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 int hash_index(hash_table_t *hash, const char *pkg_name);
  28 static int rotating(const char *key, int len, int prime);
  29
  30 static int hash_index(hash_table_t *hash, const char *pkg_name)
  31 {
  32     return rotating(pkg_name, strlen(pkg_name), hash->n_entries);
  33 }
  34
  35 static int rotating(const char *key, int len, int prime)
  36 {
  37     unsigned int hash, i;
  38     for (hash=len, i=0; i<len; ++i)
  39         hash = (hash<<4)^(hash>>28)^key[i];
  40     return (hash % prime);
  41 }
  42
  43
  44 /*
  45  * this is an open table keyed by strings
  46  */
  47 int hash_table_init(const char *name, hash_table_t *hash, int len)
  48 {
  49     static int primes_table[] = {
  50         379, 761, 983, 1423, 2711, 3361, 3931, 4679, 5519, 6701, 9587,
  51         19471, 23143, 33961, 46499, 49727, 99529, 0
  52     };
  53     int *picker;
  54
  55     if (hash->entries != NULL) {
  56         /* we have been here already */
  57         return 0;
  58     }
  59
  60     hash->name = name;
  61     hash->entries = NULL;
  62     hash->n_entries = 0;
  63     hash->hash_entry_key = NULL;
  64
  65     picker = primes_table;
  66     while(*picker && (*picker++ < len));
  67     if(!*picker)
  68         fprintf(stderr, "%s: primes table might not be big enough (! << %d)\n", __FUNCTION__, len);
  69     --picker;
  70
  71     hash->n_entries = *picker;
  72     hash->entries = xcalloc(hash->n_entries, sizeof(hash_entry_t));
  73
  74     return 0;
  75 }
  76
  77 void hash_table_deinit(hash_table_t *hash)
  78 {
  79     int i;
  80     if (!hash)
  81         return;
  82
  83     /* free the reminaing entries */
  84     for (i = 0; i < hash->n_entries; i++) {
  85         hash_entry_t *hash_entry = (hash->entries + i);
  86         free (hash_entry->key);
  87         /* skip the first entry as this is part of the array */
  88         hash_entry = hash_entry->next;
  89         while (hash_entry)
  90         {
  91           hash_entry_t *old = hash_entry;
  92           hash_entry = hash_entry->next;
  93           free (old->key);
  94           free (old);
  95         }
  96     }
  97
  98     free (hash->entries);
  99
 100     hash->entries = NULL;
 101     hash->n_entries = 0;
 102 }
 103
 104 void *hash_table_get(hash_table_t *hash, const char *key)
 105 {
 106   int ndx= hash_index(hash, key);
 107   hash_entry_t *hash_entry = hash->entries + ndx;
 108   while (hash_entry)
 109   {
 110     if (hash_entry->key)
 111     {
 112       if (strcmp(key, hash_entry->key) == 0) {
 113          // opkg_message(NULL, OPKG_DEBUG, "Function: %s. Key found for '%s' \n", __FUNCTION__, key);
 114          return hash_entry->data;
 115       }
 116     }
 117     hash_entry = hash_entry->next;
 118   }
 119   return NULL;
 120 }
 121
 122 int hash_table_insert(hash_table_t *hash, const char *key, void *value)
 123 {
 124      int ndx= hash_index(hash, key);
 125      hash_entry_t *hash_entry = hash->entries + ndx;
 126      if (hash_entry->key) {
 127           if (strcmp(hash_entry->key, key) == 0) {
 128                /* alread in table, update the value */
 129                hash_entry->data = value;
 130                return 0;
 131           } else {
 132                /*
 133                 * if this is a collision, we have to go to the end of the ll,
 134                 * then add a new entry
 135                 * before we can hook up the value
 136                 */
 137                while (hash_entry->next) {
 138                     hash_entry = hash_entry->next;
 139                     if (strcmp(hash_entry->key, key) == 0) {
 140                         hash_entry->data = value;
 141                         return 0;
 142                     }
 143                }
 144                hash_entry->next = xcalloc(1, sizeof(hash_entry_t));
 145                hash_entry = hash_entry->next;
 146                hash_entry->next = NULL;
 147           }
 148      }
 149      hash->n_elements++;
 150      hash_entry->key = xstrdup(key);
 151      hash_entry->data = value;
 152
 153      return 0;
 154 }
 155
 156 int hash_table_remove(hash_table_t *hash, const char *key)
 157 {
 158     int ndx= hash_index(hash, key);
 159     hash_entry_t *hash_entry = hash->entries + ndx;
 160     hash_entry_t *next_entry=NULL, *last_entry=NULL;
 161     while (hash_entry)
 162     {
 163         if (hash_entry->key)
 164         {
 165             if (strcmp(key, hash_entry->key) == 0) {
 166                 free(hash_entry->key);
 167                 if (last_entry) {
 168                     last_entry->next = hash_entry->next;
 169                     free(hash_entry);
 170                 } else {
 171                     next_entry = hash_entry->next;
 172                     if (next_entry) {
 173                         memmove(hash_entry, next_entry, sizeof(hash_entry_t));
 174                         free(next_entry);
 175                     } else {
 176                         memset(hash_entry, 0 , sizeof(hash_entry_t));
 177                     }
 178                 }
 179                 return 1;
 180             }
 181         }
 182         last_entry = hash_entry;
 183         hash_entry = hash_entry->next;
 184     }
 185     return 0;
 186 }
 187
 188 void hash_table_foreach(hash_table_t *hash, void (*f)(const char *key, void *entry, void *data), void *data)
 189 {
 190     int i;
 191     if (!hash || !f)
 192         return;
 193
 194     for (i = 0; i < hash->n_entries; i++) {
 195         hash_entry_t *hash_entry = (hash->entries + i);
 196         do {
 197             if(hash_entry->key) {
 198                 f(hash_entry->key, hash_entry->data, data);
 199             }
 200         } while((hash_entry = hash_entry->next));
 201     }
 202 }
 203