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TSEARCH(3) FreeBSD Library Functions Manual TSEARCH(3)
NAME
tsearch, tfind, tdelete, twalk - manipulate binary search trees
SYNOPSIS
#include <search.h>
void *
tdelete(const void * restrict key, posix_tnode ** restrict rootp,
int (*compar) (const void *, const void *));
posix_tnode *
tfind(const void *key, posix_tnode * const *rootp,
int (*compar) (const void *, const void *));
posix_tnode *
tsearch(const void *key, posix_tnode **rootp,
int (*compar) (const void *, const void *));
void
twalk(const posix_tnode *root,
void (*action) (const posix_tnode *, VISIT, int));
DESCRIPTION
The tdelete(), tfind(), tsearch(), and twalk() functions manage binary
search trees. This implementation uses a balanced AVL tree, which due to
its strong theoretical limit on the height of the tree has the advantage
of calling the comparison function relatively infrequently.
The comparison function passed in by the user has the same style of
return values as strcmp(3).
The tfind() function searches for the datum matched by the argument key
in the binary tree rooted at rootp, returning a pointer to the datum if
it is found and NULL if it is not.
The tsearch() function is identical to tfind() except that if no match is
found, key is inserted into the tree and a pointer to it is returned. 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 to be 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;
specifying the traversal type, and a node level (where level zero is the
root of the tree).
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 datum cannot be found.
it is already present. tfind() is used to find the single instance of
the fourth string, and tdelete() removes it. Finally, twalk() is used to
return and display the resulting binary search tree.
#include <stdio.h>
#include <search.h>
#include <string.h>
int
comp(const void *a, const void *b)
{
return strcmp(a, b);
}
void
printwalk(const posix_tnode * node, VISIT v, int __unused0)
{
if (v == postorder || v == leaf) {
printf("node: %s\n", *(char **)node);
}
}
int
main(void)
{
posix_tnode *root = NULL;
char one[] = "blah1";
char two[] = "blah-2";
char three[] = "blah-3";
char four[] = "blah-4";
tsearch(one, &root, comp);
tsearch(two, &root, comp);
tsearch(three, &root, comp);
tsearch(four, &root, comp);
tsearch(four, &root, comp);
printf("four: %s\n", *(char **)tfind(four, &root, comp));
tdelete(four, &root, comp);
twalk(root, printwalk);
return 0;
}
SEE ALSO
bsearch(3), hsearch(3), lsearch(3)
STANDARDS
These functions conform to IEEE Std 1003.1-2008 ("POSIX.1").
The posix_tnode type is not part of IEEE Std 1003.1-2008 ("POSIX.1"), but
is expected to be standardized by future versions of the standard. It is
defined as void for source-level compatibility. Using posix_tnode makes
distinguishing between nodes and keys easier.
FreeBSD 14.0-RELEASE-p11 June 4, 2017 FreeBSD 14.0-RELEASE-p11