bsearch(3c) [hpux man page]
bsearch(3C) bsearch(3C) NAME
bsearch() - binary search a sorted table SYNOPSIS
DESCRIPTION
is a binary search routine generalized from Knuth (6.2.1) Algorithm B. It returns a pointer into a table indicating where a datum may be found. The table must be previously sorted in increasing order according to a provided comparison function. key points to a datum instance to be sought in the table. base points to the element at the base of the table. nel is the number of elements in the table. size is the size of each element in the table. compar is the name of the comparison function, which is called with two arguments that point to the elements being compared. The function must return an integer less than, equal to, or greater than zero indicating that the first argument (the key) is to be considered less than, equal to, or greater than the second argument (the array element). NOTES
The pointers to the key and the element at the base of the table should be of type pointer-to-element, and cast to type pointer-to-void. The comparison function need not compare every byte, so arbitrary data can be contained in the elements in addition to the values being compared. Although declared as type pointer-to-void, the value returned should be cast into type pointer-to-element. RETURN VALUE
A NULL pointer is returned if the key cannot be found in the table. EXAMPLES
The example below searches a table containing pointers to nodes consisting of a string and its length. The table is ordered alphabetically on the string in the node pointed to by each entry. This code fragment reads in strings and either finds the corresponding node and prints out the string and its length, or prints an error message. #include <stdio.h> #include <stdlib.h> #include <string.h> #define TABSIZE 1000 struct node { /* these are stored in the table */ char *string; int length; }; struct node table[TABSIZE]; /* table to be searched */ . . . { struct node *node_ptr, node; /* routine to compare 2 nodes */ int node_compare(const void *, const void *); char str_space[20]; /* space to read string into */ . . . node.string = str_space; while (scanf("%s", node.string) != EOF) { node_ptr = (struct node *)bsearch((void *)(&node), (void *)table, TABSIZE, sizeof(struct node), node_compare); if (node_ptr != NULL) { (void)printf("string = %20s, length = %d ", node_ptr->string, node_ptr->length); } else { (void)printf("not found: %s ", node.string); } } } /* This routine compares two nodes based on an alphabetical ordering of the string field. */ int node_compare(const void *node1, const void *node2) struct node *node1, *node2; { return strcoll(((const struct node *)node1)->string, ((const struct node *)node2)->string); } WARNINGS
If the table being searched contains two or more entries that match the selection criteria, a random entry is returned by as determined by the search algorithm. SEE ALSO
hsearch(3C), lsearch(3C), qsort(3C), tsearch(3C), thread_safety(5). STANDARDS CONFORMANCE
bsearch(3C)
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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-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 5.11 6 Dec 2004 tsearch(3C)