c601052c8c
The utility simplifies the synchronization of a list-based data model from an XML structure.
139 lines
3.4 KiB
C++
139 lines
3.4 KiB
C++
/*
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* \brief Utility for updating an internal data model from an XML structure
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* \author Norman Feske
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* \date 2017-08-09
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*/
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/*
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* Copyright (C) 2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__UTIL__LIST_MODEL_FROM_XML_H_
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#define _INCLUDE__UTIL__LIST_MODEL_FROM_XML_H_
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#include <util/xml_node.h>
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namespace Genode {
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template <typename POLICY>
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static inline void
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update_list_model_from_xml(POLICY &policy,
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List<typename POLICY::Element> &list,
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Xml_node node);
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template <typename> struct List_model_update_policy;
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}
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/**
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* Policy interface to be supplied to 'update_list_model_from_xml'
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*
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* \param ELEM element type, must be a list element
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*
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* This class template is merely a blue print of a policy to document the
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* interface.
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*/
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template <typename ELEM>
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struct Genode::List_model_update_policy
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{
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/*
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* Types that need to be supplied by the policy implementation
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*/
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typedef ELEM Element;
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struct Unknown_element_type : Exception { };
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/**
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* Destroy element
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*
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* When this function is called, the element is no longer contained
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* in the model's list.
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*/
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void destroy_element(ELEM &elem);
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/**
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* Create element of the type given in the 'elem_node'
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*
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* \throw Unknown_element_type
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*/
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ELEM &create_element(Xml_node elem_node);
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/**
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* Import element properties from XML node
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*/
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void update_element(ELEM &elem, Xml_node elem_node);
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/**
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* Return true if element corresponds to XML node
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*/
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static bool element_matches_xml_node(Element const &, Xml_node);
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/**
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* Return true if XML node should be imported
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*
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* This method allows the policy to disregard certain XML node types from
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* building the data model.
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*/
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static bool node_is_element(Xml_node node) { return true; }
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};
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/**
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* Update 'list' data model according to XML structure 'node'
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*
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* \throw Unknown_element_type
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*/
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template <typename POLICY>
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static inline void
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Genode::update_list_model_from_xml(POLICY &policy,
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List<typename POLICY::Element> &list,
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Xml_node node)
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{
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typedef typename POLICY::Element Element;
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List<Element> updated_list;
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Element *last_updated = nullptr; /* used for appending to 'updated_list' */
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node.for_each_sub_node([&] (Xml_node sub_node) {
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/* skip XML nodes that are unrelated to the data model */
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if (!policy.node_is_element(sub_node))
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return;
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/* look up corresponding element in original list */
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Element *curr = list.first();
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while (curr && !policy.element_matches_xml_node(*curr, sub_node))
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curr = curr->next();
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/* consume existing element or create new one */
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if (curr) {
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list.remove(curr);
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} else {
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/* \throw Unknown_element_type */
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curr = &policy.create_element(sub_node);
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}
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/* append current element to 'updated_list' */
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updated_list.insert(curr, last_updated);
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last_updated = curr;
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policy.update_element(*curr, sub_node);
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});
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/* remove stale elements */
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Element *next = nullptr;
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for (Element *e = list.first(); e; e = next) {
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next = e->next();
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policy.destroy_element(*e);
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}
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/* use 'updated_list' list new data model */
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list = updated_list;
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}
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#endif /* _INCLUDE__UTIL__LIST_MODEL_FROM_XML_H_ */
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