libcamera: controls: Add a function to merge two control lists

Add a new ControlList::merge() function to merge two control lists by
copying in the values in the list passed as parameters.

This can be used by pipeline handlers to merge metadata they populate
with metadata received from an IPA.

Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[reimplement the function by not using std::unordered_map::merge()]
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
index c58ed394..b763148d 100644
--- a/src/libcamera/controls.cpp
+++ b/src/libcamera/controls.cpp
@@ -875,6 +875,36 @@ ControlList::ControlList(const ControlInfoMap &infoMap, ControlValidator *valida
  */
 
 /**
+ * \brief Merge the \a source into the ControlList
+ * \param[in] source The ControlList to merge into this object
+ *
+ * Merging two control lists copies elements from the \a source and inserts
+ * them in *this. If the \a source contains elements whose key is already
+ * present in *this, then those elements are not overwritten.
+ *
+ * Only control lists created from the same ControlIdMap or ControlInfoMap may
+ * be merged. Attempting to do otherwise results in undefined behaviour.
+ *
+ * \todo Reimplement or implement an overloaded version which internally uses
+ * std::unordered_map::merge() and accepts a non-const argument.
+ */
+void ControlList::merge(const ControlList &source)
+{
+	ASSERT(idmap_ == source.idmap_);
+
+	for (const auto &ctrl : source) {
+		if (contains(ctrl.first)) {
+			const ControlId *id = idmap_->at(ctrl.first);
+			LOG(Controls, Warning)
+				<< "Control " << id->name() << " not overwritten";
+			continue;
+		}
+
+		set(ctrl.first, ctrl.second);
+	}
+}
+
+/**
  * \brief Check if the list contains a control with the specified \a id
  * \param[in] id The control ID
  *