Utility Libraries for BREW - A Hash Table Class

Abstract

This article is the last one in a series that presents possible implementations of utility libraries in BREW. A hash table is introduced together with a XML parser.

A (Hash) Table...

Hash tables are unfortunately not part of the STL, even if unofficially several implementations are available ^[1]. They are very popular constructs in Java 1.1 (as well as J2ME) so that having a C++ equivalent implementation allows smooth code porting from one language to the other. Our implementation is very simple and offers no surprises:

template<class K, class V > 
class BrewHashtable ;

BrewHashtable() ;

BrewHashtable(int hashSize);

BrewHashtable(const BrewHashtable<K, V>&);

void put(const K& k, const V& d)  ;

int get(const K& k, V& d); //returns 0 for success, 1 otherwise

template<class T >
void keys(T& bk);

template<class T>
void elements(T& bk);

int remove(const K& key);

void remove_all();

int size() const;

bool isEmpty() const;

The only thing that might rise an eyebrow is how the return value is passed by refrence in get(), keys(), and elements() — a marginally better approach in terms of efficiency. Using BrewHashtable is straightforward:

BrewHashtable<int, int> hint;
   hint.put(10, 20);
   int res;
   hint.get(10, res);

BrewHashtable< String, int> hstr;
   hstr.put("1", 220);
   hstr.put("2", 333);
   hstr.put("3", 22440);
   hstr.put("4", 888);
   hstr.get("2", res);