }

  ASSERT_IN_SYNC;
}
 
void
nsContentList::ContentRemoved(nsIDocument *aDocument,
                              nsIContent* aContainer,
                              nsIContent* aChild,
                              PRInt32 aIndexInContainer)
{
  // Note that aContainer can be null here if we are removing from
  // the document itself; any attempted optimizations to this method
  // should deal with that.
  if (mState != LIST_DIRTY &&
      MayContainRelevantNodes(NODE_FROM(aContainer, aDocument)) &&
      nsContentUtils::IsInSameAnonymousTree(mRootNode, aChild) &&
      MatchSelf(aChild)) {
    SetDirty();
  }

  ASSERT_IN_SYNC;
}

PRBool
nsContentList::Match(nsIContent *aContent)
{
  if (!aContent)
    return PR_FALSE;

  NS_ASSERTION(aContent->IsNodeOfType(nsINode::eELEMENT),
               "Must have element here");

  if (mFunc) {
    return (*mFunc)(aContent, mMatchNameSpaceId, mMatchAtom, mData);
  }

  if (mMatchAtom) {
    nsINodeInfo *ni = aContent->NodeInfo();

    if (mMatchNameSpaceId == kNameSpaceID_Unknown) {
      return (mMatchAll || ni->QualifiedNameEquals(mMatchAtom));
    }

    if (mMatchNameSpaceId == kNameSpaceID_Wildcard) {
      return (mMatchAll || ni->Equals(mMatchAtom));
    }

    return ((mMatchAll && ni->NamespaceEquals(mMatchNameSpaceId)) ||
            ni->Equals(mMatchAtom, mMatchNameSpaceId));
  }

  return PR_FALSE;
}

PRBool 
nsContentList::MatchSelf(nsIContent *aContent)
{
  NS_PRECONDITION(aContent, "Can't match null stuff, you know");
  NS_PRECONDITION(mDeep || aContent->GetNodeParent() == mRootNode,
                  "MatchSelf called on a node that we can't possibly match");

  if (!aContent->IsNodeOfType(nsINode::eELEMENT)) {
    return PR_FALSE;
  }
  
  if (Match(aContent))
    return PR_TRUE;

  if (!mDeep)
    return PR_FALSE;

  PRUint32 i, count = aContent->GetChildCount();

  for (i = 0; i < count; i++) {
    if (MatchSelf(aContent->GetChildAt(i))) {
      return PR_TRUE;
    }
  }
  
  return PR_FALSE;
}

void
nsContentList::PopulateWith(nsIContent *aContent, PRUint32& aElementsToAppend)
{
  NS_PRECONDITION(mDeep || aContent->GetNodeParent() == mRootNode,
                  "PopulateWith called on nodes we can't possibly match");
  NS_PRECONDITION(aContent != mRootNode,
                  "We should never be trying to match mRootNode");
  NS_PRECONDITION(aContent->IsNodeOfType(nsINode::eELEMENT),
                  "Should be an element");

  if (Match(aContent)) {
    mElements.AppendObject(aContent);
    --aElementsToAppend;
    if (aElementsToAppend == 0)
      return;
  }

  // Don't recurse down if we're not doing a deep match.
  if (!mDeep)
    return;
  
#ifdef DEBUG
  nsMutationGuard debugMutationGuard;
#endif  
  PRUint32 count = aContent->GetChildCount();
  nsIContent* const* curChildPtr = aContent->GetChildArray();
  nsIContent* const* stop = curChildPtr + count;
  for (; curChildPtr != stop; ++curChildPtr) {
    nsIContent* curContent = *curChildPtr;
    if (curContent->IsNodeOfType(nsINode::eELEMENT)) {
      PopulateWith(*curChildPtr, aElementsToAppend);
      if (aElementsToAppend == 0)
        break;
    }
  }
#ifdef DEBUG
  NS_ASSERTION(!debugMutationGuard.Mutated(0),
               "Unexpected mutations happened.  Check your match function!");
#endif  
}

void 
nsContentList::PopulateWithStartingAfter(nsINode *aStartRoot,
                                         nsINode *aStartChild,
                                         PRUint32 & aElementsToAppend)
{
  NS_PRECONDITION(mDeep || aStartRoot == mRootNode ||
                  (aStartRoot->GetNodeParent() == mRootNode &&
                   aStartChild == nsnull),
                  "Bogus aStartRoot or aStartChild");

  if (mDeep || aStartRoot == mRootNode) {
#ifdef DEBUG
    PRUint32 invariant = aElementsToAppend + mElements.Count();
#endif
    PRInt32 i = 0;
    if (aStartChild) {
      i = aStartRoot->IndexOf(aStartChild);
      NS_ASSERTION(i >= 0, "The start child must be a child of the start root!");
      ++i;  // move to one past
    }

#ifdef DEBUG
    nsMutationGuard debugMutationGuard;
#endif  
    PRUint32 childCount = aStartRoot->GetChildCount();
    nsIContent* const* curChildPtr = aStartRoot->GetChildArray();
    nsIContent* const* stop = curChildPtr + childCount;
    // Now advance curChildPtr to the child we want to be starting with
    NS_ASSERTION(i <= childCount, "Unexpected index");
    curChildPtr += i;
    for ( ; curChildPtr != stop; ++curChildPtr) {
      nsIContent* content = *curChildPtr;
      if (content->IsNodeOfType(nsINode::eELEMENT)) {
        PopulateWith(content, aElementsToAppend);

        NS_ASSERTION(aElementsToAppend + mElements.Count() == invariant,
                     "Something is awry in PopulateWith!");
        if (aElementsToAppend == 0)
          break;
      }
    }
#ifdef DEBUG
    NS_ASSERTION(!debugMutationGuard.Mutated(0),
                 "Unexpected mutations happened.  Check your match function!");
#endif
  }

  if (aElementsToAppend == 0) {
    return;
  }

  // We want to make sure we don't move up past our root node. So if
  // we're there, don't move to the parent.
  if (aStartRoot == mRootNode)
    return;
  
  // We could call GetParent() here to avoid walking children of the
  // document node. However they should be very few in number and we
  // might want to walk them in the future so it's unnecessary to have
  // this be the only thing that prevents it
  nsINode* parent = aStartRoot->GetNodeParent();
  
  if (parent)
    PopulateWithStartingAfter(parent, aStartRoot, aElementsToAppend);
}

void 
nsContentList::PopulateSelf(PRUint32 aNeededLength)
{
  if (!mRootNode) {
    return;
  }

  ASSERT_IN_SYNC;

  PRUint32 count = mElements.Count();
  NS_ASSERTION(mState != LIST_DIRTY || count == 0,
               "Reset() not called when setting state to LIST_DIRTY?");

  if (count >= aNeededLength) // We're all set
    return;

  PRUint32 elementsToAppend = aNeededLength - count;
#ifdef DEBUG
  PRUint32 invariant = elementsToAppend + mElements.Count();
#endif

  // If we already have nodes start searching at the last one, otherwise
  // start searching at the root.
  nsINode* startRoot = count == 0 ? mRootNode : mElements[count - 1];

  PopulateWithStartingAfter(startRoot, nsnull, elementsToAppend);
  NS_ASSERTION(elementsToAppend + mElements.Count() == invariant,
               "Something is awry in PopulateWith!");

  if (elementsToAppend != 0)
    mState = LIST_UP_TO_DATE;
  else
    mState = LIST_LAZY;

  ASSERT_IN_SYNC;
}

void
nsContentList::RemoveFromHashtable()
{
  if (mFunc) {
    // This can't be in the table anyway
    return;
  }
  
  if (!gContentListHashTable.ops)
    return;

  PL_DHashTableOperate(&gContentListHashTable,
                       GetKey(),
                       PL_DHASH_REMOVE);

  if (gContentListHashTable.entryCount == 0) {
    PL_DHashTableFinish(&gContentListHashTable);
    gContentListHashTable.ops = nsnull;
  }
}

void
nsContentList::BringSelfUpToDate(PRBool aDoFlush)
{
  if (mRootNode && aDoFlush) {
    // XXX sXBL/XBL2 issue
    nsIDocument* doc = mRootNode->GetCurrentDoc();
    if (doc) {
      // Flush pending content changes Bug 4891.
      doc->FlushPendingNotifications(Flush_ContentAndNotify);
    }
  }

  if (mState != LIST_UP_TO_DATE)
    PopulateSelf(PRUint32(-1));
    
  ASSERT_IN_SYNC;
  NS_ASSERTION(!mRootNode || mState == LIST_UP_TO_DATE,
               "PopulateSelf dod not bring content list up to date!");
}

#ifdef DEBUG_CONTENT_LIST
void
nsContentList::AssertInSync()
{
  if (mState == LIST_DIRTY) {
    return;
  }

  if (!mRootNode) {
    NS_ASSERTION(mElements.Count() == 0 && mState == LIST_DIRTY,
                 "Empty iterator isn't quite empty?");
    return;
  }

  // XXX This code will need to change if nsContentLists can ever match
  // elements that are outside of the document element.
  nsIContent *root;
  if (mRootNode->IsNodeOfType(nsINode::eDOCUMENT)) {
    root = static_cast<nsIDocument*>(mRootNode)->GetRootContent();
  }
  else {
    root = static_cast<nsIContent*>(mRootNode);
  }

  nsCOMPtr<nsIContentIterator> iter;
  if (mDeep) {
    NS_NewPreContentIterator(getter_AddRefs(iter));
    iter->Init(root);
    iter->First();
  }

  PRInt32 cnt = 0, index = 0;
  while (PR_TRUE) {
    if (cnt == mElements.Count() && mState == LIST_LAZY) {
      break;
    }

    nsIContent *cur = mDeep ? iter->GetCurrentNode() :
                              mRootNode->GetChildAt(index++);
    if (!cur) {
      break;
    }

    if (cur->IsNodeOfType(nsINode::eELEMENT) && Match(cur)) {
      NS_ASSERTION(cnt < mElements.Count() && mElements[cnt] == cur,
                   "Elements is out of sync");
      ++cnt;
    }

    if (mDeep) {
      iter->Next();
    }
  }

  NS_ASSERTION(cnt == mElements.Count(), "Too few elements");
}
#endif