//later avoid recursive
PageIndexNodeBase <T> ReadTreePageStructure(int parent)
{
//first read the Int32 flag record
var flags = reader.ReadInt32();
//
if (flags == 0)
{
//signal tree left or right is null
return(null);
}
var thisPageNo = ++Index.NodePages;
var pageType = flags & 0b011;
switch (pageType)
{
case Consts.BTreePageNodeFlag:
//read root
var page = new PageIndexNode <T>(flags, thisPageNo, reader, KeyType);
page.Left = ReadTreePageStructure(thisPageNo);
page.Right = ReadTreePageStructure(thisPageNo);
return(page);
case Consts.BTreePageNodeItemsFlag:
return(new PageIndexItems <T>(flags, thisPageNo, reader));
default:
throw new ArgumentException("Invalid database structure!");
}
}
internal IEnumerable <KeyValuePair <T, List <int> > > DumpTreeNodesInOrder(PageIndexNodeBase <T> root)
{
var stack = new Stack <PageIndexNodeBase <T> >();
PageIndexNode <T> nodePage = null;
//set current to root
PageIndexNodeBase <T> current = root;
IEnumerable <KeyValuePair <T, List <int> > > EnumerateOffsets(PageIndexItems <T> page)
{
//find from dictionary for fast search
var metaPage = Index.IndexItems <T>()[page.Offset];
if (metaPage != null)
{
foreach (var ofs in metaPage.Items)
{
yield return(ofs);
}
}
else
{
yield break;
}
}
while (stack.Count > 0 || current != null)
{
if (current != null)
{
//if it's a items page, return all it's values
if (current.Type == MetaIndexType.Items)
{
//find items page by its offset
foreach (var ofs in EnumerateOffsets(current as PageIndexItems <T>))
{
yield return(ofs);
}
//signal end
current = null;
}
else
{
//it's a node page, push current page
stack.Push(current);
//try to go Left
current = ((PageIndexNode <T>)current).Left;
}
}
else
{
current = stack.Pop();
//return current node page items --first--
if (current.Type == MetaIndexType.Items)
{
//find items page by its offset
foreach (var ofs in EnumerateOffsets(current as PageIndexItems <T>))
{
yield return(ofs);
}
//signal end
current = null;
}
else
{
//it's a node page, return Key values, and try to go Right
nodePage = current as PageIndexNode <T>;
yield return(new KeyValuePair <T, List <int> >(nodePage.Key, nodePage.Values));
current = nodePage.Right;
}
}
}
}
