[libcamera-devel] [PATCH v3 4/4] use std::optional to handle invalid control values
Christian Rauch
Rauch.Christian at gmx.de
Sat Apr 16 21:41:21 CEST 2022
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.
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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