a simple include for hash tables in c++

hashtable.hpp

#include <string>

#define CAPACITY 100

// copied from the internet (thanks internet)
unsigned long hash_function(std::string str) {
    unsigned long i = 0;
    for (int j=0; j < str.length(); j++)
        i += str.at(j);
    return i % CAPACITY;
}

typedef struct hash_table
{
    unsigned int keys[CAPACITY];
    std::string values[CAPACITY];
    unsigned int counter;

    void append(std::string key, std::string value) {
        if (counter+1 > CAPACITY) return;

        keys[counter] = hash_function(key);
        values[counter] = value;
        counter++;
    }

    std::string get(std::string key) {
        int keyIndex = -1;

        for (int i = 0; i < counter; i++) {
            if (hash_function(key) == keys[i]) {
                keyIndex = i;
                break;
            }
        }
            

        if (keyIndex == -1) return "";

        return values[keyIndex];
    }

} hash_table;