libcamera: value_node: Support adding nested children in one operation

The GlobalConfiguration class will need to add nested children to a
ValueNode. Add a new overload to the add() function for this purpose.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>

include/libcamera/internal/value_node.h

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <initializer_list>
 #include <iterator>
 #include <map>
 #include <memory>
@@ -239,6 +240,8 @@ public:
 
 	ValueNode *add(std::unique_ptr<ValueNode> &&child);
 	ValueNode *add(std::string key, std::unique_ptr<ValueNode> &&child);
+	ValueNode *add(std::initializer_list<std::string_view> path,
+		       std::unique_ptr<ValueNode> &&child);
 
 private:
 	LIBCAMERA_DISABLE_COPY_AND_MOVE(ValueNode)

src/libcamera/value_node.cpp

@@ -13,6 +13,8 @@
 #include <string>
 #include <vector>
 
+#include <libcamera/base/log.h>
+#include <libcamera/base/span.h>
 #include <libcamera/base/utils.h>
 
 /**
@@ -22,6 +24,8 @@
 
 namespace libcamera {
 
+LOG_DEFINE_CATEGORY(ValueNode)
+
 namespace {
 
 /* Empty static ValueNode as a safe result for invalid operations */
@@ -541,4 +545,58 @@ ValueNode *ValueNode::add(std::string key, std::unique_ptr<ValueNode> &&child)
 	return list_.emplace_back(it->first, std::move(child)).value.get();
 }
 
+/**
+ * \brief Add a child node at the given path
+ * \param[in] path The path
+ * \param[in] child The child node
+ *
+ * Add the \a child node at the given \a path starting at this node. Missing
+ * nodes are created along the path. Nodes along the path must be empty (in
+ * which case they are converted to the Type::Dictionary type), be a dictionary,
+ * or be missing. Otherwise, the function returns a nullptr and the \a child is
+ * not modified.
+ *
+ * Path elements are unique in the context of a parent node. If a child with the
+ * same \a key already exist at the end of the path, the function returns a
+ * nullptr and the \a child is not modified.
+ *
+ * \note Any node added along the \a path will remain even if this function
+ * returns a failure.
+ *
+ * \return A pointer to the \a child node if successfully added, nullptr
+ * otherwise
+ */
+ValueNode *ValueNode::add(std::initializer_list<std::string_view> path,
+			  std::unique_ptr<ValueNode> &&child)
+{
+	if (!path.size())
+		return nullptr;
+
+	ValueNode *node = this;
+
+	for (const auto [i, name] : utils::enumerate(path)) {
+		auto iter = node->dictionary_.find(name);
+		if (iter == node->dictionary_.end()) {
+			std::unique_ptr<ValueNode> obj;
+
+			if (i < path.size() - 1)
+				obj = std::make_unique<ValueNode>();
+
+			node = node->add(std::string{ name },
+					 obj ? std::move(obj) : std::move(child));
+			if (!node) {
+				Span<const std::string_view> pathName{ std::data(path), i + 1 };
+				LOG(ValueNode, Error)
+					<< "Failed to populate '"
+					<< utils::join(pathName, "/") << "'";
+				return nullptr;
+			}
+		} else {
+			node = iter->second;
+		}
+	}
+
+	return node;
+}
+
 } /* namespace libcamera */