[libcamera-devel] [PATCH v2 12/14] libcamera: v4l2_controls: Turn V4L2ControlInfoMap into a class

[Laurent Pinchart]

In preparation for extending V4L2ControlInfoMap with control idmap
support, turn it into a real class. Make it inherit from std::map<>
instead of wrapping it to keep the API simple.

V4L2ControlInfoMap is meant to be constructed with a set of control
info, and never modified afterwards. To ensure this, inherit from
std::map<> with private access specifier, and explicitly expose the
std::map<> methods that do not allow insertion or removal of elements. A
custom move assignment operator is implemented to allow efficient
construction of the V4L2ControlInfoMap.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/libcamera/include/v4l2_controls.h | 16 +++++++++++++++-
 src/libcamera/v4l2_controls.cpp       | 17 ++++++++++++++++-
 src/libcamera/v4l2_device.cpp         |  9 ++++++---
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/src/libcamera/include/v4l2_controls.h b/src/libcamera/include/v4l2_controls.h
index 949ca21cb863..8990e755a385 100644
--- a/src/libcamera/include/v4l2_controls.h
+++ b/src/libcamera/include/v4l2_controls.h
@@ -43,7 +43,21 @@ private:
 	ControlRange range_;
 };
 
-using V4L2ControlInfoMap = std::map<unsigned int, V4L2ControlInfo>;
+class V4L2ControlInfoMap : private std::map<unsigned int, V4L2ControlInfo>
+{
+public:
+	V4L2ControlInfoMap &operator=(std::map<unsigned int, V4L2ControlInfo> &&info);
+
+	using std::map<unsigned int, V4L2ControlInfo>::begin;
+	using std::map<unsigned int, V4L2ControlInfo>::cbegin;
+	using std::map<unsigned int, V4L2ControlInfo>::end;
+	using std::map<unsigned int, V4L2ControlInfo>::cend;
+	using std::map<unsigned int, V4L2ControlInfo>::at;
+	using std::map<unsigned int, V4L2ControlInfo>::empty;
+	using std::map<unsigned int, V4L2ControlInfo>::size;
+	using std::map<unsigned int, V4L2ControlInfo>::count;
+	using std::map<unsigned int, V4L2ControlInfo>::find;
+};
 
 class V4L2Control
 {
diff --git a/src/libcamera/v4l2_controls.cpp b/src/libcamera/v4l2_controls.cpp
index 3f5f3ff10880..438e8d8bdb99 100644
--- a/src/libcamera/v4l2_controls.cpp
+++ b/src/libcamera/v4l2_controls.cpp
@@ -156,10 +156,25 @@ V4L2ControlInfo::V4L2ControlInfo(const struct v4l2_query_ext_ctrl &ctrl)
  */
 
 /**
- * \typedef V4L2ControlInfoMap
+ * \class V4L2ControlInfoMap
  * \brief A map of control ID to V4L2ControlInfo
  */
 
+/**
+ * \brief Move assignment operator from plain map
+ *
+ * Populate the map by replacing its contents with those of \a info using move
+ * semantics. This is the only supported
+ *
+ * \return *this
+ */
+V4L2ControlInfoMap &V4L2ControlInfoMap::operator=(std::map<unsigned int, V4L2ControlInfo> &&info)
+{
+	std::map<unsigned int, V4L2ControlInfo>::operator=(std::move(info));
+
+	return *this;
+}
+
 /**
  * \class V4L2Control
  * \brief A V4L2 control value
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 8c5998435020..1f755f0f3ef6 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -340,6 +340,7 @@ int V4L2Device::ioctl(unsigned long request, void *argp)
  */
 void V4L2Device::listControls()
 {
+	std::map<unsigned int, V4L2ControlInfo> ctrls;
 	struct v4l2_query_ext_ctrl ctrl = {};
 
 	/* \todo Add support for menu and compound controls. */
@@ -368,10 +369,12 @@ void V4L2Device::listControls()
 			continue;
 		}
 
-		controls_.emplace(std::piecewise_construct,
-				  std::forward_as_tuple(ctrl.id),
-				  std::forward_as_tuple(ctrl));
+		ctrls.emplace(std::piecewise_construct,
+			      std::forward_as_tuple(ctrl.id),
+			      std::forward_as_tuple(ctrl));
 	}
+
+	controls_ = std::move(ctrls);
 }
 
 /*
-- 
Regards,

Laurent Pinchart