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
  25
  26 static int hash_index(hash_table_t *hash, const char *pkg_name);
  27 static int rotating(const char *key, int len, int prime);
  28
  29 static int hash_index(hash_table_t *hash, const char *pkg_name)
  30 {
  31     return rotating(pkg_name, strlen(pkg_name), hash->n_entries);
  32 }
  33
  34 static int rotating(const char *key, int len, int prime)
  35 {
  36     unsigned int hash, i;
  37     for (hash=len, i=0; i<len; ++i)
  38         hash = (hash<<4)^(hash>>28)^key[i];
  39     return (hash % prime);
  40 }
  41
  42
  43 /*
  44  * this is an open table keyed by strings
  45  */
  46 int hash_table_init(const char *name, hash_table_t *hash, int len)
  47 {
  48     static int primes_table[] = {
  49         379, 761, 983, 1423, 2711, 3361, 3931, 4679, 5519, 6701, 9587,
  50         19471, 23143, 33961, 46499, 49727, 99529, 0
  51     };
  52     int *picker;
  53
  54     if (hash->entries != NULL) {
  55         /* we have been here already */
  56         return 0;
  57     }
  58
  59     hash->name = name;
  60     hash->entries = NULL;
  61     hash->n_entries = 0;
  62     hash->hash_entry_key = NULL;
  63
  64     picker = primes_table;
  65     while(*picker && (*picker++ < len));
  66     if(!*picker)
  67         fprintf(stderr, "%s: primes table might not be big enough (! << %d)\n", __FUNCTION__, len);
  68     --picker;
  69
  70     hash->n_entries = *picker;
  71     hash->entries = (hash_entry_t *)calloc(hash->n_entries, sizeof(hash_entry_t));
  72     if (hash->entries == NULL) {
  73         fprintf(stderr, "%s: Out of memory.\n", __FUNCTION__);
  74         return ENOMEM;
  75     }
  76     return 0;
  77 }
  78
  79 void hash_table_deinit(hash_table_t *hash)
  80 {
  81     free(hash->entries);
  82     hash->entries = NULL;
  83     hash->n_entries = 0;
  84 }
  85
  86 void *hash_table_get(hash_table_t *hash, const char *key)
  87 {
  88   int ndx= hash_index(hash, key);
  89   hash_entry_t *hash_entry = hash->entries + ndx;
  90   while (hash_entry)
  91   {
  92     if (hash_entry->key)
  93     {
  94       if (strcmp(key, hash_entry->key) == 0) {
  95          // opkg_message(NULL, OPKG_DEBUG, "Function: %s. Key found for '%s' \n", __FUNCTION__, key);
  96          return hash_entry->data;
  97       }
  98     }
  99     hash_entry = hash_entry->next;
 100   }
 101   return NULL;
 102 }
 103
 104 int hash_table_insert(hash_table_t *hash, const char *key, void *value)
 105 {
 106      int ndx= hash_index(hash, key);
 107      hash_entry_t *hash_entry = hash->entries + ndx;
 108      if (0) opkg_message(NULL, OPKG_DEBUG2, "Function: %s. Inserting in hash for '%s' \n", __FUNCTION__, key);
 109      if (hash_entry->key) {
 110           if (strcmp(hash_entry->key, key) == 0) {
 111                /* alread in table, update the value */
 112                if (0) opkg_message(NULL, OPKG_DEBUG2, "Function: %s. Value already in hash for '%s' \n", __FUNCTION__, key);
 113                hash_entry->data = value;
 114                return 0;
 115           } else {
 116                /*
 117                 * if this is a collision, we have to go to the end of the ll,
 118                 * then add a new entry
 119                 * before we can hook up the value
 120                 */
 121                if (0) opkg_message(NULL, OPKG_DEBUG2, "Function: %s. Value already in hash by collision for '%s' \n", __FUNCTION__, key);
 122                while (hash_entry->next)
 123                     hash_entry = hash_entry->next;
 124                hash_entry->next = (hash_entry_t *)malloc(sizeof(hash_entry_t));
 125                if (!hash_entry->next) {
 126                     return -ENOMEM;
 127                }
 128                hash_entry = hash_entry->next;
 129                hash_entry->next = NULL;
 130           }
 131      }
 132      hash->n_elements++;
 133      hash_entry->key = strdup(key);
 134      hash_entry->data = value;
 135
 136      return 0;
 137 }
 138
 139
 140 void hash_table_foreach(hash_table_t *hash, void (*f)(const char *key, void *entry, void *data), void *data)
 141 {
 142     int i;
 143     if (!hash || !f)
 144         return;
 145
 146     for (i = 0; i < hash->n_entries; i++) {
 147         hash_entry_t *hash_entry = (hash->entries + i);
 148         do {
 149             if(hash_entry->key) {
 150                 f(hash_entry->key, hash_entry->data, data);
 151             }
 152         } while((hash_entry = hash_entry->next));
 153     }
 154 }
 155