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tsearch – manipulate binary search trees

SYNOPSIS DESCRIPTION RETURN VALUES EXAMPLES SEE ALSO STANDARDS

#include <search.h>

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

posix_tnode *
tfind(const void *key, posix_tnode * const *rootp, int (*compar) (const void *, const void *));

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

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

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

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

The twalk() function returns no value.

This example uses tsearch() to search for four strings in root. Because the strings are not already present, they are added. tsearch() is called twice on the fourth string to demonstrate that a string is not added when it is already present. tfind() is used to find the single instance of the fourth string, and tdelete() removes it. Finally, twalk() is used to return and display the resulting binary search tree.

#include <stdio.h>
#include <search.h>
#include <string.h>

int
comp(const void *a, const void *b)
{

        return strcmp(a, b);
}

void
printwalk(const posix_tnode * node, VISIT v, int __unused0)
{

        if (v == postorder || v == leaf) {
                printf("node: %s\n", *(char **)node);
        }
}

int
main(void)
{
        posix_tnode *root = NULL;

        char one[] = "blah1";
        char two[] = "blah-2";
        char three[] = "blah-3";
        char four[] = "blah-4";

        tsearch(one, &root, comp);
        tsearch(two, &root, comp);
        tsearch(three, &root, comp);
        tsearch(four, &root, comp);
        tsearch(four, &root, comp);
        printf("four: %s\n", *(char **)tfind(four, &root, comp));
        tdelete(four, &root, comp);

        twalk(root, printwalk);
        return 0;
}

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

The posix_tnode type is not part of IEEE Std 1003.1-2008 ("POSIX.1"), but is expected to be standardized by future versions of the standard. It is defined as void for source-level compatibility. Using posix_tnode makes distinguishing between nodes and keys easier.