libpurple/stringref.c

   1 /**
   2  * @file stringref.c Reference-counted immutable strings
   3  * @ingroup core
   4  */
   5
   6 /* purple
   7  *
   8  * Purple is the legal property of its developers, whose names are too numerous
   9  * to list here.  Please refer to the COPYRIGHT file distributed with this
  10  * source distribution.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA
  25  *
  26  */
  27
  28 #include "internal.h"
  29
  30 #include <string.h>
  31 #include <stdarg.h>
  32
  33 #include "debug.h"
  34 #include "eventloop.h"
  35 #include "stringref.h"
  36
  37 /**
  38  * The internal representation of a stringref.
  39  *
  40  * @note For this structure to be useful, the string contained within
  41  * it must be immutable -- for this reason, do _not_ access it
  42  * directly!
  43  */
  44 struct _PurpleStringref {
  45         guint32 ref;    /**< The reference count of this string.
  46                                          *   Note that reference counts are only
  47                                          *   31 bits, and the high-order bit
  48                                          *   indicates whether this string is up
  49                                          *   for GC at the next idle handler...
  50                                          *   But you aren't going to touch this
  51                                          *   anyway, right? */
  52         char value[1];  /**< The string contained in this ref.
  53                                          *   Notice that it is simply "hanging
  54                                          *   off the end" of the ref ... this
  55                                          *   is to save an allocation. */
  56 };
  57
  58 #define REFCOUNT(x) ((x) & 0x7fffffff)
  59
  60 static GList *gclist = NULL;
  61
  62 static void stringref_free(PurpleStringref *stringref);
  63 static gboolean gs_idle_cb(gpointer data);
  64
  65 PurpleStringref *purple_stringref_new(const char *value)
  66 {
  67         PurpleStringref *newref;
  68         size_t len;
  69
  70         if (value == NULL)
  71                 return NULL;
  72
  73         len = strlen(value);
  74
  75         newref = g_malloc(sizeof(PurpleStringref) + len);
  76         g_strlcpy(newref->value, value, len);
  77         newref->ref = 1;
  78
  79         return newref;
  80 }
  81
  82 PurpleStringref *purple_stringref_new_noref(const char *value)
  83 {
  84         PurpleStringref *newref;
  85
  86         if (value == NULL)
  87                 return NULL;
  88
  89         newref = g_malloc(sizeof(PurpleStringref) + strlen(value));
  90         strcpy(newref->value, value);
  91         newref->ref = 0x80000000;
  92
  93         if (gclist == NULL)
  94                 purple_timeout_add(0, gs_idle_cb, NULL);
  95         gclist = g_list_prepend(gclist, newref);
  96
  97         return newref;
  98 }
  99
 100 PurpleStringref *purple_stringref_printf(const char *format, ...)
 101 {
 102         PurpleStringref *newref;
 103         va_list ap;
 104
 105         if (format == NULL)
 106                 return NULL;
 107
 108         va_start(ap, format);
 109         newref = g_malloc(sizeof(PurpleStringref) + g_printf_string_upper_bound(format, ap));
 110         vsprintf(newref->value, format, ap);
 111         va_end(ap);
 112         newref->ref = 1;
 113
 114         return newref;
 115 }
 116
 117 PurpleStringref *purple_stringref_ref(PurpleStringref *stringref)
 118 {
 119         if (stringref == NULL)
 120                 return NULL;
 121         stringref->ref++;
 122         return stringref;
 123 }
 124
 125 void purple_stringref_unref(PurpleStringref *stringref)
 126 {
 127         if (stringref == NULL)
 128                 return;
 129         if (REFCOUNT(--(stringref->ref)) == 0) {
 130                 if (stringref->ref & 0x80000000)
 131                         gclist = g_list_remove(gclist, stringref);
 132                 stringref_free(stringref);
 133         }
 134 }
 135
 136 const char *purple_stringref_value(const PurpleStringref *stringref)
 137 {
 138         return (stringref == NULL ? NULL : stringref->value);
 139 }
 140
 141 int purple_stringref_cmp(const PurpleStringref *s1, const PurpleStringref *s2)
 142 {
 143         return (s1 == s2 ? 0 : strcmp(purple_stringref_value(s1), purple_stringref_value(s2)));
 144 }
 145
 146 size_t purple_stringref_len(const PurpleStringref *stringref)
 147 {
 148         return strlen(purple_stringref_value(stringref));
 149 }
 150
 151 static void stringref_free(PurpleStringref *stringref)
 152 {
 153 #ifdef DEBUG
 154         if (REFCOUNT(stringref->ref) != 0) {
 155                 purple_debug(PURPLE_DEBUG_ERROR, "stringref", "Free of nonzero (%d) ref stringref!\n", REFCOUNT(stringref->ref));
 156                 return;
 157         }
 158 #endif /* DEBUG */
 159         g_free(stringref);
 160 }
 161
 162 static gboolean gs_idle_cb(gpointer data)
 163 {
 164         PurpleStringref *ref;
 165         GList *del;
 166
 167         while (gclist != NULL) {
 168                 ref = gclist->data;
 169                 if (REFCOUNT(ref->ref) == 0) {
 170                         stringref_free(ref);
 171                 }
 172                 del = gclist;
 173                 gclist = gclist->next;
 174                 g_list_free_1(del);
 175         }
 176
 177         return FALSE;
 178 }