libcamera: yaml_parser: Add function to set a YamlObject value

Add a YamlObject::set() function to set the value of an object, with
specializations for scalar types.

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

include/libcamera/internal/yaml_parser.h

@@ -182,6 +182,13 @@ public:
 		return get<T>().value_or(std::forward<U>(defaultValue));
 	}
 
+	template<typename T>
+	void set(T &&value)
+	{
+		return Accessor<std::remove_cv_t<std::remove_reference_t<T>>>{}
+			.set(*this, std::forward<T>(value));
+	}
+
 	DictAdapter asDict() const { return DictAdapter{ list_ }; }
 	ListAdapter asList() const { return ListAdapter{ list_ }; }
 
@@ -207,6 +214,7 @@ private:
 	template<typename T, typename Enable = void>
 	struct Accessor {
 		std::optional<T> get(const YamlObject &obj) const;
+		void set(YamlObject &obj, T value);
 	};
 
 	Type type_;

src/libcamera/yaml_parser.cpp

@@ -137,6 +137,22 @@ std::size_t YamlObject::size() const
  * \return The YamlObject value, or \a defaultValue if parsing failed
  */
 
+/**
+ * \fn template<typename T> YamlObject::set<T>(T &&value)
+ * \brief Set the value of a YamlObject
+ * \param[in] value The value
+ *
+ * This function sets the value stored in a YamlObject to \a value. The value is
+ * converted to a string in an implementation-specific way that guarantees that
+ * subsequent calls to get<T>() will return the same value.
+ *
+ * \todo Implement the conversion guarantee for floating point types
+ *
+ * Values can only be set on YamlObject of Type::Value type or empty YamlObject.
+ * Attempting to set a value on an object of type Type::Dict or Type::List does
+ * not modify the YamlObject.
+ */
+
 #ifndef __DOXYGEN__
 
 template<>
@@ -154,6 +170,16 @@ YamlObject::Accessor<bool>::get(const YamlObject &obj) const
 	return std::nullopt;
 }
 
+template<>
+void YamlObject::Accessor<bool>::set(YamlObject &obj, bool value)
+{
+	if (obj.type_ != Type::Empty && obj.type_ != Type::Value)
+		return;
+
+	obj.type_ = Type::Value;
+	obj.value_ = value ? "true" : "false";
+}
+
 template<typename T>
 struct YamlObject::Accessor<T, std::enable_if_t<
 	std::is_same_v<int8_t, T> ||
@@ -178,6 +204,15 @@ struct YamlObject::Accessor<T, std::enable_if_t<
 
 		return value;
 	}
+
+	void set(YamlObject &obj, T value)
+	{
+		if (obj.type_ != Type::Empty && obj.type_ != Type::Value)
+			return;
+
+		obj.type_ = Type::Value;
+		obj.value_ = std::to_string(value);
+	}
 };
 
 template struct YamlObject::Accessor<int8_t>;
@@ -194,6 +229,12 @@ YamlObject::Accessor<float>::get(const YamlObject &obj) const
 	return obj.get<double>();
 }
 
+template<>
+void YamlObject::Accessor<float>::set(YamlObject &obj, float value)
+{
+	obj.set<double>(value);
+}
+
 template<>
 std::optional<double>
 YamlObject::Accessor<double>::get(const YamlObject &obj) const
@@ -215,6 +256,16 @@ YamlObject::Accessor<double>::get(const YamlObject &obj) const
 	return value;
 }
 
+template<>
+void YamlObject::Accessor<double>::set(YamlObject &obj, double value)
+{
+	if (obj.type_ != Type::Empty && obj.type_ != Type::Value)
+		return;
+
+	obj.type_ = Type::Value;
+	obj.value_ = std::to_string(value);
+}
+
 template<>
 std::optional<std::string>
 YamlObject::Accessor<std::string>::get(const YamlObject &obj) const
@@ -225,6 +276,16 @@ YamlObject::Accessor<std::string>::get(const YamlObject &obj) const
 	return obj.value_;
 }
 
+template<>
+void YamlObject::Accessor<std::string>::set(YamlObject &obj, std::string value)
+{
+	if (obj.type_ != Type::Empty && obj.type_ != Type::Value)
+		return;
+
+	obj.type_ = Type::Value;
+	obj.value_ = std::move(value);
+}
+
 template<>
 std::optional<Size>
 YamlObject::Accessor<Size>::get(const YamlObject &obj) const