ハシ・マプを実装せむとす

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

struct hashitem {
    char* key;
    int value;
};

struct hashmap {
    struct hashitem* head;
    unsigned int size;
    unsigned int max_size;
};

void add_hashmap(struct hashmap* hmp, char* key, int val);

int hash(char* str, int max_v) {
    int v = 0;
    while(*str != '\n') v += *str++;

    return v % max_v;
}

struct hashmap init_hashmap(unsigned int init_size) {
    struct hashmap hm;
    struct hashitem* hip = (struct hashitem*) malloc(sizeof(struct hashitem) * init_size);
    if(hip == NULL) {
        printf("ERROR\n");
        exit(1);
    }

    for(int i=0; i<init_size; i++) {
        struct hashitem hi;
        hi.key = "";
        hi.value = 0;
        *(hip + i) = hi;
    }

    hm.head = hip;
    hm.size = 0;
    hm.max_size = init_size;

    return hm;
}

struct hashmap rehash(struct hashmap oldmap) {
    unsigned int size = oldmap.max_size << 1;
    struct hashmap hm = init_hashmap(size);
    struct hashitem* p = oldmap.head;

    for(int i=0; i<oldmap.max_size; i++) {
        struct hashitem item = *(p + i);
        if(strcmp(item.key, "") == 0) continue;
        add_hashmap(&hm, item.key, item.value);
    }

    free(oldmap.head);
    
    return hm;
}

void add_hashmap(struct hashmap* hmp, char* key, int val) {
    struct hashmap hm = *hmp;
    if(hm.size + 1 == hm.max_size) {
        struct hashmap new_hm = rehash(hm);
        *hmp = new_hm;
        hm = new_hm;
    }

    int index = hash(key, hm.max_size);

    while(1) {
        struct hashitem item = *(hm.head + index);
        if (strcmp(item.key, "") == 0) break;
        index = (index + 1) % hm.max_size;
    }
    struct hashitem hi;
    hi.key = key;
    hi.value = val;

    *(hm.head + index) = hi;

    hmp->size += 1;
}

int get_hashmap(struct hashmap hm, char* key) {
    int index = hash(key, hm.max_size);
    struct hashitem hi;
    while(1) {
        hi = *(hm.head + index);
        if (strcmp(hi.key, key) == 0) break;
        index = (index + 1) % hm.max_size;
    }

    return hi.value;
}


int main() {
    struct hashmap hm = init_hashmap(4);
    add_hashmap(&hm, "magic", 12);
    add_hashmap(&hm, "hac", 34);
    add_hashmap(&hm, "hashmap", 56);
    add_hashmap(&hm, "dict", 78);
    add_hashmap(&hm, "unordered_map", 90);

    int val = get_hashmap(hm, "magic");
    printf("%d\n", val);
    
    return 0;
}