libcamera: camera: Add CameraConfiguration

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.

Applications 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 in the CameraConfiguration, using the stream pointer retrieves
the stream's configuration.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 220 insertions, 0 deletions

diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index 0386671c..6038da63 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -24,6 +24,35 @@ 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 isValid() const;
+	bool isEmpty() const;
+	std::size_t size() const;
+
+	Stream *front();
+	const Stream *front() const;
+
+	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 63fde0ff..ddf5c268 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -40,6 +40,197 @@ namespace libcamera {
 LOG_DECLARE_CATEGORY(Camera)
 
 /**
+ * \class CameraConfiguration
+ * \brief Hold configuration for streams of the camera
+
+ * The CameraConfiguration holds an ordered list of streams and their associated
+ * StreamConfiguration. From a data storage point of view, the class operates as
+ * a map of Stream pointers to StreamConfiguration, with entries accessed with
+ * operator[](Stream *). Accessing an entry for a Stream pointer not yet stored
+ * in the configuration inserts a new empty entry.
+ *
+ * The class also suppors iterators, and from that point of view operates as a
+ * vector of Stream pointers. The streams are iterated in insertion order, and
+ * the operator[](int) returns the Stream pointer based on its insertion index.
+ * Accessing a stream with an invalid index returns a null pointer.
+ */
+
+/**
+ * \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 a const iterator to the first element of the streams
+ *
+ * \return A const iterator to the first stream
+ */
+std::vector<Stream *>::const_iterator CameraConfiguration::begin() const
+{
+	return order_.begin();
+}
+
+/**
+ * \brief Retrieve a const iterator pointing to the past-the-end stream in the
+ * sequence
+ *
+ * \return A const 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
+ *
+ * A camera configuration is deemed to be valid if it contains at least one
+ * stream configuration and all stream configurations contain valid information.
+ * Stream configurations are deemed to be valid if all fields are none zero.
+ *
+ * \return True if the configuration is valid
+ */
+bool CameraConfiguration::isValid() const
+{
+	if (isEmpty())
+		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::isEmpty() 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 Access the first stream in the configuration
+ *
+ * \return The first const stream pointer in the configuration
+ */
+const Stream *CameraConfiguration::front() const
+{
+	return order_.front();
+}
+
+/**
+ * \brief Retrieve a stream pointer from index
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero based 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 invalid operation
+ * and results in undefined behaviour.
+ *
+ * \return The configuration for the stream
+ */
+const StreamConfiguration &CameraConfiguration::operator[](Stream *stream) const
+{
+	return config_.at(stream);
+}
+
+/**
  * \class Camera
  * \brief Camera device
  *