#include </home/zeitlin/src/wx/github/interface/wx/hashmap.h>
This is a simple, type-safe, and reasonably efficient hash map class, whose interface is a subset of the interface of STL containers.
In particular, the interface is modelled after std::map, and the various, non-standard, std::hash_map (http://www.cppreference.com/wiki/stl/map/start).
例:
class MyClass { ... }; // declare a hash map with string keys and int values WX_DECLARE_STRING_HASH_MAP( int, MyHash5 ); // same, with int keys and MyClass* values WX_DECLARE_HASH_MAP( int, MyClass*, wxIntegerHash, wxIntegerEqual, MyHash1 ); // same, with wxString keys and int values WX_DECLARE_STRING_HASH_MAP( int, MyHash3 ); // same, with wxString keys and values WX_DECLARE_STRING_HASH_MAP( wxString, MyHash2 ); MyHash1 h1; MyHash2 h2; // store and retrieve values h1[1] = new MyClass( 1 ); h1[10000000] = NULL; h1[50000] = new MyClass( 2 ); h2["Bill"] = "ABC"; wxString tmp = h2["Bill"]; // since element with key "Joe" is not present, this will return // the default value, which is an empty string in the case of wxString MyClass tmp2 = h2["Joe"]; // iterate over all the elements in the class MyHash2::iterator it; for( it = h2.begin(); it != h2.end(); ++it ) { wxString key = it->first, value = it->second; // do something useful with key and value }
WX_DECLARE_STRING_HASH_MAP( VALUE_T, // type of the values CLASSNAME ); // name of the class
Declares a hash map class named CLASSNAME, with wxString keys and VALUE_T values.
WX_DECLARE_VOIDPTR_HASH_MAP( VALUE_T, // type of the values CLASSNAME ); // name of the class
Declares a hash map class named CLASSNAME, with void* keys and VALUE_T values.
WX_DECLARE_HASH_MAP( KEY_T, // type of the keys VALUE_T, // type of the values HASH_T, // hasher KEY_EQ_T, // key equality predicate CLASSNAME); // name of the class
The HASH_T and KEY_EQ_T are the types used for the hashing function and key comparison. wxWidgets provides three predefined hashing functions: wxIntegerHash
for integer types ( int, long, short, and their unsigned counterparts ), wxStringHash
for strings ( wxString, wxChar*, char* ), and wxPointerHash
for any kind of pointer. Similarly three equality predicates: wxIntegerEqual
, wxStringEqual
, wxPointerEqual
are provided. Using this you could declare a hash map mapping int values to wxString like this:
WX_DECLARE_HASH_MAP( int, wxString, ::wxIntegerHash, ::wxIntegerEqual, MyHash ); // using an user-defined class for keys class MyKey { ... }; // hashing function class MyKeyHash { public: MyKeyHash() { } unsigned long operator()( const MyKey& k ) const { // compute the hash } MyKeyHash& operator=(const MyKeyHash&) { return *this; } }; // comparison operator class MyKeyEqual { public: MyKeyEqual() { } bool operator()( const MyKey& a, const MyKey& b ) const { // compare for equality } MyKeyEqual& operator=(const MyKeyEqual&) { return *this; } }; WX_DECLARE_HASH_MAP( MyKey, // type of the keys SOME_TYPE, // any type you like ::MyKeyHash, // hasher ::MyKeyEqual, // key equality predicate CLASSNAME); // name of the class
In the documentation below you should replace wxHashMap with the name you used in the class declaration.
An iterator is similar to a pointer, and so you can use the usual pointer operations: ++it ( and it++ ) to move to the next element, *it to access the element pointed to, it->first ( it->second ) to access the key ( value ) of the element pointed to.
Hash maps provide forward only iterators, this means that you can't use --it, it + 3, it1 - it2.
wxWidgets defines the following hashmap types:
Public Member Functions | |
wxHashMap (size_type size=10) | |
The size parameter is just a hint, the table will resize automatically to preserve performance. | |
wxHashMap (const wxHashMap &map) | |
Copy constructor. | |
void | clear () |
Removes all elements from the hash map. | |
size_type | count (const key_type &key) const |
Counts the number of elements with the given key present in the map. | |
bool | empty () const |
Returns true if the hash map does not contain any elements, false otherwise. | |
Insert_Result | insert (const value_type &v) |
Inserts the given value in the hash map. | |
mapped_type | operator[] (const key_type &key) |
Use the key as an array subscript. | |
size_type | size () const |
Returns the number of elements in the map. | |
const_iterator | begin () const |
Returns an iterator pointing at the first element of the hash map. | |
iterator | begin () |
Returns an iterator pointing at the first element of the hash map. | |
const_iterator | end () const |
Returns an iterator pointing at the one-after-the-last element of the hash map. | |
iterator | end () |
Returns an iterator pointing at the one-after-the-last element of the hash map. | |
size_type | erase (const key_type &key) |
Erases the element with the given key, and returns the number of elements erased (either 0 or 1). | |
void | erase (iterator it) |
Erases the element pointed to by the iterator. | |
void | erase (const_iterator it) |
Erases the element with the given key, and returns the number of elements erased (either 0 or 1). | |
iterator | find (const key_type &key) const |
If an element with the given key is present, the functions returns an iterator pointing at that element, otherwise an invalid iterator is returned. | |
const_iterator | find (const key_type &key) const |
If an element with the given key is present, the functions returns an iterator pointing at that element, otherwise an invalid iterator is returned. |
wxHashMap::wxHashMap | ( | size_type | size = 10 | ) |
The size parameter is just a hint, the table will resize automatically to preserve performance.
wxHashMap::wxHashMap | ( | const wxHashMap & | map | ) |
Copy constructor.
const_iterator wxHashMap::begin | ( | ) | const |
Returns an iterator pointing at the first element of the hash map.
Please remember that hash maps do not guarantee ordering.
iterator wxHashMap::begin | ( | ) |
Returns an iterator pointing at the first element of the hash map.
Please remember that hash maps do not guarantee ordering.
void wxHashMap::clear | ( | ) |
Removes all elements from the hash map.
size_type wxHashMap::count | ( | const key_type & | key | ) | const |
Counts the number of elements with the given key present in the map.
This function returns only 0 or 1.
bool wxHashMap::empty | ( | ) | const |
Returns true if the hash map does not contain any elements, false otherwise.
const_iterator wxHashMap::end | ( | ) | const |
Returns an iterator pointing at the one-after-the-last element of the hash map.
Please remember that hash maps do not guarantee ordering.
iterator wxHashMap::end | ( | ) |
Returns an iterator pointing at the one-after-the-last element of the hash map.
Please remember that hash maps do not guarantee ordering.
size_type wxHashMap::erase | ( | const key_type & | key | ) |
Erases the element with the given key, and returns the number of elements erased (either 0 or 1).
void wxHashMap::erase | ( | iterator | it | ) |
Erases the element pointed to by the iterator.
After the deletion the iterator is no longer valid and must not be used.
void wxHashMap::erase | ( | const_iterator | it | ) |
Erases the element with the given key, and returns the number of elements erased (either 0 or 1).
iterator wxHashMap::find | ( | const key_type & | key | ) | const |
If an element with the given key is present, the functions returns an iterator pointing at that element, otherwise an invalid iterator is returned.
hashmap.find( non_existent_key ) == hashmap.end()
const_iterator wxHashMap::find | ( | const key_type & | key | ) | const |
If an element with the given key is present, the functions returns an iterator pointing at that element, otherwise an invalid iterator is returned.
hashmap.find( non_existent_key ) == hashmap.end()
Insert_Result wxHashMap::insert | ( | const value_type & | v | ) |
Inserts the given value in the hash map.
The return value is equivalent to a
std::pair<wxHashMap::iterator, bool>
The iterator points to the inserted element, the boolean value is true if v was actually inserted.
mapped_type wxHashMap::operator[] | ( | const key_type & | key | ) |
Use the key as an array subscript.
The only difference is that if the given key is not present in the hash map, an element with the default value_type()
is inserted in the table.
size_type wxHashMap::size | ( | ) | const |
Returns the number of elements in the map.