#define HTPROT(HTNAME)                                            \
    void *HTNAME##_get(struct htable *h, void *key);              \
    void HTNAME##_put(struct htable *h, void *key, void *val);    \
    void HTNAME##_adjoin(struct htable *h, void *key, void *val); \
    int HTNAME##_has(struct htable *h, void *key);                \
    int HTNAME##_remove(struct htable *h, void *key);             \
    void **HTNAME##_bp(struct htable *h, void *key);

// return value, or HT_NOTFOUND if key not found

// add key/value binding

// add binding iff key is unbound

// does key exist?

// logically remove key

// get a pointer to the location of the value for the given key.
// creates the location if it doesn't exist. only returns NULL
// if memory allocation fails.
// this should be used for updates, for example:
//     void **bp = ptrhash_bp(h, key);
//     *bp = f(*bp);
// do not reuse bp if there might be intervening calls to ptrhash_put,
// ptrhash_bp, ptrhash_reset, or ptrhash_free.