libcamera: Use const reference for range loops

Use a const reference in range-based for loops to avoid copies of the
loop elements.

While at it, change looping over controls in
PipelineHandlerUVC::processControls to use structured bindings.

Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/camera_manager.cpp

@@ -189,7 +189,7 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> camera,
 {
 	MutexLocker locker(mutex_);
 
-	for (std::shared_ptr<Camera> c : cameras_) {
+	for (const std::shared_ptr<Camera> &c : cameras_) {
 		if (c->id() == camera->id()) {
 			LOG(Camera, Fatal)
 				<< "Trying to register a camera with a duplicated ID '"

src/libcamera/device_enumerator.cpp

@@ -161,7 +161,7 @@ std::unique_ptr<DeviceEnumerator> DeviceEnumerator::create()
 
 DeviceEnumerator::~DeviceEnumerator()
 {
-	for (std::shared_ptr<MediaDevice> media : devices_) {
+	for (const std::shared_ptr<MediaDevice> &media : devices_) {
 		if (media->busy())
 			LOG(DeviceEnumerator, Error)
 				<< "Removing media device " << media->deviceNode()

src/libcamera/pipeline/uvcvideo/uvcvideo.cpp

@@ -340,12 +340,8 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
 {
 	ControlList controls(data->video_->controls());
 
-	for (auto it : request->controls()) {
-		unsigned int id = it.first;
-		ControlValue &value = it.second;
-
+	for (const auto &[id, value] : request->controls())
 		processControl(&controls, id, value);
-	}
 
 	for (const auto &ctrl : controls)
 		LOG(UVC, Debug)

src/libcamera/pipeline/vimc/vimc.cpp

@@ -378,7 +378,7 @@ int PipelineHandlerVimc::processControls(VimcCameraData *data, Request *request)
 {
 	ControlList controls(data->sensor_->controls());
 
-	for (auto it : request->controls()) {
+	for (const auto &it : request->controls()) {
 		unsigned int id = it.first;
 		unsigned int offset;
 		uint32_t cid;

src/libcamera/pipeline_handler.cpp

@@ -616,7 +616,7 @@ void PipelineHandler::disconnect()
 	 */
 	std::vector<std::weak_ptr<Camera>> cameras{ std::move(cameras_) };
 
-	for (std::weak_ptr<Camera> ptr : cameras) {
+	for (const std::weak_ptr<Camera> &ptr : cameras) {
 		std::shared_ptr<Camera> camera = ptr.lock();
 		if (!camera)
 			continue;