src/daemon/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 };
  52
  53 #define MINSIZE 8
  54 #define MAXSIZE ((size_t)-1/2 + 1)
  55
  56 static size_t keyhash(char *k)
  57 {
  58         unsigned char *p = (void *)k;
  59         size_t h = 0;
  60
  61         while (*p)
  62                 h = 31*h + *p++;
  63         return h;
  64 }
  65
  66 static int resize(struct htab *htab, size_t nel)
  67 {
  68         size_t newsize;
  69         size_t i, j;
  70         struct elem *e, *newe;
  71         struct elem *oldtab = htab->elems;
  72         struct elem *oldend = htab->elems + htab->mask + 1;
  73
  74         if (nel > MAXSIZE)
  75                 nel = MAXSIZE;
  76         for (newsize = MINSIZE; newsize < nel; newsize *= 2);
  77         htab->elems = calloc(newsize, sizeof *htab->elems);
  78         if (!htab->elems) {
  79                 htab->elems = oldtab;
  80                 return 0;
  81         }
  82         htab->mask = newsize - 1;
  83         if (!oldtab)
  84                 return 1;
  85         for (e = oldtab; e < oldend; e++)
  86                 if (e->item.key) {
  87                         for (i=e->hash,j=1; ; i+=j++) {
  88                                 newe = htab->elems + (i & htab->mask);
  89                                 if (!newe->item.key)
  90                                         break;
  91                         }
  92                         *newe = *e;
  93                 }
  94         free(oldtab);
  95         return 1;
  96 }
  97
  98 static struct elem *lookup(struct htab *htab, char *key, size_t hash)
  99 {
 100         size_t i, j;
 101         struct elem *e;
 102
 103         for (i=hash,j=1; ; i+=j++) {
 104                 e = htab->elems + (i & htab->mask);
 105                 if (!e->item.key ||
 106                     (e->hash==hash && strcmp(e->item.key, key)==0))
 107                         break;
 108         }
 109         return e;
 110 }
 111
 112 struct htab *htab_create(size_t nel)
 113 {
 114         struct htab *r = calloc(1, sizeof *r);
 115         if(r && !resize(r, nel)) {
 116                 free(r);
 117                 r = 0;
 118         }
 119         return r;
 120 }
 121
 122 void htab_destroy(struct htab *htab)
 123 {
 124         free(htab->elems);
 125         free(htab);
 126 }
 127
 128 static htab_entry *htab_find_item(struct htab *htab, char* key)
 129 {
 130         size_t hash = keyhash(key);
 131         struct elem *e = lookup(htab, key, hash);
 132
 133         if (e->item.key) {
 134                 return &e->item;
 135         }
 136         return 0;
 137 }
 138
 139 htab_value* htab_find(struct htab *htab, char* key)
 140 {
 141         htab_entry *i = htab_find_item(htab, key);
 142         if(i) return &i->data;
 143         return 0;
 144 }
 145
 146 int htab_delete(struct htab *htab, char* key)
 147 {
 148         htab_entry *i = htab_find_item(htab, key);
 149         if(!i) return 0;
 150         i->key = 0;
 151         return 1;
 152 }
 153
 154 int htab_insert(struct htab *htab, char* key, htab_value value)
 155 {
 156         size_t hash = keyhash(key);
 157         struct elem *e = lookup(htab, key, hash);
 158         if(e->item.key) {
 159                 /* it's not allowed to overwrite existing data */
 160                 return 0;
 161         }
 162
 163         e->item.key = key;
 164         e->item.data = value;
 165         e->hash = hash;
 166         if (++htab->used > htab->mask - htab->mask/4) {
 167                 if (!resize(htab, 2*htab->used)) {
 168                         htab->used--;
 169                         e->item.key = 0;
 170                         return 0;
 171                 }
 172         }
 173         return 1;
 174 }
 175
 176 size_t htab_next(struct htab *htab, size_t iterator, char** key, htab_value **v)
 177 {
 178         size_t i;
 179         for(i=iterator;i<htab->mask+1;++i) {
 180                 struct elem *e = htab->elems + i;
 181                 if(e->item.key) {
 182                         *key = e->item.key;
 183                         *v = &e->item.data;
 184                         return i+1;
 185                 }
 186         }
 187         return 0;
 188 }