Example of using glibc tsearch

tsearch.c

/** Demonstration of tsearch. */

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

typedef struct Node {
  char *name;
  int age;
} Node;

int compareNode(const void *a, const void *b) {
  const Node *aa = a;
  const Node *bb = b;
  return strcasecmp(aa->name, bb->name);
}

void delNode(
    const void *nodep, VISIT value, int level __attribute__((unused))) {
  const struct Node *n = *(const Node **)nodep;

  if (value == leaf || value == endorder) {
      printf("killing %s\n", n->name);
      free(n->name);
      free((void *)n);
      free((void *)nodep);
  }
}

void printNode(
    const void *nodep, VISIT value, int level __attribute__((unused))) {
  const struct Node *n = *(const Node **)nodep;

  if (value == leaf || value == postorder)
    printf("%s is %i\n", n->name, n->age);
}

bool add(void **tree, char *name, int age) {
  Node *mt = calloc(sizeof(Node), 1);
  mt->name = strdup(name);
  mt->age = age;
  Node *added = tsearch(mt, tree, compareNode);
  if (mt == * (Node **) added)
    return true;
  free(mt->name);
  free(mt);
  printf("(dup)\n");
  return false;
}

Node *find(void *tree, char *name) {
  Node *mt = calloc(sizeof(Node), 1);
  mt->name = strdup(name);
  Node *found = tfind(mt, &tree, compareNode);
  free(mt->name);
  free(mt);
  return * (Node **) found;
}

int main() {
  void *tree = 0;

  add(&tree, "Joel", 44);
  add(&tree, "Vi", 32);
  add(&tree, "Bob", 15);
  add(&tree, "Bob", 16);

  Node *vi = find(tree, "Vi");
  if (vi)
    printf("found %s with %i!\n", vi->name, vi->age);

  twalk(tree, printNode);
  twalk(tree, delNode);
}