tdelete(_)의 모범사용

http://austingroupbugs.net/view.php?id=551

#include <limits.h> #include <search.h> #include <stdlib.h> #include <string.h> #include <stdio.h> struct element { /* Pointers to these are stored in the tree. */     int count;     char string[]; }; void *root = NULL; /* This points to the root. */ int main(void) {     char str[_POSIX2_LINE_MAX+1];     int length = 0;     struct element *elementptr;     void *node;     void print_node(const void *, VISIT, int);     int node_compare(const void *, const void *),            delete_root(const void *, const void *);     while (fgets(str, sizeof(str), stdin)) {         /* Set element. */         length = strlen(str);         if (str[length-1] == '\n')             str[--length] = '\0';         elementptr = (struct element *)malloc(sizeof(struct element)                                               + length + 1);         strcpy(elementptr->string, str);         elementptr->count = 1;         /* Put element into the tree. */         node = tsearch((void *)elementptr, &root, node_compare);         if (node == NULL) {             fprintf(stderr,                     "tsearch: Not enough space avaialble\n");             exit(EXIT_FAILURE);         }         else if (*(struct element **)node != elementptr) {             /* A node containing the element already exists */             (*(struct element **)node)->count++;             free(elementptr);         }     }     twalk(root, print_node);     /* Delete all nodes in the tree */     while (root != NULL) {         elementptr = *(struct element **)root;         printf("deleting node: string = %s, count = %d\n",                 elementptr->string,                elementptr->count);         tdelete((void *)elementptr, &root, delete_root);         free(elementptr);     }     return 0; } /*  * This routine compares two nodes, based on an  * alphabetical ordering of the string field.  */ int node_compare(const void *node1, const void *node2) {     return strcmp(((const struct element *) node1)->string,         ((const struct element *) node2)->string); } /*  * This comparison routine can be used with tdelete()  * when explicitly deleting a root node, as no comparison  * is necessary.  */ int delete_root(const void *node1, const void *node2) {     return 0; } /*  * This routine prints out a node, the second time  * twalk encounters it or if it is a leaf.  */ void print_node(const void *ptr, VISIT order, int level) {     const struct element *p = *(const struct element **) ptr;     if (order == postorder || order == leaf) {         (void) printf("string = %s, count = %d\n",             p->string, p->count);     } }