NAME

tsearch, tfind, tdelete, twalk — manipulate binary search trees

SYNOPSIS

#include <search.h>

void *
tdelete(const void * restrict key, void ** restrict rootp, int (*compar) (const void *, const void *));

void *
tfind(const void *key, const void * const *rootp, int (*compar) (const void *, const void *));

void *
tsearch(const void *key, void **rootp, int (*compar) (const void *, const void *));

void
twalk(const void *root, void (*action) (const void *, VISIT, int));

DESCRIPTION

The tdelete(), tfind(), tsearch(), and 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 strcmp(3).

tfind() 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.

tsearch() 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.

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 tfind() and tsearch(). If the node to be deleted is the root of the binary search tree, rootp will be adjusted.

twalk() walks the binary search tree rooted in root and calls the function action on each node. Action 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).

tfind(), tsearch(), and tdelete() return NULL if rootp is NULL or the datum cannot be found.

The twalk() function returns no value.

SEE ALSO

bsearch(3), hsearch(3), lsearch(3)

STANDARDS

These functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).

CAVEATS

The IEEE Std 1003.1-2001 (“POSIX.1”) standard does not specify what value should be returned when deleting the root node. Since implementations vary, user of tdelete() should not rely on any specific behaviour. The IEEE Std 1003.1-2008 (“POSIX.1”) revision tried to clarify the issue with the following wording: “the tdelete() function shall return a pointer to the parent of the deleted node, or an unspecified non-NULL pointer if the deleted node was the root node, or a NULL pointer if the node is not found”.