New element 'proxy' to send data to in-process pipelines

This plugin is useful when you want to pipe arbitrary data to
a different pipeline within the same process. Buffers, events, and caps
are transmitted as-is without copying or manipulation.

11 files changed, 901 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 9a401e801..a446c4729 100644
--- a/configure.ac
+++ b/configure.ac
@@ -484,6 +484,7 @@ AG_GST_CHECK_PLUGIN(netsim)
 AG_GST_CHECK_PLUGIN(onvif)
 AG_GST_CHECK_PLUGIN(pcapparse)
 AG_GST_CHECK_PLUGIN(pnm)
+AG_GST_CHECK_PLUGIN(proxy)
 AG_GST_CHECK_PLUGIN(rawparse)
 AG_GST_CHECK_PLUGIN(removesilence)
 AG_GST_CHECK_PLUGIN(sdp)
@@ -3659,6 +3660,7 @@ gst/netsim/Makefile
 gst/onvif/Makefile
 gst/pcapparse/Makefile
 gst/pnm/Makefile
+gst/proxy/Makefile
 gst/rawparse/Makefile
 gst/removesilence/Makefile
 gst/sdp/Makefile
diff --git a/gst/meson.build b/gst/meson.build
index 1017adf30..b56b68d26 100644
--- a/gst/meson.build
+++ b/gst/meson.build
@@ -42,6 +42,7 @@ subdir('netsim')
 subdir('onvif')
 subdir('pcapparse')
 subdir('pnm')
+subdir('proxy')
 subdir('rawparse')
 subdir('removesilence')
 subdir('sdp')
diff --git a/gst/proxy/Makefile.am b/gst/proxy/Makefile.am
new file mode 100644
index 000000000..6231ca3ba
--- /dev/null
+++ b/gst/proxy/Makefile.am
@@ -0,0 +1,9 @@
+plugin_LTLIBRARIES = libgstproxy.la
+
+libgstproxy_la_SOURCES = gstproxy.c gstproxysink.c gstproxysrc.c
+
+libgstproxy_la_CFLAGS = $(GST_PLUGINS_BASE_CFLAGS) $(GST_CFLAGS)
+libgstproxy_la_LIBADD = $(GST_PLUGINS_BASE_LIBS) $(GST_BASE_LIBS) $(GST_LIBS)
+libgstproxy_la_LDFLAGS = $(GST_PLUGIN_LDFLAGS)
+
+noinst_HEADERS = gstproxysink.h gstproxysink-priv.h gstproxysrc.h gstproxysrc-priv.h
diff --git a/gst/proxy/gstproxy.c b/gst/proxy/gstproxy.c
new file mode 100644
index 000000000..03e188891
--- /dev/null
+++ b/gst/proxy/gstproxy.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *   Author: Sebastian Dröge <sebastian@centricular.com>
+ *   Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * 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 Street, Suite 500,
+ * Boston, MA 02110-1335, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstproxysrc.h"
+#include "gstproxysink.h"
+
+static gboolean
+plugin_init (GstPlugin * plugin)
+{
+  gst_element_register (plugin, "proxysrc", GST_RANK_NONE, GST_TYPE_PROXY_SRC);
+  gst_element_register (plugin, "proxysink", GST_RANK_NONE,
+      GST_TYPE_PROXY_SINK);
+
+  return TRUE;
+}
+
+GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
+    GST_VERSION_MINOR,
+    proxy,
+    "plugin for proxied inter-pipeline communication",
+    plugin_init, VERSION, "LGPL", "gstproxy", "http://centricular.com")
diff --git a/gst/proxy/gstproxysink-priv.h b/gst/proxy/gstproxysink-priv.h
new file mode 100644
index 000000000..bd204b2f9
--- /dev/null
+++ b/gst/proxy/gstproxysink-priv.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *     Author: Sebastian Dröge <sebastian@centricular.com>
+ *     Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#ifndef __GST_PROXY_SINK_PRIV_H__
+#define __GST_PROXY_SINK_PRIV_H__
+
+#include "gstproxysrc.h"
+
+G_BEGIN_DECLS
+
+void gst_proxy_sink_set_proxysrc (GstProxySink *sink, GstProxySrc *src);
+
+GstPad* gst_proxy_sink_get_internal_sinkpad (GstProxySink *sink);
+
+G_END_DECLS
+
+#endif /* __GST_PROXY_SINK_PRIV_H__ */
diff --git a/gst/proxy/gstproxysink.c b/gst/proxy/gstproxysink.c
new file mode 100644
index 000000000..fab2fcf2e
--- /dev/null
+++ b/gst/proxy/gstproxysink.c
@@ -0,0 +1,305 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *   Author: Sebastian Dröge <sebastian@centricular.com>
+ *   Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+/**
+ * SECTION:element-proxysink
+ *
+ * Proxysink is a sink element that proxies events, queries, and buffers to
+ * another pipeline that contains a matching proxysrc element. The purpose is
+ * to allow two decoupled pipelines to function as though they are one without
+ * having to manually shuttle buffers, events, queries, etc between the two.
+ *
+ * This element also copies sticky events onto the matching proxysrc element.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include "gstproxysink.h"
+#include "gstproxysink-priv.h"
+#include "gstproxysrc.h"
+#include "gstproxysrc-priv.h"
+
+#define GST_CAT_DEFAULT gst_proxy_sink_debug
+GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
+
+static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS_ANY);
+
+struct _GstProxySinkPrivate
+{
+  GstPad *sinkpad;
+  /* The proxysrc that we push events, buffers, queries to */
+  GWeakRef proxysrc;
+  /* Whether there are sticky events pending */
+  gboolean pending_sticky_events;
+};
+
+/* We're not subclassing from basesink because we don't want any of the special
+ * handling it has for events/queries/etc. We just pass-through everything. */
+
+/* Unlink proxysrc, we don't contain any elements so our parent is GstElement */
+#define parent_class gst_proxy_sink_parent_class
+G_DEFINE_TYPE (GstProxySink, gst_proxy_sink, GST_TYPE_ELEMENT);
+
+static gboolean gst_proxy_sink_sink_query (GstPad * pad, GstObject * parent,
+    GstQuery * query);
+static GstFlowReturn gst_proxy_sink_sink_chain (GstPad * pad,
+    GstObject * parent, GstBuffer * buffer);
+static GstFlowReturn gst_proxy_sink_sink_chain_list (GstPad * pad,
+    GstObject * parent, GstBufferList * list);
+static gboolean gst_proxy_sink_sink_event (GstPad * pad, GstObject * parent,
+    GstEvent * event);
+
+static GstStateChangeReturn gst_proxy_sink_change_state (GstElement * element,
+    GstStateChange transition);
+
+static void
+gst_proxy_sink_class_init (GstProxySinkClass * klass)
+{
+  GstElementClass *gstelement_class = (GstElementClass *) klass;
+
+  GST_DEBUG_CATEGORY_INIT (gst_proxy_sink_debug, "proxysink", 0, "proxy sink");
+
+  g_type_class_add_private (klass, sizeof (GstProxySinkPrivate));
+
+  gstelement_class->change_state = gst_proxy_sink_change_state;
+
+  gst_element_class_add_pad_template (gstelement_class,
+      gst_static_pad_template_get (&sink_template));
+
+  gst_element_class_set_static_metadata (gstelement_class, "Proxy Sink",
+      "Sink", "Proxy source for internal process communication",
+      "Sebastian Dröge <sebastian@centricular.com>");
+}
+
+static void
+gst_proxy_sink_init (GstProxySink * self)
+{
+  self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, GST_TYPE_PROXY_SINK,
+      GstProxySinkPrivate);
+  self->priv->sinkpad =
+      gst_pad_new_from_static_template (&sink_template, "sink");
+  gst_pad_set_chain_function (self->priv->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_proxy_sink_sink_chain));
+  gst_pad_set_chain_list_function (self->priv->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_proxy_sink_sink_chain_list));
+  gst_pad_set_event_function (self->priv->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_proxy_sink_sink_event));
+  gst_pad_set_query_function (self->priv->sinkpad,
+      GST_DEBUG_FUNCPTR (gst_proxy_sink_sink_query));
+  gst_element_add_pad (GST_ELEMENT (self), self->priv->sinkpad);
+}
+
+static GstStateChangeReturn
+gst_proxy_sink_change_state (GstElement * element, GstStateChange transition)
+{
+  GstElementClass *gstelement_class =
+      GST_ELEMENT_CLASS (gst_proxy_sink_parent_class);
+  GstProxySink *self = GST_PROXY_SINK (element);
+  GstStateChangeReturn ret;
+
+  switch (transition) {
+    case GST_STATE_CHANGE_READY_TO_PAUSED:
+      self->priv->pending_sticky_events = FALSE;
+      break;
+    default:
+      break;
+  }
+
+  ret = gstelement_class->change_state (element, transition);
+
+  return ret;
+}
+
+static gboolean
+gst_proxy_sink_sink_query (GstPad * pad, GstObject * parent, GstQuery * query)
+{
+  GstProxySink *self = GST_PROXY_SINK (parent);
+  GstProxySrc *src;
+  gboolean ret = FALSE;
+
+  GST_LOG_OBJECT (pad, "Handling query of type '%s'",
+      gst_query_type_get_name (GST_QUERY_TYPE (query)));
+
+  src = g_weak_ref_get (&self->priv->proxysrc);
+  if (src) {
+    GstPad *srcpad;
+    srcpad = gst_proxy_src_get_internal_srcpad (src);
+
+    ret = gst_pad_peer_query (srcpad, query);
+    gst_object_unref (srcpad);
+    gst_object_unref (src);
+  }
+
+  return ret;
+}
+
+typedef struct
+{
+  GstPad *otherpad;
+  GstFlowReturn ret;
+} CopyStickyEventsData;
+
+static gboolean
+copy_sticky_events (G_GNUC_UNUSED GstPad * pad, GstEvent ** event,
+    gpointer user_data)
+{
+  CopyStickyEventsData *data = user_data;
+
+  data->ret = gst_pad_store_sticky_event (data->otherpad, *event);
+
+  return data->ret == GST_FLOW_OK;
+}
+
+static gboolean
+gst_proxy_sink_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
+{
+  GstProxySink *self = GST_PROXY_SINK (parent);
+  GstProxySrc *src;
+  gboolean ret = FALSE;
+  gboolean sticky = GST_EVENT_IS_STICKY (event);
+
+  GST_LOG_OBJECT (pad, "Got %s event", GST_EVENT_TYPE_NAME (event));
+
+  if (GST_EVENT_TYPE (event) == GST_EVENT_FLUSH_STOP)
+    self->priv->pending_sticky_events = FALSE;
+
+  src = g_weak_ref_get (&self->priv->proxysrc);
+  if (src) {
+    GstPad *srcpad;
+    srcpad = gst_proxy_src_get_internal_srcpad (src);
+
+    if (sticky && self->priv->pending_sticky_events) {
+      CopyStickyEventsData data = { srcpad, GST_FLOW_OK };
+
+      gst_pad_sticky_events_foreach (pad, copy_sticky_events, &data);
+      self->priv->pending_sticky_events = data.ret != GST_FLOW_OK;
+    }
+
+    ret = gst_pad_push_event (srcpad, event);
+    gst_object_unref (srcpad);
+    gst_object_unref (src);
+
+    if (!ret && sticky) {
+      self->priv->pending_sticky_events = TRUE;
+      ret = TRUE;
+    }
+  } else
+    gst_event_unref (event);
+
+  return ret;
+}
+
+static GstFlowReturn
+gst_proxy_sink_sink_chain (GstPad * pad, GstObject * parent, GstBuffer * buffer)
+{
+  GstProxySink *self = GST_PROXY_SINK (parent);
+  GstProxySrc *src;
+  GstFlowReturn ret = GST_FLOW_OK;
+
+  GST_LOG_OBJECT (pad, "Chaining buffer %p", buffer);
+
+  src = g_weak_ref_get (&self->priv->proxysrc);
+  if (src) {
+    GstPad *srcpad;
+    srcpad = gst_proxy_src_get_internal_srcpad (src);
+
+    if (self->priv->pending_sticky_events) {
+      CopyStickyEventsData data = { srcpad, GST_FLOW_OK };
+
+      gst_pad_sticky_events_foreach (pad, copy_sticky_events, &data);
+      self->priv->pending_sticky_events = data.ret != GST_FLOW_OK;
+    }
+
+    ret = gst_pad_push (srcpad, buffer);
+    gst_object_unref (srcpad);
+    gst_object_unref (src);
+
+    GST_LOG_OBJECT (pad, "Chained buffer %p: %s", buffer,
+        gst_flow_get_name (ret));
+  } else {
+    gst_buffer_unref (buffer);
+    GST_LOG_OBJECT (pad, "Dropped buffer %p: no otherpad", buffer);
+  }
+
+  return GST_FLOW_OK;
+}
+
+static GstFlowReturn
+gst_proxy_sink_sink_chain_list (GstPad * pad, GstObject * parent,
+    GstBufferList * list)
+{
+  GstProxySink *self = GST_PROXY_SINK (parent);
+  GstProxySrc *src;
+  GstFlowReturn ret = GST_FLOW_OK;
+
+  GST_LOG_OBJECT (pad, "Chaining buffer list %p", list);
+
+  src = g_weak_ref_get (&self->priv->proxysrc);
+  if (src) {
+    GstPad *srcpad;
+    srcpad = gst_proxy_src_get_internal_srcpad (src);
+
+    if (self->priv->pending_sticky_events) {
+      CopyStickyEventsData data = { srcpad, GST_FLOW_OK };
+
+      gst_pad_sticky_events_foreach (pad, copy_sticky_events, &data);
+      self->priv->pending_sticky_events = data.ret != GST_FLOW_OK;
+    }
+
+    ret = gst_pad_push_list (srcpad, list);
+    gst_object_unref (srcpad);
+    gst_object_unref (src);
+    GST_LOG_OBJECT (pad, "Chained buffer list %p: %s", list,
+        gst_flow_get_name (ret));
+  } else {
+    gst_buffer_list_unref (list);
+    GST_LOG_OBJECT (pad, "Dropped buffer list %p: no otherpad", list);
+  }
+
+  return GST_FLOW_OK;
+}
+
+/* Wrapper function for accessing private member
+ * This can also be retrieved with gst_element_get_static_pad, but that depends
+ * on the implementation of GstProxySink */
+GstPad *
+gst_proxy_sink_get_internal_sinkpad (GstProxySink * self)
+{
+  g_return_val_if_fail (self, NULL);
+  return gst_object_ref (self->priv->sinkpad);
+}
+
+void
+gst_proxy_sink_set_proxysrc (GstProxySink * self, GstProxySrc * src)
+{
+  g_return_if_fail (self);
+  g_weak_ref_set (&self->priv->proxysrc, src);
+}
diff --git a/gst/proxy/gstproxysink.h b/gst/proxy/gstproxysink.h
new file mode 100644
index 000000000..00fe1ff0c
--- /dev/null
+++ b/gst/proxy/gstproxysink.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *   Author: Sebastian Dröge <sebastian@centricular.com>
+ *   Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#ifndef __GST_PROXY_SINK_H__
+#define __GST_PROXY_SINK_H__
+
+#include <gst/gst.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_PROXY_SINK             (gst_proxy_sink_get_type())
+#define GST_PROXY_SINK(obj)             (G_TYPE_CHECK_INSTANCE_CAST((obj), GST_TYPE_PROXY_SINK, GstProxySink))
+#define GST_IS_PROXY_SINK(obj)          (G_TYPE_CHECK_INSTANCE_TYPE((obj), GST_TYPE_PROXY_SINK))
+#define GST_PROXY_SINK_CLASS(klass)     (G_TYPE_CHECK_CLASS_CAST((klass) , GST_TYPE_PROXY_SINK, GstProxySinkClass))
+#define GST_IS_PROXY_SINK_CLASS(klass)  (G_TYPE_CHECK_CLASS_TYPE((klass) , GST_TYPE_PROXY_SINK))
+#define GST_PROXY_SINK_GET_CLASS(obj)   (G_TYPE_INSTANCE_GET_CLASS((obj) , GST_TYPE_PROXY_SINK, GstProxySinkClass))
+
+typedef struct _GstProxySink GstProxySink;
+typedef struct _GstProxySinkClass GstProxySinkClass;
+typedef struct _GstProxySinkPrivate GstProxySinkPrivate;
+
+struct _GstProxySink {
+  GstElement parent;
+
+  /* < private > */
+  GstProxySinkPrivate *priv;
+  gpointer _gst_reserved[GST_PADDING];
+};
+
+struct _GstProxySinkClass {
+  GstElementClass parent_class;
+};
+
+GType gst_proxy_sink_get_type (void);
+
+G_END_DECLS
+
+#endif /* __GST_PROXY_SINK_H__ */
diff --git a/gst/proxy/gstproxysrc-priv.h b/gst/proxy/gstproxysrc-priv.h
new file mode 100644
index 000000000..a8a92d86c
--- /dev/null
+++ b/gst/proxy/gstproxysrc-priv.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *     Author: Sebastian Dröge <sebastian@centricular.com>
+ *     Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#ifndef __GST_PROXY_SRC_PRIV_H__
+#define __GST_PROXY_SRC_PRIV_H__
+
+G_BEGIN_DECLS
+
+GstPad* gst_proxy_src_get_internal_srcpad (GstProxySrc *src);
+
+G_END_DECLS
+
+#endif /* __GST_PROXY_SRC_PRIV_H__ */
diff --git a/gst/proxy/gstproxysrc.c b/gst/proxy/gstproxysrc.c
new file mode 100644
index 000000000..e760d0f2a
--- /dev/null
+++ b/gst/proxy/gstproxysrc.c
@@ -0,0 +1,325 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *   Author: Sebastian Dröge <sebastian@centricular.com>
+ *   Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+/**
+ * SECTION:element-proxysrc
+ *
+ * Proxysrc is a source element that proxies events, queries, and buffers from
+ * another pipeline that contains a matching proxysink element. The purpose is
+ * to allow two decoupled pipelines to function as though they are one without
+ * having to manually shuttle buffers, events, queries, etc between the two.
+ *
+ * The element queues buffers from the matching proxysink to an internal queue,
+ * so everything downstream is properly decoupled from the upstream pipeline.
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include "gstproxysrc.h"
+#include "gstproxysrc-priv.h"
+#include "gstproxysink.h"
+#include "gstproxysink-priv.h"
+
+#define GST_CAT_DEFAULT gst_proxy_src_debug
+GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
+
+static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
+    GST_PAD_SRC,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS_ANY);
+
+enum
+{
+  PROP_0,
+  PROP_PROXYSINK,
+};
+
+struct _GstProxySrcPrivate
+{
+  /* Queue to hold buffers from proxysink */
+  GstElement *queue;
+  /* Source pad of the above queue and the proxysrc element itself */
+  GstPad *srcpad;
+  /* Our internal srcpad that proxysink pushes buffers/events/queries into */
+  GstPad *internal_srcpad;
+  /* An unlinked dummy sinkpad; see gst_proxy_src_init() */
+  GstPad *dummy_sinkpad;
+  /* The matching proxysink; queries and events are sent to its sinkpad */
+  GWeakRef proxysink;
+};
+
+/* We're not subclassing from basesrc because we don't want any of the special
+ * handling it has for events/queries/etc. We just pass-through everything. */
+
+/* Our parent type is a GstBin instead of GstElement because we contain a queue
+ * element */
+#define parent_class gst_proxy_src_parent_class
+G_DEFINE_TYPE (GstProxySrc, gst_proxy_src, GST_TYPE_BIN);
+
+static gboolean gst_proxy_src_internal_src_query (GstPad * pad,
+    GstObject * parent, GstQuery * query);
+static gboolean gst_proxy_src_internal_src_event (GstPad * pad,
+    GstObject * parent, GstEvent * event);
+
+static GstStateChangeReturn gst_proxy_src_change_state (GstElement * element,
+    GstStateChange transition);
+static void gst_proxy_src_dispose (GObject * object);
+
+static void
+gst_proxy_src_get_property (GObject * object,
+    guint prop_id, GValue * value, GParamSpec * spec)
+{
+  GstProxySrc *self = GST_PROXY_SRC (object);
+
+  switch (prop_id) {
+    case PROP_PROXYSINK:
+      g_value_take_object (value, g_weak_ref_get (&self->priv->proxysink));
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, spec);
+      break;
+  }
+}
+
+static void
+gst_proxy_src_set_property (GObject * object,
+    guint prop_id, const GValue * value, GParamSpec * spec)
+{
+  GstProxySrc *self = GST_PROXY_SRC (object);
+  GstProxySink *sink;
+
+  switch (prop_id) {
+    case PROP_PROXYSINK:
+      sink = g_value_dup_object (value);
+      if (sink == NULL) {
+        /* Unset proxysrc property on the existing proxysink to break the
+         * connection in that direction */
+        GstProxySink *old_sink = g_weak_ref_get (&self->priv->proxysink);
+        if (old_sink) {
+          gst_proxy_sink_set_proxysrc (old_sink, NULL);
+          g_object_unref (old_sink);
+        }
+        g_weak_ref_set (&self->priv->proxysink, NULL);
+      } else {
+        /* Set proxysrc property on the new proxysink to point to us */
+        gst_proxy_sink_set_proxysrc (sink, self);
+        g_weak_ref_set (&self->priv->proxysink, sink);
+        g_object_unref (sink);
+      }
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, spec);
+  }
+}
+
+static void
+gst_proxy_src_class_init (GstProxySrcClass * klass)
+{
+  GObjectClass *gobject_class = (GObjectClass *) klass;
+  GstElementClass *gstelement_class = (GstElementClass *) klass;
+
+  GST_DEBUG_CATEGORY_INIT (gst_proxy_src_debug, "proxysrc", 0, "proxy sink");
+
+  g_type_class_add_private (klass, sizeof (GstProxySrcPrivate));
+
+  gobject_class->dispose = gst_proxy_src_dispose;
+
+  gobject_class->get_property = gst_proxy_src_get_property;
+  gobject_class->set_property = gst_proxy_src_set_property;
+
+  g_object_class_install_property (gobject_class, PROP_PROXYSINK,
+      g_param_spec_object ("proxysink", "Proxysink", "Matching proxysink",
+          GST_TYPE_PROXY_SINK, G_PARAM_READWRITE));
+
+  gstelement_class->change_state = gst_proxy_src_change_state;
+  gst_element_class_add_pad_template (gstelement_class,
+      gst_static_pad_template_get (&src_template));
+
+  gst_element_class_set_static_metadata (gstelement_class, "Proxy source",
+      "Source", "Proxy source for internal process communication",
+      "Sebastian Dröge <sebastian@centricular.com>");
+}
+
+static void
+gst_proxy_src_init (GstProxySrc * self)
+{
+  GstPad *srcpad, *sinkpad;
+  GstPadTemplate *templ;
+
+  GST_OBJECT_FLAG_SET (self, GST_ELEMENT_FLAG_SOURCE);
+
+  self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, GST_TYPE_PROXY_SRC,
+      GstProxySrcPrivate);
+
+  /* We feed incoming buffers into a queue to decouple the downstream pipeline
+   * from the upstream pipeline */
+  self->priv->queue = gst_element_factory_make ("queue", NULL);
+  gst_bin_add (GST_BIN (self), self->priv->queue);
+
+  srcpad = gst_element_get_static_pad (self->priv->queue, "src");
+  templ = gst_static_pad_template_get (&src_template);
+  self->priv->srcpad = gst_ghost_pad_new_from_template ("src", srcpad, templ);
+  gst_object_unref (templ);
+  gst_object_unref (srcpad);
+
+  gst_element_add_pad (GST_ELEMENT (self), self->priv->srcpad);
+
+  /* A dummy sinkpad that's not actually used anywhere
+   * Explanation for why this is needed is below */
+  self->priv->dummy_sinkpad = gst_pad_new ("dummy_sinkpad", GST_PAD_SINK);
+  gst_object_set_parent (GST_OBJECT (self->priv->dummy_sinkpad),
+      GST_OBJECT (self));
+
+  self->priv->internal_srcpad = gst_pad_new ("internal_src", GST_PAD_SRC);
+  gst_object_set_parent (GST_OBJECT (self->priv->internal_srcpad),
+      GST_OBJECT (self->priv->dummy_sinkpad));
+  gst_pad_set_event_function (self->priv->internal_srcpad,
+      gst_proxy_src_internal_src_event);
+  gst_pad_set_query_function (self->priv->internal_srcpad,
+      gst_proxy_src_internal_src_query);
+
+  /* We need to link internal_srcpad from proxysink to the sinkpad of our
+   * queue. However, two pads can only be linked if they share a common parent.
+   * Above, we set the parent of the dummy_sinkpad as proxysrc, and then we set
+   * the parent of internal_srcpad as dummy_sinkpad. This causes both these pads
+   * to share a parent allowing us to link them.
+   * Yes, this is a hack/workaround. */
+  sinkpad = gst_element_get_static_pad (self->priv->queue, "sink");
+  gst_pad_link (self->priv->internal_srcpad, sinkpad);
+  gst_object_unref (sinkpad);
+}
+
+static void
+gst_proxy_src_dispose (GObject * object)
+{
+  GstProxySrc *self = GST_PROXY_SRC (object);
+
+  gst_object_unparent (GST_OBJECT (self->priv->dummy_sinkpad));
+  self->priv->dummy_sinkpad = NULL;
+
+  gst_object_unparent (GST_OBJECT (self->priv->internal_srcpad));
+  self->priv->internal_srcpad = NULL;
+
+  g_weak_ref_set (&self->priv->proxysink, NULL);
+
+  G_OBJECT_CLASS (gst_proxy_src_parent_class)->dispose (object);
+}
+
+static GstStateChangeReturn
+gst_proxy_src_change_state (GstElement * element, GstStateChange transition)
+{
+  GstElementClass *gstelement_class =
+      GST_ELEMENT_CLASS (gst_proxy_src_parent_class);
+  GstProxySrc *self = GST_PROXY_SRC (element);
+  GstStateChangeReturn ret;
+
+  ret = gstelement_class->change_state (element, transition);
+  if (ret == GST_STATE_CHANGE_FAILURE)
+    return ret;
+
+  switch (transition) {
+    case GST_STATE_CHANGE_READY_TO_PAUSED:
+      ret = GST_STATE_CHANGE_NO_PREROLL;
+      gst_pad_set_active (self->priv->internal_srcpad, TRUE);
+      break;
+    case GST_STATE_CHANGE_PAUSED_TO_READY:
+      gst_pad_set_active (self->priv->internal_srcpad, FALSE);
+      break;
+    default:
+      break;
+  }
+
+  return ret;
+}
+
+static gboolean
+gst_proxy_src_internal_src_query (GstPad * pad, GstObject * parent,
+    GstQuery * query)
+{
+  GstProxySrc *self = GST_PROXY_SRC (gst_object_get_parent (parent));
+  GstProxySink *sink;
+  gboolean ret = FALSE;
+
+  if (!self)
+    return ret;
+
+  GST_LOG_OBJECT (pad, "Handling query of type '%s'",
+      gst_query_type_get_name (GST_QUERY_TYPE (query)));
+
+  sink = g_weak_ref_get (&self->priv->proxysink);
+  if (sink) {
+    GstPad *sinkpad;
+    sinkpad = gst_proxy_sink_get_internal_sinkpad (sink);
+
+    ret = gst_pad_peer_query (sinkpad, query);
+    gst_object_unref (sinkpad);
+    gst_object_unref (sink);
+  }
+
+  gst_object_unref (self);
+
+  return ret;
+}
+
+static gboolean
+gst_proxy_src_internal_src_event (GstPad * pad, GstObject * parent,
+    GstEvent * event)
+{
+  GstProxySrc *self = GST_PROXY_SRC (gst_object_get_parent (parent));
+  GstProxySink *sink;
+  gboolean ret = FALSE;
+
+  if (!self)
+    return ret;
+
+  GST_LOG_OBJECT (pad, "Got %s event", GST_EVENT_TYPE_NAME (event));
+
+  sink = g_weak_ref_get (&self->priv->proxysink);
+  if (sink) {
+    GstPad *sinkpad;
+    sinkpad = gst_proxy_sink_get_internal_sinkpad (sink);
+
+    ret = gst_pad_push_event (sinkpad, event);
+    gst_object_unref (sinkpad);
+    gst_object_unref (sink);
+  } else
+    gst_event_unref (event);
+
+
+  gst_object_unref (self);
+
+  return ret;
+}
+
+/* Wrapper function for accessing private member */
+GstPad *
+gst_proxy_src_get_internal_srcpad (GstProxySrc * self)
+{
+  return gst_object_ref (self->priv->internal_srcpad);
+}
diff --git a/gst/proxy/gstproxysrc.h b/gst/proxy/gstproxysrc.h
new file mode 100644
index 000000000..2983fc85a
--- /dev/null
+++ b/gst/proxy/gstproxysrc.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2015 Centricular Ltd.
+ *   Author: Sebastian Dröge <sebastian@centricular.com>
+ *   Author: Nirbheek Chauhan <nirbheek@centricular.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this
+ * list of conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#ifndef __GST_PROXY_SRC_H__
+#define __GST_PROXY_SRC_H__
+
+#include <gst/gst.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_PROXY_SRC            (gst_proxy_src_get_type())
+#define GST_PROXY_SRC(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj), GST_TYPE_PROXY_SRC, GstProxySrc))
+#define GST_IS_PROXY_SRC(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj), GST_TYPE_PROXY_SRC))
+#define GST_PROXY_SRC_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass) , GST_TYPE_PROXY_SRC, GstProxySrcClass))
+#define GST_IS_PROXY_SRC_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass) , GST_TYPE_PROXY_SRC))
+#define GST_PROXY_SRC_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS((obj) , GST_TYPE_PROXY_SRC, GstProxySrcClass))
+
+typedef struct _GstProxySrc GstProxySrc;
+typedef struct _GstProxySrcClass GstProxySrcClass;
+typedef struct _GstProxySrcPrivate GstProxySrcPrivate;
+
+struct _GstProxySrc {
+  GstBin parent;
+
+  /* < private > */
+  GstProxySrcPrivate *priv;
+  gpointer  _gst_reserved[GST_PADDING];
+};
+
+struct _GstProxySrcClass {
+  GstBinClass parent_class;
+};
+
+GType gst_proxy_src_get_type(void);
+
+G_END_DECLS
+
+#endif /* __GST_PROXY_SRC_H__ */
diff --git a/gst/proxy/meson.build b/gst/proxy/meson.build
new file mode 100644
index 000000000..769727816
--- /dev/null
+++ b/gst/proxy/meson.build
@@ -0,0 +1,14 @@
+proxy_sources = [
+  'gstproxy.c',
+  'gstproxysink.c',
+  'gstproxysrc.c'
+]
+
+gstproxy = library('gstproxy',
+  proxy_sources,
+  c_args : gst_plugins_bad_args,
+  include_directories : [configinc],
+  dependencies : [gstbase_dep],
+  install : true,
+  install_dir : plugins_install_dir,
+)