public ImmutableItemMap <T> ConvertToImmutable(ImmutableItemMap <T> previousLinks = null)
{
// If no links were added, return the previous map
if (_groupIndices.Count == 0)
{
return(previousLinks);
}
// Sort the new links by the group index
PartialArray <int> .SortKeysAndItems(_groupIndices, _memberIndices);
// Build a new immutable map
ImmutableItemMap <T> newMap = new ImmutableItemMap <T>(_provider);
// Track how many of the sorted mutable links we've added so far
int nextIndex = 0;
// Track the group we're adding links for and what we've linked it to (to filter duplicates)
int currentGroup = -1;
HashSet <int> linksAlreadyAddedForGroup = null;
// If there was an immutable set, build from it first
if (previousLinks != null)
{
for (int groupIndex = 0; groupIndex < previousLinks._firstMemberIndexForGroup.Count; ++groupIndex)
{
linksAlreadyAddedForGroup = new HashSet <int>();
// Add all links in the old set from this group (if any)
MapEnumerator <T> oldLinks = previousLinks.LinksFrom(groupIndex);
while (oldLinks.MoveNext())
{
if (linksAlreadyAddedForGroup.Add(oldLinks.CurrentIndex))
{
newMap.AddLink(groupIndex, oldLinks.CurrentIndex);
}
}
// Add all links in the new set from this group (if any)
while (nextIndex < _groupIndices.Count && _groupIndices[nextIndex] == groupIndex)
{
if (linksAlreadyAddedForGroup.Add(_memberIndices[nextIndex]))
{
newMap.AddLink(_groupIndices[nextIndex], _memberIndices[nextIndex]);
}
nextIndex++;
}
}
}
// Add remaining links in the new set, if any are left
currentGroup = -1;
while (nextIndex < _groupIndices.Count)
{
// If we're adding links for a different group, reset the 'already added' set
if (_groupIndices[nextIndex] != currentGroup)
{
currentGroup = _groupIndices[nextIndex];
linksAlreadyAddedForGroup = new HashSet <int>();
}
if (linksAlreadyAddedForGroup.Add(_memberIndices[nextIndex]))
{
newMap.AddLink(_groupIndices[nextIndex], _memberIndices[nextIndex]);
}
nextIndex++;
}
return(newMap);
}