TLinkedBtree

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Description

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To be documented

Class definitions

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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 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 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 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;
procedure Clear;
procedure Empty;
procedure Rebuild;

Function declarations

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constructor TLinkedBtree.Create;

Description: To be documented

Note	None documented

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destructor TLinkedBtree.Destroy;

Description: To be documented

Note	None documented

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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

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function TLinkedBtree.PropogateDrop(AEntry:TBtreeObject):Boolean;

Description: To be documented

Note	None documented

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function TLinkedBtree.PropogateMerge(AEntry:TBtreeObject):Boolean;

Description: To be documented

Note	None documented

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function TLinkedBtree.PropogateSplit(AEntry:TBtreeObject):Boolean;

Description: To be documented

Note	This is currently not used by insert and must be tested before use

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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

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function TLinkedBtree.GetDepth(AEntry:TBtreeObject):LongWord;

Description: Get the depth of the supplied entry in the btree

Note	None documented

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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

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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

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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

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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

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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

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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

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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

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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

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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

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function TLinkedBtree.GetLefthand(AEntry:TBtreeObject):TBtreeObject;

Description: Get the lefthand neighbour (Node) of the supplied entries node

Note	None documented

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function TLinkedBtree.GetRighthand(AEntry:TBtreeObject):TBtreeObject;

Description: Get the righthand neighbour (Node) of the supplied entries node

Note	None documented

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function TLinkedBtree.GetLeftmost(AEntry:TBtreeObject):TBtreeObject;

Description: Get the leftmost entry in the tree of the supplied entry

Note	None documented

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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function TLinkedBtree.Unlink(AEntry:TBtreeObject):Boolean;

Description: Unlink the object from Prev/Next in linked list

Note	None documented

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function TLinkedBtree.LinkBlank(AEntry:TBtreeObject):Boolean;

Description: Link the object to Prev/Next in blank key list

Note	Always link as last

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function TLinkedBtree.UnlinkBlank(AEntry:TBtreeObject):Boolean;

Description: Unlink the object from Prev/Next in blank key list

Note	None documented

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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

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function TLinkedBtree.Detach(AEntry:TBtreeObject):Boolean;

Description: Detach the object from Parent/Left/Right in btree

Note	None documented

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function TLinkedBtree.PushNode(AEntry:TBtreeObject):Boolean;

Description: Called before a node is pushed following insert of an entry

Note	None documented

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function TLinkedBtree.SplitNode(AEntry:TBtreeObject):Boolean;

Description: Called before a node is split following insert of an entry

Note	None documented

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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

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function TLinkedBtree.MergeNode(AEntry,AMerge:TBtreeObject):Boolean;

Description: Called before a node is merged following removal of an entry

Note	None documented

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function TLinkedBtree.BorrowEntry(AEntry,ABorrow:TBtreeObject):Boolean;

Description: Called before an entry is borrowed following removal of an entry

Note	None documented

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function TLinkedBtree.SwapEntry(AEntry,ASwap:TBtreeObject; ALeft:Boolean):Boolean;

Description: Called before an entry is swapped during a merge or borrow

Note	None documented

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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

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function TLinkedBtree.CreateBlank:TBtreeObject;

Description: Create a blank key when a node is added (Split/Empty)

Note	None documented

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function TLinkedBtree.DeleteBlank(ABlank:TBtreeObject):Boolean;

Description: Delete a blank key when a node is removed (Merge)

Note	None documented

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function TLinkedBtree.AttachBlank(ABlank:TBtreeObject):Boolean;

Description: Called after a blank entry is attached to a node during split or merge

Note	None documented

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function TLinkedBtree.DetachBlank(ABlank:TBtreeObject):Boolean;

Description: Called before a blank entry is detached from a node during split or merge

Note	None documented

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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procedure TLinkedBtree.Clear;

Description: Removes all entries from the btree

Note	None documented

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procedure TLinkedBtree.Empty;

Description: Removes all entries from the btree and adds a blank root key

Note	None documented

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procedure TLinkedBtree.Rebuild;

Description: Empties the btree and rebuilds from the linked list

Note	None documented

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