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.\" Copyright 2015 Joyent, Inc.
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.Dd May 07, 2015
.Dt AVL_FIND 3AVL
.Os
.Sh NAME
.Nm avl_find
.Nd find a node in an AVL tree
.Sh SYNOPSIS
.Lb libavl
.In sys/avl.h
.Ft void *
.Fo avl_find
.Fa "avl_tree_t *tree"
.Fa "const void *node"
.Fa "avl_index_t *where"
.Fc
.Sh DESCRIPTION
The
.Fn avl_find
function is used to look up a node in the tree rooted at
.Fa tree .
.Pp
To perform a lookup, a caller should construct an instance of the data
structure, the argument
.Fa node .
.Fn avl_find
searches through the tree for a node which compares equal to the passed
in
.Fa node
using the comparison function specified when the tree was created with
.Xr avl_create 3AVL .
The only fields of
.Fa node
that need to be initialized are those that the comparison function will
use, the others may remain uninitialized.
.Pp
If a match exists in the tree, then that entry will be returned.
Otherwise,
.Sy NULL
is returned.
.Pp
If
.Fa node
does not match anything in the tree and the value of
.Fa where
is a
.Pf non- Sy NULL
pointer, then
.Fa where
will be updated to a value that can be used with both
.Xr avl_insert 3AVL
and
.Xr avl_nearest 3AVL .
This value is only valid as long as the tree is not modified. If
anything is added or removed from the tree, then the value of
.Fa where
is no longer valid. This is commonly used as part of a pattern to see if
something that should be added to the tree already exists, and if not,
insert it. For more information, see the examples in
.Xr libavl 3LIB .
.Pp
If the lookup is successful, then the contents of
.Fa where
are undefined.
.Sh RETURN VALUES
If
.Fa node
matches an entry in the tree, the matching entry is returned. Otherwise,
.Sy NULL
is returned and if
.Fa where
is
.Pf non- Sy NULL ,
it is updated to point to a location in the tree.
.Sh EXAMPLES
See the
.Sy EXAMPLES
section in
.Xr libavl 3LIB .
.Sh INTERFACE STABILITY
.Sy Committed
.Sh MT-Level
See
.Sx Locking
in
.Xr libavl 3LIB .
.Sh SEE ALSO
.Xr libavl 3LIB ,
.Xr avl_create 3AVL ,
.Xr avl_insert 3AVL ,
.Xr avl_nearest 3AVL