hash.c

#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

typedef struct node {
	int key;
	int val;
	struct node *next;
} node;

typedef struct hashmap {
	int num_elements;
	int num_buckets;
	node *buckets;
} hashmap;

typedef struct result {
	bool found;
	int val;
} result;

hashmap make_hashmap() {
	int buckets = 8;
	hashmap new_map = {0, buckets, calloc(buckets, sizeof(node))};
	return new_map;
}

// false = overwrote, true = inserted
bool set(hashmap *map, int key, int val) {
	node *current_element = &map->buckets[key % map->num_buckets];
	node *new_node = malloc(sizeof(node));
	new_node->key = key;
	new_node->val = val;
	new_node->next = NULL;

	if (current_element == NULL) {
		map->buckets[key % map->num_buckets] = *new_node;
		return true;
	}

	while (true) {
		if (current_element->key == key) {
			current_element->val = val;
			return false;
		}
		if (current_element->next == NULL) {
			current_element->next = new_node;
			return true;
		}
		current_element = current_element->next;
	}
}

result get(hashmap *map, int key)  {
	result res;
	node *current_element = &map->buckets[key % map->num_buckets];
	if (current_element == NULL) {
		res.found = false;	
		return res;
	}
	while (true) {
		if (current_element->key == key) {
			res.found = true;
			res.val = current_element->val;
			return res;
		} 
		if (current_element->next == NULL) {
			res.found = false;
			return res;
		}
		current_element = current_element->next;
	}
}

bool exists(hashmap *map, int key) {
	return get(map, key).found;
}

bool test_make_hashmap() {
	hashmap test_map  = make_hashmap();
	assert(test_map.num_elements == 0);
}

bool test_exists() {
	hashmap test_map  = make_hashmap();
	assert(!exists(&test_map, 1));
}

bool test_set() {
	hashmap test_map  = make_hashmap();
	assert(set(&test_map, 1, 8));
	assert(!set(&test_map, 1, 10));
	assert(exists(&test_map, 1));
	assert(!exists(&test_map, 2));
}

bool test_get() {
	hashmap test_map  = make_hashmap();
	assert(set(&test_map, 1, 8));
	assert(set(&test_map, 9, 12));
	assert(get(&test_map, 1).val == 8);
	assert(get(&test_map, 1).found);
	assert(get(&test_map, 9).found);
	assert(!get(&test_map, 2).found);
}

int main() {
	test_make_hashmap();
	test_exists();
	test_set();
	test_get();
	printf("Successfully finished\n");
	return 0;
}