Please note that this class is retained for backward compatibility reasons; you should use wxHashMap.
This class provides hash table functionality for wxWidgets, and for an application if it wishes. Data can be hashed on an integer or string key.
Derived from
Include files
<wx/hash.h>
Example
Below is an example of using a hash table.
wxHashTable table(wxKEY_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.
See also
Members
wxHashTable::wxHashTable
wxHashTable::~wxHashTable
wxHashTable::BeginFind
wxHashTable::Clear
wxHashTable::Delete
wxHashTable::DeleteContents
wxHashTable::Get
wxHashTable::MakeKey
wxHashTable::Next
wxHashTable::Put
wxHashTable::GetCount
wxHashTable(unsigned 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()
Destroys the hash table.
void BeginFind()
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.
void Clear()
Clears the hash table of all nodes (but as usual, doesn't delete user data).
wxObject * Delete(long key)
wxObject * Delete(const wxString& key)
Deletes entry in hash table and returns the user's data (if found).
void DeleteContents(bool flag)
If set to true data stored in hash table will be deleted when hash table object is destroyed.
wxObject * Get(long key)
wxObject * Get(const char* key)
Gets data from the hash table, using an integer or string key (depending on which has table constructor was used).
long MakeKey(const wxString& 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::Node * 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 wxHashTable::Node pointer (or NULL if there are no more nodes). The return value is functionally equivalent to wxNode but might not be implemented as a wxNode. The user will probably only wish to use the GetData method to retrieve the data; the node may also be deleted.
void Put(long key, wxObject *object)
void Put(const char* key, wxObject *object)
Inserts data into the hash table, using an integer or string key (depending on which has table constructor was used). The key string is copied and stored by the hash table implementation.
size_t GetCount() const
Returns the number of elements in the hash table.