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TSEARCH(3)              NetBSD Library Functions Manual             TSEARCH(3)


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 compar-
     ison 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 func-
     tion 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 implementa-
     tions 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''.

NetBSD 7.1                      April 30, 2010                      NetBSD 7.1