libopkg/hash_table.c

   1 /* hash.c - hash tables for opkg
   2
   3    Steven M. Ayer, Jamey Hicks
   4
   5    Copyright (C) 2002 Compaq Computer Corporation
   6
   7    This program is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU General Public License as
   9    published by the Free Software Foundation; either version 2, or (at
  10    your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful, but
  13    WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    General Public License for more details.
  16 */
  17
  18 #include <errno.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include "hash_table.h"
  23 #include "opkg_message.h"
  24 #include "libbb/libbb.h"
  25
  26
  27 static unsigned long
  28 djb2_hash(const unsigned char *str)
  29 {
  30         unsigned long hash = 5381;
  31         int c;
  32         while ((c = *str++))
  33                 hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
  34         return hash;
  35 }
  36
  37 static int
  38 hash_index(hash_table_t *hash, const char *key)
  39 {
  40         return djb2_hash((const unsigned char *)key) % hash->n_buckets;
  41 }
  42
  43 /*
  44  * this is an open table keyed by strings
  45  */
  46 void
  47 hash_table_init(const char *name, hash_table_t *hash, int len)
  48 {
  49         if (hash->entries != NULL) {
  50                 fprintf(stderr, "ERROR: %s called on a non empty hash table\n",
  51                                 __FUNCTION__);
  52                 return;
  53         }
  54
  55         memset(hash, 0, sizeof(hash_table_t));
  56
  57         hash->name = name;
  58         hash->n_buckets = len;
  59         hash->entries = xcalloc(hash->n_buckets, sizeof(hash_entry_t));
  60 }
  61
  62 void
  63 hash_print_stats(hash_table_t *hash)
  64 {
  65         printf("hash_table: %s, %d bytes\n"
  66                 "\tn_buckets=%d, n_elements=%d, n_collisions=%d\n"
  67                 "\tmax_bucket_len=%d, n_used_buckets=%d, ave_bucket_len=%.2f\n"
  68                 "\tn_hits=%d, n_misses=%d\n",
  69                 hash->name,
  70                 hash->n_buckets*(int)sizeof(hash_entry_t),
  71                 hash->n_buckets,
  72                 hash->n_elements,
  73                 hash->n_collisions,
  74                 hash->max_bucket_len,
  75                 hash->n_used_buckets,
  76                 (hash->n_used_buckets ?
  77                         ((float)hash->n_elements)/hash->n_used_buckets : 0.0f),
  78                 hash->n_hits,
  79                 hash->n_misses);
  80 }
  81
  82 void hash_table_deinit(hash_table_t *hash)
  83 {
  84     int i;
  85     if (!hash)
  86         return;
  87
  88     /* free the reminaing entries */
  89     for (i = 0; i < hash->n_buckets; i++) {
  90         hash_entry_t *hash_entry = (hash->entries + i);
  91         free (hash_entry->key);
  92         /* skip the first entry as this is part of the array */
  93         hash_entry = hash_entry->next;
  94         while (hash_entry)
  95         {
  96           hash_entry_t *old = hash_entry;
  97           hash_entry = hash_entry->next;
  98           free (old->key);
  99           free (old);
 100         }
 101     }
 102
 103     free (hash->entries);
 104
 105     hash->entries = NULL;
 106     hash->n_buckets = 0;
 107 }
 108
 109 void *hash_table_get(hash_table_t *hash, const char *key)
 110 {
 111   int ndx= hash_index(hash, key);
 112   hash_entry_t *hash_entry = hash->entries + ndx;
 113   while (hash_entry)
 114   {
 115     if (hash_entry->key)
 116     {
 117       if (strcmp(key, hash_entry->key) == 0) {
 118          // opkg_message(NULL, OPKG_DEBUG, "Function: %s. Key found for '%s' \n", __FUNCTION__, key);
 119          hash->n_hits++;
 120          return hash_entry->data;
 121       }
 122     }
 123     hash_entry = hash_entry->next;
 124   }
 125   hash->n_misses++;
 126   return NULL;
 127 }
 128
 129 int hash_table_insert(hash_table_t *hash, const char *key, void *value)
 130 {
 131      int bucket_len = 0;
 132      int ndx= hash_index(hash, key);
 133      hash_entry_t *hash_entry = hash->entries + ndx;
 134      if (hash_entry->key) {
 135           if (strcmp(hash_entry->key, key) == 0) {
 136                /* alread in table, update the value */
 137                hash_entry->data = value;
 138                return 0;
 139           } else {
 140                /*
 141                 * if this is a collision, we have to go to the end of the ll,
 142                 * then add a new entry
 143                 * before we can hook up the value
 144                 */
 145                while (hash_entry->next) {
 146                     hash_entry = hash_entry->next;
 147                     if (strcmp(hash_entry->key, key) == 0) {
 148                         hash_entry->data = value;
 149                         return 0;
 150                     }
 151                     bucket_len++;
 152                }
 153                hash_entry->next = xcalloc(1, sizeof(hash_entry_t));
 154                hash_entry = hash_entry->next;
 155                hash_entry->next = NULL;
 156
 157                hash->n_collisions++;
 158                if (++bucket_len > hash->max_bucket_len)
 159                     hash->max_bucket_len = bucket_len;
 160           }
 161      } else
 162           hash->n_used_buckets++;
 163
 164      hash->n_elements++;
 165      hash_entry->key = xstrdup(key);
 166      hash_entry->data = value;
 167
 168      return 0;
 169 }
 170
 171 int hash_table_remove(hash_table_t *hash, const char *key)
 172 {
 173     int ndx= hash_index(hash, key);
 174     hash_entry_t *hash_entry = hash->entries + ndx;
 175     hash_entry_t *next_entry=NULL, *last_entry=NULL;
 176     while (hash_entry)
 177     {
 178         if (hash_entry->key)
 179         {
 180             if (strcmp(key, hash_entry->key) == 0) {
 181                 free(hash_entry->key);
 182                 if (last_entry) {
 183                     last_entry->next = hash_entry->next;
 184                     free(hash_entry);
 185                 } else {
 186                     next_entry = hash_entry->next;
 187                     if (next_entry) {
 188                         memmove(hash_entry, next_entry, sizeof(hash_entry_t));
 189                         free(next_entry);
 190                     } else {
 191                         memset(hash_entry, 0 , sizeof(hash_entry_t));
 192                     }
 193                 }
 194                 return 1;
 195             }
 196         }
 197         last_entry = hash_entry;
 198         hash_entry = hash_entry->next;
 199     }
 200     return 0;
 201 }
 202
 203 void hash_table_foreach(hash_table_t *hash, void (*f)(const char *key, void *entry, void *data), void *data)
 204 {
 205     int i;
 206     if (!hash || !f)
 207         return;
 208
 209     for (i = 0; i < hash->n_buckets; i++) {
 210         hash_entry_t *hash_entry = (hash->entries + i);
 211         do {
 212             if(hash_entry->key) {
 213                 f(hash_entry->key, hash_entry->data, data);
 214             }
 215         } while((hash_entry = hash_entry->next));
 216     }
 217 }
 218