A key/value dictionary system in C

dict.c

/* A key/value dict system in C */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define TEST TRUE /* Comment this line out to compile without a main function (used when including into another application). */

typedef struct dict_t_struct {
    char *key;
    void *value;
    struct dict_t_struct *next;
} dict_t;

dict_t **dict_alloc(void) {
    return malloc(sizeof(dict_t));
}

void dict_dealloc(dict_t *dict) {
    dict_t *ptr;
    for (ptr = dict; ptr != NULL; ptr = ptr->next) {
        free(ptr);
    }
}

void *dict_getItem(dict_t *dict, char *key) {
    dict_t *ptr;
    for (ptr = dict; ptr != NULL; ptr = ptr->next) {
        if (strcmp(ptr->key, key) == 0) {
            return ptr->value;
        }
    }
    
    return NULL;
}

void dict_delItem(dict_t **dict, char *key) {
    dict_t *ptr, *prev;
    for (ptr = *dict, prev = NULL; ptr != NULL; prev = ptr, ptr = ptr->next) {
        if (strcmp(ptr->key, key) == 0) {
            if (ptr->next != NULL) {
                if (prev == NULL) {
                    *dict = ptr->next;
                } else {
                    prev->next = ptr->next;
                }
            } else if (prev != NULL) {
                prev->next = NULL;
            } else {
                *dict = NULL;
            }
            
            free(ptr->key);
            free(ptr);
            
            return;
        }
    }
}

void dict_addItem(dict_t **dict, char *key, void *value) {
    dict_delItem(dict, key); /* If we already have a item with this key, delete it. */
    dict_t *d = malloc(sizeof(struct dict_t_struct));
    d->key = malloc(strlen(key)+1);
    strcpy(d->key, key);
    d->value = value;
    d->next = *dict;
    *dict = d;
}

int dict_size(dict_t *dict) {
    int size = 0;
    
    dict_t *ptr;
    for (ptr = dict; ptr != NULL; ptr = ptr->next) {
        size++;
    }
    
    return size;
}

dict_t **dict_invert(dict_t *dict) {
    dict_t **invert = dict_alloc();
    
    dict_t *ptr;
    for (ptr = dict; ptr != NULL; ptr = ptr->next) {
        dict_addItem(invert, ptr->value, ptr->key);
    }
    
    return invert;
}

#ifdef TEST

int main(int argc, char **argv) {
    /* Create a dict */
    dict_t **dict = dict_alloc();
    
    /* lets add foo, and bar to the dict */
    dict_addItem(dict, "foo", "bar");
    dict_addItem(dict, "bar", "foo");
    
    /* and print their values */
    printf("%s %s (size: %i)\n", (char *)dict_getItem(*dict, "foo"), (char *)dict_getItem(*dict, "bar"), dict_size(*dict));
    
    /* lets delete them */
    dict_delItem(dict, "foo");
    dict_delItem(dict, "bar");
    
    /* see, their gone, there NULL */
    printf("%s %s (size: %i)\n", (char *)dict_getItem(*dict, "foo"), (char *)dict_getItem(*dict, "bar"), dict_size(*dict));
    
    /* add them again to proof it works */
    dict_addItem(dict, "foo", "bar");
    dict_addItem(dict, "bar", "foo");
    dict_addItem(dict, "bar", "pan");
    
    /* see, here */
    printf("%s %s (size: %i)\n", (char *)dict_getItem(*dict, "foo"), (char *)dict_getItem(*dict, "bar"), dict_size(*dict));
    
    /* invert the dict */
    dict_t **invert = dict_invert(*dict);
    printf("%s %s (size: %i)\n", (char *)dict_getItem(*invert, "bar"), (char *)dict_getItem(*invert, "pan"), dict_size(*invert));
    dict_dealloc(*invert);
    
    dict_delItem(dict, "foo");
    dict_delItem(dict, "bar");
    
    dict_dealloc(*dict);
    
    return 0;
}

#endif

Hi,

I've noticed a two bugs in this little struct. Want to make a merge request but how can I do this?

Hi,

I've noticed a two bugs in this little struct. Want to make a merge request but how can I do this?

you can't , simply make a comment with your changes and hope the author will update it.

Hello, i tried to use your functions but each time i get the error "Exception thrown: read access violation. ptr was 0xFFFFFFFFFFFFFFFF." in delItem (same thing if i just copy paste the whole code and compile it). Any idea ?