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
  69         if (value == NULL)
  70                 return NULL;
  71
  72         newref = g_malloc(sizeof(PurpleStringref) + strlen(value));
  73         strcpy(newref->value, value);
  74         newref->ref = 1;
  75
  76         return newref;
  77 }
  78
  79 PurpleStringref *purple_stringref_new_noref(const char *value)
  80 {
  81         PurpleStringref *newref;
  82
  83         if (value == NULL)
  84                 return NULL;
  85
  86         newref = g_malloc(sizeof(PurpleStringref) + strlen(value));
  87         strcpy(newref->value, value);
  88         newref->ref = 0x80000000;
  89
  90         if (gclist == NULL)
  91                 purple_timeout_add(0, gs_idle_cb, NULL);
  92         gclist = g_list_prepend(gclist, newref);
  93
  94         return newref;
  95 }
  96
  97 PurpleStringref *purple_stringref_printf(const char *format, ...)
  98 {
  99         PurpleStringref *newref;
 100         va_list ap;
 101
 102         if (format == NULL)
 103                 return NULL;
 104
 105         va_start(ap, format);
 106         newref = g_malloc(sizeof(PurpleStringref) + g_printf_string_upper_bound(format, ap));
 107         vsprintf(newref->value, format, ap);
 108         va_end(ap);
 109         newref->ref = 1;
 110
 111         return newref;
 112 }
 113
 114 PurpleStringref *purple_stringref_ref(PurpleStringref *stringref)
 115 {
 116         if (stringref == NULL)
 117                 return NULL;
 118         stringref->ref++;
 119         return stringref;
 120 }
 121
 122 void purple_stringref_unref(PurpleStringref *stringref)
 123 {
 124         if (stringref == NULL)
 125                 return;
 126         if (REFCOUNT(--(stringref->ref)) == 0) {
 127                 if (stringref->ref & 0x80000000)
 128                         gclist = g_list_remove(gclist, stringref);
 129                 stringref_free(stringref);
 130         }
 131 }
 132
 133 const char *purple_stringref_value(const PurpleStringref *stringref)
 134 {
 135         return (stringref == NULL ? NULL : stringref->value);
 136 }
 137
 138 int purple_stringref_cmp(const PurpleStringref *s1, const PurpleStringref *s2)
 139 {
 140         return (s1 == s2 ? 0 : strcmp(purple_stringref_value(s1), purple_stringref_value(s2)));
 141 }
 142
 143 size_t purple_stringref_len(const PurpleStringref *stringref)
 144 {
 145         return strlen(purple_stringref_value(stringref));
 146 }
 147
 148 static void stringref_free(PurpleStringref *stringref)
 149 {
 150 #ifdef DEBUG
 151         if (REFCOUNT(stringref->ref) != 0) {
 152                 purple_debug(PURPLE_DEBUG_ERROR, "stringref", "Free of nonzero (%d) ref stringref!\n", REFCOUNT(stringref->ref));
 153                 return;
 154         }
 155 #endif /* DEBUG */
 156         g_free(stringref);
 157 }
 158
 159 static gboolean gs_idle_cb(gpointer data)
 160 {
 161         PurpleStringref *ref;
 162         GList *del;
 163
 164         while (gclist != NULL) {
 165                 ref = gclist->data;
 166                 if (REFCOUNT(ref->ref) == 0) {
 167                         stringref_free(ref);
 168                 }
 169                 del = gclist;
 170                 gclist = gclist->next;
 171                 g_list_free_1(del);
 172         }
 173
 174         return FALSE;
 175 }