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TSEARCH(3) Library Functions Manual TSEARCH(3)

tsearch, tfind, tdelete, twalkmanipulate binary search trees

#include <search.h>

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

void *
tfind(const void *key, 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));

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. If the node to be deleted is the root of the binary search tree, rootp will be adjusted and an unspecified non-null pointer will be returned. It takes the same arguments as tfind() and tsearch().

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).

The tsearch() function returns NULL if allocation of a new node fails (usually due to a lack of free memory).

tdelete() returns a pointer to the parent of the deleted node or an unspecified non-null pointer if the root node is deleted.

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

bsearch(3), lsearch(3)

These functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

The value returned when deleting the root node was unspecified before the IEEE Std 1003.1-2008 (“POSIX.1”) standard, so users of the tdelete() function should be wary of relying on a specific behaviour.

January 25, 2019 OpenBSD-current