[libcamera-devel] [PATCH v3 7/8] libcamera: camera: Add CameraConfiguration

[Niklas Söderlund]

To properly support both multiple streams and stream usages the library
must provide a method to map the stream usages to the returned streams
configurations. Add a camera configuration object to handle this
mapping.

Applications can iterate over the returned camera configuration to
retrieve the streams selected by the library in the same order as the
usages it provided to the library.

Application can use the operator[] to retrieve the stream pointer and
the stream configuration. Using a numerical index retrieves the stream
pointer, the numerical indexes corresponds to the insertion order of
usages by the application, using the stream pointer retrieves the
stream's configuration.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
 include/libcamera/camera.h |  28 ++++++
 src/libcamera/camera.cpp   | 173 +++++++++++++++++++++++++++++++++++++
 2 files changed, 201 insertions(+)

diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index 0386671c902e55e8..8455049151d5c5a2 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -24,6 +24,34 @@ class Stream;
 class StreamConfiguration;
 class StreamUsage;
 
+class CameraConfiguration
+{
+public:
+	using iterator = std::vector<Stream *>::iterator;
+	using const_iterator = std::vector<Stream *>::const_iterator;
+
+	CameraConfiguration();
+
+	iterator begin();
+	iterator end();
+	const_iterator begin() const;
+	const_iterator end() const;
+
+	bool valid() const;
+	bool empty() const;
+	std::size_t size() const;
+
+	Stream *front();
+
+	Stream *operator[](unsigned int index) const;
+	StreamConfiguration &operator[](Stream *stream);
+	const StreamConfiguration &operator[](Stream *stream) const;
+
+private:
+	std::vector<Stream *> order_;
+	std::map<Stream *, StreamConfiguration> config_;
+};
+
 class Camera final
 {
 public:
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 63fde0ffc3d02d6c..98145edea1ac9c91 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -39,6 +39,179 @@ namespace libcamera {
 
 LOG_DECLARE_CATEGORY(Camera)
 
+/**
+ * \class CameraConfiguration
+ * \brief Hold configuration for streams of the camera
+ *
+ * The CameraConfiguration is filled with information by the application either
+ * manually or with the streamConfiguration() helper. The helper takes a list
+ * of usages describing how the application intends to use streams of the
+ * camera, the application in return are provided with a default camera
+ * configuration it can tune.
+ *
+ * Applications iterate over the CameraConfiguration to discover which streams
+ * the camera has associated to the usages, and can inspect the configuration
+ * of individual streams using the operator[].
+ */
+
+/**
+ * \typedef CameraConfiguration::iterator
+ * \brief Iterator for the streams in the configuration
+ */
+
+/**
+ * \typedef CameraConfiguration::const_iterator
+ * \brief Const iterator for the streams in the configuration
+ */
+
+/**
+ * \brief Create an empty camera configuration
+ */
+CameraConfiguration::CameraConfiguration()
+	: order_({}), config_({})
+{
+}
+
+/**
+ * \brief Retrieve an iterator to the first stream in the sequence
+ *
+ * \return An iterator to the first stream
+ */
+std::vector<Stream *>::iterator CameraConfiguration::begin()
+{
+	return order_.begin();
+}
+
+/**
+ * \brief Retrieve an iterator pointing to the past-the-end stream in the
+ * sequence
+ *
+ * \return An iterator to the element following the last stream
+ */
+std::vector<Stream *>::iterator CameraConfiguration::end()
+{
+	return order_.end();
+}
+
+/**
+ * \brief Retrieve an iterator to the first element of the streams
+ *
+ * \return An iterator to the first stream
+ */
+std::vector<Stream *>::const_iterator CameraConfiguration::begin() const
+{
+	return order_.begin();
+}
+
+/**
+ * \brief Retrieve an iterator to the end of the streams
+ *
+ * \return An iterator to the element following the last stream
+ */
+std::vector<Stream *>::const_iterator CameraConfiguration::end() const
+{
+	return order_.end();
+}
+
+/**
+ * \brief Check if the camera configuration is valid
+ *
+ * \return True if the configuration is valid
+ */
+bool CameraConfiguration::valid() const
+{
+	if (empty())
+		return false;
+
+	for (auto const &it : config_) {
+		const StreamConfiguration &conf = it.second;
+
+		if (conf.width == 0 || conf.height == 0 ||
+		    conf.pixelFormat == 0 || conf.bufferCount == 0)
+			return false;
+	}
+
+	return true;
+}
+
+/**
+ * \brief Check if the camera configuration is empty
+ *
+ * \return True if the configuration is empty
+ */
+bool CameraConfiguration::empty() const
+{
+	return order_.empty();
+}
+
+/**
+ * \brief Retrieve the number of stream configurations
+ *
+ * \return Number of stream configurations
+ */
+std::size_t CameraConfiguration::size() const
+{
+	return order_.size();
+}
+
+/**
+ * \brief Access the first stream in the configuration
+ *
+ * \return The first stream in the configuration
+ */
+Stream *CameraConfiguration::front()
+{
+	return order_.front();
+}
+/**
+ * \brief Retrieve a stream pointer from index
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero bases insertion order of stream and stream
+ * configuration into the camera configuration.
+ *
+ * \return The stream pointer at index, or a nullptr if the index is out of
+ * bounds
+ */
+Stream *CameraConfiguration::operator[](unsigned int index) const
+{
+	if (index >= order_.size())
+		return nullptr;
+
+	return order_.at(index);
+}
+
+/**
+ * \brief Retrieve a reference to a stream configuration
+ * \param[in] stream Stream to retrieve configuration for
+ *
+ * If the camera configuration does not yet contain a configuration for
+ * the requested stream, create and return an empty stream configuration.
+ *
+ * \return The configuration for the stream
+ */
+StreamConfiguration &CameraConfiguration::operator[](Stream *stream)
+{
+	if (config_.find(stream) == config_.end())
+		order_.push_back(stream);
+
+	return config_[stream];
+}
+
+/**
+ * \brief Retrieve a const reference to a stream configuration
+ * \param[in] stream Stream to retrieve configuration for
+ *
+ * No new stream configuration is created if called with \a stream that is not
+ * already part of the camera configuration, doing so is an illegal operation.
+ *
+ * \return The configuration for the stream
+ */
+const StreamConfiguration &CameraConfiguration::operator[](Stream *stream) const
+{
+	return config_.at(stream);
+}
+
 /**
  * \class Camera
  * \brief Camera device
-- 
2.21.0