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# List Processing

## Synopsis

This section contains various definitions related to list processing using doubly-linked nodes.

## FT_List

Defined in FT_TYPES_H (freetype/fttypes.h).

      typedef struct FT_ListRec_*  FT_List;

A handle to a list record (see `FT_ListRec`).

## FT_ListNode

Defined in FT_TYPES_H (freetype/fttypes.h).

      typedef struct FT_ListNodeRec_*  FT_ListNode;

Many elements and objects in FreeType are listed through an `FT_List` record (see `FT_ListRec`). As its name suggests, an FT_ListNode is a handle to a single list element.

## FT_ListRec

Defined in FT_TYPES_H (freetype/fttypes.h).

      typedef struct  FT_ListRec_
      {
        FT_ListNode  head;
        FT_ListNode  tail;

      } FT_ListRec;

A structure used to hold a simple doubly-linked list. These are used in many parts of FreeType.

#### fields

head | The head (first element) of doubly-linked list.
tail | The tail (last element) of doubly-linked list.

## FT_ListNodeRec

Defined in FT_TYPES_H (freetype/fttypes.h).

      typedef struct  FT_ListNodeRec_
      {
        FT_ListNode  prev;
        FT_ListNode  next;
        void*        data;

      } FT_ListNodeRec;

A structure used to hold a single list element.

#### fields

prev | The previous element in the list. `NULL` if first.
next | The next element in the list. `NULL` if last.
data | A typeless pointer to the listed object.

## FT_List_Add

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( void )
      FT_List_Add( FT_List      list,
                   FT_ListNode  node );

Append an element to the end of a list.

#### inout

list | A pointer to the parent list.
node | The node to append.

## FT_List_Insert

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( void )
      FT_List_Insert( FT_List      list,
                      FT_ListNode  node );

Insert an element at the head of a list.

#### inout

list | A pointer to parent list.
node | The node to insert.

## FT_List_Find

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( FT_ListNode )
      FT_List_Find( FT_List  list,
                    void*    data );

Find the list node for a given listed object.

#### input

list | A pointer to the parent list.
data | The address of the listed object.

#### return

List node. `NULL` if it wasn't found.

## FT_List_Remove

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( void )
      FT_List_Remove( FT_List      list,
                      FT_ListNode  node );

Remove a node from a list. This function doesn't check whether the node is in the list!

#### input

node | The node to remove.

#### inout

list | A pointer to the parent list.

## FT_List_Up

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( void )
      FT_List_Up( FT_List      list,
                  FT_ListNode  node );

Move a node to the head/top of a list. Used to maintain LRU lists.

#### inout

list | A pointer to the parent list.
node | The node to move.

## FT_List_Iterate

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( FT_Error )
      FT_List_Iterate( FT_List           list,
                       FT_List_Iterator  iterator,
                       void*             user );

Parse a list and calls a given iterator function on each element. Note that parsing is stopped as soon as one of the iterator calls returns a non-zero value.

#### input

list | A handle to the list.
iterator | An iterator function, called on each node of the list.
user | A user-supplied field that is passed as the second argument to the iterator.

#### return

The result (a FreeType error code) of the last iterator call.

## FT_List_Iterator

Defined in FT_LIST_H (freetype/ftlist.h).

      typedef FT_Error
      (*FT_List_Iterator)( FT_ListNode  node,
                           void*        user );

An FT_List iterator function that is called during a list parse by `FT_List_Iterate`.

#### input

node | The current iteration list node.
user | A typeless pointer passed to `FT_List_Iterate`. Can be used to point to the iteration's state.

## FT_List_Finalize

Defined in FT_LIST_H (freetype/ftlist.h).

      FT_EXPORT( void )
      FT_List_Finalize( FT_List             list,
                        FT_List_Destructor  destroy,
                        FT_Memory           memory,
                        void*               user );

Destroy all elements in the list as well as the list itself.

#### input

list | A handle to the list.
destroy | A list destructor that will be applied to each element of the list. Set this to `NULL` if not needed.
memory | The current memory object that handles deallocation.
user | A user-supplied field that is passed as the last argument to the destructor.

#### note

This function expects that all nodes added by `FT_List_Add` or `FT_List_Insert` have been dynamically allocated.

## FT_List_Destructor

Defined in FT_LIST_H (freetype/ftlist.h).

      typedef void
      (*FT_List_Destructor)( FT_Memory  memory,
                             void*      data,
                             void*      user );

An `FT_List` iterator function that is called during a list finalization by `FT_List_Finalize` to destroy all elements in a given list.

#### input

system | The current system object.
data | The current object to destroy.
user | A typeless pointer passed to `FT_List_Iterate`. It can be used to point to the iteration's state.