rhythmdb/rb-refstring.c

   1 /*
   2  *  arch-tag: Implementation of reference-counted string
   3  *
   4  *  Copyright (C) 2004 Colin Walters <walters@redhat.com>
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, write to the Free Software
  18  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA.
  19  *
  20  */
  21
  22 #include <config.h>
  23
  24 #include <glib.h>
  25 #include <string.h>
  26 #include "rb-util.h"
  27 #include "rb-cut-and-paste-code.h"
  28 #include "rb-refstring.h"
  29
  30 GHashTable *rb_refstrings;
  31 GMutex *rb_refstrings_mutex;
  32
  33 struct RBRefString
  34 {
  35         gint refcount;
  36         gpointer folded;
  37         gpointer sortkey;
  38         char value[1];
  39 };
  40
  41 static void
  42 rb_refstring_free (RBRefString *refstr)
  43 {
  44         refstr->refcount = 0xdeadbeef;
  45         g_free (refstr->folded);
  46         refstr->folded = NULL;
  47         g_free (refstr->sortkey);
  48         refstr->sortkey = NULL;
  49         g_free (refstr);
  50 }
  51
  52 void
  53 rb_refstring_system_init ()
  54 {
  55         rb_refstrings_mutex = g_mutex_new ();
  56
  57         rb_refstrings = g_hash_table_new_full (g_str_hash, g_str_equal,
  58                                                NULL, (GDestroyNotify) rb_refstring_free);
  59 }
  60
  61 RBRefString *
  62 rb_refstring_new (const char *init)
  63 {
  64         RBRefString *ret;
  65
  66         g_mutex_lock (rb_refstrings_mutex);
  67         ret = g_hash_table_lookup (rb_refstrings, init);
  68
  69         if (ret) {
  70                 rb_refstring_ref (ret);
  71                 g_mutex_unlock (rb_refstrings_mutex);
  72                 return ret;
  73         }
  74
  75         ret = g_malloc (sizeof (RBRefString) + strlen (init));
  76
  77         strcpy (ret->value, init);
  78         ret->refcount = 1;
  79         ret->folded = NULL;
  80         ret->sortkey = NULL;
  81
  82         g_hash_table_insert (rb_refstrings, ret->value, ret);
  83         g_mutex_unlock (rb_refstrings_mutex);
  84         return ret;
  85 }
  86
  87 RBRefString *
  88 rb_refstring_find (const char *init)
  89 {
  90         RBRefString *ret;
  91
  92         g_mutex_lock (rb_refstrings_mutex);
  93         ret = g_hash_table_lookup (rb_refstrings, init);
  94
  95         if (ret)
  96                 rb_refstring_ref (ret);
  97
  98         g_mutex_unlock (rb_refstrings_mutex);
  99         return ret;
 100 }
 101
 102 void
 103 rb_refstring_unref (RBRefString *val)
 104 {
 105         if (val == NULL)
 106                 return;
 107
 108         g_return_if_fail (val->refcount > 0);
 109
 110         if (g_atomic_int_dec_and_test (&val->refcount)) {
 111                 g_mutex_lock (rb_refstrings_mutex);
 112                 /* ensure it's still not referenced, as something may have called
 113                  * rb_refstring_new since we decremented the count */
 114                 if (g_atomic_int_get (&val->refcount) == 0)
 115                         g_hash_table_remove (rb_refstrings, val->value);
 116                 g_mutex_unlock (rb_refstrings_mutex);
 117         }
 118 }
 119
 120 void
 121 rb_refstring_system_shutdown (void)
 122 {
 123         g_hash_table_destroy (rb_refstrings);
 124         g_mutex_free (rb_refstrings_mutex);
 125 }
 126
 127 RBRefString *
 128 rb_refstring_ref (RBRefString *val)
 129 {
 130         if (val == NULL)
 131                 return NULL;
 132
 133         g_return_val_if_fail (val->refcount > 0, NULL);
 134
 135         g_atomic_int_inc (&val->refcount);
 136         return val;
 137 }
 138
 139 const char *
 140 rb_refstring_get (const RBRefString *val)
 141 {
 142         return val ? val->value : NULL;
 143 }
 144
 145 /*
 146  * The next two functions will compute the values if they haven't
 147  * been already done. Using g_atomic_* is much more efficient than
 148  * using mutexes (since mutexes may require kernel calls) and these
 149  * get called often.
 150  */
 151
 152 const char *
 153 rb_refstring_get_folded (RBRefString *val)
 154 {
 155         gpointer *ptr;
 156         const char *string;
 157
 158         if (val == NULL)
 159                 return NULL;
 160
 161         ptr = &val->folded;
 162         string = (const char*)g_atomic_pointer_get (ptr);
 163         if (string == NULL) {
 164                 char *newstring;
 165
 166                 newstring = rb_search_fold (rb_refstring_get (val));
 167                 if (g_atomic_pointer_compare_and_exchange (ptr, NULL, newstring)) {
 168                         string = newstring;
 169                 } else {
 170                         g_free (newstring);
 171                         string = (const char *)g_atomic_pointer_get (ptr);
 172                         g_assert (string);
 173                 }
 174         }
 175
 176         return string;
 177 }
 178
 179 const char *
 180 rb_refstring_get_sort_key (RBRefString *val)
 181 {
 182         gpointer *ptr;
 183         const char *string;
 184
 185         if (val == NULL)
 186                 return NULL;
 187
 188         ptr = &val->sortkey;
 189         string = (const char *)g_atomic_pointer_get (ptr);
 190         if (string == NULL) {
 191                 char *newstring;
 192                 const char *s;
 193
 194                 s = rb_refstring_get_folded (val);
 195                 newstring = rb_utf8_collate_key_for_filename (s, -1);
 196
 197                 if (g_atomic_pointer_compare_and_exchange (ptr, NULL, newstring)) {
 198                         string = newstring;
 199                 } else {
 200                         g_free (newstring);
 201                         string = (const char*)g_atomic_pointer_get (ptr);
 202                         g_assert (string);
 203                 }
 204         }
 205
 206         return string;
 207 }
 208
 209 guint
 210 rb_refstring_hash (gconstpointer p)
 211 {
 212         const RBRefString *ref = p;
 213         return g_str_hash (rb_refstring_get (ref));
 214 }
 215
 216 gboolean
 217 rb_refstring_equal (gconstpointer ap, gconstpointer bp)
 218 {
 219         return (ap == bp);
 220 }