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-supplied 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 argu-
       ment 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
       return 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 being 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
",
		       (*(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)