// Created on: 1993-02-26 // Created by: Remi LEQUETTE // Copyright (c) 1993-1999 Matra Datavision // Copyright (c) 1999-2014 OPEN CASCADE SAS // // This file is part of Open CASCADE Technology software library. // // This library is free software; you can redistribute it and/or modify it under // the terms of the GNU Lesser General Public License version 2.1 as published // by the Free Software Foundation, with special exception defined in the file // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT // distribution for complete text of the license and disclaimer of any warranty. // // Alternatively, this file may be used under the terms of Open CASCADE // commercial license or contractual agreement. #ifndef _TCollection_BasicMap_HeaderFile #define _TCollection_BasicMap_HeaderFile #include #include #include #include #include #include #include class TCollection_BasicMapIterator; //! Root class of all the maps, provides utilitites //! for managing the buckets. //! Maps are dynamically extended data structures where //! data is quickly accessed with a key. //! General properties of maps //! - Map items may be (complex) non-unitary data; they //! may be difficult to manage with an array. Moreover, the //! map allows a data structure to be indexed by complex data. //! - The size of a map is dynamically extended. So a map //! may be first dimensioned for a little number of items. //! Maps avoid the use of large and quasi-empty arrays. //! - The access to a map item is much faster than the one //! to a sequence, a list, a queue or a stack item. //! - The access time to a map item may be compared with //! the one to an array item. First of all, it depends on the //! size of the map. It also depends on the quality of a user //! redefinable function (the hashing function) to find //! quickly where the item is. //! - The exploration of a map may be of better performance //! than the exploration of an array because the size of the //! map is adapted to the number of inserted items. //! These properties explain why maps are commonly used as //! internal data structures for algorithms. //! Definitions //! - A map is a data structure for which data is addressed by keys. //! - Once inserted in the map, a map item is referenced as an entry of the map. //! - Each entry of the map is addressed by a key. Two //! different keys address two different entries of the map. //! - The position of an entry in the map is called a bucket. //! - A map is dimensioned by its number of buckets, i.e. the //! maximum number of entries in the map. The //! performance of a map is conditioned by the number of buckets. //! - The hashing function transforms a key into a bucket //! index. The number of values that can be computed by //! the hashing function is equal to the number of buckets of the map. //! - Both the hashing function and the equality test //! between two keys are provided by a hasher object. //! - A map may be explored by a map iterator. This //! exploration provides only inserted entries in the map //! (i.e. non empty buckets). //! Collections' generic maps //! The Collections component provides numerous generic derived maps. //! - These maps include automatic management of the //! number of buckets: they are automatically resized when //! the number of keys exceeds the number of buckets. If //! you have a fair idea of the number of items in your map, //! you can save on automatic resizing by specifying a //! number of buckets at the time of construction, or by using //! a resizing function. This may be considered for crucial optimization issues. //! - Keys, items and hashers are parameters of these generic derived maps. //! - TCollection_MapHasher class describes the //! functions required by any hasher which is to be used //! with a map instantiated from the Collections component. //! - An iterator class is automatically instantiated at the //! time of instantiation of a map provided by the //! Collections component if this map is to be explored //! with an iterator. Note that some provided generic maps //! are not to be explored with an iterator but with indexes (indexed maps). class TCollection_BasicMap { public: DEFINE_STANDARD_ALLOC //! Returns the number of buckets in . Standard_Integer NbBuckets() const; //! Returns the number of keys already stored in . Standard_Integer Extent() const; //! Returns True when the map contains no keys. //! This is exactly Extent() == 0. Standard_Boolean IsEmpty() const; //! Prints on usefull statistics about the map //! . It can be used to test the quality of the hashcoding. Standard_EXPORT void Statistics (Standard_OStream& S) const; friend class TCollection_BasicMapIterator; protected: //! Initialize the map. Single is True when the map //! uses only one table of buckets. //! //! One table : Map, DataMap //! Two tables : DoubleMap, IndexedMap, IndexedDataMap Standard_EXPORT TCollection_BasicMap(const Standard_Integer NbBuckets, const Standard_Boolean single); //! Tries to resize the Map with NbBuckets. Returns //! True if possible, NewBuckts is the new nuber of //! buckets. data1 and data2 are the new tables of //! buckets where the data must be copied. Standard_EXPORT Standard_Boolean BeginResize (const Standard_Integer NbBuckets, Standard_Integer& NewBuckets, Standard_Address& data1, Standard_Address& data2) const; //! If BeginResize was succesfull after copying the //! data to data1 and data2 this methods update the //! tables and destroys the old ones. Standard_EXPORT void EndResize (const Standard_Integer NbBuckets, const Standard_Integer NewBuckets, const Standard_Address data1, const Standard_Address data2); //! Returns True if resizing the map should be //! considered. Standard_Boolean Resizable() const; //! Decrement the extent of the map. void Increment(); //! Decrement the extent of the map. void Decrement(); //! Destroys the buckets. Standard_EXPORT void Destroy(); Standard_Address myData1; Standard_Address myData2; private: Standard_Boolean isDouble; Standard_Boolean mySaturated; Standard_Integer myNbBuckets; Standard_Integer mySize; }; #include #endif // _TCollection_BasicMap_HeaderFile