enum error_code append_string(struct string *str, char *buf)
{
    size_t i;
    size_t it = 0;
    size_t bufSize = strlen(buf);

    while (str->capacity <= (bufSize + str->size))
        str->capacity *= sizeModifier;

    str->buffer = (char *)realloc(str->buffer, sizeof(char) * str->capacity);

    for (i = str->size; i < (str->size + bufSize); i++)
        str->buffer[i] = buf[it++];

    str->buffer[i++] = '\0';
    str->size = strlen(str->buffer);

    return OK;
}