C++ nsAutoTArray::RemoveElementsAt方法代码示例

//.........这里部分代码省略.........
      else
        firstNode = NodeToParentOffset(mFirst, &firstOffset);

      lastNode = NodeToParentOffset(mLast, &lastOffset);
      ++lastOffset;
    }
  }

  // The end positions are always in the range even if it has no parent.
  // We need to allow that or 'iter->Init(root)' would assert in Last()
  // or First() for example, bug 327694.
  if (mFirst != mCurNode && mLast != mCurNode &&
      (!firstNode || !lastNode ||
       !NodeIsInTraversalRange(mCurNode, mPre, firstNode, firstOffset,
                               lastNode, lastOffset)))
  {
    mIsDone = PR_TRUE;
    return NS_ERROR_FAILURE;
  }

  // We can be at ANY node in the sequence.
  // Need to regenerate the array of indexes back to the root or common parent!
  nsAutoTArray<nsINode*, 8>     oldParentStack;
  nsAutoTArray<PRInt32, 8>      newIndexes;

  // Get a list of the parents up to the root, then compare the new node
  // with entries in that array until we find a match (lowest common
  // ancestor).  If no match, use IndexOf, take the parent, and repeat.
  // This avoids using IndexOf() N times on possibly large arrays.  We
  // still end up doing it a fair bit.  It's better to use Clone() if
  // possible.

  // we know the depth we're down (though we may not have started at the
  // top).
  if (!oldParentStack.SetCapacity(mIndexes.Length()+1))
    return NS_ERROR_FAILURE;

  // We want to loop mIndexes.Length() + 1 times here, because we want to make
  // sure we include mCommonParent in the oldParentStack, for use in the next
  // for loop, and mIndexes only has entries for nodes from tempNode up through
  // an ancestor of tempNode that's a child of mCommonParent.
  for (PRInt32 i = mIndexes.Length()+1; i > 0 && tempNode; i--)
  {
    // Insert at head since we're walking up
    oldParentStack.InsertElementAt(0, tempNode);

    nsINode *parent = tempNode->GetNodeParent();

    if (!parent)  // this node has no parent, and thus no index
      break;

    if (parent == mCurNode)
    {
      // The position was moved to a parent of the current position. 
      // All we need to do is drop some indexes.  Shortcut here.
      mIndexes.RemoveElementsAt(mIndexes.Length() - oldParentStack.Length(),
                                oldParentStack.Length());
      mIsDone = PR_FALSE;
      return NS_OK;
    }
    tempNode = parent;
  }

  // Ok.  We have the array of old parents.  Look for a match.
  while (newCurNode)
  {
    nsINode *parent = newCurNode->GetNodeParent();

    if (!parent)  // this node has no parent, and thus no index
      break;

    PRInt32 indx = parent->IndexOf(newCurNode);

    // insert at the head!
    newIndexes.InsertElementAt(0, indx);

    // look to see if the parent is in the stack
    indx = oldParentStack.IndexOf(parent);
    if (indx >= 0)
    {
      // ok, the parent IS on the old stack!  Rework things.
      // we want newIndexes to replace all nodes equal to or below the match
      // Note that index oldParentStack.Length()-1 is the last node, which is
      // one BELOW the last index in the mIndexes stack.  In other words, we
      // want to remove elements starting at index (indx+1).
      PRInt32 numToDrop = oldParentStack.Length()-(1+indx);
      if (numToDrop > 0)
        mIndexes.RemoveElementsAt(mIndexes.Length() - numToDrop, numToDrop);
      mIndexes.AppendElements(newIndexes);

      break;
    }
    newCurNode = parent;
  }

  // phew!

  mIsDone = PR_FALSE;
  return NS_OK;
}