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739 lines
19 KiB
C
739 lines
19 KiB
C
/* GStreamer
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* Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
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*
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* gstiterator.h: Base class for iterating datastructures.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:gstiterator
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* @short_description: Object to retrieve multiple elements in a threadsafe
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* way.
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* @see_also: #GstElement, #GstBin
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*
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* A GstIterator is used to retrieve multiple objects from another object in
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* a threadsafe way.
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*
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* Various GStreamer objects provide access to their internal structures using
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* an iterator.
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*
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* In general, whenever calling a GstIterator function results in your code
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* receiving a refcounted object, the refcount for that object will have been
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* increased. Your code is responsible for unrefing that object after use.
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*
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* The basic use pattern of an iterator is as follows:
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*
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* <example>
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* <title>Using an iterator</title>
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* <programlisting>
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* it = _get_iterator(object);
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* done = FALSE;
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* while (!done) {
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* switch (gst_iterator_next (it, &item)) {
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* case GST_ITERATOR_OK:
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* ... use/change item here...
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* gst_object_unref (item);
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* break;
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* case GST_ITERATOR_RESYNC:
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* ...rollback changes to items...
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* gst_iterator_resync (it);
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* break;
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* case GST_ITERATOR_ERROR:
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* ...wrong parameters were given...
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* done = TRUE;
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* break;
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* case GST_ITERATOR_DONE:
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* done = TRUE;
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* break;
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* }
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* }
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* gst_iterator_free (it);
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* </programlisting>
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* </example>
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*
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* Last reviewed on 2009-06-16 (0.10.24)
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*/
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#include "gst_private.h"
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#include <gst/gstiterator.h>
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static void
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gst_iterator_init (GstIterator * it,
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GType type,
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GMutex * lock,
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guint32 * master_cookie,
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GstIteratorNextFunction next,
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GstIteratorItemFunction item,
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GstIteratorResyncFunction resync, GstIteratorFreeFunction free)
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{
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it->type = type;
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it->lock = lock;
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it->master_cookie = master_cookie;
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it->cookie = *master_cookie;
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it->next = next;
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it->item = item;
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it->resync = resync;
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it->free = free;
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it->pushed = NULL;
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}
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/**
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* gst_iterator_new:
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* @size: the size of the iterator structure
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* @type: #GType of children
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* @lock: pointer to a #GMutex.
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* @master_cookie: pointer to a guint32 that is changed when the items in the
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* iterator changed.
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* @next: function to get next item
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* @item: function to call on each item retrieved
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* @resync: function to resync the iterator
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* @free: function to free the iterator
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*
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* Create a new iterator. This function is mainly used for objects
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* implementing the next/resync/free function to iterate a data structure.
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*
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* For each item retrieved, the @item function is called with the lock
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* held. The @free function is called when the iterator is freed.
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*
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* Returns: the new #GstIterator.
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*
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* MT safe.
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*/
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GstIterator *
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gst_iterator_new (guint size,
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GType type,
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GMutex * lock,
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guint32 * master_cookie,
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GstIteratorNextFunction next,
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GstIteratorItemFunction item,
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GstIteratorResyncFunction resync, GstIteratorFreeFunction free)
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{
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GstIterator *result;
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g_return_val_if_fail (size >= sizeof (GstIterator), NULL);
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g_return_val_if_fail (g_type_qname (type) != 0, NULL);
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g_return_val_if_fail (master_cookie != NULL, NULL);
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g_return_val_if_fail (next != NULL, NULL);
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g_return_val_if_fail (resync != NULL, NULL);
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g_return_val_if_fail (free != NULL, NULL);
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result = g_malloc (size);
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gst_iterator_init (result, type, lock, master_cookie, next, item, resync,
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free);
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return result;
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}
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/*
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* list iterator
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*/
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typedef struct _GstListIterator
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{
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GstIterator iterator;
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gpointer owner;
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GList **orig;
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GList *list; /* pointer in list */
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GstIteratorDisposeFunction freefunc;
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} GstListIterator;
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static GstIteratorResult
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gst_list_iterator_next (GstListIterator * it, gpointer * elem)
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{
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if (it->list == NULL)
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return GST_ITERATOR_DONE;
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*elem = it->list->data;
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it->list = g_list_next (it->list);
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return GST_ITERATOR_OK;
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}
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static void
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gst_list_iterator_resync (GstListIterator * it)
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{
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it->list = *it->orig;
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}
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static void
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gst_list_iterator_free (GstListIterator * it)
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{
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if (it->freefunc) {
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it->freefunc (it->owner);
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}
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g_free (it);
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}
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/**
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* gst_iterator_new_list:
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* @type: #GType of elements
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* @lock: pointer to a #GMutex protecting the list.
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* @master_cookie: pointer to a guint32 that is incremented when the list
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* is changed.
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* @list: pointer to the list
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* @owner: object owning the list
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* @item: function to call for each item
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* @free: function to call when the iterator is freed
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*
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* Create a new iterator designed for iterating @list.
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*
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* The list you iterate is usually part of a data structure @owner and is
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* protected with @lock.
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*
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* The iterator will use @lock to retrieve the next item of the list and it
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* will then call the @item function before releasing @lock again.
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*
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* The @item function usualy makes sure that the item remains alive while
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* @lock is released and the application is using the item. The application is
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* responsible for freeing/unreffing the item after usage as explained in
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* gst_iterator_next().
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*
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* When a concurrent update to the list is performed, usually by @owner while
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* holding @lock, @master_cookie will be updated. The iterator implementation
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* will notice the update of the cookie and will return %GST_ITERATOR_RESYNC to
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* the user of the iterator in the next call to gst_iterator_next().
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*
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* @owner will be passed to the @free function when the iterator is freed.
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*
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* Returns: the new #GstIterator for @list.
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*
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* MT safe.
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*/
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GstIterator *
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gst_iterator_new_list (GType type,
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GMutex * lock,
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guint32 * master_cookie,
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GList ** list,
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gpointer owner,
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GstIteratorItemFunction item, GstIteratorDisposeFunction free)
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{
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GstListIterator *result;
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/* no need to lock, nothing can change here */
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result = (GstListIterator *) gst_iterator_new (sizeof (GstListIterator),
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type,
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lock,
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master_cookie,
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(GstIteratorNextFunction) gst_list_iterator_next,
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(GstIteratorItemFunction) item,
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(GstIteratorResyncFunction) gst_list_iterator_resync,
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(GstIteratorFreeFunction) gst_list_iterator_free);
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result->owner = owner;
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result->orig = list;
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result->list = *list;
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result->freefunc = free;
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return GST_ITERATOR (result);
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}
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static void
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gst_iterator_pop (GstIterator * it)
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{
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if (it->pushed) {
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gst_iterator_free (it->pushed);
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it->pushed = NULL;
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}
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}
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/**
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* gst_iterator_next:
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* @it: The #GstIterator to iterate
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* @elem: pointer to hold next element
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*
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* Get the next item from the iterator in @elem.
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*
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* Only when this function returns %GST_ITERATOR_OK, @elem will contain a valid
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* value. For iterators that return refcounted objects, the returned object
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* will have its refcount increased and should therefore be unreffed after
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* usage.
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*
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* When this function returns %GST_ITERATOR_DONE, no more elements can be
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* retrieved from @it.
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*
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* A return value of %GST_ITERATOR_RESYNC indicates that the element list was
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* concurrently updated. The user of @it should call gst_iterator_resync() to
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* get the newly updated list.
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*
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* A return value of %GST_ITERATOR_ERROR indicates an unrecoverable fatal error.
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*
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* Returns: The result of the iteration. Unref @elem after usage if this
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* is a refcounted object.
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*
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* MT safe.
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*/
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GstIteratorResult
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gst_iterator_next (GstIterator * it, gpointer * elem)
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{
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GstIteratorResult result;
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g_return_val_if_fail (it != NULL, GST_ITERATOR_ERROR);
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g_return_val_if_fail (elem != NULL, GST_ITERATOR_ERROR);
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restart:
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if (it->pushed) {
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result = gst_iterator_next (it->pushed, elem);
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if (result == GST_ITERATOR_DONE) {
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/* we are done with this iterator, pop it and
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* fallthrough iterating the main iterator again. */
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gst_iterator_pop (it);
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} else {
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return result;
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}
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}
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if (G_LIKELY (it->lock))
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g_mutex_lock (it->lock);
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if (G_UNLIKELY (*it->master_cookie != it->cookie)) {
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result = GST_ITERATOR_RESYNC;
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goto done;
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}
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result = it->next (it, elem);
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if (result == GST_ITERATOR_OK && it->item) {
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GstIteratorItem itemres;
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itemres = it->item (it, *elem);
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switch (itemres) {
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case GST_ITERATOR_ITEM_SKIP:
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if (G_LIKELY (it->lock))
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g_mutex_unlock (it->lock);
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goto restart;
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case GST_ITERATOR_ITEM_END:
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result = GST_ITERATOR_DONE;
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break;
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case GST_ITERATOR_ITEM_PASS:
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break;
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}
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}
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done:
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if (G_LIKELY (it->lock))
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g_mutex_unlock (it->lock);
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return result;
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}
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/**
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* gst_iterator_resync:
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* @it: The #GstIterator to resync
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*
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* Resync the iterator. this function is mostly called
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* after gst_iterator_next() returned %GST_ITERATOR_RESYNC.
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*
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* When an iterator was pushed on @it, it will automatically be popped again
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* with this function.
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*
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* MT safe.
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*/
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void
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gst_iterator_resync (GstIterator * it)
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{
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g_return_if_fail (it != NULL);
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gst_iterator_pop (it);
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if (G_LIKELY (it->lock))
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g_mutex_lock (it->lock);
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it->resync (it);
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it->cookie = *it->master_cookie;
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if (G_LIKELY (it->lock))
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g_mutex_unlock (it->lock);
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}
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/**
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* gst_iterator_free:
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* @it: The #GstIterator to free
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*
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* Free the iterator.
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*
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* MT safe.
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*/
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void
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gst_iterator_free (GstIterator * it)
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{
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g_return_if_fail (it != NULL);
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gst_iterator_pop (it);
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it->free (it);
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}
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/**
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* gst_iterator_push:
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* @it: The #GstIterator to use
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* @other: The #GstIterator to push
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*
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* Pushes @other iterator onto @it. All calls performed on @it are
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* forwarded to @other. If @other returns %GST_ITERATOR_DONE, it is
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* popped again and calls are handled by @it again.
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*
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* This function is mainly used by objects implementing the iterator
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* next function to recurse into substructures.
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*
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* When gst_iterator_resync() is called on @it, @other will automatically be
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* popped.
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*
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* MT safe.
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*/
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void
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gst_iterator_push (GstIterator * it, GstIterator * other)
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{
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g_return_if_fail (it != NULL);
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g_return_if_fail (other != NULL);
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it->pushed = other;
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}
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typedef struct _GstIteratorFilter
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{
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GstIterator iterator;
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GstIterator *slave;
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GCompareFunc func;
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gpointer user_data;
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} GstIteratorFilter;
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static GstIteratorResult
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filter_next (GstIteratorFilter * it, gpointer * elem)
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{
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GstIteratorResult result = GST_ITERATOR_ERROR;
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gboolean done = FALSE;
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*elem = NULL;
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while (G_LIKELY (!done)) {
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gpointer item;
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result = gst_iterator_next (it->slave, &item);
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switch (result) {
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case GST_ITERATOR_OK:
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if (G_LIKELY (GST_ITERATOR (it)->lock))
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g_mutex_unlock (GST_ITERATOR (it)->lock);
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if (it->func (item, it->user_data) == 0) {
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*elem = item;
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done = TRUE;
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}
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if (G_LIKELY (GST_ITERATOR (it)->lock))
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g_mutex_lock (GST_ITERATOR (it)->lock);
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break;
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case GST_ITERATOR_RESYNC:
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case GST_ITERATOR_DONE:
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done = TRUE;
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break;
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default:
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g_assert_not_reached ();
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break;
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}
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}
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return result;
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}
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static void
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filter_resync (GstIteratorFilter * it)
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{
|
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gst_iterator_resync (it->slave);
|
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}
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static void
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filter_uninit (GstIteratorFilter * it)
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{
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it->slave->lock = GST_ITERATOR (it)->lock;
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}
|
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|
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static void
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filter_free (GstIteratorFilter * it)
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{
|
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filter_uninit (it);
|
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gst_iterator_free (it->slave);
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g_free (it);
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}
|
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|
|
/**
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* gst_iterator_filter:
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* @it: The #GstIterator to filter
|
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* @func: the compare function to select elements
|
|
* @user_data: user data passed to the compare function
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|
*
|
|
* Create a new iterator from an existing iterator. The new iterator
|
|
* will only return those elements that match the given compare function @func.
|
|
* @func should return 0 for elements that should be included
|
|
* in the iterator.
|
|
*
|
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* When this iterator is freed, @it will also be freed.
|
|
*
|
|
* Returns: a new #GstIterator.
|
|
*
|
|
* MT safe.
|
|
*/
|
|
GstIterator *
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gst_iterator_filter (GstIterator * it, GCompareFunc func, gpointer user_data)
|
|
{
|
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GstIteratorFilter *result;
|
|
|
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g_return_val_if_fail (it != NULL, NULL);
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g_return_val_if_fail (func != NULL, NULL);
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|
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result = (GstIteratorFilter *) gst_iterator_new (sizeof (GstIteratorFilter),
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it->type, it->lock, it->master_cookie,
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(GstIteratorNextFunction) filter_next,
|
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(GstIteratorItemFunction) NULL,
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(GstIteratorResyncFunction) filter_resync,
|
|
(GstIteratorFreeFunction) filter_free);
|
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it->lock = NULL;
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result->func = func;
|
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result->user_data = user_data;
|
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result->slave = it;
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|
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return GST_ITERATOR (result);
|
|
}
|
|
|
|
/**
|
|
* gst_iterator_fold:
|
|
* @it: The #GstIterator to fold over
|
|
* @func: the fold function
|
|
* @ret: the seed value passed to the fold function
|
|
* @user_data: 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. If object is a refcounted object its refcount will be increased
|
|
* before @func is called, and it should be unrefed after use in @func.
|
|
*
|
|
* 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)
|
|
{
|
|
gpointer item;
|
|
GstIteratorResult result;
|
|
|
|
while (1) {
|
|
result = gst_iterator_next (it, &item);
|
|
switch (result) {
|
|
case GST_ITERATOR_OK:
|
|
/* FIXME: is there a way to ref/unref items? */
|
|
if (!func (item, ret, user_data))
|
|
goto fold_done;
|
|
else
|
|
break;
|
|
case GST_ITERATOR_RESYNC:
|
|
case GST_ITERATOR_ERROR:
|
|
goto fold_done;
|
|
case GST_ITERATOR_DONE:
|
|
goto fold_done;
|
|
}
|
|
}
|
|
|
|
fold_done:
|
|
return result;
|
|
}
|
|
|
|
typedef struct
|
|
{
|
|
GFunc func;
|
|
gpointer user_data;
|
|
} ForeachFoldData;
|
|
|
|
static gboolean
|
|
foreach_fold_func (gpointer item, GValue * unused, ForeachFoldData * data)
|
|
{
|
|
data->func (item, data->user_data);
|
|
return TRUE;
|
|
}
|
|
|
|
/**
|
|
* gst_iterator_foreach:
|
|
* @it: The #GstIterator to iterate
|
|
* @func: the function to call for each element.
|
|
* @user_data: user data passed to the function
|
|
*
|
|
* Iterate over all element of @it and call the given function @func for
|
|
* each element. As in gst_iterator_fold(), the refcount of a refcounted
|
|
* object will be increased before @func is called, and should be unrefed
|
|
* after use.
|
|
*
|
|
* Returns: the result call to gst_iterator_fold(). The iterator will not be
|
|
* freed.
|
|
*
|
|
* MT safe.
|
|
*/
|
|
GstIteratorResult
|
|
gst_iterator_foreach (GstIterator * it, GFunc 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;
|
|
} FindCustomFoldData;
|
|
|
|
static gboolean
|
|
find_custom_fold_func (gpointer item, GValue * ret, FindCustomFoldData * data)
|
|
{
|
|
if (data->func (item, data->user_data) == 0) {
|
|
g_value_set_pointer (ret, item);
|
|
return FALSE;
|
|
} else {
|
|
return TRUE;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* gst_iterator_find_custom:
|
|
* @it: The #GstIterator to iterate
|
|
* @func: the compare function to use
|
|
* @user_data: 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. As in gst_iterator_fold(),
|
|
* the refcount of a refcounted object will be increased before @func is
|
|
* called, and should be unrefed after use.
|
|
*
|
|
* The iterator will not be freed.
|
|
*
|
|
* This function will return NULL if an error or resync happened to
|
|
* the iterator.
|
|
*
|
|
* Returns: The element in the iterator that matches the compare
|
|
* function or NULL when no element matched.
|
|
*
|
|
* MT safe.
|
|
*/
|
|
gpointer
|
|
gst_iterator_find_custom (GstIterator * it, GCompareFunc func,
|
|
gpointer user_data)
|
|
{
|
|
GValue ret = { 0, };
|
|
GstIteratorResult res;
|
|
FindCustomFoldData data;
|
|
|
|
g_value_init (&ret, G_TYPE_POINTER);
|
|
data.func = func;
|
|
data.user_data = user_data;
|
|
|
|
/* FIXME, we totally ignore RESYNC and return NULL so that the
|
|
* app does not know if the element was not found or a resync happened */
|
|
res =
|
|
gst_iterator_fold (it, (GstIteratorFoldFunction) find_custom_fold_func,
|
|
&ret, &data);
|
|
|
|
/* no need to unset, it's just a pointer */
|
|
return g_value_get_pointer (&ret);
|
|
}
|
|
|
|
typedef struct
|
|
{
|
|
GstIterator parent;
|
|
gpointer object;
|
|
GstCopyFunction copy;
|
|
GFreeFunc free;
|
|
gboolean visited;
|
|
} GstSingleObjectIterator;
|
|
|
|
static guint32 _single_object_dummy_cookie = 0;
|
|
|
|
static GstIteratorResult
|
|
gst_single_object_iterator_iterator_next (GstSingleObjectIterator * it,
|
|
gpointer * result)
|
|
{
|
|
if (it->visited || !it->object) {
|
|
*result = NULL;
|
|
return GST_ITERATOR_DONE;
|
|
}
|
|
|
|
*result = it->copy (it->object);
|
|
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->object)
|
|
it->free (it->object);
|
|
g_free (it);
|
|
}
|
|
|
|
/**
|
|
* gst_iterator_new_single:
|
|
* @type: #GType of the passed object
|
|
* @object: object that this iterator should return
|
|
* @copy: Function that returns a copy of @object or increases its refcount
|
|
* @free: Function to be called for freeing @object
|
|
*
|
|
* This #GstIterator is a convenient iterator for the common
|
|
* case where a #GstIterator needs to be returned but only
|
|
* a single object has the be considered. This happens often
|
|
* for the #GstPadIterIntLinkFunction.
|
|
*
|
|
* Returns: the new #GstIterator for @object.
|
|
*
|
|
* Since: 0.10.25
|
|
*/
|
|
GstIterator *
|
|
gst_iterator_new_single (GType type, gpointer object, GstCopyFunction copy,
|
|
GFreeFunc free)
|
|
{
|
|
GstSingleObjectIterator *result;
|
|
|
|
g_return_val_if_fail (copy != NULL, NULL);
|
|
g_return_val_if_fail (free != NULL, NULL);
|
|
|
|
result = (GstSingleObjectIterator *)
|
|
gst_iterator_new (sizeof (GstSingleObjectIterator),
|
|
type, NULL, &_single_object_dummy_cookie,
|
|
(GstIteratorNextFunction) gst_single_object_iterator_iterator_next, NULL,
|
|
(GstIteratorResyncFunction) gst_single_object_iterator_resync,
|
|
(GstIteratorFreeFunction) gst_single_object_iterator_free);
|
|
|
|
result->object = (object) ? copy (object) : NULL;
|
|
result->copy = copy;
|
|
result->free = free;
|
|
result->visited = FALSE;
|
|
|
|
return (GstIterator *) result;
|
|
}
|