dup.c

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <search.h>
#include <errno.h>

#define HASH_SIZE 1000
#define LINE_SIZE 512

/* define client data */
typedef struct client {
    int count;
} CLIENT;

/* duplicate client data */
CLIENT *datadup(CLIENT *data) {
    CLIENT *r = malloc(sizeof(CLIENT));
    if (r == NULL) return NULL;
    *r = *data;
    return r;
}

/* free dynamic allocated entry */
void free_entry(ENTRY *e) {
    if (e == NULL) return;
    free(e->key);
    free(e->data);
}

int main() {
    int hindex = 0;
    char key[LINE_SIZE];
    ENTRY map[HASH_SIZE];
    struct hsearch_data htab = {};

    /* create hash map */
    hcreate_r(HASH_SIZE, &htab);
    ENTRY *rep;
    /* run through key */
    while (fgets(key, LINE_SIZE, stdin) > 0) {
        /* construct entry */
        CLIENT data = {.count = 1};
        ENTRY e = {.key = strdup(key), .data = datadup(&data)};
        /* check entry */
        if (hsearch_r(e, FIND, &rep, &htab)) {
            /* update data */
            if (rep != NULL) {
                CLIENT *cp = rep->data;
                cp->count++;
            }
            free_entry(&e);
        } else {
            /* enter entry */
            if (hsearch_r(e, ENTER, &rep, &htab) && hindex < HASH_SIZE) {
                map[hindex++] = e;
            } else {
                fprintf(stderr, "increase HASH_SIZE: %s\n", strerror(errno));
                exit(1);
            }
        }
    }

    /* print hash */
    for (int i = 0; i < hindex; i++) {
        CLIENT *cp = map[i].data;
        if (cp->count > 1)
            printf("%3d %s", cp->count, map[i].key);
    }
    /* free entries */
    for (int i = 0; i < hindex; i++)
        free_entry(&map[i]);

    hdestroy_r(&htab);
    exit(0);
}