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tsearch(3C)		 Standard C Library Functions		   tsearch(3C)

NAME
       tsearch,	tfind, tdelete,	twalk -	manage binary search trees

SYNOPSIS
       #include	<search.h>

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

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

DESCRIPTION
       The tsearch(), tfind(), tdelete(), and twalk() functions	 are  routines
       for  manipulating binary	search trees. They are generalized from	 Knuth
       (6.2.2) Algorithms T and	D. All comparisons are done with  a  user-sup-
       plied  routine. This routine is called with two arguments, the pointers
       to the elements being compared. It returns an integer less than,	 equal
       to, or greater than 0, according	to whether the first argument is to be
       considered less than, equal to or greater than the second argument. The
       comparison  function need not compare every byte, so arbitrary data may
       be contained in the elements in addition	to the values being compared.

       The tsearch() function is used to build and access the tree.   The  key
       argument	 is a pointer to a datum to be accessed	or stored. If there is
       a datum in the tree equal to *key (the value  pointed  to  by  key),  a
       pointer	to  this found datum is	returned. Otherwise, *key is inserted,
       and a pointer to	it returned. Only pointers are copied, so the  calling
       routine	must  store  the data. The rootp argument points to a variable
       that points to the root of the tree. A  null  value  for	 the  variable
       pointed	to  by rootp denotes an	empty tree; in this case, the variable
       will be set to point to the datum which will be at the root of the  new
       tree.

       Like  tsearch(),	tfind()	will search for	a datum	in the tree, returning
       a pointer to it if found. However, if it	is not found, tfind() will re-
       turn  a	null  pointer.	The  arguments for tfind() are the same	as for
       tsearch().

       The tdelete() function deletes a	node from a binary  search  tree.  The
       arguments  are  the  same as for	 tsearch(). The	variable pointed to by
       rootp will be changed if	the deleted node was the  root	of  the	 tree.
       tdelete()  returns  a  pointer  to the parent of	the deleted node, or a
       null pointer if the node	is not found.

       The twalk() function traverses a	binary search tree. The	root  argument
       is  the	root  of  the tree to be traversed. (Any node in a tree	may be
       used as the root	for a walk below that node.) action is the name	 of  a
       routine	to  be	invoked	at each	node. This routine is, in turn,	called
       with three arguments. The first argument	is the address of the node be-
       ing  visited.  The  second argument is a	value from an enumeration data
       type

       typedef enum { preorder,	postorder, endorder, leaf } VISIT;

       (defined	in <search.h>),	depending on whether this is the first,	second
       or  third  time	that  the node has been	visited	(during	a depth-first,
       left-to-right traversal of the tree), or	whether	the node  is  a	 leaf.
       The  third argument is the level	of the node in the tree, with the root
       being level zero.

       The pointers to the key and the root of the  tree  should  be  of  type
       pointer-to-element,  and	 cast to type pointer-to-character. Similarly,
       although	declared as  type  pointer-to-character,  the  value  returned
       should be cast into type	pointer-to-element.

RETURN VALUES
       If  the	node  is found,	both tsearch() and tfind() return a pointer to
       it.  If not, tfind() returns a null pointer, and	 tsearch()  returns  a
       pointer to the inserted item.

       A  null	pointer	 is returned by	tsearch() if there is not enough space
       available to create a new node.

       A null pointer is returned by tsearch(),	tfind()	and tdelete() if rootp
       is a null pointer on entry.

       The  tdelete()  function	returns	a pointer to the parent	of the deleted
       node, or	a null pointer if the node is not found.

       The twalk() function returns no value.

ERRORS
       No errors are defined.

USAGE
       The root	argument to  twalk() is	one level of indirection less than the
       rootp arguments to tsearch() and	tdelete().

       There  are  two	nomenclatures used to refer to the order in which tree
       nodes are visited. tsearch() uses preorder, postorder and  endorder  to
       refer respectively to visiting a	node before any	of its children, after
       its left	child and before its right, and	after both its children.   The
       alternate nomenclature uses preorder, inorder and postorder to refer to
       the same	visits,	which could result in some confusion over the  meaning
       of postorder.

       If the calling function alters the pointer to the root, the results are
       unpredictable.

       These functions safely allows concurrent	access by multiple threads  to
       disjoint	data, such as overlapping subtrees or tables.

EXAMPLES
       Example 1: A sample program of using tsearch() function.

       The  following code reads in strings and	stores structures containing a
       pointer to each string and a count of its length.  It  then  walks  the
       tree, printing out the stored strings and their lengths in alphabetical
       order.

       #include	<string.h>
       #include	<stdio.h>
       #include	<search.h>
       struct node {
	       char *string;
	       int length;
       };
       char string_space[10000];
       struct node nodes[500];
       void *root = NULL;

       int node_compare(const void *node1, const void *node2) {
	       return strcmp(((const struct node *) node1)->string,
			     ((const struct node *) node2)->string);
       }

       void print_node(const void *node, VISIT order, int level) {
	       if (order == preorder ||	order == leaf) {
		       printf("length=%d, string=%20s\n",
		       (*(struct node **)node)->length,
		       (*(struct node **)node)->string);
	       }
       }

       main()
       {
	       char *strptr = string_space;
	       struct node *nodeptr = nodes;
	       int i = 0;

	       while (gets(strptr) != NULL && i++ < 500) {
		       nodeptr->string = strptr;
		       nodeptr->length = strlen(strptr);
		       (void) tsearch((void *)nodeptr,
			       &root, node_compare);
		       strptr += nodeptr->length + 1;
		       nodeptr++;
	       }
	       twalk(root, print_node);
       }

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       bsearch(3C), hsearch(3C), lsearch(3C), attributes(5), standards(5)

SunOS 5.10			  6 Dec	2004			   tsearch(3C)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | USAGE | EXAMPLES | ATTRIBUTES | SEE ALSO

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