cwchash/hashtable_itr.c

   1 /* Copyright (C) 2002, 2004 Christopher Clark  <firstname.lastname@cl.cam.ac.uk> */
   2
   3 #include "hashtable.h"
   4 #include "hashtable_private.h"
   5 #include "hashtable_itr.h"
   6 #include <stdlib.h> /* defines NULL */
   7
   8 /*****************************************************************************/
   9 /* hashtable_iterator    - iterator constructor */
  10
  11 struct hashtable_itr *
  12 hashtable_iterator(struct hashtable *h)
  13 {
  14     unsigned int i, tablelength;
  15     struct hashtable_itr *itr = (struct hashtable_itr *)
  16         malloc(sizeof(struct hashtable_itr));
  17     if (NULL == itr) return NULL;
  18     itr->h = h;
  19     itr->e = NULL;
  20     itr->parent = NULL;
  21     tablelength = h->tablelength;
  22     itr->index = tablelength;
  23     if (0 == h->entrycount) return itr;
  24
  25     for (i = 0; i < tablelength; i++)
  26     {
  27         if (NULL != h->table[i])
  28         {
  29             itr->e = h->table[i];
  30             itr->index = i;
  31             break;
  32         }
  33     }
  34     return itr;
  35 }
  36
  37 /*****************************************************************************/
  38 /* key      - return the key of the (key,value) pair at the current position */
  39 /* value    - return the value of the (key,value) pair at the current position */
  40
  41 void *
  42 hashtable_iterator_key(struct hashtable_itr *i)
  43 { return i->e->k; }
  44
  45 void *
  46 hashtable_iterator_value(struct hashtable_itr *i)
  47 { return i->e->v; }
  48
  49 /*****************************************************************************/
  50 /* advance - advance the iterator to the next element
  51  *           returns zero if advanced to end of table */
  52
  53 int
  54 hashtable_iterator_advance(struct hashtable_itr *itr)
  55 {
  56     unsigned int j,tablelength;
  57     struct entry **table;
  58     struct entry *next;
  59     if (NULL == itr->e) return 0; /* stupidity check */
  60
  61     next = itr->e->next;
  62     if (NULL != next)
  63     {
  64         itr->parent = itr->e;
  65         itr->e = next;
  66         return -1;
  67     }
  68     tablelength = itr->h->tablelength;
  69     itr->parent = NULL;
  70     if (tablelength <= (j = ++(itr->index)))
  71     {
  72         itr->e = NULL;
  73         return 0;
  74     }
  75     table = itr->h->table;
  76     while (NULL == (next = table[j]))
  77     {
  78         if (++j >= tablelength)
  79         {
  80             itr->index = tablelength;
  81             itr->e = NULL;
  82             return 0;
  83         }
  84     }
  85     itr->index = j;
  86     itr->e = next;
  87     return -1;
  88 }
  89
  90 /*****************************************************************************/
  91 /* remove - remove the entry at the current iterator position
  92  *          and advance the iterator, if there is a successive
  93  *          element.
  94  *          If you want the value, read it before you remove:
  95  *          beware memory leaks if you don't.
  96  *          Returns zero if end of iteration. */
  97
  98 int
  99 hashtable_iterator_remove(struct hashtable_itr *itr)
 100 {
 101     struct entry *remember_e, *remember_parent;
 102     int ret;
 103
 104     /* Do the removal */
 105     if (NULL == (itr->parent))
 106     {
 107         /* element is head of a chain */
 108         itr->h->table[itr->index] = itr->e->next;
 109     } else {
 110         /* element is mid-chain */
 111         itr->parent->next = itr->e->next;
 112     }
 113     /* itr->e is now outside the hashtable */
 114     remember_e = itr->e;
 115     itr->h->entrycount--;
 116     freekey(remember_e->k);
 117
 118     /* Advance the iterator, correcting the parent */
 119     remember_parent = itr->parent;
 120     ret = hashtable_iterator_advance(itr);
 121     if (itr->parent == remember_e) { itr->parent = remember_parent; }
 122     free(remember_e);
 123     return ret;
 124 }
 125
 126 /*****************************************************************************/
 127 int /* returns zero if not found */
 128 hashtable_iterator_search(struct hashtable_itr *itr,
 129                           struct hashtable *h, void *k)
 130 {
 131     struct entry *e, *parent;
 132     unsigned int hashvalue, index;
 133
 134     hashvalue = hash(h,k);
 135     index = indexFor(h->tablelength,hashvalue);
 136
 137     e = h->table[index];
 138     parent = NULL;
 139     while (NULL != e)
 140     {
 141         /* Check hash value to short circuit heavier comparison */
 142         if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
 143         {
 144             itr->index = index;
 145             itr->e = e;
 146             itr->parent = parent;
 147             itr->h = h;
 148             return -1;
 149         }
 150         parent = e;
 151         e = e->next;
 152     }
 153     return 0;
 154 }
 155
 156
 157 /*
 158  * Copyright (c) 2002, 2004, Christopher Clark
 159  * All rights reserved.
 160  *
 161  * Redistribution and use in source and binary forms, with or without
 162  * modification, are permitted provided that the following conditions
 163  * are met:
 164  *
 165  * * Redistributions of source code must retain the above copyright
 166  * notice, this list of conditions and the following disclaimer.
 167  *
 168  * * Redistributions in binary form must reproduce the above copyright
 169  * notice, this list of conditions and the following disclaimer in the
 170  * documentation and/or other materials provided with the distribution.
 171  *
 172  * * Neither the name of the original author; nor the names of any contributors
 173  * may be used to endorse or promote products derived from this software
 174  * without specific prior written permission.
 175  *
 176  *
 177  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 178  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 179  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 180  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER
 181  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 182  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 183  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 184  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 185  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 186  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 187  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 188 */