1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
3 * Copyright (C) 1998 Tim Janik
5 * gquark.c: Functions for dealing with quarks and interned strings
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
22 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
23 * file for a list of people on the GLib Team. See the ChangeLog
24 * files for a list of changes. These files are distributed with
25 * GLib at ftp://ftp.gtk.org/pub/gtk/.
39 #include "gstrfuncs.h"
41 #include "gtestutils.h"
42 #include "glib_trace.h"
44 #define QUARK_BLOCK_SIZE 2048
45 #define QUARK_STRING_BLOCK_SIZE (4096 - sizeof (gsize))
47 static inline GQuark quark_new (gchar *string);
49 G_LOCK_DEFINE_STATIC (quark_global);
50 static GHashTable *quark_ht = NULL;
51 static gchar **quarks = NULL;
52 static gint quark_seq_id = 0;
53 static gchar *quark_block = NULL;
54 static gint quark_block_offset = 0;
59 * @short_description: a 2-way association between a string and a
60 * unique integer identifier
62 * Quarks are associations between strings and integer identifiers.
63 * Given either the string or the #GQuark identifier it is possible to
66 * Quarks are used for both <link
67 * linkend="glib-Datasets">Datasets</link> and <link
68 * linkend="glib-Keyed-Data-Lists">Keyed Data Lists</link>.
70 * To create a new quark from a string, use g_quark_from_string() or
71 * g_quark_from_static_string().
73 * To find the string corresponding to a given #GQuark, use
74 * g_quark_to_string().
76 * To find the #GQuark corresponding to a given string, use
77 * g_quark_try_string().
79 * Another use for the string pool maintained for the quark functions
80 * is string interning, using g_intern_string() or
81 * g_intern_static_string(). An interned string is a canonical
82 * representation for a string. One important advantage of interned
83 * strings is that they can be compared for equality by a simple
84 * pointer comparison, rather than using strcmp().
90 * A GQuark is a non-zero integer which uniquely identifies a
91 * particular string. A GQuark value of zero is associated to %NULL.
96 * @QN: the name to return a #GQuark for
97 * @q_n: prefix for the function name
99 * A convenience macro which defines a function returning the
100 * #GQuark for the name @QN. The function will be named
101 * @q_n<!-- -->_quark().
102 * Note that the quark name will be stringified automatically in the
103 * macro, so you shouldn't use double quotes.
109 * g_quark_try_string:
110 * @string: (allow-none): a string.
111 * @Returns: the #GQuark associated with the string, or 0 if @string is
112 * %NULL or there is no #GQuark associated with it.
114 * Gets the #GQuark associated with the given string, or 0 if string is
115 * %NULL or it has no associated #GQuark.
117 * If you want the GQuark to be created if it doesn't already exist,
118 * use g_quark_from_string() or g_quark_from_static_string().
121 g_quark_try_string (const gchar *string)
128 G_LOCK (quark_global);
130 quark = GPOINTER_TO_UINT (g_hash_table_lookup (quark_ht, string));
131 G_UNLOCK (quark_global);
136 /* HOLDS: quark_global_lock */
138 quark_strdup (const gchar *string)
143 len = strlen (string) + 1;
145 /* For strings longer than half the block size, fall back
146 to strdup so that we fill our blocks at least 50%. */
147 if (len > QUARK_STRING_BLOCK_SIZE / 2)
148 return g_strdup (string);
150 if (quark_block == NULL ||
151 QUARK_STRING_BLOCK_SIZE - quark_block_offset < len)
153 quark_block = g_malloc (QUARK_STRING_BLOCK_SIZE);
154 quark_block_offset = 0;
157 copy = quark_block + quark_block_offset;
158 memcpy (copy, string, len);
159 quark_block_offset += len;
164 /* HOLDS: quark_global_lock */
166 quark_from_string (const gchar *string,
172 quark = GPOINTER_TO_UINT (g_hash_table_lookup (quark_ht, string));
176 quark = quark_new (duplicate ? quark_strdup (string) : (gchar *)string);
177 TRACE(GLIB_QUARK_NEW(string, quark));
184 * g_quark_from_string:
185 * @string: (allow-none): a string.
187 * Gets the #GQuark identifying the given string. If the string does
188 * not currently have an associated #GQuark, a new #GQuark is created,
189 * using a copy of the string.
191 * Returns: the #GQuark identifying the string, or 0 if @string is
195 g_quark_from_string (const gchar *string)
202 G_LOCK (quark_global);
203 quark = quark_from_string (string, TRUE);
204 G_UNLOCK (quark_global);
210 * g_quark_from_static_string:
211 * @string: (allow-none): a string.
213 * Gets the #GQuark identifying the given (static) string. If the
214 * string does not currently have an associated #GQuark, a new #GQuark
215 * is created, linked to the given string.
217 * Note that this function is identical to g_quark_from_string() except
218 * that if a new #GQuark is created the string itself is used rather
219 * than a copy. This saves memory, but can only be used if the string
220 * will <emphasis>always</emphasis> exist. It can be used with
221 * statically allocated strings in the main program, but not with
222 * statically allocated memory in dynamically loaded modules, if you
223 * expect to ever unload the module again (e.g. do not use this
224 * function in GTK+ theme engines).
226 * Returns: the #GQuark identifying the string, or 0 if @string is
230 g_quark_from_static_string (const gchar *string)
237 G_LOCK (quark_global);
238 quark = quark_from_string (string, FALSE);
239 G_UNLOCK (quark_global);
248 * Gets the string associated with the given #GQuark.
250 * Returns: the string associated with the #GQuark
253 g_quark_to_string (GQuark quark)
255 gchar* result = NULL;
259 seq_id = g_atomic_int_get (&quark_seq_id);
260 strings = g_atomic_pointer_get (&quarks);
263 result = strings[quark];
268 /* HOLDS: g_quark_global_lock */
270 quark_new (gchar *string)
275 if (quark_seq_id % QUARK_BLOCK_SIZE == 0)
277 quarks_new = g_new (gchar*, quark_seq_id + QUARK_BLOCK_SIZE);
278 if (quark_seq_id != 0)
279 memcpy (quarks_new, quarks, sizeof (char *) * quark_seq_id);
280 memset (quarks_new + quark_seq_id, 0, sizeof (char *) * QUARK_BLOCK_SIZE);
281 /* This leaks the old quarks array. Its unfortunate, but it allows
282 * us to do lockless lookup of the arrays, and there shouldn't be that
283 * many quarks in an app
285 g_atomic_pointer_set (&quarks, quarks_new);
289 g_assert (quark_seq_id == 0);
290 quark_ht = g_hash_table_new (g_str_hash, g_str_equal);
291 quarks[quark_seq_id] = NULL;
292 g_atomic_int_inc (&quark_seq_id);
295 quark = quark_seq_id;
296 g_atomic_pointer_set (&quarks[quark], string);
297 g_hash_table_insert (quark_ht, string, GUINT_TO_POINTER (quark));
298 g_atomic_int_inc (&quark_seq_id);
305 * @string: (allow-none): a string
307 * Returns a canonical representation for @string. Interned strings
308 * can be compared for equality by comparing the pointers, instead of
311 * Returns: a canonical representation for the string
316 g_intern_string (const gchar *string)
324 G_LOCK (quark_global);
325 quark = quark_from_string (string, TRUE);
326 result = quarks[quark];
327 G_UNLOCK (quark_global);
333 * g_intern_static_string:
334 * @string: (allow-none): a static string
336 * Returns a canonical representation for @string. Interned strings
337 * can be compared for equality by comparing the pointers, instead of
338 * using strcmp(). g_intern_static_string() does not copy the string,
339 * therefore @string must not be freed or modified.
341 * Returns: a canonical representation for the string
346 g_intern_static_string (const gchar *string)
354 G_LOCK (quark_global);
355 quark = quark_from_string (string, FALSE);
356 result = quarks[quark];
357 G_UNLOCK (quark_global);