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// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
//
// Copyright (C) 2021 Intel Corporation
#ifndef OPENCV_GAPI_STREAMING_GSTREAMER_GSTREAMERPTR_HPP
#define OPENCV_GAPI_STREAMING_GSTREAMER_GSTREAMERPTR_HPP
#include <opencv2/gapi.hpp>
#include <utility>
#ifdef HAVE_GSTREAMER
#include <gst/gst.h>
#include <gst/video/video-frame.h>
namespace cv {
namespace gapi {
namespace wip {
namespace gst {
template<typename T> static inline void GStreamerPtrUnrefObject(T* ptr)
{
if (ptr)
{
gst_object_unref(G_OBJECT(ptr));
}
}
template<typename T> static inline void GStreamerPtrRelease(T* ptr);
template<> inline void GStreamerPtrRelease<GError>(GError* ptr)
{
if (ptr)
{
g_error_free(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstElement>(GstElement* ptr)
{
GStreamerPtrUnrefObject<GstElement>(ptr);
}
template<> inline void GStreamerPtrRelease<GstElementFactory>(GstElementFactory* ptr)
{
GStreamerPtrUnrefObject<GstElementFactory>(ptr);
}
template<> inline void GStreamerPtrRelease<GstPad>(GstPad* ptr)
{
GStreamerPtrUnrefObject<GstPad>(ptr);
}
template<> inline void GStreamerPtrRelease<GstBus>(GstBus* ptr)
{
GStreamerPtrUnrefObject<GstBus>(ptr);
}
template<> inline void GStreamerPtrRelease<GstAllocator>(GstAllocator* ptr)
{
GStreamerPtrUnrefObject<GstAllocator>(ptr);
}
template<> inline void GStreamerPtrRelease<GstVideoInfo>(GstVideoInfo* ptr)
{
if (ptr)
{
gst_video_info_free(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstCaps>(GstCaps* ptr)
{
if (ptr)
{
gst_caps_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstMemory>(GstMemory* ptr)
{
if (ptr)
{
gst_memory_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstBuffer>(GstBuffer* ptr)
{
if (ptr)
{
gst_buffer_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstSample>(GstSample* ptr)
{
if (ptr)
{
gst_sample_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstMessage>(GstMessage* ptr)
{
if (ptr)
{
gst_message_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstIterator>(GstIterator* ptr)
{
if (ptr)
{
gst_iterator_free(ptr);
}
}
template<> inline void GStreamerPtrRelease<GstQuery>(GstQuery* ptr)
{
if (ptr)
{
gst_query_unref(ptr);
}
}
template<> inline void GStreamerPtrRelease<char>(char* ptr)
{
if (ptr)
{
g_free(ptr);
}
}
// NOTE: The main concept of this class is to be owner of some passed to it piece of memory.
// (be owner = free this memory or reduce reference count to it after use).
// More specifically, GStreamerPtr is designed to own memory returned from GStreamer/GLib
// functions, which are marked as [transfer full] in documentation.
// [transfer full] means that function fully transfers ownership of returned memory to the
// receiving piece of code.
//
// Memory ownership and ownership transfer concept:
// https://developer.gnome.org/programming-guidelines/stable/memory-management.html.en#g-clear-object
// NOTE: GStreamerPtr can only own strong references, not floating ones.
// For floating references please call g_object_ref_sink(reference) before wrapping
// it with GStreamerPtr.
// See https://developer.gnome.org/gobject/stable/gobject-The-Base-Object-Type.html#floating-ref
// for floating references.
// NOTE: GStreamerPtr doesn't support pointers to arrays, only pointers to single objects.
template<typename T> class GStreamerPtr :
public std::unique_ptr<T, decltype(&GStreamerPtrRelease<T>)>
{
using BaseClass = std::unique_ptr<T, decltype(&GStreamerPtrRelease<T>)>;
public:
constexpr GStreamerPtr() noexcept : BaseClass(nullptr, GStreamerPtrRelease<T>) { }
constexpr GStreamerPtr(std::nullptr_t) noexcept : BaseClass(nullptr, GStreamerPtrRelease<T>) { }
explicit GStreamerPtr(typename BaseClass::pointer p) noexcept :
BaseClass(p, GStreamerPtrRelease<T>) { }
GStreamerPtr& operator=(T* p) noexcept { *this = std::move(GStreamerPtr<T>(p)); return *this; }
inline operator T*() noexcept { return this->get(); }
// There is no const correctness in GStreamer C API
inline operator /*const*/ T*() const noexcept { return (T*)this->get(); }
};
} // namespace gst
} // namespace wip
} // namespace gapi
} // namespace cv
#endif // HAVE_GSTREAMER
#endif // OPENCV_GAPI_STREAMING_GSTREAMER_GSTREAMERPTR_HPP
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