[PATCH v1] treewide: Avoid some copies in range-based for loops

Barnabás Pőcze pobrn at protonmail.com
Tue Nov 26 23:28:52 CET 2024


Hi


2024. november 26., kedd 22:08 keltezéssel, Laurent Pinchart <laurent.pinchart at ideasonboard.com> írta:

> Hi Barnabás,
> 
> (CC'ing Harvey)
> 
> Thank you for the patch.
> 
> On Tue, Nov 26, 2024 at 06:03:10PM +0000, Barnabás Pőcze wrote:
> > Most of these have been found by the `performance-for-range-copy`
> > check of `clang-tidy`.
> >
> > Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> > ---
> >  src/libcamera/camera_manager.cpp                         | 2 +-
> >  src/libcamera/converter.cpp                              | 5 +++--
> >  src/libcamera/pipeline/virtual/image_frame_generator.cpp | 2 +-
> >  src/libcamera/pipeline_handler.cpp                       | 2 +-
> >  test/gstreamer/gstreamer_device_provider_test.cpp        | 9 ++-------
> >  5 files changed, 8 insertions(+), 12 deletions(-)
> >
> > diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
> > index c7cc5adb..87e6717e 100644
> > --- a/src/libcamera/camera_manager.cpp
> > +++ b/src/libcamera/camera_manager.cpp
> > @@ -388,7 +388,7 @@ std::shared_ptr<Camera> CameraManager::get(const std::string &id)
> >
> >  	MutexLocker locker(d->mutex_);
> >
> > -	for (std::shared_ptr<Camera> camera : d->cameras_) {
> > +	for (const std::shared_ptr<Camera> &camera : d->cameras_) {
> >  		if (camera->id() == id)
> >  			return camera;
> >  	}
> > diff --git a/src/libcamera/converter.cpp b/src/libcamera/converter.cpp
> > index 945f2527..3a3f8434 100644
> > --- a/src/libcamera/converter.cpp
> > +++ b/src/libcamera/converter.cpp
> > @@ -325,8 +325,9 @@ std::vector<std::string> ConverterFactoryBase::names()
> >
> >  	for (ConverterFactoryBase *factory : factories) {
> >  		list.push_back(factory->name_);
> > -		for (auto alias : factory->compatibles())
> > -			list.push_back(alias);
> > +
> > +		const auto &compatibles = factory->compatibles();
> > +		list.insert(list.end(), compatibles.begin(), compatibles.end());
> >  	}
> >
> >  	return list;
> > diff --git a/src/libcamera/pipeline/virtual/image_frame_generator.cpp b/src/libcamera/pipeline/virtual/image_frame_generator.cpp
> > index 2baef588..277efbb0 100644
> > --- a/src/libcamera/pipeline/virtual/image_frame_generator.cpp
> > +++ b/src/libcamera/pipeline/virtual/image_frame_generator.cpp
> > @@ -39,7 +39,7 @@ ImageFrameGenerator::create(ImageFrames &imageFrames)
> >  	 * For each file in the directory, load the image,
> >  	 * convert it to NV12, and store the pointer.
> >  	 */
> > -	for (std::filesystem::path path : imageFrames.files) {
> > +	for (const auto &path : imageFrames.files) {
> 
> Unrelated to this patch, just because I notice this now in the virtual
> pipeline handler that was merged recently. A while ago, we merged
> 
> commit 6a2f971035c2df711b10200f9c8c011d9a420e58
> Author: Nicholas Roth <nicholas at rothemail.net>
> Date:   Thu Oct 27 22:17:21 2022 -0500
> 
>     android: remove references to std::filesystem
> 
>     Android 11's toolchain does not support std::filesystem, but
>     camera_hal_config.cpp currently uses it. Remove references to
>     std::filesystem in order to support Android <= 11.
> 
> We should drop usage of std::filesystem in
> src/libcamera/pipeline/virtual/. I've been thinking of either extending
> the libcamera base File class, or implementing new classes, with APIs
> influenced by https://doc.qt.io/qt-6/qfileinfo.html and
> https://doc.qt.io/qt-6/qdir.html. This would also replace existing use
> of stat() and fstat() through the code base.

That is quite unfortunate... I think it was me who suggested using std::filesystem.
Sadly it will not be as easy as in the referenced commit.

What is the android support policy?

Also, I am a bit puzzled by that commit. According to https://developer.android.com/ndk/downloads/revision_history
NDK r22b (March 2021) added std::filesystem support. Additionally,
https://github.com/android/ndk/wiki/Compatibility implies that r23 supports
everything above API 16 (Jelly Bean), which, according to https://apilevels.com/
is around android 4.

In any case, my experience is limited with android is limited, so I could've
missed an important detail.


Regards,
Barnabás Pőcze

> 
> >  		File file(path);
> >  		if (!file.open(File::OpenModeFlag::ReadOnly)) {
> >  			LOG(Virtual, Error) << "Failed to open image file " << file.fileName()
> > diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> > index 991b06f2..caa5c20e 100644
> > --- a/src/libcamera/pipeline_handler.cpp
> > +++ b/src/libcamera/pipeline_handler.cpp
> > @@ -74,7 +74,7 @@ PipelineHandler::PipelineHandler(CameraManager *manager)
> >
> >  PipelineHandler::~PipelineHandler()
> >  {
> > -	for (std::shared_ptr<MediaDevice> media : mediaDevices_)
> > +	for (std::shared_ptr<MediaDevice> &media : mediaDevices_)
> >  		media->release();
> >  }
> >
> > diff --git a/test/gstreamer/gstreamer_device_provider_test.cpp b/test/gstreamer/gstreamer_device_provider_test.cpp
> > index 8b8e7cba..4b087fcb 100644
> > --- a/test/gstreamer/gstreamer_device_provider_test.cpp
> > +++ b/test/gstreamer/gstreamer_device_provider_test.cpp
> > @@ -52,17 +52,12 @@ protected:
> >  		for (l = devices; l != NULL; l = g_list_next(l)) {
> >  			GstDevice *device = GST_DEVICE(l->data);
> >  			g_autofree gchar *gst_name;
> > -			bool matched = false;
> >
> >  			g_autoptr(GstElement) element = gst_device_create_element(device, NULL);
> >  			g_object_get(element, "camera-name", &gst_name, NULL);
> >
> > -			for (auto name : cameraNames) {
> > -				if (strcmp(name.c_str(), gst_name) == 0) {
> > -					matched = true;
> > -					break;
> > -				}
> > -			}
> > +			bool matched =
> > +				std::find(cameraNames.begin(), cameraNames.end(), gst_name) != cameraNames.end();
> >
> >  			if (!matched)
> >  				return TestFail;
> 
> Maybe you could now drop the matched variable and write
> 
> 			if (std::find(cameraNames.begin(), cameraNames.end(), gst_name) !=
> 			    cameraNames.end())
> 				return TestFail;
> 
> ?
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> This makes me wish C++ had std::contains(). I suppose C++23's
> std::ranges:contains() will do the job in several years. There's also
> 
> 			if (std::any_of(cameraNames.begin(), cameraNames.end(),
> 				        [&gst_name](const std::string &name) { return name == gst_name; })
> 				return TestFail;
> 
> which I don't think would be much of an improvement :-)
> 
> --
> Regards,
> 
> Laurent Pinchart


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