libcamera: controls: Extend ControlList to access controls by ID

The ControlList class implements a map from control specifier to control
ID. To avoid constant lookups of ControlInfo when using the class in the
libcamera core or in pipeline handlers, the map uses ControlInfo
pointers instead of ControlId values. This is however not very
convenient for applications or pipeline handlers, as they would be
forced to first look up the ControlInfo pointers for the controls they
want to access. Facilitate ease of use of ControlLists by implementing
an internal lookup of the ControlInfo from the controls provided by the
Camera.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

include/libcamera/controls.h

@@ -117,11 +117,13 @@ public:
 	const_iterator begin() const { return controls_.begin(); }
 	const_iterator end() const { return controls_.end(); }
 
+	bool contains(ControlId id) const;
 	bool contains(const ControlInfo *info) const;
 	bool empty() const { return controls_.empty(); }
 	std::size_t size() const { return controls_.size(); }
 	void clear() { controls_.clear(); }
 
+	ControlValue &operator[](ControlId id);
 	ControlValue &operator[](const ControlInfo *info) { return controls_[info]; }
 
 	void update(const ControlList &list);

src/libcamera/controls.cpp

@@ -10,6 +10,8 @@
 #include <sstream>
 #include <string>
 
+#include <libcamera/camera.h>
+
 #include "log.h"
 #include "utils.h"
 
@@ -387,6 +389,30 @@ ControlList::ControlList(Camera *camera)
  * list
  */
 
+/**
+ * \brief Check if the list contains a control with the specified \a id
+ * \param[in] id The control ID
+ *
+ * The behaviour is undefined if the control \a id is not supported by the
+ * camera that the ControlList refers to.
+ *
+ * \return True if the list contains a matching control, false otherwise
+ */
+bool ControlList::contains(ControlId id) const
+{
+	const ControlInfoMap &controls = camera_->controls();
+	const auto iter = controls.find(id);
+	if (iter == controls.end()) {
+		LOG(Controls, Error)
+			<< "Camera " << camera_->name()
+			<< " does not support control " << id;
+
+		return false;
+	}
+
+	return controls_.find(&iter->second) != controls_.end();
+}
+
 /**
  * \brief Check if the list contains a control with the specified \a info
  * \param[in] info The control info
@@ -414,6 +440,34 @@ bool ControlList::contains(const ControlInfo *info) const
  * \brief Removes all controls from the list
  */
 
+/**
+ * \brief Access or insert the control specified by \a id
+ * \param[in] id The control ID
+ *
+ * This method returns a reference to the control identified by \a id, inserting
+ * it in the list if the ID is not already present.
+ *
+ * The behaviour is undefined if the control \a id is not supported by the
+ * camera that the ControlList refers to.
+ *
+ * \return A reference to the value of the control identified by \a id
+ */
+ControlValue &ControlList::operator[](ControlId id)
+{
+	const ControlInfoMap &controls = camera_->controls();
+	const auto iter = controls.find(id);
+	if (iter == controls.end()) {
+		LOG(Controls, Error)
+			<< "Camera " << camera_->name()
+			<< " does not support control " << id;
+
+		static ControlValue empty;
+		return empty;
+	}
+
+	return controls_[&iter->second];
+}
+
 /**
  * \fn ControlList::operator[](const ControlInfo *info)
  * \brief Access or insert the control specified by \a info