Unigine::Hash class
| Header: | #include <UnigineHash.h> |
A Hash is a collection of unique keys and their values, much like a dictionary. Hashes are also referred to as associative arrays; they are similar to arrays, but while an array uses integers as an index, a Hash can use any type of object.
Let's check some examples of class functions usage:
- You can get the hash size and check whether the hash contains a specific key:
Source code (C++)
// create an empty hash set HashSet<String> set; // create two equal strings const char *initial_str = "aaa"; const String aaa0(initial_str), aaa1(initial_str); // add one of the strings as a key to the hash set set.insert(aaa0); // check the result if (set.contains(initial_str)) Log::message("The hash set contains the recently added key\n"); Log::message("The size is %d\n", set.size()); // add the duplicate string as a key to the hash set set.insert(aaa1); // check the result - the size of the hash set remains the same Log::message("The size is %d\n", set.size()); - You can get the iterator pointing to the first key in the hash. Also, you can remove some specific key from the hash if you know its iterator.
Source code (C++)
// create a hash set HashSet<String> set0{ "1", "2", "3" }; // copy one hash set to another HashSet<String> set1(set0); // remove the first key from the first hash set set0.erase(set0.begin()); // check the result if (set0 != set1) { for (const auto &i : set0) Log::message("%s ", i.key.get()); Log::message("\n"); for (const auto &j : set1) Log::message("%s ", j.key.get()); } - To clear the hash set, you should use the clear() function:
Source code (C++)
// create a hash set HashSet<String> set{ "1", "2", "3", "4", "5" }; // remove all keys from the hash set set.clear(); // check if the set is empty if (set.empty()) Log::message("The set is empty\n");
Hash Class
Members
bool is_need_realloc ( ) #
Indicates whether reallocation is needed.Return value
true if reallocation is needed, otherwise false.void shrink ( ) #
Reduces memory usage by removing unused capacity.Data * do_append ( const Key & key ) #
Appends an element with the specified key to the hash.Arguments
- const Key & key - Key of an element to be appended.
Return value
Pointer to Data.void rehash ( Counter new_capacity ) #
Rebuilds the hash based on a specified capacity.Arguments
- Counter new_capacity - New hash capacity value.
Iterator begin ( ) #
Returns an iterator that points to the first element in the hash.Return value
Iterator pointing to the first element.ConstIterator end ( ) #
Returns a const iterator that points to the location succeeding the last element in the hash.Return value
Const iterator pointing to the location after the last element.Vector<Key> keys ( ) #
Returns a vector containing all the keys in the hash.Return value
Vector of keys.bool remove ( const ConstIterator & it ) #
Removes an element currently pointed to by the iterator from the hash.Arguments
- const ConstIterator & it - Iterator pointing to an element to be removed.
Return value
true on success, otherwise false.Counter space ( ) #
Returns current capacity (number of elements the hash can currently contain).Return value
Number of elements the hash can currently contain.Data * do_append ( Key && key ) #
Appends an element with the specified key to the hash.Arguments
- Key && key - Key of an element to be appended.
Return value
Pointer to Data.bool erase ( const ConstIterator & it ) #
Removes an element currently pointed to by the iterator from the hash.Arguments
- const ConstIterator & it - Iterator pointing to the element to be removed.
Return value
true on success, otherwise false.bool erase ( const Iterator & it ) #
Removes an element currently pointed to by the iterator from the hash.Arguments
- const Iterator & it - Iterator pointing to the element to be removed.
Return value
true on success, otherwise false.Counter round_up ( Counter v ) #
Performs rounding and returns the result.Arguments
- Counter v
void swap ( Hash<Key, Data, HashType, Counter> & hash ) #
Swaps this hash with the specified one.Arguments
- Hash<Key, Data, HashType, Counter> & hash - Specified hash.
Data * do_append ( HashType hash, const Key & key ) #
Appends an element with the specified key to the specified hash.Arguments
- HashType hash - Specified hash.
- const Key & key - Key of an element to be appended.
Return value
Pointer to Data.void rehash_data ( Counter index ) #
Rebuilds the hash.Arguments
- Counter index
Counter empty ( ) #
Checks if the hash is empty or not.Return value
1 if the hash is empty, otherwise 0bool contains ( const Key & key ) #
Checks if the given key is present in the hash.Arguments
- const Key & key - Key to be looked for.
Return value
true if the given key is present in the hash, otherwise false.void clear ( ) #
Removes all key-value pairs from the hash.bool do_remove ( HashType hash, const Key & key ) #
Removes an element with the specified key from the specified hash.Arguments
- HashType hash - Specified hash.
- const Key & key - Key of an element to be removed.
Return value
true on success, otherwise false.void getKeys ( Vector<Key> & keys ) #
Adds keys of the hash to the specified vector.Arguments
- Vector<Key> & keys - Specified vector to store the keys in.
void reserve ( Counter size ) #
Reserves storage to avoid repeated reallocation.Arguments
- Counter size - Hash size to be reserved.
bool erase ( const Key & key ) #
Removes an element having the specified key from the hash.Arguments
- const Key & key - Key of an element to be removed.
Return value
true on success, otherwise false.Data ** do_find ( const Key & key ) #
Finds an element with a specified key.Arguments
- const Key & key - Key to look for.
Return value
Data of the element with the specified key if it exists, otherwise nullptr.void realloc ( ) #
Performs memory reallocation.bool remove ( const Key & key ) #
Removes an element having the specified key from the hash.Arguments
- const Key & key - Key of an element to be removed.
bool remove ( const Iterator & it ) #
Removes an element currently pointed to by the iterator from the hash.Arguments
- const Iterator & it - Iterator pointing to the element to be removed.
Return value
true on success, otherwise false.void destroy ( ) #
Deletes the hash.Counter size ( ) #
Returns the number of key-value pairs in the hash.Return value
Number of key-value pairs in the hash.Iterator end ( ) #
Returns an iterator that points to the location succeeding the last element in the hash.Return value
Iterator pointing to the location after the last element.ConstIterator begin ( ) #
Returns a const iterator that points to the first element in the hash.Return value
Iterator pointing to the first element.ConstIterator find ( const Key & key ) #
Finds an element with a specified key.Arguments
- const Key & key - Key to look for.
Return value
Iterator pointing to the element with a specified key if it exists, or to the end of the hash if it does not.Iterator find ( const Key & key ) #
Finds an element with a specified key.Arguments
- const Key & key - Key to look for.
Return value
Iterator pointing to the element with a specified key if it exists, or to the end of the hash if it does not.Last update:
2024-08-16
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