epan/fifo_string_cache.c

   1 /* fifo_string_cache.c
   2  * A string cache, possibly with a bounded size, using FIFO order to control
   3  * the size.
   4  *
   5  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  */
  11 #include <stdio.h>
  12 #include "fifo_string_cache.h"
  13
  14 void
  15 fifo_string_cache_init(fifo_string_cache_t *fcache, unsigned max_entries, GDestroyNotify string_free_func)
  16 {
  17     fcache->set = g_hash_table_new_full(g_str_hash, g_str_equal, string_free_func, NULL);
  18     fcache->head = NULL;
  19     fcache->tail = NULL;
  20     fcache->max_entries = max_entries;
  21 }
  22
  23 void
  24 fifo_string_cache_free(fifo_string_cache_t *fcache)
  25 {
  26     if (fcache->set != NULL) {
  27         g_hash_table_destroy(fcache->set);
  28         fcache->set = NULL;
  29     }
  30     if (fcache->head != NULL) {
  31         g_slist_free(fcache->head);
  32         fcache->head = NULL;
  33         fcache->tail = NULL;
  34     }
  35 }
  36
  37 bool
  38 fifo_string_cache_contains(fifo_string_cache_t *fcache, const char *entry)
  39 {
  40     return g_hash_table_contains(fcache->set, entry);
  41 }
  42
  43 bool
  44 fifo_string_cache_insert(fifo_string_cache_t *fcache, const char *entry)
  45 {
  46     GSList *prev_head;
  47     GSList *new_start_of_tail;
  48
  49     // In GLIB 2.40, g_hash_table_insert() returns a bool that gives us what we
  50     // need (did the entry exist already?). But, if we're not using that
  51     // version, we need to first check if the entry exists. So we just check
  52     // the hash all the time, regardless of GLIB version.
  53     bool exists;
  54     exists = g_hash_table_contains(fcache->set, entry);
  55     if (exists) {
  56         return true;
  57     }
  58
  59     // Shall we remove one item?
  60     if (fcache->max_entries > 0) {
  61         if (g_hash_table_size(fcache->set) == fcache->max_entries) {
  62             g_hash_table_remove(fcache->set, fcache->head->data);
  63             prev_head = fcache->head;
  64             fcache->head = fcache->head->next;
  65             g_slist_free_1(prev_head);
  66
  67             // If max_entries is 1, the head was also the tail. Reset the tail.
  68             if (fcache->tail == prev_head) {
  69                 fcache->tail = NULL;
  70             }
  71
  72             // Now the size of the hash table is max_entries
  73         }
  74     }
  75
  76     g_hash_table_insert(fcache->set, (void *) entry, /*value=*/NULL);
  77     // Do we need to constrain the number of entries?
  78     if (fcache->max_entries > 0) {
  79         // Keep track of the new entry at the end of the queue
  80         new_start_of_tail = g_slist_append(fcache->tail, (void *) entry);
  81         // Set the new tail
  82         if (fcache->tail == NULL) {
  83             fcache->tail = new_start_of_tail;
  84             // This is the first entry, so head is NULL too. Set it.
  85             fcache->head = new_start_of_tail;
  86         } else {
  87             fcache->tail = new_start_of_tail->next;
  88         }
  89     }
  90
  91     return false;
  92 }