/* GObject - GLib Type, Object, Parameter and Signal Library

 * Copyright (C) 2000-2001 Red Hat, Inc.

 * Copyright (C) 2005 Imendio AB

 *

 * 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/>.

 */

/*

 * MT safe with regards to reference counting.

 */

#include "config.h"

#include "../glib/gvalgrind.h"

#include <string.h>

#include <ffi.h>

#include "gclosure.h"

#include "gboxed.h"

#include "gobject.h"

#include "genums.h"

#include "gvalue.h"

#include "gvaluetypes.h"

#include "gtype-private.h"

/**

 * GClosure:

 * @in_marshal: Indicates whether the closure is currently being invoked with

 *   g_closure_invoke()

 * @is_invalid: Indicates whether the closure has been invalidated by

 *   g_closure_invalidate()

 *

 * A `GClosure` represents a callback supplied by the programmer.

 *

 * It will generally comprise a function of some kind and a marshaller

 * used to call it. It is the responsibility of the marshaller to

 * convert the arguments for the invocation from #GValues into

 * a suitable form, perform the callback on the converted arguments,

 * and transform the return value back into a #GValue.

 *

 * In the case of C programs, a closure usually just holds a pointer

 * to a function and maybe a data argument, and the marshaller

 * converts between #GValue and native C types. The GObject

 * library provides the #GCClosure type for this purpose. Bindings for

 * other languages need marshallers which convert between #GValues

 * and suitable representations in the runtime of the language in

 * order to use functions written in that language as callbacks. Use

 * g_closure_set_marshal() to set the marshaller on such a custom

 * closure implementation.

 *

 * Within GObject, closures play an important role in the

 * implementation of signals. When a signal is registered, the

 * @c_marshaller argument to g_signal_new() specifies the default C

 * marshaller for any closure which is connected to this

 * signal. GObject provides a number of C marshallers for this

 * purpose, see the g_cclosure_marshal_*() functions. Additional C

 * marshallers can be generated with the [glib-genmarshal][glib-genmarshal]

 * utility.  Closures can be explicitly connected to signals with

 * g_signal_connect_closure(), but it usually more convenient to let

 * GObject create a closure automatically by using one of the

 * g_signal_connect_*() functions which take a callback function/user

 * data pair.

 *

 * Using closures has a number of important advantages over a simple

 * callback function/data pointer combination:

 *

 * - Closures allow the callee to get the types of the callback parameters,

 *   which means that language bindings don't have to write individual glue

 *   for each callback type.

 *

 * - The reference counting of #GClosure makes it easy to handle reentrancy

 *   right; if a callback is removed while it is being invoked, the closure

 *   and its parameters won't be freed until the invocation finishes.

 *

 * - g_closure_invalidate() and invalidation notifiers allow callbacks to be

 *   automatically removed when the objects they point to go away.

 */

#define CLOSURE_MAX_REF_COUNT   ((1 << 15) - 1)

#define CLOSURE_MAX_N_GUARDS    ((1 << 1) - 1)

#define CLOSURE_MAX_N_FNOTIFIERS  ((1 << 2) - 1)

#define CLOSURE_MAX_N_INOTIFIERS  ((1 << 8) - 1)

#define CLOSURE_N_MFUNCS(cl)    (((cl)->n_guards << 1L))

/* same as G_CLOSURE_N_NOTIFIERS() (keep in sync) */

#define CLOSURE_N_NOTIFIERS(cl)   (CLOSURE_N_MFUNCS (cl) + \

                                         (cl)->n_fnotifiers + \

                                         (cl)->n_inotifiers)

typedef union {

  GClosure closure;

  gint vint;

} ClosureInt;

#define CHANGE_FIELD(_closure, _field, _OP, _value, _must_set, _SET_OLD, _SET_NEW)      \

G_STMT_START {                                                                          \

  ClosureInt *cunion = (ClosureInt*) _closure;                                    \

  gint new_int, old_int, success;                                                 \

  do                                                                        \

    {                                                                       \

      ClosureInt tmp;                                                       \

      tmp.vint = old_int = cunion->vint;                                    \

      _SET_OLD tmp.closure._field;                                                      \

      tmp.closure._field _OP _value;                                          \

      _SET_NEW tmp.closure._field;                                                      \

      new_int = tmp.vint;                                                   \

      success = g_atomic_int_compare_and_exchange (&cunion->vint, old_int, new_int);    \

    }                                                                       \

  while (!success && _must_set);                                                        \

} G_STMT_END

#define SWAP(_closure, _field, _value, _oldv)   CHANGE_FIELD (_closure, _field, =, _value, TRUE, *(_oldv) =,     (void) )

#define SET(_closure, _field, _value)           CHANGE_FIELD (_closure, _field, =, _value, TRUE,     (void),     (void) )

#define INC(_closure, _field)                   CHANGE_FIELD (_closure, _field, +=,     1, TRUE,     (void),     (void) )

#define INC_ASSIGN(_closure, _field, _newv)     CHANGE_FIELD (_closure, _field, +=,     1, TRUE,     (void), *(_newv) = )

#define DEC(_closure, _field)                   CHANGE_FIELD (_closure, _field, -=,     1, TRUE,     (void),     (void) )

#define DEC_ASSIGN(_closure, _field, _newv)     CHANGE_FIELD (_closure, _field, -=,     1, TRUE,     (void), *(_newv) = )

#if 0   /* for non-thread-safe closures */

#define SWAP(cl,f,v,o)     (void) (*(o) = cl->f, cl->f = v)

#define SET(cl,f,v)        (void) (cl->f = v)

#define INC(cl,f)          (void) (cl->f += 1)

#define INC_ASSIGN(cl,f,n) (void) (cl->f += 1, *(n) = cl->f)

#define DEC(cl,f)          (void) (cl->f -= 1)

#define DEC_ASSIGN(cl,f,n) (void) (cl->f -= 1, *(n) = cl->f)

#endif

enum {

  FNOTIFY,

  INOTIFY,

  PRE_NOTIFY,

  POST_NOTIFY

};

/* --- functions --- */

/**

 * g_closure_new_simple:

 * @sizeof_closure: the size of the structure to allocate, must be at least

 *                  `sizeof (GClosure)`

 * @data: data to store in the @data field of the newly allocated #GClosure

 *

 * Allocates a struct of the given size and initializes the initial

 * part as a #GClosure.

 *

 * This function is mainly useful when implementing new types of closures:

 *

 * |[<!-- language="C" --> 

 * typedef struct _MyClosure MyClosure;

 * struct _MyClosure

 * {

 *   GClosure closure;

 *   // extra data goes here

 * };

 *

 * static void

 * my_closure_finalize (gpointer  notify_data,

 *                      GClosure *closure)

 * {

 *   MyClosure *my_closure = (MyClosure *)closure;

 *

 *   // free extra data here

 * }

 *

 * MyClosure *my_closure_new (gpointer data)

 * {

 *   GClosure *closure;

 *   MyClosure *my_closure;

 *

 *   closure = g_closure_new_simple (sizeof (MyClosure), data);

 *   my_closure = (MyClosure *) closure;

 *

 *   // initialize extra data here

 *

 *   g_closure_add_finalize_notifier (closure, notify_data,

 *                                    my_closure_finalize);

 *   return my_closure;

 * }

 * ]|

 *

 * Returns: (transfer floating): a floating reference to a new #GClosure

 */

GClosure*

g_closure_new_simple (guint           sizeof_closure,

          gpointer        data)

{

  GClosure *closure;

  gint private_size;

  gchar *allocated;

  g_return_val_if_fail (sizeof_closure >= sizeof (GClosure), NULL);

  private_size = sizeof (GRealClosure) - sizeof (GClosure);

#ifdef ENABLE_VALGRIND

  /* See comments in gtype.c about what's going on here... */

  if (RUNNING_ON_VALGRIND)

    {

      private_size += sizeof (gpointer);

      allocated = g_malloc0 (private_size + sizeof_closure + sizeof (gpointer));

      *(gpointer *) (allocated + private_size + sizeof_closure) = allocated + sizeof (gpointer);

      VALGRIND_MALLOCLIKE_BLOCK (allocated + private_size, sizeof_closure + sizeof (gpointer), 0, TRUE);

      VALGRIND_MALLOCLIKE_BLOCK (allocated + sizeof (gpointer), private_size - sizeof (gpointer), 0, TRUE);

    }

  else

#endif

    allocated = g_malloc0 (private_size + sizeof_closure);

  closure = (GClosure *) (allocated + private_size);

  SET (closure, ref_count, 1);

  SET (closure, floating, TRUE);

  closure->data = data;

  return closure;

}

static inline void

closure_invoke_notifiers (GClosure *closure,

        guint     notify_type)

{

  /* notifier layout:

   *     n_guards    n_guards     n_fnotif.  n_inotifiers

   * ->[[pre_guards][post_guards][fnotifiers][inotifiers]]

   *

   * CLOSURE_N_MFUNCS(cl)    = n_guards + n_guards;

   * CLOSURE_N_NOTIFIERS(cl) = CLOSURE_N_MFUNCS(cl) + n_fnotifiers + n_inotifiers

   *

   * constrains/catches:

   * - closure->notifiers may be reloacted during callback

   * - closure->n_fnotifiers and closure->n_inotifiers may change during callback

   * - i.e. callbacks can be removed/added during invocation

   * - must prepare for callback removal during FNOTIFY and INOTIFY (done via ->marshal= & ->data=)

   * - must distinguish (->marshal= & ->data=) for INOTIFY vs. FNOTIFY (via ->in_inotify)

   * + closure->n_guards is const during PRE_NOTIFY & POST_NOTIFY

   * + none of the callbacks can cause recursion

   * + closure->n_inotifiers is const 0 during FNOTIFY

   */

  switch (notify_type)

    {

      GClosureNotifyData *ndata;

      guint i, offs;

    case FNOTIFY:

      while (closure->n_fnotifiers)

  {

          guint n;

    DEC_ASSIGN (closure, n_fnotifiers, &n);

    ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + n;

    closure->marshal = (GClosureMarshal) ndata->notify;

    closure->data = ndata->data;

    ndata->notify (ndata->data, closure);

  }

      closure->marshal = NULL;

      closure->data = NULL;

      break;

    case INOTIFY:

      SET (closure, in_inotify, TRUE);

      while (closure->n_inotifiers)

  {

          guint n;

          DEC_ASSIGN (closure, n_inotifiers, &n);

    ndata = closure->notifiers + CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + n;

    closure->marshal = (GClosureMarshal) ndata->notify;

    closure->data = ndata->data;

    ndata->notify (ndata->data, closure);

  }

      closure->marshal = NULL;

      closure->data = NULL;

      SET (closure, in_inotify, FALSE);

      break;

    case PRE_NOTIFY:

      i = closure->n_guards;

      offs = 0;

      while (i--)

  {

    ndata = closure->notifiers + offs + i;

    ndata->notify (ndata->data, closure);

  }

      break;

    case POST_NOTIFY:

      i = closure->n_guards;

      offs = i;

      while (i--)

  {

    ndata = closure->notifiers + offs + i;

    ndata->notify (ndata->data, closure);

  }

      break;

    }

}

static void

g_closure_set_meta_va_marshal (GClosure       *closure,

             GVaClosureMarshal va_meta_marshal)

{

  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (va_meta_marshal != NULL);

  g_return_if_fail (closure->is_invalid == FALSE);

  g_return_if_fail (closure->in_marshal == FALSE);

  real_closure = G_REAL_CLOSURE (closure);

  g_return_if_fail (real_closure->meta_marshal != NULL);

  real_closure->va_meta_marshal = va_meta_marshal;

}

/**

 * g_closure_set_meta_marshal: (skip)

 * @closure: a #GClosure

 * @marshal_data: (closure meta_marshal): context-dependent data to pass

 *  to @meta_marshal

 * @meta_marshal: a #GClosureMarshal function

 *

 * Sets the meta marshaller of @closure.

 *

 * A meta marshaller wraps the @closure's marshal and modifies the way

 * it is called in some fashion. The most common use of this facility

 * is for C callbacks.

 *

 * The same marshallers (generated by [glib-genmarshal][glib-genmarshal]),

 * are used everywhere, but the way that we get the callback function

 * differs. In most cases we want to use the @closure's callback, but in

 * other cases we want to use some different technique to retrieve the

 * callback function.

 *

 * For example, class closures for signals (see

 * g_signal_type_cclosure_new()) retrieve the callback function from a

 * fixed offset in the class structure.  The meta marshaller retrieves

 * the right callback and passes it to the marshaller as the

 * @marshal_data argument.

 */

void

g_closure_set_meta_marshal (GClosure       *closure,

          gpointer        marshal_data,

          GClosureMarshal meta_marshal)

{

  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (meta_marshal != NULL);

  g_return_if_fail (closure->is_invalid == FALSE);

  g_return_if_fail (closure->in_marshal == FALSE);

  real_closure = G_REAL_CLOSURE (closure);

  g_return_if_fail (real_closure->meta_marshal == NULL);

  real_closure->meta_marshal = meta_marshal;

  real_closure->meta_marshal_data = marshal_data;

}

/**

 * g_closure_add_marshal_guards: (skip)

 * @closure: a #GClosure

 * @pre_marshal_data: (closure pre_marshal_notify): data to pass

 *  to @pre_marshal_notify

 * @pre_marshal_notify: a function to call before the closure callback

 * @post_marshal_data: (closure post_marshal_notify): data to pass

 *  to @post_marshal_notify

 * @post_marshal_notify: a function to call after the closure callback

 *

 * Adds a pair of notifiers which get invoked before and after the

 * closure callback, respectively.

 *

 * This is typically used to protect the extra arguments for the

 * duration of the callback. See g_object_watch_closure() for an

 * example of marshal guards.

 */

void

g_closure_add_marshal_guards (GClosure      *closure,

            gpointer       pre_marshal_data,

            GClosureNotify pre_marshal_notify,

            gpointer       post_marshal_data,

            GClosureNotify post_marshal_notify)

{

  guint i;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (pre_marshal_notify != NULL);

  g_return_if_fail (post_marshal_notify != NULL);

  g_return_if_fail (closure->is_invalid == FALSE);

  g_return_if_fail (closure->in_marshal == FALSE);

  g_return_if_fail (closure->n_guards < CLOSURE_MAX_N_GUARDS);

  closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 2);

  if (closure->n_inotifiers)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

      closure->n_fnotifiers +

      closure->n_inotifiers + 1)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

                    closure->n_fnotifiers + 0)];

  if (closure->n_inotifiers > 1)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

      closure->n_fnotifiers +

      closure->n_inotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

                      closure->n_fnotifiers + 1)];

  if (closure->n_fnotifiers)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

      closure->n_fnotifiers + 1)] = closure->notifiers[CLOSURE_N_MFUNCS (closure) + 0];

  if (closure->n_fnotifiers > 1)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

      closure->n_fnotifiers)] = closure->notifiers[CLOSURE_N_MFUNCS (closure) + 1];

  if (closure->n_guards)

    closure->notifiers[(closure->n_guards +

      closure->n_guards + 1)] = closure->notifiers[closure->n_guards];

  i = closure->n_guards;

  closure->notifiers[i].data = pre_marshal_data;

  closure->notifiers[i].notify = pre_marshal_notify;

  closure->notifiers[i + 1].data = post_marshal_data;

  closure->notifiers[i + 1].notify = post_marshal_notify;

  INC (closure, n_guards);

}

/**

 * g_closure_add_finalize_notifier: (skip)

 * @closure: a #GClosure

 * @notify_data: (closure notify_func): data to pass to @notify_func

 * @notify_func: the callback function to register

 *

 * Registers a finalization notifier which will be called when the

 * reference count of @closure goes down to 0.

 *

 * Multiple finalization notifiers on a single closure are invoked in

 * unspecified order. If a single call to g_closure_unref() results in

 * the closure being both invalidated and finalized, then the invalidate

 * notifiers will be run before the finalize notifiers.

 */

void

g_closure_add_finalize_notifier (GClosure      *closure,

         gpointer       notify_data,

         GClosureNotify notify_func)

{

  guint i;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (notify_func != NULL);

  g_return_if_fail (closure->n_fnotifiers < CLOSURE_MAX_N_FNOTIFIERS);

  closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 1);

  if (closure->n_inotifiers)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

      closure->n_fnotifiers +

      closure->n_inotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

                      closure->n_fnotifiers + 0)];

  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers;

  closure->notifiers[i].data = notify_data;

  closure->notifiers[i].notify = notify_func;

  INC (closure, n_fnotifiers);

}

/**

 * g_closure_add_invalidate_notifier: (skip)

 * @closure: a #GClosure

 * @notify_data: (closure notify_func): data to pass to @notify_func

 * @notify_func: the callback function to register

 *

 * Registers an invalidation notifier which will be called when the

 * @closure is invalidated with g_closure_invalidate().

 *

 * Invalidation notifiers are invoked before finalization notifiers,

 * in an unspecified order.

 */

void

g_closure_add_invalidate_notifier (GClosure      *closure,

           gpointer       notify_data,

           GClosureNotify notify_func)

{

  guint i;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (notify_func != NULL);

  g_return_if_fail (closure->is_invalid == FALSE);

  g_return_if_fail (closure->n_inotifiers < CLOSURE_MAX_N_INOTIFIERS);

  closure->notifiers = g_renew (GClosureNotifyData, closure->notifiers, CLOSURE_N_NOTIFIERS (closure) + 1);

  i = CLOSURE_N_MFUNCS (closure) + closure->n_fnotifiers + closure->n_inotifiers;

  closure->notifiers[i].data = notify_data;

  closure->notifiers[i].notify = notify_func;

  INC (closure, n_inotifiers);

}

static inline gboolean

closure_try_remove_inotify (GClosure       *closure,

          gpointer       notify_data,

          GClosureNotify notify_func)

{

  GClosureNotifyData *ndata, *nlast;

  nlast = closure->notifiers + CLOSURE_N_NOTIFIERS (closure) - 1;

  for (ndata = nlast + 1 - closure->n_inotifiers; ndata <= nlast; ndata++)

    if (ndata->notify == notify_func && ndata->data == notify_data)

      {

  DEC (closure, n_inotifiers);

  if (ndata < nlast)

    *ndata = *nlast;

  return TRUE;

      }

  return FALSE;

}

static inline gboolean

closure_try_remove_fnotify (GClosure       *closure,

          gpointer       notify_data,

          GClosureNotify notify_func)

{

  GClosureNotifyData *ndata, *nlast;

  nlast = closure->notifiers + CLOSURE_N_NOTIFIERS (closure) - closure->n_inotifiers - 1;

  for (ndata = nlast + 1 - closure->n_fnotifiers; ndata <= nlast; ndata++)

    if (ndata->notify == notify_func && ndata->data == notify_data)

      {

  DEC (closure, n_fnotifiers);

  if (ndata < nlast)

    *ndata = *nlast;

  if (closure->n_inotifiers)

    closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

            closure->n_fnotifiers)] = closure->notifiers[(CLOSURE_N_MFUNCS (closure) +

                      closure->n_fnotifiers +

                      closure->n_inotifiers)];

  return TRUE;

      }

  return FALSE;

}

/**

 * g_closure_ref:

 * @closure: #GClosure to increment the reference count on

 *

 * Increments the reference count on a closure to force it staying

 * alive while the caller holds a pointer to it.

 *

 * Returns: (transfer none): The @closure passed in, for convenience

 */

GClosure*

g_closure_ref (GClosure *closure)

{

  guint new_ref_count;

  g_return_val_if_fail (closure != NULL, NULL);

  g_return_val_if_fail (closure->ref_count > 0, NULL);

  g_return_val_if_fail (closure->ref_count < CLOSURE_MAX_REF_COUNT, NULL);

  INC_ASSIGN (closure, ref_count, &new_ref_count);

  g_return_val_if_fail (new_ref_count > 1, NULL);

  return closure;

}

/**

 * g_closure_invalidate:

 * @closure: #GClosure to invalidate

 *

 * Sets a flag on the closure to indicate that its calling

 * environment has become invalid, and thus causes any future

 * invocations of g_closure_invoke() on this @closure to be

 * ignored.

 *

 * Also, invalidation notifiers installed on the closure will

 * be called at this point. Note that unless you are holding a

 * reference to the closure yourself, the invalidation notifiers may

 * unref the closure and cause it to be destroyed, so if you need to

 * access the closure after calling g_closure_invalidate(), make sure

 * that you've previously called g_closure_ref().

 *

 * Note that g_closure_invalidate() will also be called when the

 * reference count of a closure drops to zero (unless it has already

 * been invalidated before).

 */

void

g_closure_invalidate (GClosure *closure)

{

  g_return_if_fail (closure != NULL);

  if (!closure->is_invalid)

    {

      gboolean was_invalid;

      g_closure_ref (closure);           /* preserve floating flag */

      SWAP (closure, is_invalid, TRUE, &was_invalid);

      /* invalidate only once */

      if (!was_invalid)

        closure_invoke_notifiers (closure, INOTIFY);

      g_closure_unref (closure);

    }

}

/**

 * g_closure_unref:

 * @closure: #GClosure to decrement the reference count on

 *

 * Decrements the reference count of a closure after it was previously

 * incremented by the same caller.

 *

 * If no other callers are using the closure, then the closure will be

 * destroyed and freed.

 */

void

g_closure_unref (GClosure *closure)

{

  guint new_ref_count;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (closure->ref_count > 0);

  if (closure->ref_count == 1)  /* last unref, invalidate first */

    g_closure_invalidate (closure);

  DEC_ASSIGN (closure, ref_count, &new_ref_count);

  if (new_ref_count == 0)

    {

      closure_invoke_notifiers (closure, FNOTIFY);

      g_free (closure->notifiers);

#ifdef ENABLE_VALGRIND

      /* See comments in gtype.c about what's going on here... */

      if (RUNNING_ON_VALGRIND)

        {

          gchar *allocated;

          allocated = (gchar *) G_REAL_CLOSURE (closure);

          allocated -= sizeof (gpointer);

          g_free (allocated);

          VALGRIND_FREELIKE_BLOCK (allocated + sizeof (gpointer), 0);

          VALGRIND_FREELIKE_BLOCK (closure, 0);

        }

      else

#endif

        g_free (G_REAL_CLOSURE (closure));

    }

}

/**

 * g_closure_sink:

 * @closure: #GClosure to decrement the initial reference count on, if it's

 *           still being held

 *

 * Takes over the initial ownership of a closure.

 *

 * Each closure is initially created in a "floating" state, which means

 * that the initial reference count is not owned by any caller.

 *

 * This function checks to see if the object is still floating, and if so,

 * unsets the floating state and decreases the reference count. If the

 * closure is not floating, g_closure_sink() does nothing.

 *

 * The reason for the existence of the floating state is to prevent

 * cumbersome code sequences like:

 *

 * |[<!-- language="C" --> 

 * closure = g_cclosure_new (cb_func, cb_data);

 * g_source_set_closure (source, closure);

 * g_closure_unref (closure); // GObject doesn't really need this

 * ]|

 *

 * Because g_source_set_closure() (and similar functions) take ownership of the

 * initial reference count, if it is unowned, we instead can write:

 *

 * |[<!-- language="C" --> 

 * g_source_set_closure (source, g_cclosure_new (cb_func, cb_data));

 * ]|

 *

 * Generally, this function is used together with g_closure_ref(). An example

 * of storing a closure for later notification looks like:

 *

 * |[<!-- language="C" --> 

 * static GClosure *notify_closure = NULL;

 * void

 * foo_notify_set_closure (GClosure *closure)

 * {

 *   if (notify_closure)

 *     g_closure_unref (notify_closure);

 *   notify_closure = closure;

 *   if (notify_closure)

 *     {

 *       g_closure_ref (notify_closure);

 *       g_closure_sink (notify_closure);

 *     }

 * }

 * ]|

 *

 * Because g_closure_sink() may decrement the reference count of a closure

 * (if it hasn't been called on @closure yet) just like g_closure_unref(),

 * g_closure_ref() should be called prior to this function.

 */

void

g_closure_sink (GClosure *closure)

{

  g_return_if_fail (closure != NULL);

  g_return_if_fail (closure->ref_count > 0);

  /* floating is basically a kludge to avoid creating closures

   * with a ref_count of 0. so the initial ref_count a closure has

   * is unowned. with invoking g_closure_sink() code may

   * indicate that it takes over that initial ref_count.

   */

  if (closure->floating)

    {

      gboolean was_floating;

      SWAP (closure, floating, FALSE, &was_floating);

      /* unref floating flag only once */

      if (was_floating)

        g_closure_unref (closure);

    }

}

/**

 * g_closure_remove_invalidate_notifier: (skip)

 * @closure: a #GClosure

 * @notify_data: data which was passed to g_closure_add_invalidate_notifier()

 *               when registering @notify_func

 * @notify_func: the callback function to remove

 *

 * Removes an invalidation notifier.

 *

 * Notice that notifiers are automatically removed after they are run.

 */

void

g_closure_remove_invalidate_notifier (GClosure      *closure,

              gpointer       notify_data,

              GClosureNotify notify_func)

{

  g_return_if_fail (closure != NULL);

  g_return_if_fail (notify_func != NULL);

  if (closure->is_invalid && closure->in_inotify && /* account removal of notify_func() while it's called */

      ((gpointer) closure->marshal) == ((gpointer) notify_func) &&

      closure->data == notify_data)

    closure->marshal = NULL;

  else if (!closure_try_remove_inotify (closure, notify_data, notify_func))

    g_critical (G_STRLOC ": unable to remove uninstalled invalidation notifier: %p (%p)",

          notify_func, notify_data);

}

/**

 * g_closure_remove_finalize_notifier: (skip)

 * @closure: a #GClosure

 * @notify_data: data which was passed to g_closure_add_finalize_notifier()

 *  when registering @notify_func

 * @notify_func: the callback function to remove

 *

 * Removes a finalization notifier.

 *

 * Notice that notifiers are automatically removed after they are run.

 */

void

g_closure_remove_finalize_notifier (GClosure      *closure,

            gpointer       notify_data,

            GClosureNotify notify_func)

{

  g_return_if_fail (closure != NULL);

  g_return_if_fail (notify_func != NULL);

  if (closure->is_invalid && !closure->in_inotify && /* account removal of notify_func() while it's called */

      ((gpointer) closure->marshal) == ((gpointer) notify_func) &&

      closure->data == notify_data)

    closure->marshal = NULL;

  else if (!closure_try_remove_fnotify (closure, notify_data, notify_func))

    g_critical (G_STRLOC ": unable to remove uninstalled finalization notifier: %p (%p)",

                notify_func, notify_data);

}

/**

 * g_closure_invoke:

 * @closure: a #GClosure

 * @return_value: (optional) (out): a #GValue to store the return

 *                value. May be %NULL if the callback of @closure

 *                doesn't return a value.

 * @n_param_values: the length of the @param_values array

 * @param_values: (array length=n_param_values): an array of

 *                #GValues holding the arguments on which to

 *                invoke the callback of @closure

 * @invocation_hint: (nullable): a context-dependent invocation hint

 *

 * Invokes the closure, i.e. executes the callback represented by the @closure.

 */

void

g_closure_invoke (GClosure       *closure,

      GValue /*out*/ *return_value,

      guint           n_param_values,

      const GValue   *param_values,

      gpointer        invocation_hint)

{

  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  real_closure = G_REAL_CLOSURE (closure);

  g_closure_ref (closure);      /* preserve floating flag */

  if (!closure->is_invalid)

    {

      GClosureMarshal marshal;

      gpointer marshal_data;

      gboolean in_marshal = closure->in_marshal;

      g_return_if_fail (closure->marshal || real_closure->meta_marshal);

      SET (closure, in_marshal, TRUE);

      if (real_closure->meta_marshal)

  {

    marshal_data = real_closure->meta_marshal_data;

    marshal = real_closure->meta_marshal;

  }

      else

  {

    marshal_data = NULL;

    marshal = closure->marshal;

  }

      if (!in_marshal)

  closure_invoke_notifiers (closure, PRE_NOTIFY);

      marshal (closure,

         return_value,

         n_param_values, param_values,

         invocation_hint,

         marshal_data);

      if (!in_marshal)

  closure_invoke_notifiers (closure, POST_NOTIFY);

      SET (closure, in_marshal, in_marshal);

    }

  g_closure_unref (closure);

}

gboolean

_g_closure_supports_invoke_va (GClosure       *closure)

{

  GRealClosure *real_closure;

  g_return_val_if_fail (closure != NULL, FALSE);

  real_closure = G_REAL_CLOSURE (closure);

  return

    real_closure->va_marshal != NULL &&

    (real_closure->meta_marshal == NULL ||

     real_closure->va_meta_marshal != NULL);

}

void

_g_closure_invoke_va (GClosure       *closure,

          GValue /*out*/ *return_value,

          gpointer        instance,

          va_list         args,

          int             n_params,

          GType          *param_types)

{

  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  real_closure = G_REAL_CLOSURE (closure);

  g_closure_ref (closure);      /* preserve floating flag */

  if (!closure->is_invalid)

    {

      GVaClosureMarshal marshal;

      gpointer marshal_data;

      gboolean in_marshal = closure->in_marshal;

      g_return_if_fail (closure->marshal || real_closure->meta_marshal);

      SET (closure, in_marshal, TRUE);

      if (real_closure->va_meta_marshal)

  {

    marshal_data = real_closure->meta_marshal_data;

    marshal = real_closure->va_meta_marshal;

  }

      else

  {

    marshal_data = NULL;

    marshal = real_closure->va_marshal;

  }

      if (!in_marshal)

  closure_invoke_notifiers (closure, PRE_NOTIFY);

      marshal (closure,

         return_value,

         instance, args,

         marshal_data,

         n_params, param_types);

      if (!in_marshal)

  closure_invoke_notifiers (closure, POST_NOTIFY);

      SET (closure, in_marshal, in_marshal);

    }

  g_closure_unref (closure);

}

/**

 * g_closure_set_marshal: (skip)

 * @closure: a #GClosure

 * @marshal: a #GClosureMarshal function

 *

 * Sets the marshaller of @closure.

 *

 * The `marshal_data` of @marshal provides a way for a meta marshaller to

 * provide additional information to the marshaller.

 *

 * For GObject's C predefined marshallers (the `g_cclosure_marshal_*()`

 * functions), what it provides is a callback function to use instead of

 * @closure->callback.

 *

 * See also: g_closure_set_meta_marshal()

 */

void

g_closure_set_marshal (GClosure       *closure,

           GClosureMarshal marshal)

{

  g_return_if_fail (closure != NULL);

  g_return_if_fail (marshal != NULL);

  if (closure->marshal && closure->marshal != marshal)

    g_critical ("attempt to override closure->marshal (%p) with new marshal (%p)",

          closure->marshal, marshal);

  else

    closure->marshal = marshal;

}

void

_g_closure_set_va_marshal (GClosure       *closure,

         GVaClosureMarshal marshal)

{

  GRealClosure *real_closure;

  g_return_if_fail (closure != NULL);

  g_return_if_fail (marshal != NULL);

  real_closure = G_REAL_CLOSURE (closure);

  if (real_closure->va_marshal && real_closure->va_marshal != marshal)

    g_critical ("attempt to override closure->va_marshal (%p) with new marshal (%p)",

          real_closure->va_marshal, marshal);

  else

    real_closure->va_marshal = marshal;

}

/**

 * g_cclosure_new: (skip)

 * @callback_func: the function to invoke

 * @user_data: (closure callback_func): user data to pass to @callback_func

 * @destroy_data: destroy notify to be called when @user_data is no longer used

 *

 * Creates a new closure which invokes @callback_func with @user_data as

 * the last parameter.

 *

 * @destroy_data will be called as a finalize notifier on the #GClosure.

 *

 * Returns: (transfer floating): a floating reference to a new #GCClosure

 */

GClosure*

g_cclosure_new (GCallback      callback_func,

    gpointer       user_data,

    GClosureNotify destroy_data)

{

  GClosure *closure;

  g_return_val_if_fail (callback_func != NULL, NULL);

  closure = g_closure_new_simple (sizeof (GCClosure), user_data);

  if (destroy_data)

    g_closure_add_finalize_notifier (closure, user_data, destroy_data);

  ((GCClosure*) closure)->callback = (gpointer) callback_func;

  return closure;

}

/**

 * g_cclosure_new_swap: (skip)

 * @callback_func: the function to invoke

 * @user_data: (closure callback_func): user data to pass to @callback_func

 * @destroy_data: destroy notify to be called when @user_data is no longer used

 *

 * Creates a new closure which invokes @callback_func with @user_data as

 * the first parameter.

 *