hsearch.c

   1 /*
   2 musl license, hsearch.c originally written by Szabolcs Nagy
   3
   4 Copyright © 2005-2020 Rich Felker, et al.
   5
   6 Permission is hereby granted, free of charge, to any person obtaining
   7 a copy of this software and associated documentation files (the
   8 "Software"), to deal in the Software without restriction, including
   9 without limitation the rights to use, copy, modify, merge, publish,
  10 distribute, sublicense, and/or sell copies of the Software, and to
  11 permit persons to whom the Software is furnished to do so, subject to
  12 the following conditions:
  13
  14 The above copyright notice and this permission notice shall be
  15 included in all copies or substantial portions of the Software.
  16
  17 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  18 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  19 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  20 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  21 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  22 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  23 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  24 */
  25
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include "hsearch.h"
  29
  30 /*
  31 open addressing hash table with 2^n table size
  32 quadratic probing is used in case of hash collision
  33 tab indices and hash are size_t
  34 after resize fails with ENOMEM the state of tab is still usable
  35 */
  36
  37 typedef struct htab_entry {
  38         char *key;
  39         htab_value data;
  40 } htab_entry;
  41
  42 struct elem {
  43         htab_entry item;
  44         size_t hash;
  45 };
  46
  47 struct htab {
  48         struct elem *elems;
  49         size_t mask;
  50         size_t used;
  51         size_t dead;
  52 };
  53
  54 #define MINSIZE 8
  55 #define MAXSIZE ((size_t)-1/2 + 1)
  56
  57 static size_t keyhash(char *k)
  58 {
  59         unsigned char *p = (void *)k;
  60         size_t h = 0;
  61
  62         while (*p)
  63                 h = 31*h + *p++;
  64         return h;
  65 }
  66
  67 static int resize(struct htab *htab, size_t nel)
  68 {
  69         size_t newsize;
  70         size_t i, j;
  71         struct elem *e, *newe;
  72         struct elem *oldtab = htab->elems;
  73         struct elem *oldend = htab->elems + htab->mask + 1;
  74 #ifdef HTAB_OOM_TEST
  75         if(oldtab) return 0;
  76 #endif
  77
  78         if (nel > MAXSIZE)
  79                 nel = MAXSIZE;
  80         for (newsize = MINSIZE; newsize < nel; newsize *= 2);
  81         htab->elems = calloc(newsize, sizeof *htab->elems);
  82         if (!htab->elems) {
  83                 htab->elems = oldtab;
  84                 return 0;
  85         }
  86         htab->mask = newsize - 1;
  87         if (!oldtab)
  88                 return 1;
  89         for (e = oldtab; e < oldend; e++)
  90                 if (e->item.key) {
  91                         for (i=e->hash,j=1; ; i+=j++) {
  92                                 newe = htab->elems + (i & htab->mask);
  93                                 if (!newe->item.key)
  94                                         break;
  95                         }
  96                         *newe = *e;
  97                 }
  98         free(oldtab);
  99         return 1;
 100 }
 101
 102 static struct elem *lookup(struct htab *htab, char *key, size_t hash, size_t dead)
 103 {
 104         size_t i, j;
 105         struct elem *e;
 106
 107         for (i=hash,j=1; ; i+=j++) {
 108                 e = htab->elems + (i & htab->mask);
 109                 if ((!e->item.key && (!e->hash || e->hash == dead)) ||
 110                     (e->hash==hash && strcmp(e->item.key, key)==0))
 111                         break;
 112         }
 113         return e;
 114 }
 115
 116 struct htab *htab_create(size_t nel)
 117 {
 118         struct htab *r = calloc(1, sizeof *r);
 119         if(r && !resize(r, nel)) {
 120                 free(r);
 121                 r = 0;
 122         }
 123         return r;
 124 }
 125
 126 void htab_destroy(struct htab *htab)
 127 {
 128         free(htab->elems);
 129         free(htab);
 130 }
 131
 132 static struct elem *htab_find_elem(struct htab *htab, char* key)
 133 {
 134         size_t hash = keyhash(key);
 135         struct elem *e = lookup(htab, key, hash, 0);
 136
 137         if (e->item.key) {
 138                 return e;
 139         }
 140         return 0;
 141 }
 142
 143 htab_value* htab_find(struct htab *htab, char* key)
 144 {
 145         struct elem *e = htab_find_elem(htab, key);
 146         if(!e) return 0;
 147         return &e->item.data;
 148 }
 149
 150 htab_value* htab_find2(struct htab *htab, char* key, char **saved_key)
 151 {
 152         struct elem *e = htab_find_elem(htab, key);
 153         if(!e) return 0;
 154         *saved_key = e->item.key;
 155         return &e->item.data;
 156 }
 157
 158 int htab_delete(struct htab *htab, char* key)
 159 {
 160         struct elem *e = htab_find_elem(htab, key);
 161         if(!e) return 0;
 162         e->item.key = 0;
 163         e->hash = 0xdeadc0de;
 164         --htab->used;
 165         ++htab->dead;
 166         return 1;
 167 }
 168
 169 int htab_insert(struct htab *htab, char* key, htab_value value)
 170 {
 171         size_t hash = keyhash(key), oh;
 172         struct elem *e = lookup(htab, key, hash, 0xdeadc0de);
 173         if(e->item.key) {
 174                 /* it's not allowed to overwrite existing data */
 175                 return 0;
 176         }
 177
 178         oh = e->hash; /* save old hash in case it's tombstone marker */
 179         e->item.key = key;
 180         e->item.data = value;
 181         e->hash = hash;
 182         if (++htab->used + htab->dead > htab->mask - htab->mask/4) {
 183                 if (!resize(htab, 2*htab->used)) {
 184                         htab->used--;
 185                         e->item.key = 0;
 186                         e->hash = oh;
 187                         return 0;
 188                 }
 189                 htab->dead = 0;
 190         } else if (oh == 0xdeadc0de) {
 191                 /* re-used tomb */
 192                 --htab->dead;
 193         }
 194         return 1;
 195 }
 196
 197 size_t htab_next(struct htab *htab, size_t iterator, char** key, htab_value **v)
 198 {
 199         size_t i;
 200         for(i=iterator;i<htab->mask+1;++i) {
 201                 struct elem *e = htab->elems + i;
 202                 if(e->item.key) {
 203                         *key = e->item.key;
 204                         *v = &e->item.data;
 205                         return i+1;
 206                 }
 207         }
 208         return 0;
 209 }