hashtable.h

   1 /** @file hashtable.h
   2  *  @brief Hashtable.  Standard chained bucket variety.
   3  */
   4
   5 #ifndef HASHTABLE_H
   6 #define HASHTABLE_H
   7
   8 #include <stdlib.h>
   9 #include <stdio.h>
  10
  11 template<typename _Key, typename _Val>
  12         struct hashlistnode {
  13                 _Key key;
  14                 _Val val;
  15                 struct hashlistnode<_Key,_Val> *next;
  16         };
  17
  18 /** Hashtable class.  By default it is snapshotting, but you can pass
  19                 in your own allocation functions. */
  20
  21 template<typename _Key, typename _Val, typename _KeyInt, int _Shift=0, void * (* _malloc)(size_t)=malloc, void * (* _calloc)(size_t, size_t)=calloc, void (*_free)(void *)=free>
  22         class HashTable {
  23  public:
  24         HashTable(unsigned int initialcapacity=1024, double factor=0.5) {
  25                 // Allocate space for the hash table
  26                 table = (struct hashlistnode<_Key,_Val> **) _calloc(initialcapacity, sizeof(struct hashlistnode<_Key,_Val> *));
  27                 loadfactor = factor;
  28                 capacity = initialcapacity;
  29                 threshold = (unsigned int) (initialcapacity*loadfactor);
  30                 mask = (capacity << _Shift)-1;
  31                 size = 0; // Initial number of elements in the hash
  32         }
  33
  34         ~HashTable() {
  35                 for(unsigned int i=0;i<capacity;i++) {
  36                         struct hashlistnode<_Key,_Val> * bin = table[i];
  37                         while(bin!=NULL) {
  38                                 struct hashlistnode<_Key,_Val> * next=bin->next;
  39                                 delete bin;
  40                                 bin=next;
  41                         }
  42                 }
  43                 _free(table);
  44         }
  45
  46         void * operator new(size_t size) {
  47                 return _malloc(size);
  48         }
  49
  50         void operator delete(void *p, size_t size) {
  51                 _free(p);
  52         }
  53
  54         void * operator new[](size_t size) {
  55                 return _malloc(size);
  56         }
  57
  58         void operator delete[](void *p, size_t size) {\
  59                 _free(p);
  60         }
  61
  62         /** Reset the table to its initial state. */
  63         void reset() {
  64                 for(int i=0;i<capacity;i++) {
  65                         struct hashlistnode<_Key,_Val> * bin = table[i];
  66                         while(bin!=NULL) {
  67                                 struct hashlistnode<_Key,_Val> * next=bin->next;
  68                                 delete bin;
  69                                 bin=next;
  70                         }
  71                 }
  72                 memset(table, 0, capacity*sizeof(struct hashlistnode<_Key, _Val> *));
  73                 size=0;
  74         }
  75
  76         /** Put a key value pair into the table. */
  77         void put(_Key key, _Val val) {
  78                 if(size > threshold) {
  79                         //Resize
  80                         unsigned int newsize = capacity << 1;
  81                         resize(newsize);
  82                 }
  83
  84                 struct hashlistnode<_Key,_Val> *ptr = table[(((_KeyInt)key) & mask)>>_Shift];
  85                 size++;
  86                 struct hashlistnode<_Key,_Val> *search = ptr;
  87
  88                 while(search!=NULL) {
  89                         if (search->key==key) {
  90                                 search->val=val;
  91                                 return;
  92                         }
  93                         search=search->next;
  94                 }
  95
  96                 struct hashlistnode<_Key,_Val> *newptr=(struct hashlistnode<_Key,_Val> *)new struct hashlistnode<_Key,_Val>;
  97                 newptr->key=key;
  98                 newptr->val=val;
  99                 newptr->next=ptr;
 100                 table[(((_KeyInt)key)&mask)>>_Shift]=newptr;
 101         }
 102
 103         /** Put a key entry into the table. */
 104   _Val * ensureptr(_Key key) {
 105                 if(size > threshold) {
 106                         //Resize
 107                   unsigned int newsize = capacity << 1;
 108                   resize(newsize);
 109           }
 110
 111           struct hashlistnode<_Key,_Val> *ptr = table[(((_KeyInt)key) & mask)>>_Shift];
 112                 size++;
 113                 struct hashlistnode<_Key,_Val> *search = ptr;
 114
 115                 while(search!=NULL) {
 116                         if (search->key==key) {
 117                                 return &search->val;
 118                         }
 119                         search=search->next;
 120                 }
 121
 122                 struct hashlistnode<_Key,_Val> *newptr=(struct hashlistnode<_Key,_Val> *)new struct hashlistnode<_Key,_Val>;
 123                 newptr->key=key;
 124                 newptr->next=ptr;
 125                 table[(((_KeyInt)key)&mask)>>_Shift]=newptr;
 126                 return &newptr->val;
 127         }
 128
 129         /** Lookup the corresponding value for the given key. */
 130         _Val get(_Key key) {
 131                 struct hashlistnode<_Key,_Val> *search = table[(((_KeyInt)key) & mask)>>_Shift];
 132
 133                 while(search!=NULL) {
 134                         if (search->key==key) {
 135                                 return search->val;
 136                         }
 137                         search=search->next;
 138                 }
 139                 return (_Val)0;
 140         }
 141
 142         /** Lookup the corresponding value for the given key. */
 143         _Val * getptr(_Key key) {
 144                 struct hashlistnode<_Key,_Val> *search = table[(((_KeyInt)key) & mask)>>_Shift];
 145
 146                 while(search!=NULL) {
 147                         if (search->key==key) {
 148                                 return & search->val;
 149                         }
 150                         search=search->next;
 151                 }
 152                 return (_Val *) NULL;
 153         }
 154
 155         /** Check whether the table contains a value for the given key. */
 156         bool contains(_Key key) {
 157                 struct hashlistnode<_Key,_Val> *search = table[(((_KeyInt)key) & mask)>>_Shift];
 158
 159                 while(search!=NULL) {
 160                         if (search->key==key) {
 161                                 return true;
 162                         }
 163                         search=search->next;
 164                 }
 165                 return false;
 166         }
 167
 168         /** Resize the table. */
 169         void resize(unsigned int newsize) {
 170                 struct hashlistnode<_Key,_Val> ** oldtable = table;
 171                 struct hashlistnode<_Key,_Val> ** newtable;
 172                 unsigned int oldcapacity = capacity;
 173
 174                 if((newtable = (struct hashlistnode<_Key,_Val> **) _calloc(newsize, sizeof(struct hashlistnode<_Key,_Val> *))) == NULL) {
 175                         printf("Calloc error %s %d\n", __FILE__, __LINE__);
 176                         exit(-1);
 177                 }
 178
 179                 table = newtable;          //Update the global hashtable upon resize()
 180                 capacity = newsize;
 181                 threshold = (unsigned int) (newsize * loadfactor);
 182                 mask = (newsize << _Shift)-1;
 183
 184                 for(unsigned int i = 0; i < oldcapacity; i++) {
 185                         struct hashlistnode<_Key, _Val> * bin = oldtable[i];
 186
 187                         while(bin!=NULL) {
 188                                 _Key key=bin->key;
 189                                 struct hashlistnode<_Key, _Val> * next=bin->next;
 190
 191                                 unsigned int index = (((_KeyInt)key) & mask) >>_Shift;
 192                                 struct hashlistnode<_Key, _Val> * tmp=newtable[index];
 193                                 bin->next=tmp;
 194                                 newtable[index]=bin;
 195                                 bin = next;
 196                         }
 197                 }
 198
 199                 _free(oldtable);            //Free the memory of the old hash table
 200         }
 201
 202  private:
 203         struct hashlistnode<_Key,_Val> **table;
 204         unsigned int capacity;
 205         _KeyInt mask;
 206         unsigned int size;
 207         unsigned int threshold;
 208         double loadfactor;
 209 };
 210 #endif