.\" $OpenBSD: tsearch.3,v 1.16 2007/05/31 19:19:32 jmc Exp $
.\"
.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\"
.Dd $Mdocdate: May 31 2007 $
.Dt TSEARCH 3
.Os
.Sh NAME
.Nm tsearch ,
.Nm tfind ,
.Nm tdelete ,
.Nm twalk
.Nd manipulate binary search trees
.Sh SYNOPSIS
.Fd #include <search.h>
.Ft void *
.Fn tdelete "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
.Ft void *
.Fn tfind "const void *key" "void * const *rootp" "int (*compar) (const void *, const void *)"
.Ft void *
.Fn tsearch "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
.Ft void
.Fn twalk "const void *root" "void (*action) (const void *, VISIT, int)"
.Sh DESCRIPTION
The
.Fn tdelete ,
.Fn tfind ,
.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
.Xr strcmp 3 .
.Pp
.Fn tfind
searches for the datum matched by the argument
.Fa key
in the binary tree rooted at
.Fa rootp ,
returning a pointer to the datum if it is found and
.Dv NULL
if it is not.
.Pp
.Fn tsearch
is identical to
.Fn tfind
except that if no match is found,
.Fa key
is inserted into the tree and a pointer to it is returned.
If
.Fa rootp
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.
It takes the same arguments as
.Fn tfind
and
.Fn tsearch .
If the node to be deleted is the root of the binary search tree,
.Fa rootp
will be adjusted and a pointer to the new root will be returned.
.Pp
.Fn twalk
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,
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 RETURN VALUES
The
.Fn tsearch
function returns
.Dv NULL
if allocation of a new node fails (usually
due to a lack of free memory).
.Pp
.Fn tfind ,
.Fn tsearch ,
and
.Fn tdelete
return
.Dv NULL
if
.Fa rootp
is
.Dv NULL
or the datum cannot be found.
.Pp
The
.Fn twalk
function returns no value.
.Sh SEE ALSO
.Xr bsearch 3 ,
.Xr lsearch 3
.Sh STANDARDS
These functions conform to
.St -p1003.1-2004 .
.Sh CAVEATS
The
.St -p1003.1-2004
standard does not specify what value should be returned when deleting the
root node.
Since implementations vary, the user of the
.Fn tdelete
function should not rely on a specific behaviour.