wxHashTable: wxObject

This class provides hash table functionality for wxWindows, and for an application if it wishes. Data can be hashed on an integer or string key. Below is an example of using a hash table.

  wxHashTable table(KEY_STRING);

  wxPoint *point = new wxPoint(100, 200);
  table.Put("point 1", point);

  ....

  wxPoint *found_point = (wxPoint *)table.Get("point 1");

A hash table is implemented as an array of pointers to lists. When no data has been stored, the hash table takes only a little more space than this array (default size is 1000). When a data item is added, an integer is constructed from the integer or string key that is within the bounds of the array. If the array element is NULL, a new (keyed) list is created for the element. Then the data object is appended to the list, storing the key in case other data objects need to be stored in the list also (when a `collision' occurs).

Retrieval involves recalculating the array index from the key, and searching along the keyed list for the data object whose stored key matches the passed key. Obviously this is quicker when there are fewer collisions, so hashing will become inefficient if the number of items to be stored greatly exceeds the size of the hash table.

wxHashTable::wxHashTable

voidwxHashTableunsigned int key_type, int size = 1000

Constructor. key_type is one of wxKEY_INTEGER, or wxKEY_STRING, and indicates what sort of keying is required. size is optional.

wxHashTable::wxHashTable

voidwxHashTable

Destroys the hash table.

wxHashTable::BeginFind

voidBeginFind

The counterpart of Next. If the application wishes to iterate through all the data in the hash table, it can call BeginFind and then loop on Next.

wxHashTable::Clear

voidClear

Clears the hash table of all nodes (but as usual, doesn't delete user data).

wxHashTable::Delete

wxObject *Deletelong key

wxObject *Deletechar * key

Deletes entry in hash table and returns the user's data (if found).

wxHashTable::Get

wxObject *Getlong key

wxObject *Getchar * key

Gets data from the hash table, using an integer or string key (depending on which has table constructor was used).

wxHashTable::MakeKey

longMakeKeychar *string

Makes an integer key out of a string. An application may wish to make a key explicitly (for instance when combining two data values to form a key).

wxHashTable::Next

wxNode *Next

If the application wishes to iterate through all the data in the hash table, it can call BeginFind and then loop on Next. This function returns a wxNode pointer (or NULL if there are no more nodes). See the wxNode description. The user will probably only wish to use the wxNode::Data function to retrieve the data; the node may also be deleted.

wxHashTable::Put

voidPutlong key, wxObject *object

voidPutchar * key, wxObject *object

Inserts data into the hash table, using an integer or string key (depending on which has table constructor was used). Note that only the pointer to the string key is stored, so it should not be deallocated by the calling program.