/* GStreamer
* Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
* Copyright (C) 2011 Sebastian Dröge <sebastian.droege@collabora.co.uk>
*
* gstiterator.h: Base class for iterating datastructures.
*
* 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:gstiterator
* @title: GstIterator
* @short_description: Object to retrieve multiple elements in a threadsafe
* way.
* @see_also: #GstElement, #GstBin
*
* A GstIterator is used to retrieve multiple objects from another object in
* a threadsafe way.
*
* Various GStreamer objects provide access to their internal structures using
* an iterator.
*
* Note that if calling a GstIterator function results in your code receiving
* a refcounted object (with, say, g_value_get_object()), the refcount for that
* object will not be increased. Your code is responsible for taking a reference
* if it wants to continue using it later.
*
* The basic use pattern of an iterator is as follows:
* |[<!-- language="C" -->
* GstIterator *it = _get_iterator(object);
* GValue item = G_VALUE_INIT;
* done = FALSE;
* while (!done) {
* switch (gst_iterator_next (it, &item)) {
* case GST_ITERATOR_OK:
* ...get/use/change item here...
* g_value_reset (&item);
* break;
* case GST_ITERATOR_RESYNC:
* ...rollback changes to items...
* gst_iterator_resync (it);
* break;
* case GST_ITERATOR_ERROR:
* ...wrong parameters were given...
* done = TRUE;
* break;
* case GST_ITERATOR_DONE:
* done = TRUE;
* break;
* }
* }
* g_value_unset (&item);
* gst_iterator_free (it);
* ]|
*/
#include "gst_private.h"
#include <gst/gstiterator.h>
/**
* gst_iterator_copy:
* @it: a #GstIterator
*
* Copy the iterator and its state.
*
* Returns: a new copy of @it.
*/
GstIterator *
gst_iterator_copy (const GstIterator * it)
{
GstIterator *copy;
copy = g_slice_copy (it->size, it);
if (it->copy)
it->copy (it, copy);
return copy;
}
G_DEFINE_BOXED_TYPE (GstIterator, gst_iterator,
(GBoxedCopyFunc) gst_iterator_copy, (GBoxedFreeFunc) gst_iterator_free);
static void
gst_iterator_init (GstIterator * it,
guint size,
GType type,
GMutex * lock,
guint32 * master_cookie,
GstIteratorCopyFunction copy,
GstIteratorNextFunction next,
GstIteratorItemFunction item,
GstIteratorResyncFunction resync, GstIteratorFreeFunction free)
{
it->size = size;
it->type = type;
it->lock = lock;
it->master_cookie = master_cookie;
it->cookie = *master_cookie;
it->copy = copy;
it->next = next;
it->item = item;
it->resync = resync;
it->free = free;
it->pushed = NULL;
}
/**
* gst_iterator_new: (skip)
* @size: the size of the iterator structure
* @type: #GType of children
* @lock: pointer to a #GMutex.
* @master_cookie: pointer to a guint32 that is changed when the items in the
* iterator changed.
* @copy: copy function
* @next: function to get next item
* @item: function to call on each item retrieved
* @resync: function to resync the iterator
* @free: function to free the iterator
*
* Create a new iterator. This function is mainly used for objects
* implementing the next/resync/free function to iterate a data structure.
*
* For each item retrieved, the @item function is called with the lock
* held. The @free function is called when the iterator is freed.
*
* Returns: the new #GstIterator.
*
* MT safe.
*/
GstIterator *
gst_iterator_new (guint size,
GType type,
GMutex * lock,
guint32 * master_cookie,
GstIteratorCopyFunction copy,
GstIteratorNextFunction next,
GstIteratorItemFunction item,
GstIteratorResyncFunction resync, GstIteratorFreeFunction free)
{
GstIterator *result;
g_return_val_if_fail (size >= sizeof (GstIterator), NULL);
g_return_val_if_fail (g_type_qname (type) != 0, NULL);
g_return_val_if_fail (master_cookie != NULL, NULL);
g_return_val_if_fail (next != NULL, NULL);
g_return_val_if_fail (resync != NULL, NULL);
g_return_val_if_fail (free != NULL, NULL);
result = g_slice_alloc0 (size);
gst_iterator_init (result, size, type, lock, master_cookie, copy, next, item,
resync, free);
return result;
}
/*
* list iterator
*/
typedef struct _GstListIterator
{
GstIterator iterator;
GObject *owner;
GList **orig;
GList *list; /* pointer in list */
void (*set_value) (GValue * value, gpointer item);
} GstListIterator;
static void
gst_list_iterator_copy (const GstListIterator * it, GstListIterator * copy)
{
if (copy->owner)
g_object_ref (copy->owner);
}
static GstIteratorResult
gst_list_iterator_next (GstListIterator * it, GValue * elem)
{
gpointer data;
if (it->list == NULL)
return GST_ITERATOR_DONE;
data = it->list->data;
it->list = g_list_next (it->list);
it->set_value (elem, data);
return GST_ITERATOR_OK;
}
static void
gst_list_iterator_resync (GstListIterator * it)
{
it->list = *it->orig;
}
static void
gst_list_iterator_free (GstListIterator * it)
{
if (it->owner)
g_object_unref (it->owner);
}
/**
* gst_iterator_new_list: (skip)
* @type: #GType of elements
* @lock: pointer to a #GMutex protecting the list.
* @master_cookie: pointer to a guint32 that is incremented when the list
* is changed.
* @list: pointer to the list
* @owner: object owning the list
* @item: function to call on each item retrieved
*
* Create a new iterator designed for iterating @list.
*
* The list you iterate is usually part of a data structure @owner and is
* protected with @lock.
*
* The iterator will use @lock to retrieve the next item of the list and it
* will then call the @item function before releasing @lock again.
*
* When a concurrent update to the list is performed, usually by @owner while
* holding @lock, @master_cookie will be updated. The iterator implementation
* will notice the update of the cookie and will return %GST_ITERATOR_RESYNC to
* the user of the iterator in the next call to gst_iterator_next().
*
* Returns: the new #GstIterator for @list.
*
* MT safe.
*/
GstIterator *
gst_iterator_new_list (GType type,
GMutex * lock, guint32 * master_cookie, GList ** list, GObject * owner,
GstIteratorItemFunction item)
{
GstListIterator *result;
gpointer set_value;
if (g_type_is_a (type, G_TYPE_OBJECT)) {
set_value = g_value_set_object;
} else if (g_type_is_a (type, G_TYPE_BOXED)) {
set_value = g_value_set_boxed;
} else if (g_type_is_a (type, G_TYPE_POINTER)) {
set_value = g_value_set_pointer;
} else if (g_type_is_a (type, G_TYPE_STRING)) {
set_value = g_value_set_string;
} else {
g_critical ("List iterators can only be created for lists containing "
"instances of GObject, boxed types, pointer types and strings");
return NULL;
}
/* no need to lock, nothing can change here */
result = (GstListIterator *) gst_iterator_new (sizeof (GstListIterator),
type,
lock,
master_cookie,
(GstIteratorCopyFunction) gst_list_iterator_copy,
(GstIteratorNextFunction) gst_list_iterator_next,
(GstIteratorItemFunction) item,
(GstIteratorResyncFunction) gst_list_iterator_resync,
(GstIteratorFreeFunction) gst_list_iterator_free);
result->owner = owner ? g_object_ref (owner) : NULL;
result->orig = list;
result->list = *list;
result->set_value = set_value;
return GST_ITERATOR (result);
}
static void
gst_iterator_pop (GstIterator * it)
{
if (it->pushed) {
gst_iterator_free (it->pushed);
it->pushed = NULL;
}
}
/**
* gst_iterator_next:
* @it: The #GstIterator to iterate
* @elem: (out caller-allocates): pointer to hold next element
*
* Get the next item from the iterator in @elem.
*
* Only when this function returns %GST_ITERATOR_OK, @elem will contain a valid
* value. @elem must have been initialized to the type of the iterator or
* initialized to zeroes with g_value_unset(). The caller is responsible for
* unsetting or resetting @elem with g_value_unset() or g_value_reset()
* after usage.
*
* When this function returns %GST_ITERATOR_DONE, no more elements can be
* retrieved from @it.
*
* A return value of %GST_ITERATOR_RESYNC indicates that the element list was
* concurrently updated. The user of @it should call gst_iterator_resync() to
* get the newly updated list.
*
* A return value of %GST_ITERATOR_ERROR indicates an unrecoverable fatal error.
*
* Returns: The result of the iteration. Unset @elem after usage.
*
* MT safe.
*/
GstIteratorResult
gst_iterator_next (GstIterator * it, GValue * elem)
{
GstIteratorResult result;
g_return_val_if_fail (it != NULL, GST_ITERATOR_ERROR);
g_return_val_if_fail (elem != NULL, GST_ITERATOR_ERROR);
g_return_val_if_fail (G_VALUE_TYPE (elem) == G_TYPE_INVALID
|| G_VALUE_HOLDS (elem, it->type), GST_ITERATOR_ERROR);
if (G_VALUE_TYPE (elem) == G_TYPE_INVALID)
g_value_init (elem, it->type);
restart:
if (it->pushed) {
result = gst_iterator_next (it->pushed, elem);
if (result == GST_ITERATOR_DONE) {
/* we are done with this iterator, pop it and
* fallthrough iterating the main iterator again. */
gst_iterator_pop (it);
} else {
return result;
}
}
if (G_LIKELY (it->lock))
g_mutex_lock (it->lock);
if (G_UNLIKELY (*it->master_cookie != it->cookie)) {
result = GST_ITERATOR_RESYNC;
goto done;
}
result = it->next (it, elem);
if (result == GST_ITERATOR_OK && it->item) {
GstIteratorItem itemres;
itemres = it->item (it, elem);
switch (itemres) {
case GST_ITERATOR_ITEM_SKIP:
if (G_LIKELY (it->lock))
g_mutex_unlock (it->lock);
g_value_reset (elem);
goto restart;
case GST_ITERATOR_ITEM_END:
result = GST_ITERATOR_DONE;
g_value_reset (elem);
break;
case GST_ITERATOR_ITEM_PASS:
break;
}
}
done:
if (G_LIKELY (it->lock))
g_mutex_unlock (it->lock);
return result;
}
/**
* gst_iterator_resync:
* @it: The #GstIterator to resync
*
* Resync the iterator. this function is mostly called
* after gst_iterator_next() returned %GST_ITERATOR_RESYNC.
*
* When an iterator was pushed on @it, it will automatically be popped again
* with this function.
*
* MT safe.
*/
void
gst_iterator_resync (GstIterator * it)
{
g_return_if_fail (it != NULL);
gst_iterator_pop (it);
if (G_LIKELY (it->lock))
g_mutex_lock (it->lock);
it->resync (it);
it->cookie = *it->master_cookie;
if (G_LIKELY (it->lock))
g_mutex_unlock (it->lock);
}
/**
* gst_iterator_free:
* @it: The #GstIterator to free
*
* Free the iterator.
*
* MT safe.
*/
void
gst_iterator_free (GstIterator * it)
{
g_return_if_fail (it != NULL);
gst_iterator_pop (it);
it->free (it);
g_slice_free1 (it->size, it);
}
/**
* gst_iterator_push:
* @it: The #GstIterator to use
* @other: The #GstIterator to push
*
* Pushes @other iterator onto @it. All calls performed on @it are
* forwarded to @other. If @other returns %GST_ITERATOR_DONE, it is
* popped again and calls are handled by @it again.
*
* This function is mainly used by objects implementing the iterator
* next function to recurse into substructures.
*
* When gst_iterator_resync() is called on @it, @other will automatically be
* popped.
*
* MT safe.
*/
void
gst_iterator_push (GstIterator * it, GstIterator * other)
{
g_return_if_fail (it != NULL);
g_return_if_fail (other != NULL);
it->pushed = other;
}
typedef struct _GstIteratorFilter
{
GstIterator iterator;
GstIterator *slave;
GMutex *master_lock;
GCompareFunc func;
GValue user_data;
gboolean have_user_data;
} GstIteratorFilter;
static GstIteratorResult
filter_next (GstIteratorFilter * it, GValue * elem)
{
GstIteratorResult result = GST_ITERATOR_ERROR;
gboolean done = FALSE;
GValue item = { 0, };
while (G_LIKELY (!done)) {
result = gst_iterator_next (it->slave, &item);
switch (result) {
case GST_ITERATOR_OK:
if (G_LIKELY (it->master_lock))
g_mutex_unlock (it->master_lock);
if (it->func (&item, &it->user_data) == 0) {
g_value_copy (&item, elem);
done = TRUE;
}
g_value_reset (&item);
if (G_LIKELY (it->master_lock))
g_mutex_lock (it->master_lock);
break;
case GST_ITERATOR_RESYNC:
case GST_ITERATOR_DONE:
done = TRUE;
break;
default:
g_assert_not_reached ();
break;
}
}
g_value_unset (&item);
return result;
}
static void
filter_copy (const GstIteratorFilter * it, GstIteratorFilter * copy)
{
copy->slave = gst_iterator_copy (it->slave);
copy->master_lock = copy->slave->lock ? copy->slave->lock : it->master_lock;
copy->slave->lock = NULL;
if (it->have_user_data) {
memset (©->user_data, 0, sizeof (copy->user_data));
g_value_init (©->user_data, G_VALUE_TYPE (&it->user_data));
g_value_copy (&it->user_data, ©->user_data);
}
}
static void
filter_resync (GstIteratorFilter * it)
{
gst_iterator_resync (it->slave);
}
static void
filter_free (GstIteratorFilter * it)
{
if (it->have_user_data)
g_value_unset (&it->user_data);
gst_iterator_free (it->slave);
}
/**
* gst_iterator_filter:
* @it: The #GstIterator to filter
* @func: (scope call): the compare function to select elements
* @user_data: (closure): user data passed to the compare function
*
* Create a new iterator from an existing iterator. The new iterator
* will only return those elements that match the given compare function @func.
* The first parameter that is passed to @func is the #GValue of the current
* iterator element and the second parameter is @user_data. @func should
* return 0 for elements that should be included in the filtered iterator.
*
* When this iterator is freed, @it will also be freed.
*
* Returns: (transfer full): a new #GstIterator.
*
* MT safe.
*/
GstIterator *
gst_iterator_filter (GstIterator * it, GCompareFunc func,
const GValue * user_data)
{
GstIteratorFilter *result;
g_return_val_if_fail (it != NULL, NULL);
g_return_val_if_fail (func != NULL, NULL);
result = (GstIteratorFilter *) gst_iterator_new (sizeof (GstIteratorFilter),
it->type, it->lock, it->master_cookie,
(GstIteratorCopyFunction) filter_copy,
(GstIteratorNextFunction) filter_next,
(GstIteratorItemFunction) NULL,
(GstIteratorResyncFunction) filter_resync,
(GstIteratorFreeFunction) filter_free);
result->master_lock = it->lock;
it->lock = NULL;
result->func = func;
if (user_data) {
g_value_init (&result->user_data, G_VALUE_TYPE (user_data));
g_value_copy (user_data, &result->user_data);
result->have_user_data = TRUE;
} else {
result->have_user_data = FALSE;
}
result->slave = it;
return GST_ITERATOR (result);
}
/**
* gst_iterator_fold:
* @it: The #GstIterator to fold over
* @func: (scope call): the fold function
* @ret: the seed value passed to the fold function
* @user_data: (closure): user data passed to the fold function
*
* Folds @func over the elements of @iter. That is to say, @func will be called
* as @func (object, @ret, @user_data) for each object in @it. The normal use
* of this procedure is to accumulate the results of operating on the objects in
* @ret.
*
* This procedure can be used (and is used internally) to implement the
* gst_iterator_foreach() and gst_iterator_find_custom() operations.
*
* The fold will proceed as long as @func returns %TRUE. When the iterator has no
* more arguments, %GST_ITERATOR_DONE will be returned. If @func returns %FALSE,
* the fold will stop, and %GST_ITERATOR_OK will be returned. Errors or resyncs
* will cause fold to return %GST_ITERATOR_ERROR or %GST_ITERATOR_RESYNC as
* appropriate.
*
* The iterator will not be freed.
*
* Returns: A #GstIteratorResult, as described above.
*
* MT safe.
*/
GstIteratorResult
gst_iterator_fold (GstIterator * it, GstIteratorFoldFunction func,
GValue * ret, gpointer user_data)
{
GValue item = { 0, };
GstIteratorResult result;
g_return_val_if_fail (it != NULL, GST_ITERATOR_ERROR);
while (1) {
result = gst_iterator_next (it, &item);
switch (result) {
case GST_ITERATOR_OK:
if (!func (&item, ret, user_data))
goto fold_done;
g_value_reset (&item);
break;
case GST_ITERATOR_RESYNC:
case GST_ITERATOR_ERROR:
goto fold_done;
case GST_ITERATOR_DONE:
goto fold_done;
}
}
fold_done:
#if GLIB_CHECK_VERSION (2, 48, 0)
g_value_unset (&item);
#else
if (item.g_type != 0)
g_value_unset (&item);
#endif
return result;
}
typedef struct
{
GstIteratorForeachFunction func;
gpointer user_data;
} ForeachFoldData;
static gboolean
foreach_fold_func (const GValue * item, GValue * unused, ForeachFoldData * data)
{
data->func (item, data->user_data);
return TRUE;
}
/**
* gst_iterator_foreach:
* @it: The #GstIterator to iterate
* @func: (scope call): the function to call for each element.
* @user_data: (closure): user data passed to the function
*
* Iterate over all element of @it and call the given function @func for
* each element.
*
* Returns: the result call to gst_iterator_fold(). The iterator will not be
* freed.
*
* MT safe.
*/
GstIteratorResult
gst_iterator_foreach (GstIterator * it, GstIteratorForeachFunction func,
gpointer user_data)
{
ForeachFoldData data;
data.func = func;
data.user_data = user_data;
return gst_iterator_fold (it, (GstIteratorFoldFunction) foreach_fold_func,
NULL, &data);
}
typedef struct
{
GCompareFunc func;
gpointer user_data;
gboolean found;
} FindCustomFoldData;
static gboolean
find_custom_fold_func (const GValue * item, GValue * ret,
FindCustomFoldData * data)
{
if (data->func (item, data->user_data) == 0) {
data->found = TRUE;
g_value_copy (item, ret);
return FALSE;
} else {
return TRUE;
}
}
/**
* gst_iterator_find_custom:
* @it: The #GstIterator to iterate
* @func: (scope call): the compare function to use
* @elem: (out): pointer to a #GValue where to store the result
* @user_data: (closure): user data passed to the compare function
*
* Find the first element in @it that matches the compare function @func.
* @func should return 0 when the element is found. The first parameter
* to @func will be the current element of the iterator and the
* second parameter will be @user_data.
* The result will be stored in @elem if a result is found.
*
* The iterator will not be freed.
*
* This function will return %FALSE if an error happened to the iterator
* or if the element wasn't found.
*
* Returns: Returns %TRUE if the element was found, else %FALSE.
*
* MT safe.
*/
gboolean
gst_iterator_find_custom (GstIterator * it, GCompareFunc func,
GValue * elem, gpointer user_data)
{
GstIteratorResult res;
FindCustomFoldData data;
g_return_val_if_fail (G_VALUE_TYPE (elem) == G_TYPE_INVALID
|| G_VALUE_HOLDS (elem, it->type), GST_ITERATOR_ERROR);
if (G_VALUE_TYPE (elem) == G_TYPE_INVALID)
g_value_init (elem, it->type);
data.func = func;
data.user_data = user_data;
data.found = FALSE;
do {
res =
gst_iterator_fold (it, (GstIteratorFoldFunction) find_custom_fold_func,
elem, &data);
if (res == GST_ITERATOR_RESYNC)
gst_iterator_resync (it);
} while (res == GST_ITERATOR_RESYNC);
if (!data.found)
g_value_unset (elem);
return data.found;
}
typedef struct
{
GstIterator parent;
GValue object;
gboolean visited;
gboolean empty;
} GstSingleObjectIterator;
static guint32 _single_object_dummy_cookie = 0;
static void
gst_single_object_iterator_copy (const GstSingleObjectIterator * it,
GstSingleObjectIterator * copy)
{
if (!it->empty) {
memset (©->object, 0, sizeof (copy->object));
g_value_init (©->object, it->parent.type);
g_value_copy (&it->object, ©->object);
}
}
static GstIteratorResult
gst_single_object_iterator_next (GstSingleObjectIterator * it, GValue * result)
{
if (it->visited || it->empty)
return GST_ITERATOR_DONE;
g_value_copy (&it->object, result);
it->visited = TRUE;
return GST_ITERATOR_OK;
}
static void
gst_single_object_iterator_resync (GstSingleObjectIterator * it)
{
it->visited = FALSE;
}
static void
gst_single_object_iterator_free (GstSingleObjectIterator * it)
{
if (!it->empty)
g_value_unset (&it->object);
}
/**
* gst_iterator_new_single:
* @type: #GType of the passed object
* @object: object that this iterator should return
*
* This #GstIterator is a convenient iterator for the common
* case where a #GstIterator needs to be returned but only
* a single object has to be considered. This happens often
* for the #GstPadIterIntLinkFunction.
*
* Returns: the new #GstIterator for @object.
*/
GstIterator *
gst_iterator_new_single (GType type, const GValue * object)
{
GstSingleObjectIterator *result;
result = (GstSingleObjectIterator *)
gst_iterator_new (sizeof (GstSingleObjectIterator),
type, NULL, &_single_object_dummy_cookie,
(GstIteratorCopyFunction) gst_single_object_iterator_copy,
(GstIteratorNextFunction) gst_single_object_iterator_next,
(GstIteratorItemFunction) NULL,
(GstIteratorResyncFunction) gst_single_object_iterator_resync,
(GstIteratorFreeFunction) gst_single_object_iterator_free);
if (object) {
g_value_init (&result->object, type);
g_value_copy (object, &result->object);
result->empty = FALSE;
} else {
result->empty = TRUE;
}
result->visited = FALSE;
return GST_ITERATOR (result);
}