TSEARCH(3) BSD Library Functions Manual TSEARCH(3)NAME
tdelete, tfind, tsearch, twalk — manipulate binary search trees
SYNOPSIS
#include <search.h>
void *
tdelete(const void *restrict key, void **restrict rootp,
int (*compar) (const void *key1, const void *key2));
void *
tfind(const void *key, void *const *rootp,
int (*compar) (const void *key1, const void *key2));
void *
tsearch(const void *key, void **rootp,
int (*compar) (const void *key1, const void *key2));
void
twalk(const void *root,
void (*action) (const void *node, VISIT order, int level));
DESCRIPTION
The tdelete(), tfind(), tsearch(), and twalk() functions manage binary
search trees, based on algorithms T and D from Knuth (6.2.2). The com‐
parison 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
strcmp(3).
The tfind() function searches for a node whose key matches the argument
key in the binary tree rooted at rootp, returning a pointer to the node
if it is found and NULL if it is not.
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 indi‐
rection to retrieve the original key value.
The tsearch() function is identical to tfind() except that, if no match
is found, it inserts a new node for the key into the tree and returns a
pointer to the node. If rootp points to a NULL value, a new binary
search tree is created.
The 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 tfind() and tsearch(). If the node to be
deleted is the root of the binary search tree, rootp will be adjusted.
The twalk() function walks the binary search tree rooted in root and
calls the function action on each node. The action function is called
with three arguments: a pointer to the current node, a value from the
enum typedef enum { preorder, postorder, endorder, leaf } VISIT; specify‐
ing the traversal type, and a node level (where level zero is the root of
the tree).
As twalk() traverses the tree, it calls the action function with the tra‐
versal type "preorder" before visiting the left subtree of the node, with
the traversal type "postorder" before visiting the right subtree of the
node, and with the traversal type "endorder" after visiting the right
subtree of the node. The action function is called only once for a leaf-
node, with the traversal type "leaf."
Note: the names for the traversal types differ somewhat from common par‐
lance. The traversal type "postorder" corresponds to what would typi‐
cally be referred to as in-order, and the traversal type "endorder" cor‐
responds to what would typically be referred to as post-order.
RETURN VALUES
The tsearch() function returns NULL if allocation of a new node fails
(usually due to a lack of free memory).
The tfind(), tsearch(), and tdelete() functions return NULL if rootp is
NULL or the node cannot be found.
The twalk() function returns no value.
SEE ALSObsearch(3), hsearch(3), lsearch(3)BSD June 15, 1997 BSD
