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Hash table
[D-BUS internal implementation details]

DBusHashTable data structure. More...

Typedefs

typedef int(* KeyCompareFunc )(const void *key_a, const void *key_b)
 Key comparison function.
typedef DBusHashIter DBusHashIter
 Public opaque hash table iterator object.
typedef DBusHashTable DBusHashTable
 Public opaque hash table object.

Enumerations

enum  DBusHashType {
  DBUS_HASH_STRING, DBUS_HASH_TWO_STRINGS, DBUS_HASH_INT, DBUS_HASH_POINTER,
  DBUS_HASH_ULONG
}
 Indicates the type of a key in the hash table.

Functions

DBusHashTable_dbus_hash_table_new (DBusHashType type, DBusFreeFunction key_free_function, DBusFreeFunction value_free_function)
 Constructs a new hash table.
DBusHashTable_dbus_hash_table_ref (DBusHashTable *table)
 Increments the reference count for a hash table.
void _dbus_hash_table_unref (DBusHashTable *table)
 Decrements the reference count for a hash table, freeing the hash table if the count reaches zero.
void _dbus_hash_iter_init (DBusHashTable *table, DBusHashIter *iter)
 Initializes a hash table iterator.
dbus_bool_t _dbus_hash_iter_next (DBusHashIter *iter)
 Move the hash iterator forward one step, to the next hash entry.
void _dbus_hash_iter_remove_entry (DBusHashIter *iter)
 Removes the current entry from the hash table.
void * _dbus_hash_iter_get_value (DBusHashIter *iter)
 Gets the value of the current entry.
void _dbus_hash_iter_set_value (DBusHashIter *iter, void *value)
 Sets the value of the current entry.
int _dbus_hash_iter_get_int_key (DBusHashIter *iter)
 Gets the key for the current entry.
unsigned long _dbus_hash_iter_get_ulong_key (DBusHashIter *iter)
 Gets the key for the current entry.
const char * _dbus_hash_iter_get_string_key (DBusHashIter *iter)
 Gets the key for the current entry.
const char * _dbus_hash_iter_get_two_strings_key (DBusHashIter *iter)
 Gets the key for the current entry.
dbus_bool_t _dbus_hash_iter_lookup (DBusHashTable *table, void *key, dbus_bool_t create_if_not_found, DBusHashIter *iter)
 A low-level but efficient interface for manipulating the hash table.
void * _dbus_hash_table_lookup_string (DBusHashTable *table, const char *key)
 Looks up the value for a given string in a hash table of type #DBUS_HASH_STRING.
void * _dbus_hash_table_lookup_two_strings (DBusHashTable *table, const char *key)
 Looks up the value for a given string in a hash table of type #DBUS_HASH_TWO_STRINGS.
void * _dbus_hash_table_lookup_int (DBusHashTable *table, int key)
 Looks up the value for a given integer in a hash table of type #DBUS_HASH_INT.
void * _dbus_hash_table_lookup_ulong (DBusHashTable *table, unsigned long key)
 Looks up the value for a given integer in a hash table of type #DBUS_HASH_ULONG.
dbus_bool_t _dbus_hash_table_remove_string (DBusHashTable *table, const char *key)
 Removes the hash entry for the given key.
dbus_bool_t _dbus_hash_table_remove_two_strings (DBusHashTable *table, const char *key)
 Removes the hash entry for the given key.
dbus_bool_t _dbus_hash_table_remove_int (DBusHashTable *table, int key)
 Removes the hash entry for the given key.
dbus_bool_t _dbus_hash_table_remove_ulong (DBusHashTable *table, unsigned long key)
 Removes the hash entry for the given key.
dbus_bool_t _dbus_hash_table_insert_string (DBusHashTable *table, char *key, void *value)
 Creates a hash entry with the given key and value.
dbus_bool_t _dbus_hash_table_insert_two_strings (DBusHashTable *table, char *key, void *value)
 Creates a hash entry with the given key and value.
dbus_bool_t _dbus_hash_table_insert_int (DBusHashTable *table, int key, void *value)
 Creates a hash entry with the given key and value.
dbus_bool_t _dbus_hash_table_insert_ulong (DBusHashTable *table, unsigned long key, void *value)
 Creates a hash entry with the given key and value.
DBusPreallocatedHash * _dbus_hash_table_preallocate_entry (DBusHashTable *table)
 Preallocate an opaque data blob that allows us to insert into the hash table at a later time without allocating any memory.
void _dbus_hash_table_free_preallocated_entry (DBusHashTable *table, DBusPreallocatedHash *preallocated)
 Frees an opaque DBusPreallocatedHash that was *not* used in order to insert into the hash table.
void _dbus_hash_table_insert_string_preallocated (DBusHashTable *table, DBusPreallocatedHash *preallocated, char *key, void *value)
 Inserts a string-keyed entry into the hash table, using a preallocated data block from _dbus_hash_table_preallocate_entry().
int _dbus_hash_table_get_n_entries (DBusHashTable *table)
 Gets the number of hash entries in a hash table.

Detailed Description

DBusHashTable data structure.

Types and functions related to DBusHashTable.


Function Documentation

int _dbus_hash_iter_get_int_key DBusHashIter iter  ) 
 

Gets the key for the current entry.

Only works for hash tables of type #DBUS_HASH_INT.

Parameters:
iter the hash table iterator.

Definition at line 650 of file dbus-hash.c.

References _dbus_assert, _DBUS_POINTER_TO_INT, DBusRealHashIter::entry, DBusHashEntry::key, NULL, and DBusRealHashIter::table.

const char* _dbus_hash_iter_get_string_key DBusHashIter iter  ) 
 

Gets the key for the current entry.

Only works for hash tables of type #DBUS_HASH_STRING

Parameters:
iter the hash table iterator.

Definition at line 687 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::entry, DBusHashEntry::key, NULL, and DBusRealHashIter::table.

const char* _dbus_hash_iter_get_two_strings_key DBusHashIter iter  ) 
 

Gets the key for the current entry.

Only works for hash tables of type #DBUS_HASH_TWO_STRINGS

Parameters:
iter the hash table iterator.

Definition at line 705 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::entry, DBusHashEntry::key, NULL, and DBusRealHashIter::table.

unsigned long _dbus_hash_iter_get_ulong_key DBusHashIter iter  ) 
 

Gets the key for the current entry.

Only works for hash tables of type #DBUS_HASH_ULONG.

Parameters:
iter the hash table iterator.

Definition at line 669 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::entry, DBusHashEntry::key, NULL, and DBusRealHashIter::table.

void* _dbus_hash_iter_get_value DBusHashIter iter  ) 
 

Gets the value of the current entry.

Parameters:
iter the hash table iterator.

Definition at line 604 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::entry, NULL, DBusRealHashIter::table, and DBusHashEntry::value.

void _dbus_hash_iter_init DBusHashTable table,
DBusHashIter iter
 

Initializes a hash table iterator.

To iterate over all entries in a hash table, use the following code (the printf assumes a hash from strings to strings obviously):

 DBusHashIter iter;

 _dbus_hash_iter_init (table, &iter);
 while (_dbus_hash_iter_next (&iter))
   {
      printf ("The first key is %s and value is %s\n",
              _dbus_hash_iter_get_string_key (&iter),
              _dbus_hash_iter_get_value (&iter));
   }

The iterator is initialized pointing "one before" the first hash entry. The first call to _dbus_hash_iter_next() moves it onto the first valid entry or returns FALSE if the hash table is empty. Subsequent calls move to the next valid entry or return FALSE if there are no more entries.

Note that it is guaranteed to be safe to remove a hash entry during iteration, but it is not safe to add a hash entry.

Parameters:
table the hash table to iterate over.
iter the iterator to initialize.

Definition at line 508 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::bucket, DBusRealHashIter::entry, n_entries, DBusRealHashIter::n_entries_on_init, DBusRealHashIter::next_bucket, DBusRealHashIter::next_entry, NULL, and DBusRealHashIter::table.

dbus_bool_t _dbus_hash_iter_lookup DBusHashTable table,
void *  key,
dbus_bool_t  create_if_not_found,
DBusHashIter iter
 

A low-level but efficient interface for manipulating the hash table.

It's efficient because you can get, set, and optionally create the hash entry while only running the hash function one time.

Note that while calling _dbus_hash_iter_next() on the iterator filled in by this function may work, it's completely undefined which entries are after this iter and which are before it. So it would be silly to iterate using this iterator.

If the hash entry is created, its value will be initialized to all bits zero.

FALSE may be returned due to memory allocation failure, or because create_if_not_found was FALSE and the entry did not exist.

If create_if_not_found is TRUE and the entry is created, the hash table takes ownership of the key that's passed in.

For a hash table of type #DBUS_HASH_INT, cast the int key to the key parameter using _DBUS_INT_TO_POINTER().

Parameters:
table the hash table.
key the hash key.
create_if_not_found if TRUE, create the entry if it didn't exist.
iter the iterator to initialize.
Returns:
TRUE if the hash entry now exists (and the iterator is thus valid).

Definition at line 749 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::bucket, buckets, DBusRealHashIter::entry, FALSE, find_function, n_entries, DBusRealHashIter::n_entries_on_init, DBusHashEntry::next, DBusRealHashIter::next_bucket, DBusRealHashIter::next_entry, NULL, DBusRealHashIter::table, and TRUE.

dbus_bool_t _dbus_hash_iter_next DBusHashIter iter  ) 
 

Move the hash iterator forward one step, to the next hash entry.

The documentation for _dbus_hash_iter_init() explains in more detail.

Parameters:
iter the iterator to move forward.
Returns:
FALSE if there are no more entries to move to.

Definition at line 534 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::bucket, buckets, DBusRealHashIter::entry, FALSE, n_buckets, n_entries, DBusRealHashIter::n_entries_on_init, DBusHashEntry::next, DBusRealHashIter::next_bucket, DBusRealHashIter::next_entry, NULL, DBusRealHashIter::table, and TRUE.

void _dbus_hash_iter_remove_entry DBusHashIter iter  ) 
 

Removes the current entry from the hash table.

If a key_free_function or value_free_function was provided to _dbus_hash_table_new(), frees the key and/or value for this entry.

Parameters:
iter the hash table iterator.

Definition at line 583 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::bucket, DBusRealHashIter::entry, NULL, and DBusRealHashIter::table.

void _dbus_hash_iter_set_value DBusHashIter iter,
void *  value
 

Sets the value of the current entry.

If the hash table has a value_free_function it will be used to free the previous value. The hash table will own the passed-in value (it will not be copied).

Parameters:
iter the hash table iterator.
value the new value.

Definition at line 627 of file dbus-hash.c.

References _dbus_assert, DBusRealHashIter::entry, free_value_function, NULL, DBusRealHashIter::table, and DBusHashEntry::value.

void _dbus_hash_table_free_preallocated_entry DBusHashTable table,
DBusPreallocatedHash *  preallocated
 

Frees an opaque DBusPreallocatedHash that was *not* used in order to insert into the hash table.

Parameters:
table the hash table
preallocated the preallocated data

Definition at line 1602 of file dbus-hash.c.

References _dbus_assert, and _dbus_mem_pool_dealloc().

int _dbus_hash_table_get_n_entries DBusHashTable table  ) 
 

Gets the number of hash entries in a hash table.

Parameters:
table the hash table.
Returns:
the number of entries in the table.

Definition at line 1660 of file dbus-hash.c.

dbus_bool_t _dbus_hash_table_insert_int DBusHashTable table,
int  key,
void *  value
 

Creates a hash entry with the given key and value.

The key and value are not copied; they are stored in the hash table by reference. If an entry with the given key already exists, the previous key and value are overwritten (and freed if the hash table has a key_free_function and/or value_free_function).

Returns FALSE if memory for the new hash entry can't be allocated.

Parameters:
table the hash table.
key the hash entry key.
value the hash entry value.

Definition at line 1467 of file dbus-hash.c.

References _dbus_assert, _DBUS_INT_TO_POINTER, DBusHashEntry::key, TRUE, and DBusHashEntry::value.

dbus_bool_t _dbus_hash_table_insert_string DBusHashTable table,
char *  key,
void *  value
 

Creates a hash entry with the given key and value.

The key and value are not copied; they are stored in the hash table by reference. If an entry with the given key already exists, the previous key and value are overwritten (and freed if the hash table has a key_free_function and/or value_free_function).

Returns FALSE if memory for the new hash entry can't be allocated.

Parameters:
table the hash table.
key the hash entry key.
value the hash entry value.

Definition at line 1392 of file dbus-hash.c.

References _dbus_assert, _dbus_hash_table_insert_string_preallocated(), _dbus_hash_table_preallocate_entry(), key_type, and TRUE.

void _dbus_hash_table_insert_string_preallocated DBusHashTable table,
DBusPreallocatedHash *  preallocated,
char *  key,
void *  value
 

Inserts a string-keyed entry into the hash table, using a preallocated data block from _dbus_hash_table_preallocate_entry().

This function cannot fail due to lack of memory. The DBusPreallocatedHash object is consumed and should not be reused or freed. Otherwise this function works just like _dbus_hash_table_insert_string().

Parameters:
table the hash table
preallocated the preallocated data
key the hash key
value the value

Definition at line 1629 of file dbus-hash.c.

References _dbus_assert, find_function, free_key_function, free_value_function, DBusHashEntry::key, key_type, and DBusHashEntry::value.

Referenced by _dbus_hash_table_insert_string().

dbus_bool_t _dbus_hash_table_insert_two_strings DBusHashTable table,
char *  key,
void *  value
 

Creates a hash entry with the given key and value.

The key and value are not copied; they are stored in the hash table by reference. If an entry with the given key already exists, the previous key and value are overwritten (and freed if the hash table has a key_free_function and/or value_free_function).

Returns FALSE if memory for the new hash entry can't be allocated.

Parameters:
table the hash table.
key the hash entry key.
value the hash entry value.

Definition at line 1426 of file dbus-hash.c.

References _dbus_assert, find_function, free_key_function, free_value_function, DBusHashEntry::key, key_type, TRUE, and DBusHashEntry::value.

dbus_bool_t _dbus_hash_table_insert_ulong DBusHashTable table,
unsigned long  key,
void *  value
 

Creates a hash entry with the given key and value.

The key and value are not copied; they are stored in the hash table by reference. If an entry with the given key already exists, the previous key and value are overwritten (and freed if the hash table has a key_free_function and/or value_free_function).

Returns FALSE if memory for the new hash entry can't be allocated.

Parameters:
table the hash table.
key the hash entry key.
value the hash entry value.

Definition at line 1552 of file dbus-hash.c.

References _dbus_assert, DBusHashEntry::key, and DBusHashEntry::value.

void* _dbus_hash_table_lookup_int DBusHashTable table,
int  key
 

Looks up the value for a given integer in a hash table of type #DBUS_HASH_INT.

Returns NULL if the value is not present. (A not-present entry is indistinguishable from an entry with a value of NULL.)

Parameters:
table the hash table.
key the integer to look up.
Returns:
the value of the hash entry.

Definition at line 1165 of file dbus-hash.c.

References _dbus_assert, _DBUS_INT_TO_POINTER, FALSE, NULL, and DBusHashEntry::value.

Referenced by _dbus_connection_queue_received_message_link(), and dbus_connection_dispatch().

void* _dbus_hash_table_lookup_string DBusHashTable table,
const char *  key
 

Looks up the value for a given string in a hash table of type #DBUS_HASH_STRING.

Returns NULL if the value is not present. (A not-present entry is indistinguishable from an entry with a value of NULL.)

Parameters:
table the hash table.
key the string to look up.
Returns:
the value of the hash entry.

Definition at line 1115 of file dbus-hash.c.

References _dbus_assert, FALSE, find_function, key_type, NULL, and DBusHashEntry::value.

void* _dbus_hash_table_lookup_two_strings DBusHashTable table,
const char *  key
 

Looks up the value for a given string in a hash table of type #DBUS_HASH_TWO_STRINGS.

Returns NULL if the value is not present. (A not-present entry is indistinguishable from an entry with a value of NULL.)

Parameters:
table the hash table.
key the string to look up.
Returns:
the value of the hash entry.

Definition at line 1140 of file dbus-hash.c.

References _dbus_assert, FALSE, NULL, and DBusHashEntry::value.

void* _dbus_hash_table_lookup_ulong DBusHashTable table,
unsigned long  key
 

Looks up the value for a given integer in a hash table of type #DBUS_HASH_ULONG.

Returns NULL if the value is not present. (A not-present entry is indistinguishable from an entry with a value of NULL.)

Parameters:
table the hash table.
key the integer to look up.
Returns:
the value of the hash entry.

Definition at line 1218 of file dbus-hash.c.

References _dbus_assert, and DBusHashEntry::value.

DBusHashTable* _dbus_hash_table_new DBusHashType  type,
DBusFreeFunction  key_free_function,
DBusFreeFunction  value_free_function
 

Constructs a new hash table.

Should be freed with _dbus_hash_table_unref(). If memory cannot be allocated for the hash table, returns NULL.

Parameters:
type the type of hash key to use.
key_free_function function to free hash keys.
value_free_function function to free hash values.
Returns:
a new DBusHashTable or NULL if no memory.

Definition at line 288 of file dbus-hash.c.

References _dbus_assert, _dbus_assert_not_reached, _dbus_mem_pool_new(), _DBUS_N_ELEMENTS, buckets, dbus_free(), dbus_new0, DBUS_SMALL_HASH_TABLE, down_shift, entry_pool, find_function, free_key_function, free_value_function, hi_rebuild_size, key_type, lo_rebuild_size, mask, n_buckets, n_entries, NULL, REBUILD_MULTIPLIER, refcount, static_buckets, and TRUE.

Referenced by _dbus_connection_new_for_transport(), and _dbus_user_database_new().

DBusPreallocatedHash* _dbus_hash_table_preallocate_entry DBusHashTable table  ) 
 

Preallocate an opaque data blob that allows us to insert into the hash table at a later time without allocating any memory.

Parameters:
table the hash table
Returns:
the preallocated data, or NULL if no memory

Definition at line 1585 of file dbus-hash.c.

Referenced by _dbus_hash_table_insert_string().

DBusHashTable* _dbus_hash_table_ref DBusHashTable table  ) 
 

Increments the reference count for a hash table.

Parameters:
table the hash table to add a reference to.
Returns:
the hash table.

Definition at line 354 of file dbus-hash.c.

References refcount.

dbus_bool_t _dbus_hash_table_remove_int DBusHashTable table,
int  key
 

Removes the hash entry for the given key.

If no hash entry for the key exists, does nothing.

Parameters:
table the hash table.
key the hash key.
Returns:
TRUE if the entry existed

Definition at line 1298 of file dbus-hash.c.

References _dbus_assert, _DBUS_INT_TO_POINTER, find_function, key_type, and TRUE.

dbus_bool_t _dbus_hash_table_remove_string DBusHashTable table,
const char *  key
 

Removes the hash entry for the given key.

If no hash entry for the key exists, does nothing.

Parameters:
table the hash table.
key the hash key.
Returns:
TRUE if the entry existed

Definition at line 1242 of file dbus-hash.c.

References _dbus_assert, and TRUE.

dbus_bool_t _dbus_hash_table_remove_two_strings DBusHashTable table,
const char *  key
 

Removes the hash entry for the given key.

If no hash entry for the key exists, does nothing.

Parameters:
table the hash table.
key the hash key.
Returns:
TRUE if the entry existed

Definition at line 1270 of file dbus-hash.c.

References _dbus_assert, find_function, key_type, and TRUE.

dbus_bool_t _dbus_hash_table_remove_ulong DBusHashTable table,
unsigned long  key
 

Removes the hash entry for the given key.

If no hash entry for the key exists, does nothing.

Parameters:
table the hash table.
key the hash key.
Returns:
TRUE if the entry existed

Definition at line 1357 of file dbus-hash.c.

References _dbus_assert, find_function, key_type, and TRUE.

void _dbus_hash_table_unref DBusHashTable table  ) 
 

Decrements the reference count for a hash table, freeing the hash table if the count reaches zero.

Parameters:
table the hash table to remove a reference from.

Definition at line 368 of file dbus-hash.c.

References _dbus_mem_pool_free(), buckets, dbus_free(), entry_pool, DBusHashEntry::next, NULL, refcount, and static_buckets.

Referenced by _dbus_connection_new_for_transport(), and _dbus_user_database_unref().


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