cwchash/hashtable.c

   1 /* Copyright (C) 2004 Christopher Clark <firstname.lastname@cl.cam.ac.uk> */
   2
   3 #include "hashtable.h"
   4 #include "hashtable_private.h"
   5 #include <stdlib.h>
   6 #include <stdio.h>
   7 #include <string.h>
   8 #include <math.h>
   9
  10 /*
  11 Credit for primes table: Aaron Krowne
  12  http://br.endernet.org/~akrowne/
  13  http://planetmath.org/encyclopedia/GoodHashTablePrimes.html
  14 */
  15 static const unsigned int primes[] = {
  16 53, 97, 193, 389,
  17 769, 1543, 3079, 6151,
  18 12289, 24593, 49157, 98317,
  19 196613, 393241, 786433, 1572869,
  20 3145739, 6291469, 12582917, 25165843,
  21 50331653, 100663319, 201326611, 402653189,
  22 805306457, 1610612741
  23 };
  24 const unsigned int prime_table_length = sizeof(primes)/sizeof(primes[0]);
  25 const float max_load_factor = 0.65;
  26
  27 /*****************************************************************************/
  28 struct hashtable *
  29 create_hashtable(unsigned int minsize,
  30                  unsigned int (*hashf) (void*),
  31                  int (*eqf) (void*,void*))
  32 {
  33     struct hashtable *h;
  34     unsigned int pindex, size = primes[0];
  35     /* Check requested hashtable isn't too large */
  36     if (minsize > (1u << 30)) return NULL;
  37     /* Enforce size as prime */
  38     for (pindex=0; pindex < prime_table_length; pindex++) {
  39         if (primes[pindex] > minsize) { size = primes[pindex]; break; }
  40     }
  41     h = (struct hashtable *)malloc(sizeof(struct hashtable));
  42     if (NULL == h) return NULL; /*oom*/
  43     h->table = (struct entry **)malloc(sizeof(struct entry*) * size);
  44     if (NULL == h->table) { free(h); return NULL; } /*oom*/
  45     memset(h->table, 0, size * sizeof(struct entry *));
  46     h->tablelength  = size;
  47     h->primeindex   = pindex;
  48     h->entrycount   = 0;
  49     h->hashfn       = hashf;
  50     h->eqfn         = eqf;
  51     h->loadlimit    = (unsigned int) ceil(size * max_load_factor);
  52     return h;
  53 }
  54
  55 /*****************************************************************************/
  56 unsigned int
  57 hash(struct hashtable *h, void *k)
  58 {
  59     /* Aim to protect against poor hash functions by adding logic here
  60      * - logic taken from java 1.4 hashtable source */
  61     unsigned int i = h->hashfn(k);
  62     i += ~(i << 9);
  63     i ^=  ((i >> 14) | (i << 18)); /* >>> */
  64     i +=  (i << 4);
  65     i ^=  ((i >> 10) | (i << 22)); /* >>> */
  66     return i;
  67 }
  68
  69 /*****************************************************************************/
  70 static int
  71 hashtable_expand(struct hashtable *h)
  72 {
  73     /* Double the size of the table to accomodate more entries */
  74     struct entry **newtable;
  75     struct entry *e;
  76     struct entry **pE;
  77     unsigned int newsize, i, index;
  78     /* Check we're not hitting max capacity */
  79     if (h->primeindex == (prime_table_length - 1)) return 0;
  80     newsize = primes[++(h->primeindex)];
  81
  82     newtable = (struct entry **)malloc(sizeof(struct entry*) * newsize);
  83     if (NULL != newtable)
  84     {
  85         memset(newtable, 0, newsize * sizeof(struct entry *));
  86         /* This algorithm is not 'stable'. ie. it reverses the list
  87          * when it transfers entries between the tables */
  88         for (i = 0; i < h->tablelength; i++) {
  89             while (NULL != (e = h->table[i])) {
  90                 h->table[i] = e->next;
  91                 index = indexFor(newsize,e->h);
  92                 e->next = newtable[index];
  93                 newtable[index] = e;
  94             }
  95         }
  96         free(h->table);
  97         h->table = newtable;
  98     }
  99     /* Plan B: realloc instead */
 100     else
 101     {
 102         newtable = (struct entry **)
 103                    realloc(h->table, newsize * sizeof(struct entry *));
 104         if (NULL == newtable) { (h->primeindex)--; return 0; }
 105         h->table = newtable;
 106         memset(newtable[h->tablelength], 0, newsize - h->tablelength);
 107         for (i = 0; i < h->tablelength; i++) {
 108             for (pE = &(newtable[i]), e = *pE; e != NULL; e = *pE) {
 109                 index = indexFor(newsize,e->h);
 110                 if (index == i)
 111                 {
 112                     pE = &(e->next);
 113                 }
 114                 else
 115                 {
 116                     *pE = e->next;
 117                     e->next = newtable[index];
 118                     newtable[index] = e;
 119                 }
 120             }
 121         }
 122     }
 123     h->tablelength = newsize;
 124     h->loadlimit   = (unsigned int) ceil(newsize * max_load_factor);
 125     return -1;
 126 }
 127
 128 /*****************************************************************************/
 129 unsigned int
 130 hashtable_count(struct hashtable *h)
 131 {
 132     return h->entrycount;
 133 }
 134
 135 /*****************************************************************************/
 136 int
 137 hashtable_insert(struct hashtable *h, void *k, void *v)
 138 {
 139     /* This method allows duplicate keys - but they shouldn't be used */
 140     unsigned int index;
 141     struct entry *e;
 142     if (++(h->entrycount) > h->loadlimit)
 143     {
 144         /* Ignore the return value. If expand fails, we should
 145          * still try cramming just this value into the existing table
 146          * -- we may not have memory for a larger table, but one more
 147          * element may be ok. Next time we insert, we'll try expanding again.*/
 148         hashtable_expand(h);
 149     }
 150     e = (struct entry *)malloc(sizeof(struct entry));
 151     if (NULL == e) { --(h->entrycount); return 0; } /*oom*/
 152     e->h = hash(h,k);
 153     index = indexFor(h->tablelength,e->h);
 154     e->k = k;
 155     e->v = v;
 156     e->next = h->table[index];
 157     h->table[index] = e;
 158     return -1;
 159 }
 160
 161 /*****************************************************************************/
 162 void * /* returns value associated with key */
 163 hashtable_search(struct hashtable *h, void *k)
 164 {
 165     struct entry *e;
 166     unsigned int hashvalue, index;
 167     hashvalue = hash(h,k);
 168     index = indexFor(h->tablelength,hashvalue);
 169     e = h->table[index];
 170     while (NULL != e)
 171     {
 172         /* Check hash value to short circuit heavier comparison */
 173         if ((hashvalue == e->h) && (h->eqfn(k, e->k))) return e->v;
 174         e = e->next;
 175     }
 176     return NULL;
 177 }
 178
 179 /*****************************************************************************/
 180 void * /* returns value associated with key */
 181 hashtable_remove(struct hashtable *h, void *k)
 182 {
 183     /* TODO: consider compacting the table when the load factor drops enough,
 184      *       or provide a 'compact' method. */
 185
 186     struct entry *e;
 187     struct entry **pE;
 188     void *v;
 189     unsigned int hashvalue, index;
 190
 191     hashvalue = hash(h,k);
 192     index = indexFor(h->tablelength,hash(h,k));
 193     pE = &(h->table[index]);
 194     e = *pE;
 195     while (NULL != e)
 196     {
 197         /* Check hash value to short circuit heavier comparison */
 198         if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
 199         {
 200             *pE = e->next;
 201             h->entrycount--;
 202             v = e->v;
 203             freekey(e->k);
 204             free(e);
 205             return v;
 206         }
 207         pE = &(e->next);
 208         e = e->next;
 209     }
 210     return NULL;
 211 }
 212
 213 /*****************************************************************************/
 214 /* destroy */
 215 void
 216 hashtable_destroy(struct hashtable *h, int free_values)
 217 {
 218     unsigned int i;
 219     struct entry *e, *f;
 220     struct entry **table = h->table;
 221     if (free_values)
 222     {
 223         for (i = 0; i < h->tablelength; i++)
 224         {
 225             e = table[i];
 226             while (NULL != e)
 227             { f = e; e = e->next; freekey(f->k); free(f->v); free(f); }
 228         }
 229     }
 230     else
 231     {
 232         for (i = 0; i < h->tablelength; i++)
 233         {
 234             e = table[i];
 235             while (NULL != e)
 236             { f = e; e = e->next; freekey(f->k); free(f); }
 237         }
 238     }
 239     free(h->table);
 240     free(h);
 241 }
 242
 243 /*
 244  * Copyright (c) 2002, Christopher Clark
 245  * All rights reserved.
 246  *
 247  * Redistribution and use in source and binary forms, with or without
 248  * modification, are permitted provided that the following conditions
 249  * are met:
 250  *
 251  * * Redistributions of source code must retain the above copyright
 252  * notice, this list of conditions and the following disclaimer.
 253  *
 254  * * Redistributions in binary form must reproduce the above copyright
 255  * notice, this list of conditions and the following disclaimer in the
 256  * documentation and/or other materials provided with the distribution.
 257  *
 258  * * Neither the name of the original author; nor the names of any contributors
 259  * may be used to endorse or promote products derived from this software
 260  * without specific prior written permission.
 261  *
 262  *
 263  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 264  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 265  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 266  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER
 267  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 268  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 269  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 270  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 271  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 272  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 273  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 274 */