Dogcows Code - chaz/yoink/blob - src/Moof/stlplus/hash.hpp

   1 #ifndef STLPLUS_HASH
   2 #define STLPLUS_HASH
   3 ////////////////////////////////////////////////////////////////////////////////
   4
   5 //   Author:    Andy Rushton
   6 //   Copyright: (c) Southampton University 1999-2004
   7 //              (c) Andy Rushton           2004-2009
   8 //   License:   BSD License, see ../docs/license.html
   9
  10 //   A chained hash table using STL semantics
  11
  12 ////////////////////////////////////////////////////////////////////////////////
  13 #include "containers_fixes.hpp"
  14 #include "exceptions.hpp"
  15 #include "safe_iterator.hpp"
  16 #include <map>
  17
  18 namespace stlplus
  19 {
  20
  21   ////////////////////////////////////////////////////////////////////////////////
  22   // internals
  23
  24   template<typename K, typename T, class H, class E> class hash;
  25   template<typename K, typename T, class H, class E> class hash_element;
  26
  27   ////////////////////////////////////////////////////////////////////////////////
  28   // iterator class
  29
  30   template<typename K, typename T, class H, class E, typename V>
  31   class hash_iterator : public safe_iterator<hash<K,T,H,E>,hash_element<K,T,H,E> >
  32   {
  33   public:
  34     friend class hash<K,T,H,E>;
  35
  36     // local type definitions
  37     // an iterator points to a value whilst a const_iterator points to a const value
  38     typedef V                                                  value_type;
  39     typedef hash_iterator<K,T,H,E,std::pair<const K,T> >       iterator;
  40     typedef hash_iterator<K,T,H,E,const std::pair<const K,T> > const_iterator;
  41     typedef hash_iterator<K,T,H,E,V>                           this_iterator;
  42     typedef V&                                                 reference;
  43     typedef V*                                                 pointer;
  44
  45     // constructor to create a null iterator - you must assign a valid value to this iterator before using it
  46     // any attempt to dereference or use a null iterator is an error
  47     // the only valid thing you can do is assign an iterator to it
  48     hash_iterator(void);
  49     ~hash_iterator(void);
  50
  51     // Type conversion methods allow const_iterator and iterator to be converted
  52     // convert an iterator/const_iterator to a const_iterator
  53     const_iterator constify(void) const;
  54     // convert an iterator/const_iterator to an iterator
  55     iterator deconstify(void) const;
  56
  57     // increment operators used to step through the set of all values in a hash
  58     // it is only legal to increment a valid iterator
  59     // there's no decrement - I've only implemented this as a unidirectional iterator
  60     // pre-increment
  61     this_iterator& operator ++ (void)
  62       throw(null_dereference,end_dereference);
  63     // post-increment
  64     this_iterator operator ++ (int)
  65       throw(null_dereference,end_dereference);
  66
  67     // test useful for testing whether iteration has completed
  68     bool operator == (const this_iterator& r) const;
  69     bool operator != (const this_iterator& r) const;
  70     bool operator < (const this_iterator& r) const;
  71
  72     // access the value - a const_iterator gives you a const value, an iterator a non-const value
  73     // it is illegal to dereference an invalid (i.e. null or end) iterator
  74     reference operator*(void) const
  75       throw(null_dereference,end_dereference);
  76     pointer operator->(void) const
  77       throw(null_dereference,end_dereference);
  78
  79   private:
  80     friend class hash_element<K,T,H,E>;
  81
  82     // constructor used by hash to create a non-null iterator
  83     // you cannot create a valid iterator except by calling a hash method that returns one
  84     explicit hash_iterator(hash_element<K,T,H,E>* element);
  85     // constructor used to create an end iterator
  86     explicit hash_iterator(const hash<K,T,H,E>* owner);
  87     // used to create an alias of an iterator
  88     explicit hash_iterator(const safe_iterator<hash<K,T,H,E>, hash_element<K,T,H,E> >& iterator);
  89   };
  90
  91   ////////////////////////////////////////////////////////////////////////////////
  92   // Hash class
  93   // K = key type
  94   // T = value type
  95   // H = hash function object with the profile 'unsigned H(const K&)'
  96   // E = equal function object with profile 'bool E(const K&, const K&)' defaults to equal_to which in turn calls '=='
  97
  98   template<typename K, typename T, class H, class E = std::equal_to<K> >
  99   class hash
 100   {
 101   public:
 102     typedef unsigned                                size_type;
 103     typedef K                                       key_type;
 104     typedef T                                       data_type;
 105     typedef T                                       mapped_type;
 106     typedef std::pair<const K, T>                   value_type;
 107     typedef hash_iterator<K,T,H,E,value_type>       iterator;
 108     typedef hash_iterator<K,T,H,E,const value_type> const_iterator;
 109
 110     // construct a hash table with specified number of bins
 111     // the default 0 bins means leave it to the table to decide
 112     // specifying 0 bins also enables auto-rehashing, otherwise auto-rehashing defaults off
 113     hash(unsigned bins = 0);
 114     ~hash(void);
 115
 116     // copy and equality copy the data elements but not the size of the copied table
 117     hash(const hash&);
 118     hash& operator = (const hash&);
 119
 120     // test for an empty table and for the size of a table
 121     // efficient because the size is stored separately from the table contents
 122     bool empty(void) const;
 123     unsigned size(void) const;
 124
 125     // test for equality - two hashes are equal if they contain equal values
 126     bool operator == (const hash&) const;
 127     bool operator != (const hash&) const;
 128
 129     // switch auto-rehash on
 130     void auto_rehash(void);
 131     // switch auto-rehash off
 132     void manual_rehash(void);
 133     // force a rehash now
 134     // default of 0 means implement built-in size calculation for rehashing (recommended - it doubles the number of bins)
 135     void rehash(unsigned bins = 0);
 136     // test the loading ratio, which is the size divided by the number of bins
 137     // use this if you are doing your own rehashing
 138     // the recommendation is to double the bins when the loading exceeds 0.5 which is what auto-rehashing does
 139     float loading(void) const;
 140
 141     // test for the presence of a key
 142     bool present(const K& key) const;
 143     // provide map equivalent key count function (0 or 1, as not a multimap)
 144     size_type count(const K& key) const;
 145
 146     // insert a new key/data pair - replaces any previous value for this key
 147     iterator insert(const K& key, const T& data);
 148     // insert a copy of the pair into the table (std::map compatible)
 149     std::pair<iterator, bool> insert(const value_type& value);
 150     // insert a new key and return the iterator so that the data can be filled in
 151     iterator insert(const K& key);
 152
 153     // remove a key/data pair from the hash table
 154     bool erase(const K& key);
 155     // remove all elements from the hash table
 156     void erase(void);
 157     // provide the std::map equivalent clear function
 158     void clear(void);
 159
 160     // find a key and return an iterator to it
 161     // The iterator is like a pointer to a pair<const K,T>
 162     // end() is returned if the find fails
 163     const_iterator find(const K& key) const;
 164     iterator find(const K& key);
 165
 166     // returns the data corresponding to the key
 167     // const version is used for const hashes and cannot change the hash, so failure causes an exception
 168     // non-const version is for non-const hashes and is like map - it creates a new key/data pair if find fails
 169     const T& operator[] (const K& key) const throw(std::out_of_range);
 170     T& operator[] (const K& key);
 171
 172     // iterators allow the hash table to be traversed
 173     // iterators remain valid unless an item is removed or unless a rehash happens
 174     const_iterator begin(void) const;
 175     iterator begin(void);
 176     const_iterator end(void) const;
 177     iterator end(void);
 178
 179     // internals
 180   private:
 181     friend class hash_element<K,T,H,E>;
 182     friend class hash_iterator<K,T,H,E,std::pair<const K,T> >;
 183     friend class hash_iterator<K,T,H,E,const std::pair<const K,T> >;
 184
 185     unsigned m_rehash;
 186     unsigned m_bins;
 187     unsigned m_size;
 188     hash_element<K,T,H,E>** m_values;
 189   };
 190
 191   ////////////////////////////////////////////////////////////////////////////////
 192
 193 } // end namespace stlplus
 194
 195 #include "hash.tpp"
 196 #endif