#include "hash.h"
This is the internal module for doing hash tables. A hash table uses a hash function to compute an index. On each index there is a separate linked list of entries.
Create a hash table. Add items. Retrieve items. Remove items. Destroy table.
void Curl_hash_init(struct Curl_hash *h,
size_t slots,
hash_function hfunc,
comp_function comparator,
Curl_hash_dtor dtor);
The call initializes a struct Curl_hash
.
slots
is the number of entries to create in the hash table. Larger is
better (faster lookups) but also uses more memory.hfunc
is a function pointer to a function that returns a size_t
value as
a checksum for an entry in this hash table. Ideally, it returns a unique
value for every entry ever added to the hash table, but hash collisions are
handled.comparator
is a function pointer to a function that compares two hash
table entries. It should return non-zero if the compared items are
identical.dtor
is a function pointer to a destructor called when an entry is removed
from the tablevoid *
Curl_hash_add(struct Curl_hash *h, void *key, size_t key_len, void *p)
This call adds an entry to the hash. key
points to the hash key and
key_len
is the length of the hash key. p
is a custom pointer.
If there already was a match in the hash, that data is replaced with this new entry.
This function also lazily allocates the table if needed, as it is not done in
the Curl_hash_init
function.
Returns NULL on error, otherwise it returns a pointer to p
.
void *Curl_hash_add2(struct Curl_hash *h, void *key, size_t key_len, void *p,
Curl_hash_elem_dtor dtor)
This works like Curl_hash_add
but has an extra argument: dtor
, which is a
destructor call for this specific entry. When this entry is removed, this
function is called instead of the function stored for the whole hash table.
int Curl_hash_delete(struct Curl_hash *h, void *key, size_t key_len);
This function removes an entry from the hash table. If successful, it returns zero. If the entry was not found, it returns 1.
void *Curl_hash_pick(struct Curl_hash *h, void *key, size_t key_len);
If there is an entry in the hash that matches the given key
with size of
key_len
, that its custom pointer is returned. The pointer that was called
p
when the entry was added.
It returns NULL if there is no matching entry in the hash.
void Curl_hash_destroy(struct Curl_hash *h);
This function destroys a hash and cleanups up all its related data. Calling it multiple times is fine.
void Curl_hash_clean(struct Curl_hash *h);
This function removes all the entries in the given hash.
void
Curl_hash_clean_with_criterium(struct Curl_hash *h, void *user,
int (*comp)(void *, void *))
This function removes all the entries in the given hash that matches the
criterion. The provided comp
function determines if the criteria is met by
returning non-zero.
size_t Curl_hash_count(struct Curl_hash *h)
Returns the number of entries stored in the hash.
void Curl_hash_start_iterate(struct Curl_hash *hash,
struct Curl_hash_iterator *iter):
This function initializes a struct Curl_hash_iterator
that iter
points to.
It can then be used to iterate over all the entries in the hash.
struct Curl_hash_element *
Curl_hash_next_element(struct Curl_hash_iterator *iter);
Given the iterator iter
, this function returns a pointer to the next hash
entry if there is one, or NULL if there is no more entries.
Called repeatedly, it iterates over all the entries in the hash table.
Note: it only guarantees functionality if the hash table remains untouched during its iteration.
void Curl_hash_offt_init(struct Curl_hash *h,
size_t slots,
Curl_hash_dtor dtor);
Initializes a hash table for curl_off_t
values. Pass in desired number of
slots
and dtor
function.
void *Curl_hash_offt_set(struct Curl_hash *h, curl_off_t id, void *elem);
Associate a custom elem
pointer with the given id
.
int Curl_hash_offt_remove(struct Curl_hash *h, curl_off_t id);
Remove the id
from the hash.
void *Curl_hash_offt_get(struct Curl_hash *h, curl_off_t id);
Get the pointer associated with the specified id
.