mdw@git.distorted.org.uk Git - mLib/blob - struct/assoc.c

   1 /* -*-c-*-
   2  *
   3  * Assocation tables
   4  *
   5  * (c) 2000 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include "alloc.h"
  31 #include "assoc.h"
  32 #include "atom.h"
  33 #include "hash.h"
  34
  35 /*----- Main code ---------------------------------------------------------*/
  36
  37 /* --- @assoc_create@ --- *
  38  *
  39  * Arguments:   @assoc_table *t@ = pointer to an association table
  40  *
  41  * Returns:     ---
  42  *
  43  * Use:         Creates a new association table.
  44  */
  45
  46 void assoc_create(assoc_table *t)
  47 {
  48   hash_create(&t->t, SYM_INITSZ);
  49   t->load = SYM_LIMIT(SYM_INITSZ);
  50 }
  51
  52 /* --- @assoc_destroy@ --- *
  53  *
  54  * Arguments:   @assoc_table *t@ = pointer to an association table
  55  *
  56  * Returns:     ---
  57  *
  58  * Use:         Destroys an association table.
  59  */
  60
  61 void assoc_destroy(assoc_table *t)
  62 {
  63   hash_iter i;
  64
  65   HASH_MKITER(&i, &t->t);
  66   for (;;) {
  67     hash_base *p;
  68     HASH_NEXT(&i, p);
  69     if (!p)
  70       break;
  71     x_free(t->t.a, p);
  72   }
  73   hash_destroy(&t->t);
  74 }
  75
  76 /* --- @assoc_find@ --- *
  77  *
  78  * Arguments:   @assoc_table *t@ = pointer to an association table
  79  *              @atom *a@ = an atom to label the item
  80  *              @size_t sz@ = size of block to allocate
  81  *              @unsigned *f@ = pointer to `found' flag
  82  *
  83  * Returns:     A pointer to the item located or null.
  84  *
  85  * Use:         Looks up an atom in an association table.  If the atom is
  86  *              found, the association is returned.  If not, and @sz@ is
  87  *              zero, a null pointer is returned.  Otherwise, a block of size
  88  *              @sz@ is allocated, its @assoc_base@ header is filled in, and
  89  *              the pointer returned.  The flag @*f@ is cleared if the item
  90  *              couldn't be found, or set if it was.
  91  *
  92  *              All the atoms used in a particular table should come from the
  93  *              same atom table.
  94  */
  95
  96 void *assoc_find(assoc_table *t, atom *a, size_t sz, unsigned *f)
  97 {
  98   hash_base **bin = HASH_BIN(&t->t, ATOM_HASH(a)), **p;
  99   assoc_base *q;
 100
 101   /* --- Try to find the association --- */
 102
 103   for (p = bin; *p; p = &(*p)->next) {
 104     q = (assoc_base *)*p;
 105     if (q->a == a) {
 106       *p = q->b.next;
 107       q->b.next = *bin;
 108       *bin = &q->b;
 109       if (f) *f = 1;
 110       return (q);
 111     }
 112   }
 113
 114   /* --- Failed to find a match --- */
 115
 116   if (f) *f = 0;
 117   if (!sz) return (0);
 118
 119   /* --- Make a new association --- */
 120
 121   q = x_alloc(t->t.a, sz);
 122   q->a = a;
 123   q->b.next = *bin;
 124   q->b.hash = ATOM_HASH(a);
 125   *bin = &q->b;
 126
 127   /* --- Maybe extend the table --- */
 128
 129   if (t->load)
 130     t->load--;
 131   if (!t->load && hash_extend(&t->t))
 132     t->load = SYM_LIMIT(t->t.mask + 1);
 133   return (q);
 134 }
 135
 136 /* --- @assoc_remove@ --- *
 137  *
 138  * Arguments:   @assoc_table *t@ = pointer to an association table
 139  *              @void *p@ = pointer to a block to remove
 140  *
 141  * Returns:     ---
 142  *
 143  * Use:         Removes an association from a table.
 144  */
 145
 146 void assoc_remove(assoc_table *t, void *p)
 147 {
 148   assoc_base *q = p;
 149   hash_remove(&t->t, &q->b);
 150   x_free(t->t.a, q);
 151   t->load++;
 152 }
 153
 154 /* --- @assoc_mkiter@, @assoc_next@ --- *
 155  *
 156  * Arguments:   @assoc_iter *i@ = pointer to an iterator
 157  *              @assoc_table *t@ = pointer to an association table
 158  *
 159  * Returns:     Next association, or null, for @assoc_next@; nothing for
 160  *              @assoc_mkiter@.
 161  *
 162  * Use:         Iterates over the associations in a table.
 163  */
 164
 165 void assoc_mkiter(assoc_iter *i, assoc_table *t) { ASSOC_MKITER(i, t); }
 166 void *assoc_next(assoc_iter *i) { void *p; ASSOC_NEXT(i, p); return (p); }
 167
 168 /*----- That's all, folks -------------------------------------------------*/