/* GStreamer

 * Copyright (C) 2005 David Schleef <ds@schleef.org>

 *

 * gstminiobject.h: Header for GstMiniObject

 *

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

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

 * License as published by the Free Software Foundation; either

 * version 2 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

 * Library General Public License for more details.

 *

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

 * License along with this library; if not, write to the

 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,

 * Boston, MA 02110-1301, USA.

 */

/**

 * SECTION:gstminiobject

 * @title: GstMiniObject

 * @short_description: Lightweight base class for the GStreamer object hierarchy

 *

 * #GstMiniObject is a simple structure that can be used to implement refcounted

 * types.

 *

 * Subclasses will include #GstMiniObject as the first member in their structure

 * and then call gst_mini_object_init() to initialize the #GstMiniObject fields.

 *

 * gst_mini_object_ref() and gst_mini_object_unref() increment and decrement the

 * refcount respectively. When the refcount of a mini-object reaches 0, the

 * dispose function is called first and when this returns %TRUE, the free

 * function of the miniobject is called.

 *

 * A copy can be made with gst_mini_object_copy().

 *

 * gst_mini_object_is_writable() will return %TRUE when the refcount of the

 * object is exactly 1, meaning the current caller has the only reference to the

 * object. gst_mini_object_make_writable() will return a writable version of the

 * object, which might be a new copy when the refcount was not 1.

 *

 * Opaque data can be associated with a #GstMiniObject with

 * gst_mini_object_set_qdata() and gst_mini_object_get_qdata(). The data is

 * meant to be specific to the particular object and is not automatically copied

 * with gst_mini_object_copy() or similar methods.

 *

 * A weak reference can be added and remove with gst_mini_object_weak_ref()

 * and gst_mini_object_weak_unref() respectively.

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "gst/gst_private.h"

#include "gst/gstminiobject.h"

#include "gst/gstinfo.h"

#include <gobject/gvaluecollector.h>

/* Mutex used for weak referencing */

G_LOCK_DEFINE_STATIC (qdata_mutex);

static GQuark weak_ref_quark;

#define SHARE_ONE (1 << 16)

#define SHARE_TWO (2 << 16)

#define SHARE_MASK (~(SHARE_ONE - 1))

#define IS_SHARED(state) (state >= SHARE_TWO)

#define LOCK_ONE (GST_LOCK_FLAG_LAST)

#define FLAG_MASK (GST_LOCK_FLAG_LAST - 1)

#define LOCK_MASK ((SHARE_ONE - 1) - FLAG_MASK)

#define LOCK_FLAG_MASK (SHARE_ONE - 1)

typedef struct

{

  GQuark quark;

  GstMiniObjectNotify notify;

  gpointer data;

  GDestroyNotify destroy;

} GstQData;

#define QDATA(o,i)          ((GstQData *)(o)->qdata)[(i)]

#define QDATA_QUARK(o,i)    (QDATA(o,i).quark)

#define QDATA_NOTIFY(o,i)   (QDATA(o,i).notify)

#define QDATA_DATA(o,i)     (QDATA(o,i).data)

#define QDATA_DESTROY(o,i)  (QDATA(o,i).destroy)

void

_priv_gst_mini_object_initialize (void)

{

  weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");

}

/**

 * gst_mini_object_init: (skip)

 * @mini_object: a #GstMiniObject

 * @flags: initial #GstMiniObjectFlags

 * @type: the #GType of the mini-object to create

 * @copy_func: (allow-none): the copy function, or %NULL

 * @dispose_func: (allow-none): the dispose function, or %NULL

 * @free_func: (allow-none): the free function or %NULL

 *

 * Initializes a mini-object with the desired type and copy/dispose/free

 * functions.

 */

void

gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,

    GstMiniObjectCopyFunction copy_func,

    GstMiniObjectDisposeFunction dispose_func,

    GstMiniObjectFreeFunction free_func)

{

  mini_object->type = type;

  mini_object->refcount = 1;

  mini_object->lockstate = 0;

  mini_object->flags = flags;

  mini_object->copy = copy_func;

  mini_object->dispose = dispose_func;

  mini_object->free = free_func;

  mini_object->n_qdata = 0;

  mini_object->qdata = NULL;

  GST_TRACER_MINI_OBJECT_CREATED (mini_object);

}

/**

 * gst_mini_object_copy: (skip)

 * @mini_object: the mini-object to copy

 *

 * Creates a copy of the mini-object.

 *

 * MT safe

 *

 * Returns: (transfer full) (nullable): the new mini-object if copying is

 * possible, %NULL otherwise.

 */

GstMiniObject *

gst_mini_object_copy (const GstMiniObject * mini_object)

{

  GstMiniObject *copy;

  g_return_val_if_fail (mini_object != NULL, NULL);

  if (mini_object->copy)

    copy = mini_object->copy (mini_object);

  else

    copy = NULL;

  return copy;

}

/**

 * gst_mini_object_lock:

 * @object: the mini-object to lock

 * @flags: #GstLockFlags

 *

 * Lock the mini-object with the specified access mode in @flags.

 *

 * Returns: %TRUE if @object could be locked.

 */

gboolean

gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)

{

  gint access_mode, state, newstate;

  g_return_val_if_fail (object != NULL, FALSE);

  g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);

  if (G_UNLIKELY (object->flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY &&

          flags & GST_LOCK_FLAG_WRITE))

    return FALSE;

  do {

    access_mode = flags & FLAG_MASK;

    newstate = state = g_atomic_int_get (&object->lockstate);

    GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",

        object, state, access_mode);

    if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {

      /* shared ref */

      newstate += SHARE_ONE;

      access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;

    }

    /* shared counter > 1 and write access is not allowed */

    if (((state & GST_LOCK_FLAG_WRITE) != 0

            || (access_mode & GST_LOCK_FLAG_WRITE) != 0)

        && IS_SHARED (newstate))

      goto lock_failed;

    if (access_mode) {

      if ((state & LOCK_FLAG_MASK) == 0) {

        /* nothing mapped, set access_mode */

        newstate |= access_mode;

      } else {

        /* access_mode must match */

        if ((state & access_mode) != access_mode)

          goto lock_failed;

      }

      /* increase refcount */

      newstate += LOCK_ONE;

    }

  } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,

          newstate));

  return TRUE;

lock_failed:

  {

    GST_CAT_DEBUG (GST_CAT_LOCKING,

        "lock failed %p: state %08x, access_mode %d", object, state,

        access_mode);

    return FALSE;

  }

}

/**

 * gst_mini_object_unlock:

 * @object: the mini-object to unlock

 * @flags: #GstLockFlags

 *

 * Unlock the mini-object with the specified access mode in @flags.

 */

void

gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)

{

  gint access_mode, state, newstate;

  g_return_if_fail (object != NULL);

  g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));

  do {

    access_mode = flags & FLAG_MASK;

    newstate = state = g_atomic_int_get (&object->lockstate);

    GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",

        object, state, access_mode);

    if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {

      /* shared counter */

      g_return_if_fail (state >= SHARE_ONE);

      newstate -= SHARE_ONE;

      access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;

    }

    if (access_mode) {

      g_return_if_fail ((state & access_mode) == access_mode);

      /* decrease the refcount */

      newstate -= LOCK_ONE;

      /* last refcount, unset access_mode */

      if ((newstate & LOCK_FLAG_MASK) == access_mode)

        newstate &= ~LOCK_FLAG_MASK;

    }

  } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,

          newstate));

}

/**

 * gst_mini_object_is_writable:

 * @mini_object: the mini-object to check

 *

 * If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE

 * lock on @object is the only one, this means that changes to the object will

 * not be visible to any other object.

 *

 * If the LOCKABLE flag is not set, check if the refcount of @mini_object is

 * exactly 1, meaning that no other reference exists to the object and that the

 * object is therefore writable.

 *

 * Modification of a mini-object should only be done after verifying that it

 * is writable.

 *

 * Returns: %TRUE if the object is writable.

 */

gboolean

gst_mini_object_is_writable (const GstMiniObject * mini_object)

{

  gboolean result;

  g_return_val_if_fail (mini_object != NULL, FALSE);

  if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {

    result = !IS_SHARED (g_atomic_int_get (&mini_object->lockstate));

  } else {

    result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);

  }

  return result;

}

/**

 * gst_mini_object_make_writable: (skip)

 * @mini_object: (transfer full): the mini-object to make writable

 *

 * Checks if a mini-object is writable.  If not, a writable copy is made and

 * returned.  This gives away the reference to the original mini object,

 * and returns a reference to the new object.

 *

 * MT safe

 *

 * Returns: (transfer full): a mini-object (possibly the same pointer) that

 *     is writable.

 */

GstMiniObject *

gst_mini_object_make_writable (GstMiniObject * mini_object)

{

  GstMiniObject *ret;

  g_return_val_if_fail (mini_object != NULL, NULL);

  if (gst_mini_object_is_writable (mini_object)) {

    ret = mini_object;

  } else {

    ret = gst_mini_object_copy (mini_object);

    GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",

        g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);

    gst_mini_object_unref (mini_object);

  }

  return ret;

}

/**

 * gst_mini_object_ref: (skip)

 * @mini_object: the mini-object

 *

 * Increase the reference count of the mini-object.

 *

 * Note that the refcount affects the writability

 * of @mini-object, see gst_mini_object_is_writable(). It is

 * important to note that keeping additional references to

 * GstMiniObject instances can potentially increase the number

 * of memcpy operations in a pipeline, especially if the miniobject

 * is a #GstBuffer.

 *

 * Returns: (transfer full): the mini-object.

 */

GstMiniObject *

gst_mini_object_ref (GstMiniObject * mini_object)

{

  gint old_refcount, new_refcount;

  g_return_val_if_fail (mini_object != NULL, NULL);

  /* we can't assert that the refcount > 0 since the _free functions

   * increments the refcount from 0 to 1 again to allow resurecting

   * the object

   g_return_val_if_fail (mini_object->refcount > 0, NULL);

   */

  old_refcount = g_atomic_int_add (&mini_object->refcount, 1);

  new_refcount = old_refcount + 1;

  GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,

      old_refcount, new_refcount);

  GST_TRACER_MINI_OBJECT_REFFED (mini_object, new_refcount);

  return mini_object;

}

static gint

find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,

    GstMiniObjectNotify notify, gpointer data)

{

  guint i;

  for (i = 0; i < object->n_qdata; i++) {

    if (QDATA_QUARK (object, i) == quark) {

      /* check if we need to match the callback too */

      if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&

              QDATA_DATA (object, i) == data))

        return i;

    }

  }

  return -1;

}

static void

remove_notify (GstMiniObject * object, gint index)

{

  /* remove item */

  if (--object->n_qdata == 0) {

    /* we don't shrink but free when everything is gone */

    g_free (object->qdata);

    object->qdata = NULL;

  } else if (index != object->n_qdata)

    QDATA (object, index) = QDATA (object, object->n_qdata);

}

static void

set_notify (GstMiniObject * object, gint index, GQuark quark,

    GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)

{

  if (index == -1) {

    /* add item */

    index = object->n_qdata++;

    object->qdata =

        g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);

  }

  QDATA_QUARK (object, index) = quark;

  QDATA_NOTIFY (object, index) = notify;

  QDATA_DATA (object, index) = data;

  QDATA_DESTROY (object, index) = destroy;

}

static void

call_finalize_notify (GstMiniObject * obj)

{

  guint i;

  for (i = 0; i < obj->n_qdata; i++) {

    if (QDATA_QUARK (obj, i) == weak_ref_quark)

      QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);

    if (QDATA_DESTROY (obj, i))

      QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));

  }

}

/**

 * gst_mini_object_unref: (skip)

 * @mini_object: the mini-object

 *

 * Decreases the reference count of the mini-object, possibly freeing

 * the mini-object.

 */

void

gst_mini_object_unref (GstMiniObject * mini_object)

{

  gint old_refcount, new_refcount;

  g_return_if_fail (mini_object != NULL);

  g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) > 0);

  old_refcount = g_atomic_int_add (&mini_object->refcount, -1);

  new_refcount = old_refcount - 1;

  g_return_if_fail (old_refcount > 0);

  GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",

      mini_object, old_refcount, new_refcount);

  GST_TRACER_MINI_OBJECT_UNREFFED (mini_object, new_refcount);

  if (new_refcount == 0) {

    gboolean do_free;

    if (mini_object->dispose)

      do_free = mini_object->dispose (mini_object);

    else

      do_free = TRUE;

    /* if the subclass recycled the object (and returned FALSE) we don't

     * want to free the instance anymore */

    if (G_LIKELY (do_free)) {

      /* there should be no outstanding locks */

      g_return_if_fail ((g_atomic_int_get (&mini_object->lockstate) & LOCK_MASK)

          < 4);

      if (mini_object->n_qdata) {

        call_finalize_notify (mini_object);

        g_free (mini_object->qdata);

      }

      GST_TRACER_MINI_OBJECT_DESTROYED (mini_object);

      if (mini_object->free)

        mini_object->free (mini_object);

    }

  }

}

/**

 * gst_mini_object_replace:

 * @olddata: (inout) (transfer full) (nullable): pointer to a pointer to a

 *     mini-object to be replaced

 * @newdata: (allow-none): pointer to new mini-object

 *

 * Atomically modifies a pointer to point to a new mini-object.

 * The reference count of @olddata is decreased and the reference count of

 * @newdata is increased.

 *

 * Either @newdata and the value pointed to by @olddata may be %NULL.

 *

 * Returns: %TRUE if @newdata was different from @olddata

 */

gboolean

gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)

{

  GstMiniObject *olddata_val;

  g_return_val_if_fail (olddata != NULL, FALSE);

  GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",

      *olddata, *olddata ? (*olddata)->refcount : 0,

      newdata, newdata ? newdata->refcount : 0);

  olddata_val = g_atomic_pointer_get ((gpointer *) olddata);

  if (G_UNLIKELY (olddata_val == newdata))

    return FALSE;

  if (newdata)

    gst_mini_object_ref (newdata);

  while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)

              olddata, olddata_val, newdata))) {

    olddata_val = g_atomic_pointer_get ((gpointer *) olddata);

    if (G_UNLIKELY (olddata_val == newdata))

      break;

  }

  if (olddata_val)

    gst_mini_object_unref (olddata_val);

  return olddata_val != newdata;

}

/**

 * gst_mini_object_steal: (skip)

 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to

 *     be stolen

 *

 * Replace the current #GstMiniObject pointer to by @olddata with %NULL and

 * return the old value.

 *

 * Returns: (nullable): the #GstMiniObject at @oldata

 */

GstMiniObject *

gst_mini_object_steal (GstMiniObject ** olddata)

{

  GstMiniObject *olddata_val;

  g_return_val_if_fail (olddata != NULL, NULL);

  GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",

      *olddata, *olddata ? (*olddata)->refcount : 0);

  do {

    olddata_val = g_atomic_pointer_get ((gpointer *) olddata);

    if (olddata_val == NULL)

      break;

  } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)

              olddata, olddata_val, NULL)));

  return olddata_val;

}

/**

 * gst_mini_object_take:

 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to

 *     be replaced

 * @newdata: pointer to new mini-object

 *

 * Modifies a pointer to point to a new mini-object. The modification

 * is done atomically. This version is similar to gst_mini_object_replace()

 * except that it does not increase the refcount of @newdata and thus

 * takes ownership of @newdata.

 *

 * Either @newdata and the value pointed to by @olddata may be %NULL.

 *

 * Returns: %TRUE if @newdata was different from @olddata

 */

gboolean

gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)

{

  GstMiniObject *olddata_val;

  g_return_val_if_fail (olddata != NULL, FALSE);

  GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",

      *olddata, *olddata ? (*olddata)->refcount : 0,

      newdata, newdata ? newdata->refcount : 0);

  do {

    olddata_val = g_atomic_pointer_get ((gpointer *) olddata);

    if (G_UNLIKELY (olddata_val == newdata))

      break;

  } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)

              olddata, olddata_val, newdata)));

  if (olddata_val)

    gst_mini_object_unref (olddata_val);

  return olddata_val != newdata;

}

/**

 * gst_mini_object_weak_ref: (skip)

 * @object: #GstMiniObject to reference weakly

 * @notify: callback to invoke before the mini object is freed

 * @data: extra data to pass to notify

 *

 * Adds a weak reference callback to a mini object. Weak references are

 * used for notification when a mini object is finalized. They are called

 * "weak references" because they allow you to safely hold a pointer

 * to the mini object without calling gst_mini_object_ref()

 * (gst_mini_object_ref() adds a strong reference, that is, forces the object

 * to stay alive).

 */

void

gst_mini_object_weak_ref (GstMiniObject * object,

    GstMiniObjectNotify notify, gpointer data)

{

  g_return_if_fail (object != NULL);

  g_return_if_fail (notify != NULL);

  g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);

  G_LOCK (qdata_mutex);

  set_notify (object, -1, weak_ref_quark, notify, data, NULL);

  G_UNLOCK (qdata_mutex);

}

/**

 * gst_mini_object_weak_unref: (skip)

 * @object: #GstMiniObject to remove a weak reference from

 * @notify: callback to search for

 * @data: data to search for

 *

 * Removes a weak reference callback from a mini object.

 */

void

gst_mini_object_weak_unref (GstMiniObject * object,

    GstMiniObjectNotify notify, gpointer data)

{

  gint i;

  g_return_if_fail (object != NULL);

  g_return_if_fail (notify != NULL);

  G_LOCK (qdata_mutex);

  if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {

    remove_notify (object, i);

  } else {

    g_warning ("%s: couldn't find weak ref %p (object:%p data:%p)", G_STRFUNC,

        notify, object, data);

  }

  G_UNLOCK (qdata_mutex);

}

/**

 * gst_mini_object_set_qdata:

 * @object: a #GstMiniObject

 * @quark: A #GQuark, naming the user data pointer

 * @data: An opaque user data pointer

 * @destroy: Function to invoke with @data as argument, when @data

 *           needs to be freed

 *

 * This sets an opaque, named pointer on a miniobject.

 * The name is specified through a #GQuark (retrieved e.g. via

 * g_quark_from_static_string()), and the pointer

 * can be gotten back from the @object with gst_mini_object_get_qdata()

 * until the @object is disposed.

 * Setting a previously set user data pointer, overrides (frees)

 * the old pointer set, using %NULL as pointer essentially

 * removes the data stored.

 *

 * @destroy may be specified which is called with @data as argument

 * when the @object is disposed, or the data is being overwritten by

 * a call to gst_mini_object_set_qdata() with the same @quark.

 */

void

gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,

    gpointer data, GDestroyNotify destroy)

{

  gint i;

  gpointer old_data = NULL;

  GDestroyNotify old_notify = NULL;

  g_return_if_fail (object != NULL);

  g_return_if_fail (quark > 0);

  G_LOCK (qdata_mutex);

  if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {

    old_data = QDATA_DATA (object, i);

    old_notify = QDATA_DESTROY (object, i);

    if (data == NULL)

      remove_notify (object, i);

  }

  if (data != NULL)

    set_notify (object, i, quark, NULL, data, destroy);

  G_UNLOCK (qdata_mutex);

  if (old_notify)

    old_notify (old_data);

}

/**

 * gst_mini_object_get_qdata:

 * @object: The GstMiniObject to get a stored user data pointer from

 * @quark: A #GQuark, naming the user data pointer

 *

 * This function gets back user data pointers stored via

 * gst_mini_object_set_qdata().

 *

 * Returns: (transfer none) (nullable): The user data pointer set, or

 * %NULL

 */

gpointer

gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)

{

  guint i;

  gpointer result;

  g_return_val_if_fail (object != NULL, NULL);

  g_return_val_if_fail (quark > 0, NULL);

  G_LOCK (qdata_mutex);

  if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)

    result = QDATA_DATA (object, i);

  else

    result = NULL;

  G_UNLOCK (qdata_mutex);

  return result;

}

/**

 * gst_mini_object_steal_qdata:

 * @object: The GstMiniObject to get a stored user data pointer from

 * @quark: A #GQuark, naming the user data pointer

 *

 * This function gets back user data pointers stored via gst_mini_object_set_qdata()

 * and removes the data from @object without invoking its destroy() function (if

 * any was set).

 *

 * Returns: (transfer full) (nullable): The user data pointer set, or

 * %NULL

 */

gpointer

gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)

{

  guint i;

  gpointer result;

  g_return_val_if_fail (object != NULL, NULL);

  g_return_val_if_fail (quark > 0, NULL);

  G_LOCK (qdata_mutex);

  if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {

    result = QDATA_DATA (object, i);

    remove_notify (object, i);

  } else {

    result = NULL;

  }

  G_UNLOCK (qdata_mutex);

  return result;

}