.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" OpenBSD: tsearch.3,v 1.2 1998/06/21 22:13:49 millert Exp
-.\" $FreeBSD: src/lib/libc/stdlib/tsearch.3,v 1.7 2001/09/07 14:46:36 asmodai Exp $
+.\" $FreeBSD: src/lib/libc/stdlib/tsearch.3,v 1.15 2006/06/23 13:36:33 keramida Exp $
.\"
.Dd June 15, 1997
.Dt TSEARCH 3
.Os
.Sh NAME
-.Nm tsearch , tfind , tdelete , twalk
+.Nm tdelete ,
+.Nm tfind ,
+.Nm tsearch ,
+.Nm twalk
.Nd manipulate binary search trees
.Sh SYNOPSIS
.In search.h
.Ft void *
-.Fn tdelete "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
+.Fo tdelete
+.Fa "const void *restrict key"
+.Fa "void **restrict rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
.Ft void *
-.Fn tfind "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
+.Fo tfind
+.Fa "const void *key"
+.Fa "void *const *rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
.Ft void *
-.Fn tsearch "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
+.Fo tsearch
+.Fa "const void *key"
+.Fa "void **rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
.Ft void
-.Fn twalk "const void *root" "void (*compar) (const void *, VISIT, int)"
+.Fo twalk
+.Fa "const void *root"
+.Fa "void (*action) (const void *node, VISIT order, int level)"
+.Fc
.Sh DESCRIPTION
The
.Fn tdelete ,
.Fn tsearch ,
and
.Fn twalk
-functions manage binary search trees based on algorithms T and D
-from Knuth (6.2.2). The comparison function passed in by
-the user has the same style of return values as
+functions manage binary search trees, based on algorithms T and D
+from Knuth (6.2.2).
+The comparison function passed in by
+the user takes two arguments, each of which is a key
+pointer.
+This function has the same style of return values as
.Xr strcmp 3 .
.Pp
-.Fn Tfind
-searches for the datum matched by the argument
+The
+.Fn tfind
+function
+searches for a node whose key matches the argument
.Fa key
in the binary tree rooted at
.Fa rootp ,
-returning a pointer to the datum if it is found and NULL
+returning a pointer to the node if it is found and NULL
if it is not.
.Pp
-.Fn Tsearch
-is identical to
+Note that a node is itself a pointer to the key of the node.
+Thus, you should generally cast this result to a
+double pointer to the data type stored in the tree, for example
+(struct myType **), and use double indirection to retrieve the
+original key value.
+.Pp
+The
+.Fn tsearch
+function is identical to
.Fn tfind
-except that if no match is found,
+except that, if no match is found,
+it inserts a new node for the
.Fa key
-is inserted into the tree and a pointer to it is returned. If
+into the tree and returns a pointer to the node.
+If
.Fa rootp
-points to a NULL value a new binary search tree is created.
+points to a NULL value, a new binary search tree is created.
.Pp
-.Fn Tdelete
-deletes a node from the specified binary search tree and returns
-a pointer to the parent of the node to be deleted.
+The
+.Fn tdelete
+function deletes a node from the specified binary search tree
+and returns a pointer to the parent of the node that was deleted.
It takes the same arguments as
.Fn tfind
and
.Fa rootp
will be adjusted.
.Pp
-.Fn Twalk
-walks the binary search tree rooted in
+The
+.Fn twalk
+function walks the binary search tree rooted in
.Fa root
and calls the function
.Fa action
on each node.
-.Fa Action
-is called with three arguments: a pointer to the current node,
+The
+.Fa action
+function is called with three arguments: a pointer to the current node,
a value from the enum
.Sy "typedef enum { preorder, postorder, endorder, leaf } VISIT;"
specifying the traversal type, and a node level (where level
zero is the root of the tree).
-.Sh SEE ALSO
-.Xr bsearch 3 ,
-.Xr hsearch 3 ,
-.Xr lsearch 3
+.Pp
+As
+.Fn twalk
+traverses the tree, it calls the
+.Fa action
+function with the traversal type "preorder"
+before visiting the left subtree of the
+.Fa node ,
+with the
+traversal type "postorder" before visiting the right subtree
+of the
+.Fa node ,
+and with the traversal type "endorder" after
+visiting the right subtree of the
+.Fa node .
+.Pp.
+The
+.Fa action
+function is called only once for a leaf-node, with the
+traversal type "leaf."
+.Pp
+Note: the names for the traversal types differ somewhat from
+common parlance. The traversal type "postorder" corresponds
+to what would typically be referred to as in-order, and the
+traversal type "endorder" corresponds to what would typically
+be referred to as post-order.
.Sh RETURN VALUES
The
.Fn tsearch
function returns NULL if allocation of a new node fails (usually
due to a lack of free memory).
.Pp
-.Fn Tfind ,
+The
+.Fn tfind ,
.Fn tsearch ,
and
.Fn tdelete
+functions
return NULL if
.Fa rootp
-is NULL or the datum cannot be found.
+is NULL or the node cannot be found.
.Pp
The
.Fn twalk
function returns no value.
+.Sh SEE ALSO
+.Xr bsearch 3 ,
+.Xr hsearch 3 ,
+.Xr lsearch 3
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