/* GLIB - Library of useful routines for C programming

 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald

 * Copyright (C) 1998 Tim Janik

 *

 * gquark.c: Functions for dealing with quarks and interned strings

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/.

 */

/*

 * MT safe

 */

#include "config.h"

#include <string.h>

#include "gslice.h"

#include "ghash.h"

#include "gquark.h"

#include "gstrfuncs.h"

#include "gthread.h"

#include "gtestutils.h"

#include "glib_trace.h"

#include "glib-init.h"

#define QUARK_BLOCK_SIZE         2048

#define QUARK_STRING_BLOCK_SIZE (4096 - sizeof (gsize))

static inline GQuark  quark_new (gchar *string);

G_LOCK_DEFINE_STATIC (quark_global);

static GHashTable    *quark_ht = NULL;

static gchar        **quarks = NULL;

static gint           quark_seq_id = 0;

static gchar         *quark_block = NULL;

static gint           quark_block_offset = 0;

void

g_quark_init (void)

{

  g_assert (quark_seq_id == 0);

  quark_ht = g_hash_table_new (g_str_hash, g_str_equal);

  quarks = g_new (gchar*, QUARK_BLOCK_SIZE);

  quarks[0] = NULL;

  quark_seq_id = 1;

}

/**

 * SECTION:quarks

 * @title: Quarks

 * @short_description: a 2-way association between a string and a

 *     unique integer identifier

 *

 * Quarks are associations between strings and integer identifiers.

 * Given either the string or the #GQuark identifier it is possible to

 * retrieve the other.

 *

 * Quarks are used for both [datasets][glib-Datasets] and

 * [keyed data lists][glib-Keyed-Data-Lists].

 *

 * To create a new quark from a string, use g_quark_from_string() or

 * g_quark_from_static_string().

 *

 * To find the string corresponding to a given #GQuark, use

 * g_quark_to_string().

 *

 * To find the #GQuark corresponding to a given string, use

 * g_quark_try_string().

 *

 * Another use for the string pool maintained for the quark functions

 * is string interning, using g_intern_string() or

 * g_intern_static_string(). An interned string is a canonical

 * representation for a string. One important advantage of interned

 * strings is that they can be compared for equality by a simple

 * pointer comparison, rather than using strcmp().

 */

/**

 * GQuark:

 *

 * A GQuark is a non-zero integer which uniquely identifies a

 * particular string. A GQuark value of zero is associated to %NULL.

 */

/**

 * G_DEFINE_QUARK:

 * @QN: the name to return a #GQuark for

 * @q_n: prefix for the function name

 *

 * A convenience macro which defines a function returning the

 * #GQuark for the name @QN. The function will be named

 * @q_n_quark().

 *

 * Note that the quark name will be stringified automatically

 * in the macro, so you shouldn't use double quotes.

 *

 * Since: 2.34

 */

/**

 * g_quark_try_string:

 * @string: (nullable): a string

 *

 * Gets the #GQuark associated with the given string, or 0 if string is

 * %NULL or it has no associated #GQuark.

 *

 * If you want the GQuark to be created if it doesn't already exist,

 * use g_quark_from_string() or g_quark_from_static_string().

 *

 * This function must not be used before library constructors have finished

 * running.

 *

 * Returns: the #GQuark associated with the string, or 0 if @string is

 *     %NULL or there is no #GQuark associated with it

 */

GQuark

g_quark_try_string (const gchar *string)

{

  GQuark quark = 0;

  if (string == NULL)

    return 0;

  G_LOCK (quark_global);

  quark = GPOINTER_TO_UINT (g_hash_table_lookup (quark_ht, string));

  G_UNLOCK (quark_global);

  return quark;

}

/* HOLDS: quark_global_lock */

static char *

quark_strdup (const gchar *string)

{

  gchar *copy;

  gsize len;

  len = strlen (string) + 1;

  /* For strings longer than half the block size, fall back

     to strdup so that we fill our blocks at least 50%. */

  if (len > QUARK_STRING_BLOCK_SIZE / 2)

    return g_strdup (string);

  if (quark_block == NULL ||

      QUARK_STRING_BLOCK_SIZE - quark_block_offset < len)

    {

      quark_block = g_malloc (QUARK_STRING_BLOCK_SIZE);

      quark_block_offset = 0;

    }

  copy = quark_block + quark_block_offset;

  memcpy (copy, string, len);

  quark_block_offset += len;

  return copy;

}

/* HOLDS: quark_global_lock */

static inline GQuark

quark_from_string (const gchar *string,

                   gboolean     duplicate)

{

  GQuark quark = 0;

  quark = GPOINTER_TO_UINT (g_hash_table_lookup (quark_ht, string));

  if (!quark)

    {

      quark = quark_new (duplicate ? quark_strdup (string) : (gchar *)string);

      TRACE(GLIB_QUARK_NEW(string, quark));

    }

  return quark;

}

static inline GQuark

quark_from_string_locked (const gchar   *string,

                          gboolean       duplicate)

{

  GQuark quark = 0;

  if (!string)

    return 0;

  G_LOCK (quark_global);

  quark = quark_from_string (string, duplicate);

  G_UNLOCK (quark_global);

  return quark;

}

/**

 * g_quark_from_string:

 * @string: (nullable): a string

 *

 * Gets the #GQuark identifying the given string. If the string does

 * not currently have an associated #GQuark, a new #GQuark is created,

 * using a copy of the string.

 *

 * This function must not be used before library constructors have finished

 * running. In particular, this means it cannot be used to initialize global

 * variables in C++.

 *

 * Returns: the #GQuark identifying the string, or 0 if @string is %NULL

 */

GQuark

g_quark_from_string (const gchar *string)

{

  return quark_from_string_locked (string, TRUE);

}

/**

 * g_quark_from_static_string:

 * @string: (nullable): a string

 *

 * Gets the #GQuark identifying the given (static) string. If the

 * string does not currently have an associated #GQuark, a new #GQuark

 * is created, linked to the given string.

 *

 * Note that this function is identical to g_quark_from_string() except

 * that if a new #GQuark is created the string itself is used rather

 * than a copy. This saves memory, but can only be used if the string

 * will continue to exist until the program terminates. It can be used

 * with statically allocated strings in the main program, but not with

 * statically allocated memory in dynamically loaded modules, if you

 * expect to ever unload the module again (e.g. do not use this

 * function in GTK+ theme engines).

 *

 * This function must not be used before library constructors have finished

 * running. In particular, this means it cannot be used to initialize global

 * variables in C++.

 *

 * Returns: the #GQuark identifying the string, or 0 if @string is %NULL

 */

GQuark

g_quark_from_static_string (const gchar *string)

{

  return quark_from_string_locked (string, FALSE);

}

/**

 * g_quark_to_string:

 * @quark: a #GQuark.

 *

 * Gets the string associated with the given #GQuark.

 *

 * Returns: the string associated with the #GQuark

 */

const gchar *

g_quark_to_string (GQuark quark)

{

  gchar* result = NULL;

  gchar **strings;

  guint seq_id;

  seq_id = (guint) g_atomic_int_get (&quark_seq_id);

  strings = g_atomic_pointer_get (&quarks);

  if (quark < seq_id)

    result = strings[quark];

  return result;

}

/* HOLDS: g_quark_global_lock */

static inline GQuark

quark_new (gchar *string)

{

  GQuark quark;

  gchar **quarks_new;

  if (quark_seq_id % QUARK_BLOCK_SIZE == 0)

    {

      quarks_new = g_new (gchar*, quark_seq_id + QUARK_BLOCK_SIZE);

      if (quark_seq_id != 0)

        memcpy (quarks_new, quarks, sizeof (char *) * quark_seq_id);

      memset (quarks_new + quark_seq_id, 0, sizeof (char *) * QUARK_BLOCK_SIZE);

      /* This leaks the old quarks array. Its unfortunate, but it allows

       * us to do lockless lookup of the arrays, and there shouldn't be that

       * many quarks in an app

       */

      g_atomic_pointer_set (&quarks, quarks_new);

    }

  quark = quark_seq_id;

  g_atomic_pointer_set (&quarks[quark], string);

  g_hash_table_insert (quark_ht, string, GUINT_TO_POINTER (quark));

  g_atomic_int_inc (&quark_seq_id);

  return quark;

}

static inline const gchar *

quark_intern_string_locked (const gchar   *string,

                            gboolean       duplicate)

{

  const gchar *result;

  GQuark quark;

  if (!string)

    return NULL;

  G_LOCK (quark_global);

  quark = quark_from_string (string, duplicate);

  result = quarks[quark];

  G_UNLOCK (quark_global);

  return result;

}

/**

 * g_intern_string:

 * @string: (nullable): a string

 *

 * Returns a canonical representation for @string. Interned strings

 * can be compared for equality by comparing the pointers, instead of

 * using strcmp().

 *

 * This function must not be used before library constructors have finished

 * running. In particular, this means it cannot be used to initialize global

 * variables in C++.

 *

 * Returns: a canonical representation for the string

 *

 * Since: 2.10

 */

const gchar *

g_intern_string (const gchar *string)

{

  return quark_intern_string_locked (string, TRUE);

}

/**

 * g_intern_static_string:

 * @string: (nullable): a static string

 *

 * Returns a canonical representation for @string. Interned strings

 * can be compared for equality by comparing the pointers, instead of

 * using strcmp(). g_intern_static_string() does not copy the string,

 * therefore @string must not be freed or modified.

 *

 * This function must not be used before library constructors have finished

 * running. In particular, this means it cannot be used to initialize global

 * variables in C++.

 *

 * Returns: a canonical representation for the string

 *

 * Since: 2.10

 */

const gchar *

g_intern_static_string (const gchar *string)

{

  return quark_intern_string_locked (string, FALSE);

}