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Description

To be documented

Class definitions


TLinkedBtree = class(TObject)

Note: A B-Tree of TBtreeObjects with automatic Left/Right etc Links

Linked B-Tree which does not Free nodes on Destroy

 
Note: Search/Find should be implemented by descendants. Compare must always be implemented by descendants. Blank keys are not included in the linked list. Blank key always compares as higher than anything. Linked list allows easy traversal in either direction. Also allows implementation of the rebalance function.
 
constructor Create;  
destructor Destroy; override;  
private
procedure SetOrder(AOrder:LongWord);  
 
function PropogateDrop(AEntry:TBtreeObject):Boolean;  
function PropogateDropOld(AEntry:TBtreeObject):Boolean;  
function PropogateDropOldOld(AEntry:TBtreeObject):Boolean;  
function PropogateMerge(AEntry:TBtreeObject):Boolean;  
function PropogateSplit(AEntry:TBtreeObject):Boolean;  
protected
FOrder:LongWord; Order N of B-Tree (N - 1 Keys per Node)
FMedian:LongWord; Ceil(N / 2) (Median - 1 Keys as Minimum)
 
FSwapLeft:Boolean; If True then Remove will Swap with Left not Right
 
FRoot:TBtreeObject; Root Node of B-Tree
FFirst:TBtreeObject; First object in Linked List (Sorted)
FLast:TBtreeObject; Last object in Linked List (Sorted)
FFirstBlank:TBtreeObject; First blank key in Linked List (Not Sorted)
FLastBlank:TBtreeObject; Last blank key in Linked List (Not Sorted)
 
function GetCount(AEntry:TBtreeObject):LongWord; virtual;  
function GetDepth(AEntry:TBtreeObject):LongWord; virtual;  
 
function GetEnd(AEntry:TBtreeObject):TBtreeObject; virtual;  
function GetStart(AEntry:TBtreeObject):TBtreeObject; virtual;  
function GetBlank(AEntry:TBtreeObject):TBtreeObject; virtual;  
function GetMedian(AEntry:TBtreeObject):TBtreeObject; virtual;  
 
function GetDrop(AEntry:TBtreeObject; var ALeft:Boolean):TBtreeObject; virtual;  
function GetMerge(AEntry:TBtreeObject):TBtreeObject; virtual;  
function GetBorrow(AEntry:TBtreeObject):TBtreeObject; virtual;  
function GetTarget(ADrop:TBtreeObject; ALeft:Boolean):TBtreeObject; virtual;  
 
function SetParent(AEntry,AParent:TBtreeObject):Boolean;  
 
function GetLefthand(AEntry:TBtreeObject):TBtreeObject;  
function GetRighthand(AEntry:TBtreeObject):TBtreeObject;  
 
function GetLeftmost(AEntry:TBtreeObject):TBtreeObject;  
function GetRightmost(AEntry:TBtreeObject):TBtreeObject;  
 
function GetSuccessor(AEntry:TBtreeObject):TBtreeObject;  
function GetPredecessor(AEntry:TBtreeObject):TBtreeObject;  
 
function GetPosition(AStart,AEntry:TBtreeObject):TBtreeObject;  
 
function Push(AEntry:TBtreeObject):Boolean;  
function Split(AEntry:TBtreeObject):Boolean;  
function Swap(AEntry,ASwap:TBtreeObject; ALeft:Boolean):Boolean;  
function Drop(AEntry,ADrop,ATarget:TBtreeObject; ALeft:Boolean):Boolean;  
function DropOld(AEntry,ADrop:TBtreeObject; ALeft:Boolean):Boolean;  
function DropOldOld(AEntry,ADrop:TBtreeObject; ALeft:Boolean):Boolean;  
function DropOldOldOld(AEntry,ADrop:TBtreeObject; ALeft:Boolean):Boolean;  
function Merge(AEntry,AMerge:TBtreeObject):Boolean;  
function Borrow(AEntry,ABorrow:TBtreeObject):Boolean;  
 
function Link(AEntry,ANext:TBtreeObject):Boolean;  
function Unlink(AEntry:TBtreeObject):Boolean;  
 
function LinkBlank(AEntry:TBtreeObject):Boolean;  
function UnlinkBlank(AEntry:TBtreeObject):Boolean;  
 
function Attach(AParent,AEntry,ARight:TBtreeObject):Boolean;  
function Detach(AEntry:TBtreeObject):Boolean;  
 
function PushNode(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to monitor node pus
function SplitNode(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to monitor node split
function DropNode(AEntry,ADrop,ATarget:TBtreeObject; ALeft:Boolean):Boolean; virtual; Allows descendants to monitor node drop
function DropNodeOld(AEntry,ADrop:TBtreeObject; ALeft:Boolean):Boolean; virtual; Allows descendants to monitor node drop
function MergeNode(AEntry,AMerge:TBtreeObject):Boolean; virtual; Allows descendants to monitor node merge
function BorrowEntry(AEntry,ABorrow:TBtreeObject):Boolean; virtual; Allows descendants to monitor entry borrow
 
function SwapEntry(AEntry,ASwap:TBtreeObject;ALeft:Boolean):Boolean; virtual; Allows descendants to monitor entry swap
function SetParentEntry(AEntry,AParent:TBtreeObject):Boolean; virtual; Allows descendants to monitor entry parent
 
function CreateBlank:TBtreeObject; virtual; Allows descendants to monitor node creation
function DeleteBlank(ABlank:TBtreeObject):Boolean; virtual; Allows descendants to monitor node deletion
 
function AttachBlank(ABlank:TBtreeObject):Boolean; virtual; Allows descendants to monitor node modification
function DetachBlank(ABlank:TBtreeObject):Boolean; virtual; Allows descendants to monitor node modification
 
function AttachEntry(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to monitor node modification
function DetachEntry(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to monitor node modification
 
function RequirePush(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to modify balancing behaviour
function RequireSplit(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to modify balancing behaviour
function RequireDrop(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to modify balancing behaviour
function RequireMerge(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to modify balancing behaviour
function RequireBorrow(AEntry:TBtreeObject):Boolean; virtual; Allows descendants to modify balancing behaviour
 
function Compare(AEntry1,AEntry2:TBtreeObject):Integer; virtual;  
public
property Order:LongWord read FOrder write SetOrder;  
property Median:LongWord read FMedian;  
 
property SwapLeft:Boolean read FSwapLeft;  
 
property Root:TBtreeObject read FRoot;  
property First:TBtreeObject read FFirst;  
property Last:TBtreeObject read FLast;  
 
function Add(AParent,AEntry:TBtreeObject):Boolean;  
 
function Insert(AEntry:TBtreeObject):Boolean;  
function Remove(AEntry:TBtreeObject):Boolean;  
function RemoveOld(AEntry:TBtreeObject):Boolean;  
function RemoveOldOld(AEntry:TBtreeObject):Boolean;  
 
procedure Clear;  
procedure Empty;  
procedure Rebuild;  


Function declarations


constructor TLinkedBtree.Create;
Description: To be documented
Note None documented 


destructor TLinkedBtree.Destroy;
Description: To be documented
Note None documented 


procedure TLinkedBtree.SetOrder(AOrder:LongWord);
Description: Set a new Order and calculate a new Median value
Note Minimum Order is 5 and minimum Median is 3 


function TLinkedBtree.PropogateDrop(AEntry:TBtreeObject):Boolean;
Description: To be documented
Note None documented 


function TLinkedBtree.PropogateMerge(AEntry:TBtreeObject):Boolean;
Description: To be documented
Note None documented 


function TLinkedBtree.PropogateSplit(AEntry:TBtreeObject):Boolean;
Description: To be documented
Note This is currently not used by insert and must be tested before use 


function TLinkedBtree.GetCount(AEntry:TBtreeObject):LongWord;
Description: Get the count of entries in the node of the supplied entry
Note Does not include the blank key 


function TLinkedBtree.GetDepth(AEntry:TBtreeObject):LongWord;
Description: Get the depth of the supplied entry in the btree
Note None documented 


function TLinkedBtree.GetEnd(AEntry:TBtreeObject):TBtreeObject;
Description: Get the end entry in the node of the supplied entry
Note Includes the blank key which may be the only key 


function TLinkedBtree.GetStart(AEntry:TBtreeObject):TBtreeObject;
Description: Get the start entry in the node of the supplied entry
Note Includes the blank key which may be the only key 


function TLinkedBtree.GetBlank(AEntry:TBtreeObject):TBtreeObject;
Description: Get the blank entry in the node of the supplied entry
Note Blank entry is always the last entry in every node 


function TLinkedBtree.GetMedian(AEntry:TBtreeObject):TBtreeObject;
Description: Get the median entry in the node of the supplied entry
Note Does not include the blank key 


function TLinkedBtree.GetDrop(AEntry:TBtreeObject; var ALeft:Boolean):TBtreeObject;
Description: Get the neighbour with appropriate number of keys to drop
Note Always drop with the Righthand neighbour if available

Only supported by descendant classes with non balanced nodes 


function TLinkedBtree.GetMerge(AEntry:TBtreeObject):TBtreeObject;
Description: Get the neighbour with appropriate number of keys to merge
Note Always merge with the Righthand neighbour if available 


function TLinkedBtree.GetBorrow(AEntry:TBtreeObject):TBtreeObject;
Description: Get the neighbour with sufficient keys to borrow one
Note Always borrow from the Righthand neighbour if available 


function TLinkedBtree.GetTarget(ADrop:TBtreeObject; ALeft:Boolean):TBtreeObject;
Description: Get the actual target within the neighbour that is appropriate to drop
Note Only supported by descendant classes with non balanced nodes 


function TLinkedBtree.SetParent(AEntry,AParent:TBtreeObject):Boolean;
Description: Set the parent for all entries in a node and set the child of the parent
Note Includes the blank key which may be the only key 


function TLinkedBtree.GetLefthand(AEntry:TBtreeObject):TBtreeObject;
Description: Get the lefthand neighbour (Node) of the supplied entries node
Note None documented 


function TLinkedBtree.GetRighthand(AEntry:TBtreeObject):TBtreeObject;
Description: Get the righthand neighbour (Node) of the supplied entries node
Note None documented 


function TLinkedBtree.GetLeftmost(AEntry:TBtreeObject):TBtreeObject;
Description: Get the leftmost entry in the tree of the supplied entry
Note None documented 


function TLinkedBtree.GetRightmost(AEntry:TBtreeObject):TBtreeObject;
Description: Get the rightmost entry in the tree of the supplied entry
Note Does not include the blank key 


function TLinkedBtree.GetSuccessor(AEntry:TBtreeObject):TBtreeObject;
Description: Get the successor (Right) entry of the supplied entry
Note The returned entry may be a blank key or a real key 


function TLinkedBtree.GetPredecessor(AEntry:TBtreeObject):TBtreeObject;
Description: Get the predecessor (Left) entry of the supplied entry
Note The returned entry may be a blank key or a real key 


function TLinkedBtree.GetPosition(AStart,AEntry:TBtreeObject):TBtreeObject;
Description: Get the position where entry should be inserted into the btree
Note The returned entry will be the entry to the right in insert node

The returned entry may be the blank key or may be a real key 


function TLinkedBtree.Push(AEntry:TBtreeObject):Boolean;
Description: Push the node containing the supplied entry
Note Will create a new blank as root

All keys will be parented by new blank root
Push can only occur on the root node 


function TLinkedBtree.Split(AEntry:TBtreeObject):Boolean;
Description: Split the node containing the supplied entry
Note Will promote the median entry to the parent

Keys left of median will be parented by median
Keys right of median will retain current parent
Child of median will parent to new blank on left
Median will be attached to the left of the parent
Split can propogate all the way to root since median is promoted 


function TLinkedBtree.Swap(AEntry,ASwap:TBtreeObject; ALeft:Boolean):Boolean;
Description: Swap the supplied entries directly from node to node
Note Entry is always a parent and Swap is always a leaf

No balancing is done as the entry is to be deleted or borrowed 


function TLinkedBtree.Drop(AEntry,ADrop,ATarget:TBtreeObject; ALeft:Boolean):Boolean;
Description: Drop the nodes of the supplied entries into one
Note Will demote the parent entry to the drop node

Drop with Right (Entry has no child)
Parent of left node will become part of target node (start)
Parent of right node will remain as parent of drop node
Left node will be deleted
Drop with Right (Entry has a child)
Node will be deleted
Child of node will be parented by parent of node
Drop with Left (Entry has no child)
Parent of left node will become part of target node (last before blank)
Parent of right node will become parent of drop node
Right node will be deleted
Drop with Left (Entry has a child)
Node will be deleted
Child of node will be parented by parent of node
Drop with no Neighbour
Node will be deleted
Child of node will be parented by parent of node

Drop can propogate all the way to root since parent is demoted 


function TLinkedBtree.Merge(AEntry,AMerge:TBtreeObject):Boolean;
Description: Merge the nodes of the supplied entries into one
Note Will demote the parent entry to the merged node

Merge with Right
Parent of left node will become part of child node (Between last of left and start of right)
Parent of right node will become parent of merged child
Merge with Left
Convert to merge with right by calling itself with swapped parameters

Merge can propogate all the way to root since parent is demoted 


function TLinkedBtree.Borrow(AEntry,ABorrow:TBtreeObject):Boolean;
Description: Borrow an entry from the supplied node to balance the tree
Note Will demote the parent and premote the successor

Borrow from Right
Start key of right node will become the parent key of left node
Parent key of left node will become the last key of left node
Borrow from Left
Last key of left node will become the parent key of left node
Parent key of left node will become the start key of right node

Borrow does not propogate to parent since their is a promote and a demote
Borrow can occur in non leaf nodes due to merge of child nodes which demotes
Borrow with Child
Child of promoted key will go to blank key of left node
Child of blank key of left node will go to demoted key 


function TLinkedBtree.Link(AEntry,ANext:TBtreeObject):Boolean;
Description: Link the object to Prev/Next in linked list
Note If Next is nil then link as last 


function TLinkedBtree.Unlink(AEntry:TBtreeObject):Boolean;
Description: Unlink the object from Prev/Next in linked list
Note None documented 


function TLinkedBtree.LinkBlank(AEntry:TBtreeObject):Boolean;
Description: Link the object to Prev/Next in blank key list
Note Always link as last 


function TLinkedBtree.UnlinkBlank(AEntry:TBtreeObject):Boolean;
Description: Unlink the object from Prev/Next in blank key list
Note None documented 


function TLinkedBtree.Attach(AParent,AEntry,ARight:TBtreeObject):Boolean;
Description: Attach the object to Parent/Left/Right in btree
Note If Right is nil then attach as last

If Parent is nil then attach at root 


function TLinkedBtree.Detach(AEntry:TBtreeObject):Boolean;
Description: Detach the object from Parent/Left/Right in btree
Note None documented 


function TLinkedBtree.PushNode(AEntry:TBtreeObject):Boolean;
Description: Called before a node is pushed following insert of an entry
Note None documented 


function TLinkedBtree.SplitNode(AEntry:TBtreeObject):Boolean;
Description: Called before a node is split following insert of an entry
Note None documented 


function TLinkedBtree.DropNode(AEntry,ADrop,ATarget:TBtreeObject; ALeft:Boolean):Boolean;
Description: Called before a node is dropped following removal of an entry
Note None documented 


function TLinkedBtree.MergeNode(AEntry,AMerge:TBtreeObject):Boolean;
Description: Called before a node is merged following removal of an entry
Note None documented 


function TLinkedBtree.BorrowEntry(AEntry,ABorrow:TBtreeObject):Boolean;
Description: Called before an entry is borrowed following removal of an entry
Note None documented 


function TLinkedBtree.SwapEntry(AEntry,ASwap:TBtreeObject; ALeft:Boolean):Boolean;
Description: Called before an entry is swapped during a merge or borrow
Note None documented 


function TLinkedBtree.SetParentEntry(AEntry,AParent:TBtreeObject):Boolean;
Description: Called after an entry is reparented during a push, split, merge, borrow or swap
Note None documented 


function TLinkedBtree.CreateBlank:TBtreeObject;
Description: Create a blank key when a node is added (Split/Empty)
Note None documented 


function TLinkedBtree.DeleteBlank(ABlank:TBtreeObject):Boolean;
Description: Delete a blank key when a node is removed (Merge)
Note None documented 


function TLinkedBtree.AttachBlank(ABlank:TBtreeObject):Boolean;
Description: Called after a blank entry is attached to a node during split or merge
Note None documented 


function TLinkedBtree.DetachBlank(ABlank:TBtreeObject):Boolean;
Description: Called before a blank entry is detached from a node during split or merge
Note None documented 


function TLinkedBtree.AttachEntry(AEntry:TBtreeObject):Boolean;
Description: Called after a non blank entry is attached to a node during insert or remove
Note None documented 


function TLinkedBtree.DetachEntry(AEntry:TBtreeObject):Boolean;
Description: Called before a non blank entry is detached from a node during insert or remove
Note None documented 


function TLinkedBtree.RequirePush(AEntry:TBtreeObject):Boolean;
Description: Called after an entry is inserted to determine if a push is required
Entry Entry is the key that was inserted

Or a key in a parent node of the node where the entry was inserted

Note Only supported by descendant classes with non balanced nodes 


function TLinkedBtree.RequireSplit(AEntry:TBtreeObject):Boolean;
Description: Called after an entry is inserted to determine if a split is required
Entry Entry is the key that was inserted

Or a key in a parent node of the node where the entry was inserted 


function TLinkedBtree.RequireDrop(AEntry:TBtreeObject):Boolean;
Description: Called after an entry is removed to determine if a drop is required
Entry Entry is the start key of the node where the entry was removed

Or a key in a parent node of the node where the entry was removed

Note Only supported by descendant classes with non balanced nodes 


function TLinkedBtree.RequireMerge(AEntry:TBtreeObject):Boolean;
Description: Called after an entry is removed to determine if a merge is required
Entry Entry is the start key of the node where the entry was removed

Or a key in a parent node of the node where the entry was removed 


function TLinkedBtree.RequireBorrow(AEntry:TBtreeObject):Boolean;
Description: Called after an entry is removed to determine if a borrow is required
Entry Entry is the start key of the node where the entry was removed

Or a key in a parent node of the node where the entry was removed 


function TLinkedBtree.Compare(AEntry1,AEntry2:TBtreeObject):Integer;
Description: Always returns greater than unless the second entry is a blank key
Note This means keys will end up in added order if no compare is provided 


function TLinkedBtree.Add(AParent,AEntry:TBtreeObject):Boolean;
Description: Add an entry to the btree without doing the full insert
Entry Entries must be added in btree order to obtain final order
Note Both real and blank keys can be added

No events are triggered by Add 


function TLinkedBtree.Insert(AEntry:TBtreeObject):Boolean;
Description: Insert an entry in the btree by finding its position
Note Rebalances the tree after inserting the new entry

Blank keys cannot be inserted
Entry must be created by the caller 


function TLinkedBtree.Remove(AEntry:TBtreeObject):Boolean;
Description: Remove an entry from the btree by deleting it
Note Rebalances the tree after deleting the entry

Blank keys cannot be removed
Entry must be destroyed by the caller 


procedure TLinkedBtree.Clear;
Description: Removes all entries from the btree
Note None documented 


procedure TLinkedBtree.Empty;
Description: Removes all entries from the btree and adds a blank root key
Note None documented 


procedure TLinkedBtree.Rebuild;
Description: Empties the btree and rebuilds from the linked list
Note None documented


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