[libcamera-devel] [PATCH v3 4/4] use std::optional to handle invalid control values
Kieran Bingham
kieran.bingham at ideasonboard.com
Tue Apr 19 12:48:53 CEST 2022
Quoting Christian Rauch via libcamera-devel (2022-04-16 20:41:21)
> Hi Kieran,
>
> Is my patch series, including the std::optional change, something you
> would consider? I think it's a useful addition as it properly "types"
> the Span Controls and makes the handling of invalid return "get" values
> explicit.
>
I think overall it sounded good - but I think Laurent mentioned he has
some concerens about std::optional in public API, as we may have some
limitations there, that are preventing us having a full C++17 usage.
I can't recall what is holding us to C++14 on public API - but I would
hope we can look at what is required to bring that up to '17.
> Best,
> Christian
>
>
> Am 08.04.22 um 23:29 schrieb Christian Rauch via libcamera-devel:
> > Hi Kieran,
> >
> > Am 08.04.22 um 13:06 schrieb Kieran Bingham:
> >> Hi Christian,
> >>
> >> Quoting Christian Rauch via libcamera-devel (2022-04-08 02:42:31)
> >>> Previously, ControlList::get<T>() would use default constructed objects to
> >>> indicate that a ControlList does not have the requested Control. This has
> >>> several disadvantages: 1) It requires types to be default constructible,
> >>> 2) it does not differentiate between a default constructed object and an
> >>> object that happens to have the same state as a default constructed object.
> >>>
> >>> std::optional<T> additionally stores the information if the object is valid
> >>> or not, and therefore is more expressive than a default constructed object.
> >>
> >> This looks like a really good way to express the controls from a list. I
> >> really like the value_or() that it brings to allow the code to set a
> >> default.
> >>
> >>
> >> I expect this will have knock-on effects to other out of tree
> >> applications using the control framework so we might want to coordinate
> >> the merge of this.
> >>
> >> Though I notice there's fairly minimal changes to cam and qcam. Do you
> >> know if your build includes the v4l2 adaptation layer and gstreamer?
> >> Does this API change cause definate breakage to users?
> >>
> >> (It's ok if it does, that's preciesly why we are not ABI stable).
> >
> > This is definitely a breaking change as it changes the public API. But
> > the changes that have to be made are quite trivial. You only have to add
> > ".value()" or ".value_or(...)" to the old code.
> >
> > I don't know about the v4l2 wrapper and gstreamer. There might be some
> > code that is not compiled on my setup. But the "qcam" application still
> > works. And I think this one is using the v4l2 wrapper.
> >
> >>
> >>
> >>>
> >>> Signed-off-by: Christian Rauch <Rauch.Christian at gmx.de>
> >>> ---
> >>> include/libcamera/controls.h | 6 +++---
> >>> src/cam/main.cpp | 4 ++--
> >>> src/ipa/raspberrypi/raspberrypi.cpp | 2 +-
> >>> src/libcamera/pipeline/ipu3/ipu3.cpp | 9 ++++-----
> >>> .../pipeline/raspberrypi/raspberrypi.cpp | 9 +++++----
> >>> src/qcam/dng_writer.cpp | 15 +++++++++------
> >>> 6 files changed, 24 insertions(+), 21 deletions(-)
> >>>
> >>> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> >>> index 665bcac1..57b777e9 100644
> >>> --- a/include/libcamera/controls.h
> >>> +++ b/include/libcamera/controls.h
> >>> @@ -167,7 +167,7 @@ public:
> >>>
> >>> using V = typename T::value_type;
> >>> const V *value = reinterpret_cast<const V *>(data().data());
> >>> - return { value, numElements_ };
> >>> + return T{ value, numElements_ };
> >>> }
> >>>
> >>> #ifndef __DOXYGEN__
> >>> @@ -373,11 +373,11 @@ public:
> >>> bool contains(unsigned int id) const;
> >>>
> >>> template<typename T>
> >>> - T get(const Control<T> &ctrl) const
> >>> + std::optional<T> get(const Control<T> &ctrl) const
> >>> {
> >>> const ControlValue *val = find(ctrl.id());
> >>> if (!val)
> >>> - return T{};
> >>> + return std::nullopt;
> >>>
> >>> return val->get<T>();
> >>> }
> >>> diff --git a/src/cam/main.cpp b/src/cam/main.cpp
> >>> index c7f664b9..853a78ed 100644
> >>> --- a/src/cam/main.cpp
> >>> +++ b/src/cam/main.cpp
> >>> @@ -293,7 +293,7 @@ std::string CamApp::cameraName(const Camera *camera)
> >>> * is only used if the location isn't present or is set to External.
> >>> */
> >>> if (props.contains(properties::Location)) {
> >>> - switch (props.get(properties::Location)) {
> >>> + switch (props.get(properties::Location).value_or(int32_t{})) {
> >>
> >> Is there a way to do this without the value_or() in conditions where the
> >> value has already been guaranteed to exist?
> >>
> >> Here we have just checked that the lists contains a
> >> properties::Lcoation, so we 'know' that it will never process the
> >> '_or()' part.
> >>
> >> Looking at https://en.cppreference.com/w/cpp/utility/optional
> >>
> >> I guess we can just use .value() in the locations where we already check
> >> for the presence. I suspect this could lead to a code refactor to just
> >> use the optional to determine the properties existance instead of
> >> .contains() - but that could certainly be done on top.
> >>
> >> Perhaps it might be better for consistency to use the value_or() variant
> >> on occasions though - even if we know it must already exist?
> >
> > ".value()" will throw an exception if the "std::optional" does not
> > contain a value. If you can guarantee that a ControlValue contains a
> > value, then you can skip the check via ".has_value()" or the fallback
> > via ".value_or(...)" and use ".value()" directly.
> >
> >>
> >>
> >>> case properties::CameraLocationFront:
> >>> addModel = false;
> >>> name = "Internal front camera ";
> >>> @@ -313,7 +313,7 @@ std::string CamApp::cameraName(const Camera *camera)
> >>> * If the camera location is not availble use the camera model
> >>> * to build the camera name.
> >>> */
> >>> - name = "'" + props.get(properties::Model) + "' ";
> >>> + name = "'" + props.get(properties::Model).value_or(std::string{}) + "' ";
> >>> }
> >>>
> >>> name += "(" + camera->id() + ")";
> >>> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> >>> index 5a5cdf66..93b32e94 100644
> >>> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> >>> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> >>> @@ -934,7 +934,7 @@ void IPARPi::returnEmbeddedBuffer(unsigned int bufferId)
> >>>
> >>> void IPARPi::prepareISP(const ipa::RPi::ISPConfig &data)
> >>> {
> >>> - int64_t frameTimestamp = data.controls.get(controls::SensorTimestamp);
> >>> + int64_t frameTimestamp = data.controls.get(controls::SensorTimestamp).value_or(int64_t{});
> >>> RPiController::Metadata lastMetadata;
> >>> Span<uint8_t> embeddedBuffer;
> >>>
> >>> diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> >>> index 60e01917..394221cb 100644
> >>> --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> >>> +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> >>> @@ -1146,7 +1146,7 @@ int PipelineHandlerIPU3::registerCameras()
> >>> /* Convert the sensor rotation to a transformation */
> >>> int32_t rotation = 0;
> >>> if (data->properties_.contains(properties::Rotation))
> >>> - rotation = data->properties_.get(properties::Rotation);
> >>> + rotation = data->properties_.get(properties::Rotation).value_or(int32_t{});
> >>> else
> >>> LOG(IPU3, Warning) << "Rotation control not exposed by "
> >>> << cio2->sensor()->id()
> >>> @@ -1341,7 +1341,7 @@ void IPU3CameraData::imguOutputBufferReady(FrameBuffer *buffer)
> >>> request->metadata().set(controls::draft::PipelineDepth, 3);
> >>> /* \todo Actually apply the scaler crop region to the ImgU. */
> >>> if (request->controls().contains(controls::ScalerCrop))
> >>> - cropRegion_ = request->controls().get(controls::ScalerCrop);
> >>> + cropRegion_ = request->controls().get(controls::ScalerCrop).value_or(Rectangle{});
> >>> request->metadata().set(controls::ScalerCrop, cropRegion_);
> >>>
> >>> if (frameInfos_.tryComplete(info))
> >>> @@ -1442,7 +1442,7 @@ void IPU3CameraData::statBufferReady(FrameBuffer *buffer)
> >>> ev.op = ipa::ipu3::EventStatReady;
> >>> ev.frame = info->id;
> >>> ev.bufferId = info->statBuffer->cookie();
> >>> - ev.frameTimestamp = request->metadata().get(controls::SensorTimestamp);
> >>> + ev.frameTimestamp = request->metadata().get(controls::SensorTimestamp).value_or(int64_t{});
> >>> ev.sensorControls = info->effectiveSensorControls;
> >>> ipa_->processEvent(ev);
> >>> }
> >>> @@ -1477,8 +1477,7 @@ void IPU3CameraData::frameStart(uint32_t sequence)
> >>> if (!request->controls().contains(controls::draft::TestPatternMode))
> >>> return;
> >>>
> >>> - const int32_t testPatternMode = request->controls().get(
> >>> - controls::draft::TestPatternMode);
> >>> + const int32_t testPatternMode = request->controls().get(controls::draft::TestPatternMode).value_or(int32_t{});
> >>
> >> This looks like a section of code that could now use optional for
> >> cleaner code I think. I see above we return early if the control is not
> >> present, and only call setTestPatternMode if it is set.
> >>
> >>
> >> Again, I think this patch is just bringing in the std::optional - so it
> >> shouldn't have to 'make everything use the best implementation' - but I
> >> can see benefits it can bring.
> >>
> >> I think even though we know it's guaranteed to exist here, the use of
> >> value_or() is fine with me, as it highlights that this code could
> >> perhaps be simplified later.
> >>
> >
> > The current ".value_or(...)" implementation is the closest to the old
> > behaviour, which would return a default contructed object in case of
> > failure. You certainly can change that behaviour if you arec ertain that
> > a value exists.
> >
> >>
> >>>
> >>> int ret = cio2_.sensor()->setTestPatternMode(
> >>> static_cast<controls::draft::TestPatternModeEnum>(testPatternMode));
> >>> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> >>> index 0fa294d4..63d57033 100644
> >>> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> >>> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> >>> @@ -365,7 +365,7 @@ CameraConfiguration::Status RPiCameraConfiguration::validate()
> >>> * error means the platform can never run. Let's just print a warning
> >>> * and continue regardless; the rotation is effectively set to zero.
> >>> */
> >>> - int32_t rotation = data_->sensor_->properties().get(properties::Rotation);
> >>> + int32_t rotation = data_->sensor_->properties().get(properties::Rotation).value_or(int32_t{});
> >>> bool success;
> >>> Transform rotationTransform = transformFromRotation(rotation, &success);
> >>> if (!success)
> >>> @@ -1696,7 +1696,8 @@ void RPiCameraData::statsMetadataComplete(uint32_t bufferId, const ControlList &
> >>> * V4L2_CID_NOTIFY_GAINS control (which means notifyGainsUnity_ is set).
> >>> */
> >>> if (notifyGainsUnity_ && controls.contains(libcamera::controls::ColourGains)) {
> >>> - libcamera::Span<const float, 2> colourGains = controls.get(libcamera::controls::ColourGains);
> >>> + libcamera::Span<const float, 2> colourGains =
> >>> + controls.get(libcamera::controls::ColourGains).value_or(libcamera::Span<const float, 2>({ 0, 0 }));
> >>> /* The control wants linear gains in the order B, Gb, Gr, R. */
> >>> ControlList ctrls(sensor_->controls());
> >>> std::array<int32_t, 4> gains{
> >>> @@ -2031,7 +2032,7 @@ Rectangle RPiCameraData::scaleIspCrop(const Rectangle &ispCrop) const
> >>> void RPiCameraData::applyScalerCrop(const ControlList &controls)
> >>> {
> >>> if (controls.contains(controls::ScalerCrop)) {
> >>> - Rectangle nativeCrop = controls.get<Rectangle>(controls::ScalerCrop);
> >>> + Rectangle nativeCrop = controls.get<Rectangle>(controls::ScalerCrop).value_or(Rectangle{});
> >>
> >> I'm starting to wonder if a templated get_or would be useful as the type
> >> would be defined there (doesn't have to be here, just an idea)
> >>
> >> It would reduce line length on null initialisers:
> >>
> >> controls.get_or<Rectangle>(controls::ScalerCrop, {});
> >>
> >> And easily allow default parameters to be defined:
> >>
> >> controls.get_or<Rectangle>(controls::ScalerCrop, {640,480});
> >>
> >> I suspect seeing how this all gets used will determine if it has value
> >> though.
> >
> > This is probably dependent on the situation, but I don't think that
> > initialising control values with the default is a good idea in every
> > case. The biggest advantage of "std::optional" is that you can properly
> > test for errors. In most cases, it is probably better to notify the user
> > about missing controls etc. instead of silently replacing the requested
> > values with the defaults.
> >
> >>
> >>>
> >>> if (!nativeCrop.width || !nativeCrop.height)
> >>> nativeCrop = { 0, 0, 1, 1 };
> >>> @@ -2069,7 +2070,7 @@ void RPiCameraData::fillRequestMetadata(const ControlList &bufferControls,
> >>> Request *request)
> >>> {
> >>> request->metadata().set(controls::SensorTimestamp,
> >>> - bufferControls.get(controls::SensorTimestamp));
> >>> + bufferControls.get(controls::SensorTimestamp).value_or(int64_t{}));
> >>>
> >>> request->metadata().set(controls::ScalerCrop, scalerCrop_);
> >>> }
> >>> diff --git a/src/qcam/dng_writer.cpp b/src/qcam/dng_writer.cpp
> >>> index 2fb527d8..030432e3 100644
> >>> --- a/src/qcam/dng_writer.cpp
> >>> +++ b/src/qcam/dng_writer.cpp
> >>> @@ -392,7 +392,7 @@ int DNGWriter::write(const char *filename, const Camera *camera,
> >>> TIFFSetField(tif, TIFFTAG_MAKE, "libcamera");
> >>>
> >>> if (cameraProperties.contains(properties::Model)) {
> >>> - std::string model = cameraProperties.get(properties::Model);
> >>> + std::string model = cameraProperties.get(properties::Model).value_or(std::string{});
> >>> TIFFSetField(tif, TIFFTAG_MODEL, model.c_str());
> >>> /* \todo set TIFFTAG_UNIQUECAMERAMODEL. */
> >>> }
> >>> @@ -438,7 +438,8 @@ int DNGWriter::write(const char *filename, const Camera *camera,
> >>> const double eps = 1e-2;
> >>>
> >>> if (metadata.contains(controls::ColourGains)) {
> >>> - Span<const float, 2> const &colourGains = metadata.get(controls::ColourGains);
> >>> + Span<const float, 2> const &colourGains =
> >>> + metadata.get(controls::ColourGains).value_or(libcamera::Span<const float, 2>({ 0, 0 }));
> >>> if (colourGains[0] > eps && colourGains[1] > eps) {
> >>> wbGain = Matrix3d::diag(colourGains[0], 1, colourGains[1]);
> >>> neutral[0] = 1.0 / colourGains[0]; /* red */
> >>> @@ -446,7 +447,8 @@ int DNGWriter::write(const char *filename, const Camera *camera,
> >>> }
> >>> }
> >>> if (metadata.contains(controls::ColourCorrectionMatrix)) {
> >>> - Span<const float, 9> const &coeffs = metadata.get(controls::ColourCorrectionMatrix);
> >>> + Span<const float, 9> const &coeffs =
> >>> + metadata.get(controls::ColourCorrectionMatrix).value_or(Span<const float, 9>({ 0, 0, 0, 0, 0, 0, 0, 0, 0 }));
> >>> Matrix3d ccmSupplied(coeffs);
> >>> if (ccmSupplied.determinant() > eps)
> >>> ccm = ccmSupplied;
> >>> @@ -515,7 +517,8 @@ int DNGWriter::write(const char *filename, const Camera *camera,
> >>> uint32_t whiteLevel = (1 << info->bitsPerSample) - 1;
> >>>
> >>> if (metadata.contains(controls::SensorBlackLevels)) {
> >>> - Span<const int32_t, 4> levels = metadata.get(controls::SensorBlackLevels);
> >>> + Span<const int32_t, 4> levels =
> >>> + metadata.get(controls::SensorBlackLevels).value_or(Span<const int32_t, 4>({ 0, 0, 0, 0 }));
> >>>
> >>> /*
> >>> * The black levels control is specified in R, Gr, Gb, B order.
> >>> @@ -593,13 +596,13 @@ int DNGWriter::write(const char *filename, const Camera *camera,
> >>> TIFFSetField(tif, EXIFTAG_DATETIMEDIGITIZED, strTime);
> >>>
> >>> if (metadata.contains(controls::AnalogueGain)) {
> >>> - float gain = metadata.get(controls::AnalogueGain);
> >>> + float gain = metadata.get(controls::AnalogueGain).value_or(float{});
> >>> uint16_t iso = std::min(std::max(gain * 100, 0.0f), 65535.0f);
> >>> TIFFSetField(tif, EXIFTAG_ISOSPEEDRATINGS, 1, &iso);
> >>> }
> >>>
> >>> if (metadata.contains(controls::ExposureTime)) {
> >>> - float exposureTime = metadata.get(controls::ExposureTime) / 1e6;
> >>> + float exposureTime = metadata.get(controls::ExposureTime).value_or(float{}) / 1e6;
> >>> TIFFSetField(tif, EXIFTAG_EXPOSURETIME, exposureTime);
> >>> }
> >>>
> >>> --
> >>> 2.25.1
> >>>
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