man-pages/man3/stailq.3

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.TH STAILQ 3 2020-10-21 "GNU" "Linux Programmer's Manual"
.SH NAME
.Nm STAILQ_CONCAT ,
.Nm STAILQ_EMPTY ,
.Nm STAILQ_ENTRY ,
.Nm STAILQ_FIRST ,
.Nm STAILQ_FOREACH ,
.\" .Nm STAILQ_FOREACH_FROM ,
.\" .Nm STAILQ_FOREACH_FROM_SAFE ,
.\" .Nm STAILQ_FOREACH_SAFE ,
.Nm STAILQ_HEAD ,
.Nm STAILQ_HEAD_INITIALIZER ,
.Nm STAILQ_INIT ,
.Nm STAILQ_INSERT_AFTER ,
.Nm STAILQ_INSERT_HEAD ,
.Nm STAILQ_INSERT_TAIL ,
.\" .Nm STAILQ_LAST ,
.Nm STAILQ_NEXT ,
.Nm STAILQ_REMOVE ,
.\" .Nm STAILQ_REMOVE_AFTER ,
.Nm STAILQ_REMOVE_HEAD ,
.\" .Nm STAILQ_SWAP ,
.SH SYNOPSIS
.Fn STAILQ_CONCAT "STAILQ_HEAD *head1" "STAILQ_HEAD *head2"
.Fn STAILQ_EMPTY "STAILQ_HEAD *head"
.Fn STAILQ_ENTRY "TYPE"
.Fn STAILQ_FIRST "STAILQ_HEAD *head"
.Fn STAILQ_FOREACH "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
.\" .Fn STAILQ_FOREACH_FROM "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
.\" .Fn STAILQ_FOREACH_FROM_SAFE "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME" "TYPE *temp_var"
.\" .Fn STAILQ_FOREACH_SAFE "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME" "TYPE *temp_var"
.Fn STAILQ_HEAD "HEADNAME" "TYPE"
.Fn STAILQ_HEAD_INITIALIZER "STAILQ_HEAD head"
.Fn STAILQ_INIT "STAILQ_HEAD *head"
.Fn STAILQ_INSERT_AFTER "STAILQ_HEAD *head" "TYPE *listelm" "TYPE *elm" "STAILQ_ENTRY NAME"
.Fn STAILQ_INSERT_HEAD "STAILQ_HEAD *head" "TYPE *elm" "STAILQ_ENTRY NAME"
.Fn STAILQ_INSERT_TAIL "STAILQ_HEAD *head" "TYPE *elm" "STAILQ_ENTRY NAME"
.\" .Fn STAILQ_LAST "STAILQ_HEAD *head" "TYPE" "STAILQ_ENTRY NAME"
.Fn STAILQ_NEXT "TYPE *elm" "STAILQ_ENTRY NAME"
.Fn STAILQ_REMOVE "STAILQ_HEAD *head" "TYPE *elm" "TYPE" "STAILQ_ENTRY NAME"
.\" .Fn STAILQ_REMOVE_AFTER "STAILQ_HEAD *head" "TYPE *elm" "STAILQ_ENTRY NAME"
.Fn STAILQ_REMOVE_HEAD "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
.\" .Fn STAILQ_SWAP "STAILQ_HEAD *head1" "STAILQ_HEAD *head2" "STAILQ_ENTRY NAME"
.\"
.SH DESCRIPTION
.Ss Singly-linked tail queues
A singly-linked tail queue is headed by a structure defined by the
.Nm STAILQ_HEAD
macro.
This structure contains a pair of pointers,
one to the first element in the tail queue and the other to
the last element in the tail queue.
The elements are singly linked for minimum space and pointer
manipulation overhead at the expense of O(n) removal for arbitrary
elements.
New elements can be added to the tail queue after an existing element,
at the head of the tail queue, or at the end of the tail queue.
A
.Fa STAILQ_HEAD
structure is declared as follows:
.Bd -literal -offset indent
STAILQ_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Li HEADNAME
is the name of the structure to be defined, and
.Li TYPE
is the type of the elements to be linked into the tail queue.
A pointer to the head of the tail queue can later be declared as:
.Bd -literal -offset indent
struct HEADNAME *headp;
.Ed
.Pp
(The names
.Li head
and
.Li headp
are user selectable.)
.Pp
The macro
.Nm STAILQ_HEAD_INITIALIZER
evaluates to an initializer for the tail queue
.Fa head .
.Pp
The macro
.Nm STAILQ_CONCAT
concatenates the tail queue headed by
.Fa head2
onto the end of the one headed by
.Fa head1
removing all entries from the former.
.Pp
The macro
.Nm STAILQ_EMPTY
evaluates to true if there are no items on the tail queue.
.Pp
The macro
.Nm STAILQ_ENTRY
declares a structure that connects the elements in
the tail queue.
.Pp
The macro
.Nm STAILQ_FIRST
returns the first item on the tail queue or NULL if the tail queue
is empty.
.Pp
The macro
.Nm STAILQ_FOREACH
traverses the tail queue referenced by
.Fa head
in the forward direction, assigning each element
in turn to
.Fa var .
.\" .Pp
.\" The macro
.\" .Nm STAILQ_FOREACH_FROM
.\" behaves identically to
.\" .Nm STAILQ_FOREACH
.\" when
.\" .Fa var
.\" is NULL, else it treats
.\" .Fa var
.\" as a previously found STAILQ element and begins the loop at
.\" .Fa var
.\" instead of the first element in the STAILQ referenced by
.\" .Fa head .
.\" .Pp
.\" The macro
.\" .Nm STAILQ_FOREACH_SAFE
.\" traverses the tail queue referenced by
.\" .Fa head
.\" in the forward direction, assigning each element
.\" in turn to
.\" .Fa var .
.\" However, unlike
.\" .Fn STAILQ_FOREACH
.\" here it is permitted to both remove
.\" .Fa var
.\" as well as free it from within the loop safely without interfering with the
.\" traversal.
.\" .Pp
.\" The macro
.\" .Nm STAILQ_FOREACH_FROM_SAFE
.\" behaves identically to
.\" .Nm STAILQ_FOREACH_SAFE
.\" when
.\" .Fa var
.\" is NULL, else it treats
.\" .Fa var
.\" as a previously found STAILQ element and begins the loop at
.\" .Fa var
.\" instead of the first element in the STAILQ referenced by
.\" .Fa head .
.Pp
The macro
.Nm STAILQ_INIT
initializes the tail queue referenced by
.Fa head .
.Pp
The macro
.Nm STAILQ_INSERT_HEAD
inserts the new element
.Fa elm
at the head of the tail queue.
.Pp
The macro
.Nm STAILQ_INSERT_TAIL
inserts the new element
.Fa elm
at the end of the tail queue.
.Pp
The macro
.Nm STAILQ_INSERT_AFTER
inserts the new element
.Fa elm
after the element
.Fa listelm .
.\" .Pp
.\" The macro
.\" .Nm STAILQ_LAST
.\" returns the last item on the tail queue.
.\" If the tail queue is empty the return value is
.\" .Dv NULL .
.Pp
The macro
.Nm STAILQ_NEXT
returns the next item on the tail queue, or NULL this item is the last.
.\" .Pp
.\" The macro
.\" .Nm STAILQ_REMOVE_AFTER
.\" removes the element after
.\" .Fa elm
.\" from the tail queue.
.\" Unlike
.\" .Fa STAILQ_REMOVE ,
.\" this macro does not traverse the entire tail queue.
.Pp
The macro
.Nm STAILQ_REMOVE_HEAD
removes the element at the head of the tail queue.
For optimum efficiency,
elements being removed from the head of the tail queue should
use this macro explicitly rather than the generic
.Fa STAILQ_REMOVE
macro.
.Pp
The macro
.Nm STAILQ_REMOVE
removes the element
.Fa elm
from the tail queue.
.\" .Pp
.\" The macro
.\" .Nm STAILQ_SWAP
.\" swaps the contents of
.\" .Fa head1
.\" and
.\" .Fa head2 .
.Pp
See the EXAMPLES section below for an example program
using a singly-linked tail queue.
.SH RETURN VALUE
.SH CONFORMING TO
.SH BUGS
.SH EXAMPLES
.SH SEE ALSO