lhash.h

All headers

lhash is a traditional, chaining hash table that automatically expands and contracts as needed. One should not use the lh_* functions directly, rather use the type-safe macro wrappers:

A hash table of a specific type of object has type LHASH_OF(type). This can be defined (once) with DEFINE_LHASH_OF(type) and declared where needed with DECLARE_LHASH_OF(type). For example:

struct foo { int bar; };

DEFINE_LHASH_OF(struct foo)

Although note that the hash table will contain /pointers/ to foo.

A macro will be defined for each of the lh_* functions below. For LHASH_OF(foo), the macros would be lh_foo_new, lh_foo_num_items etc.

  1. LHASH_OF
  2. DECLARE_LHASH_OF
  3. lh_new
  4. lh_free
  5. lh_num_items
  6. lh_retrieve
  7. lh_retrieve_key
  8. lh_insert
  9. lh_delete
  10. lh_doall_arg
  11. lh_strhash
  12. DEFINE_LHASH_OF
#define LHASH_OF(type) struct lhash_st_##type
#define DECLARE_LHASH_OF(type) LHASH_OF(type);

lhash_item_st is an element of a hash chain. It points to the opaque data for this element and to the next item in the chain. The linked-list is NULL terminated.

typedef struct lhash_item_st {
  void *data;
  struct lhash_item_st *next;
  // hash contains the cached, hash value of |data|.
  uint32_t hash;
} LHASH_ITEM;

lhash_cmp_func is a comparison function that returns a value equal, or not equal, to zero depending on whether *a is equal, or not equal to *b, respectively. Note the difference between this and stack_cmp_func in that this takes pointers to the objects directly.

This function's actual type signature is int (*)(const T*, const T*). The low-level lh_* functions will be passed a type-specific wrapper to call it correctly.

typedef int (*lhash_cmp_func)(const void *a, const void *b);
typedef int (*lhash_cmp_func_helper)(lhash_cmp_func func, const void *a,
                                     const void *b);

lhash_hash_func is a function that maps an object to a uniformly distributed uint32_t.

This function's actual type signature is uint32_t (*)(const T*). The low-level lh_* functions will be passed a type-specific wrapper to call it correctly.

typedef uint32_t (*lhash_hash_func)(const void *a);
typedef uint32_t (*lhash_hash_func_helper)(lhash_hash_func func, const void *a);
typedef struct lhash_st _LHASH;

lh_new returns a new, empty hash table or NULL on error.

OPENSSL_EXPORT _LHASH *lh_new(lhash_hash_func hash, lhash_cmp_func comp);

lh_free frees the hash table itself but none of the elements. See lh_doall.

OPENSSL_EXPORT void lh_free(_LHASH *lh);

lh_num_items returns the number of items in lh.

OPENSSL_EXPORT size_t lh_num_items(const _LHASH *lh);

lh_retrieve finds an element equal to data in the hash table and returns it. If no such element exists, it returns NULL.

OPENSSL_EXPORT void *lh_retrieve(const _LHASH *lh, const void *data,
                                 lhash_hash_func_helper call_hash_func,
                                 lhash_cmp_func_helper call_cmp_func);

lh_retrieve_key finds an element matching key, given the specified hash and comparison function. This differs from lh_retrieve in that the key may be a different type than the values stored in lh. key_hash and cmp_key must be compatible with the functions passed into lh_new.

OPENSSL_EXPORT void *lh_retrieve_key(const _LHASH *lh, const void *key,
                                     uint32_t key_hash,
                                     int (*cmp_key)(const void *key,
                                                    const void *value));

lh_insert inserts data into the hash table. If an existing element is equal to data (with respect to the comparison function) then *old_data will be set to that value and it will be replaced. Otherwise, or in the event of an error, *old_data will be set to NULL. It returns one on success or zero in the case of an allocation error.

OPENSSL_EXPORT int lh_insert(_LHASH *lh, void **old_data, void *data,
                             lhash_hash_func_helper call_hash_func,
                             lhash_cmp_func_helper call_cmp_func);

lh_delete removes an element equal to data from the hash table and returns it. If no such element is found, it returns NULL.

OPENSSL_EXPORT void *lh_delete(_LHASH *lh, const void *data,
                               lhash_hash_func_helper call_hash_func,
                               lhash_cmp_func_helper call_cmp_func);

lh_doall_arg calls func on each element of the hash table and also passes arg as the second argument. TODO(fork): rename this

OPENSSL_EXPORT void lh_doall_arg(_LHASH *lh, void (*func)(void *, void *),
                                 void *arg);

lh_strhash is the default hash function which processes NUL-terminated strings.

OPENSSL_EXPORT uint32_t lh_strhash(const char *c);
#define DEFINE_LHASH_OF(type)                                                  \
  DECLARE_LHASH_OF(type)                                                       \
                                                                               \
  typedef int (*lhash_##type##_cmp_func)(const type *, const type *);          \
  typedef uint32_t (*lhash_##type##_hash_func)(const type *);                  \
                                                                               \
  OPENSSL_INLINE int lh_##type##_call_cmp_func(lhash_cmp_func func,            \
                                               const void *a, const void *b) { \
    return ((lhash_##type##_cmp_func)func)((const type *)a, (const type *)b);  \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE uint32_t lh_##type##_call_hash_func(lhash_hash_func func,     \
                                                     const void *a) {          \
    return ((lhash_##type##_hash_func)func)((const type *)a);                  \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE LHASH_OF(type) *                                              \
      lh_##type##_new(lhash_##type##_hash_func hash,                           \
                      lhash_##type##_cmp_func comp) {                          \
    return (LHASH_OF(type) *)lh_new((lhash_hash_func)hash,                     \
                                    (lhash_cmp_func)comp);                     \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE void lh_##type##_free(LHASH_OF(type) *lh) {                   \
    lh_free((_LHASH *)lh);                                                     \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE size_t lh_##type##_num_items(const LHASH_OF(type) *lh) {      \
    return lh_num_items((const _LHASH *)lh);                                   \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE type *lh_##type##_retrieve(const LHASH_OF(type) *lh,          \
                                            const type *data) {                \
    return (type *)lh_retrieve((const _LHASH *)lh, data,                       \
                               lh_##type##_call_hash_func,                     \
                               lh_##type##_call_cmp_func);                     \
  }                                                                            \
                                                                               \
  typedef struct {                                                             \
    int (*cmp_key)(const void *key, const type *value);                        \
    const void *key;                                                           \
  } LHASH_CMP_KEY_##type;                                                      \
                                                                               \
  OPENSSL_INLINE int lh_##type##_call_cmp_key(const void *key,                 \
                                              const void *value) {             \
    const LHASH_CMP_KEY_##type *cb = (const LHASH_CMP_KEY_##type *)key;        \
    return cb->cmp_key(cb->key, (const type *)value);                          \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE type *lh_##type##_retrieve_key(                               \
      const LHASH_OF(type) *lh, const void *key, uint32_t key_hash,            \
      int (*cmp_key)(const void *key, const type *value)) {                    \
    LHASH_CMP_KEY_##type cb = {cmp_key, key};                                  \
    return (type *)lh_retrieve_key((const _LHASH *)lh, &cb, key_hash,          \
                                   lh_##type##_call_cmp_key);                  \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE int lh_##type##_insert(LHASH_OF(type) *lh, type **old_data,   \
                                        type *data) {                          \
    void *old_data_void = NULL;                                                \
    int ret =                                                                  \
        lh_insert((_LHASH *)lh, &old_data_void, data,                          \
                  lh_##type##_call_hash_func, lh_##type##_call_cmp_func);      \
    *old_data = (type *)old_data_void;                                         \
    return ret;                                                                \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE type *lh_##type##_delete(LHASH_OF(type) *lh,                  \
                                          const type *data) {                  \
    return (type *)lh_delete((_LHASH *)lh, data, lh_##type##_call_hash_func,   \
                             lh_##type##_call_cmp_func);                       \
  }                                                                            \
                                                                               \
  typedef struct {                                                             \
    void (*doall)(type *);                                                     \
    void (*doall_arg)(type *, void *);                                         \
    void *arg;                                                                 \
  } LHASH_DOALL_##type;                                                        \
                                                                               \
  OPENSSL_INLINE void lh_##type##_call_doall(void *value, void *arg) {         \
    const LHASH_DOALL_##type *cb = (const LHASH_DOALL_##type *)arg;            \
    cb->doall((type *)value);                                                  \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE void lh_##type##_call_doall_arg(void *value, void *arg) {     \
    const LHASH_DOALL_##type *cb = (const LHASH_DOALL_##type *)arg;            \
    cb->doall_arg((type *)value, cb->arg);                                     \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE void lh_##type##_doall(LHASH_OF(type) *lh,                    \
                                        void (*func)(type *)) {                \
    LHASH_DOALL_##type cb = {func, NULL, NULL};                                \
    lh_doall_arg((_LHASH *)lh, lh_##type##_call_doall, &cb);                   \
  }                                                                            \
                                                                               \
  OPENSSL_INLINE void lh_##type##_doall_arg(                                   \
      LHASH_OF(type) *lh, void (*func)(type *, void *), void *arg) {           \
    LHASH_DOALL_##type cb = {NULL, func, arg};                                 \
    lh_doall_arg((_LHASH *)lh, lh_##type##_call_doall_arg, &cb);               \
  }