<?xml version="1.0" encoding="UTF-8"?>
<!--

Documentation for LCL (Lazarus Component Library) and LazUtils (Lazarus 
Utilities) are published under the Creative Commons Attribution-ShareAlike 4.0 
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https://gitlab.com/freepascal.org/lazarus/lazarus/-/blob/main/docs/cc-by-sa-4-0.txt

Copyright (c) 1997-2025, by the Lazarus Development Team.

-->
<fpdoc-descriptions>
<package name="lazutils">
<!--
====================================================================
LazLinkedList
====================================================================
-->
<module name="LazLinkedList">
<short>Defines a simple doubly linked list.</short>
<descr>
<p>
<file>lazlinkedlist.pas</file> defines a simple doubly linked list 
(TLinkList). It supports Adding, Deleting, getting First and getting Last in 
O(1). Finding can be done in time O(n).
</p>
<p>
<file>lazlinkedlist.pas</file> is part of the <file>LazUtils</file> package.
</p>
<p>
Authors: Mattias Gaertner, Jeroen van Iddekinge
</p>
</descr>

<!-- used units -->
<element name="Classes"/>
<element name="SysUtils"/>

<element name="TLinkListItem">
<short>Implements an item in a doubly linked list.</short>
<descr>
<p>
<var>TLinkListItem</var> is a class which implements an item in a doubly 
linked list. It represents the traversal nodes used in <var>TLinkList</var>, 
including the terminal (or sentinel) node. Properties are provided to access 
and maintain the <var>Prior</var> and <var>Next</var> items in the node 
traversal order.
</p>
</descr>
<seealso>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
<link id="TLinkList.First"/>
<link id="TLinkList.Last"/>
</seealso>
</element>

<element name="TLinkListItem.Next">
<short>
Contains a reference to the next item in the doubly linked list.
</short>
<descr></descr>
<seealso></seealso>
</element>

<element name="TLinkListItem.Prior">
<short>
Contains a reference to the previous item in the doubly linked list.
</short>
<descr></descr>
<seealso></seealso>
</element>

<element name="TLinkListItem.ResetItem">
<short>
Removes the references to the previous and next items for the list item.
</short>
<descr>
<p>
<var>ResetItem</var> sets the values in the <var>Prior</var> and 
<var>Next</var> properties to <b>Nil</b>.
</p>
</descr>
<seealso>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>

<element name="TLinkList">
<short>Defines a simple doubly linked list class.</short>
<descr>
<p>
<var>TLinkList</var> is a class which defines a navigational interface for a 
simple doubly linked list.
</p>
<p>
TLinkList provides properties used to access the First and Last items in the 
linked list, the number of list items in Count, and the first free item in 
the linked list. Items in the linked list are represented using the 
TLinkListItem class, which provides Prior and Next properties for navigation 
of items in the list.
</p>
<p>
TLinkList contains an abstract virtual <var>CreateItem</var> method that is 
used to create new items for the linked list. The method <b>must</b> be 
implemented in a descendent class to provided implementation details that 
address storage and ownership of the linked list items. See TGtkMessageQueue 
for an example of a concrete implementation of the TLinkList class.
</p>
</descr>
<seealso></seealso>
</element>

<element name="TLinkList.FFirstFree">
<short>First free item in the linked list.</short>
</element>

<element name="TLinkList.FFreeCount">
<short>Number of free items in the linked list.</short>
</element>

<element name="TLinkList.FFirst">
<short>First list item in the linked list.</short>
</element>

<element name="TLinkList.FLast">
<short>Last list item in the linked list.</short>
</element>

<element name="TLinkList.FCount">
<short>Number of items in the linked list.</short>
</element>

<element name="TLinkList.DisposeItem">
<short>
Removes the specified item from the linked list, and optionally frees the 
item instance.
</short>
<descr></descr>
<seealso></seealso>
</element>
<element name="TLinkList.DisposeItem.AnItem">
<short>List item updated in the method.</short>
</element>

<element name="TLinkList.Unbind">
<short>Removes the traversal nodes for the specified linked list item.</short>
<descr></descr>
<seealso></seealso>
</element>
<element name="TLinkList.Unbind.AnItem">
<short>Linked list item updated in the method.</short>
</element>

<element name="TLinkList.CreateItem">
<short>
Specifies the interface used to create a new linked list item for the class.
</short>
<descr>
<p>
<var>CreateItem</var> is an abstract virtual method which specifies the 
interface used to create a new linked list item for the class. The return 
value is the <var>TLinkListItem</var> class instance allocated in the method. 
CreateItem must be be implemented in a descendent class to handle storage and 
ownership for the items created in the linked list.
</p>
<p>
CreateItem is used in the implementation of the <var>GetNewItem</var> method.
</p>
</descr>
<seealso>
<link id="TLinkList.GetNewItem"/>
</seealso>
</element>
<element name="TLinkList.CreateItem.Result">
<short>New link list item allocated in the method.</short>
</element>

<element name="TLinkList.GetNewItem">
<short>
Gets a new linked list item by reusing a free item or creating a new one.
</short>
<descr>
<p>
<var>GetNewItem</var> is a <var>TLinkListItem</var> function used to get a 
new item for the doubly linked list. GetNewItem checks for an unused item in 
the linked list, and creates a new TLinkListItem instance when a free item is 
not found. A reused item is updated to remove the <var>Prior</var> and 
<var>Next</var> traversal nodes in the linked list item. A new item is 
retrieved by calling the CreateItem method.
</p>
</descr>
<seealso>
<link id="TLinkList.CreateItem"/>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>
<element name="TLinkList.GetNewItem.Result">
<short>Linked list item reused or created in the method.</short>
</element>

<element name="TLinkList.AddAsLast">
<short>
Configures and adds the specified item as the terminal node for the doubly 
linked list.
</short>
<descr>
<p>
<var>AddAsLast</var> is a procedure used to make the specified list item the 
terminal node in the doubly linked list. AddAsLast updates the list item in 
<var>AnItem</var> by setting its <var>Prior</var> property to the node in 
<var>Last</var>. The value in its <var>Next</var> property is set to 
<b>Nil</b>. The updated list item is then assigned as the new value for the 
Last property. The value in <var>First</var> may be set to the value in 
AnItem when a prior node in the traversal order is not available.
</p>
<p>
AddAdLast increments the value in the Count property.
</p>
</descr>
<seealso>
<link id="TLinkList.Count"/>
<link id="TLinkList.Last"/>
<link id="TLinkList.First"/>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>
<element name="TLinkList.AddAsLast.AnItem">
<short>Item saved as the last item in the linked list.</short>
</element>

<element name="TLinkList.First">
<short>First item in the doubly linked list.</short>
<descr>
<p>
<var>First</var> is a read-only <var>TLinkListItem</var> property which 
represents the first traversal node in the doubly linked list. The value in 
First is updated in methods like <var>Unbind</var> and <var>AddAsLast</var>.
</p>
</descr>
<seealso>
<link id="TLinkList.Last"/>
<link id="TLinkList.AddAsLast"/>
</seealso>
</element>

<element name="TLinkList.Last">
<short>Last item in the doubly linked list.</short>
<descr>
<p>
<var>Last</var> is a read-only <var>TLinkListItem</var> property which 
represents the last (or terminal) traversal node in the doubly linked list. 
The value in Last is updated in methods like <var>Unbind</var> and 
<var>AddAsLast</var>.
</p>
</descr>
<seealso>
<link id="TLinkList.AddAsLast"/>
</seealso>
</element>

<element name="TLinkList.Count">
<short>Total number of items used in the doubly linked list.</short>
<descr>
<p>
<var>Count</var> is a read-only <var>Integer</var> property which contains 
the number of traversal nodes in the doubly linked list. The value in Count 
is updated in method like <var>Unbind</var> and <var>AddAsLast</var>.
</p>
</descr>
<seealso>
<link id="TLinkList.AddAsLast"/>
</seealso>
</element>

<element name="TLinkList.Delete">
<short>Removes the specified list item from the doubly linked list.</short>
<descr>
<p>
<var>Delete</var> is a procedure used to remove the specified list item from 
the traversal nodes in the doubly linked list. No actions are performed in 
the method when <var>AnItem</var> is unassigned (contains <b>Nil</b>).
</p>
<p>
Delete calls <var>Unbind</var> to update the traversal node for the affected 
list items. The <var>Prior</var> and <var>Next</var> nodes in 
<var>AnItem</var> are set to <b>Nil</b> to remove the item from the node 
order. Delete decrements the value in the <var>Count</var> property.
</p>
</descr>
<seealso>
<link id="TLinkList.Count"/>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>
<element name="TLinkList.Delete.AnItem">
<short>Item removed from the traversal nodes in the list.</short>
</element>

<element name="TLinkList.MoveToLast">
<short>
Relocates the specified list item to the last (or terminal) node for the 
linked list.
</short>
<descr>
<p>
<var>MoveToLast</var> is a procedure used to move the specified list item to 
the last (or terminal) node in the doubly linked list. No actions are 
performed in the method when <var>AnItem</var> is unassigned (contains 
<b>Nil</b>).
</p>
<p>
MoveToLast calls <var>Unbind</var> to ensure that AnItem is removed from the 
node traversal order in the linked list. MoveToLast calls 
<var>AddAsLast</var> to update the values in the Prior and Next properties in 
AnItem making it the terminal node in the traversal order.
</p>
</descr>
<seealso>
<link id="TLinkList.AddAsLast"/>
<link id="TLinkListItem.Prior"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>
<element name="TLinkList.MoveToLast.AnItem">
<short>Item moved to the last node in the linked list.</short>
</element>

<element name="TLinkList.Clear">
<short>Removes all items in the doubly linked list.</short>
<descr>
<p>
<var>Clear</var> is a procedure used to remove all items in the doubly linked 
list. Clear uses the class instance in <var>First</var> as the initial 
TLinkListItem in the node traversal order. While the node is assigned, it 
calls the    <var>Delete</var> method for each of the 
<var>TLinkListItem</var> instances.
</p>
</descr>
<seealso>
<link id="TLinkList.FIrst"/>
<link id="TLinkList.Delete"/>
</seealso>
</element>

<element name="TLinkList.ConsistencyCheck">
<short>
Checks the validity of traversal nodes and node counts in the doubly linked 
list.
</short>
<descr></descr>
<seealso></seealso>
</element>
<element name="TLinkList.ConsistencyCheck.Result">
<short>
Returns 0 when the traversal nodes and counts are valid, or a negative value 
an inconsistency is found.
</short>
</element>

<element name="TLinkList.Create">
<short>Constructor for the class instance.</short>
<descr>
<p>
Create calls the inherited constructor.
</p>
</descr>
<seealso></seealso>
</element>

<element name="TLinkList.Destroy">
<short>Destructor for the class instance.</short>
<descr>
<p>
<var>Destroy</var> calls <var>Clear</var>, and frees the unused items in the 
linked list. Destroy calls the inherited destructor prior to exiting from the 
method.
</p>
</descr>
<seealso>
<link id="TLinkList.Clear"/>
<link id="TLinkListItem.Next"/>
</seealso>
</element>

</module>
<!-- LazLinkedList -->
</package>
</fpdoc-descriptions>
