[BL] added config tree builder

BaseLib/ConfigTreeUtil.cpp

+/**
+ * \copyright
+ * Copyright (c) 2012-2016, OpenGeoSys Community (http://www.opengeosys.org)
+ *            Distributed under a Modified BSD License.
+ *              See accompanying file LICENSE.txt or
+ *              http://www.opengeosys.org/project/license
+ *
+ */
+
+#include <boost/property_tree/xml_parser.hpp>
+
+#include "ConfigTreeUtil.h"
+
+namespace BaseLib
+{
+
+ConfigTreeTopLevel::ConfigTreeTopLevel(
+        const std::string& filepath,
+        const bool be_ruthless,
+        ConfigTreeNew::PTree&& ptree)
+    : _ptree(std::move(ptree))
+    , _ctree(_ptree, filepath,
+             be_ruthless ? ConfigTreeNew::onerror : ConfigTreeNew::onwarning)
+{
+}
+
+ConfigTreeNew const&
+ConfigTreeTopLevel::operator*() const
+{
+    return _ctree;
+}
+
+ConfigTreeNew const*
+ConfigTreeTopLevel::operator->() const
+{
+    return &_ctree;
+}
+
+void
+ConfigTreeTopLevel::checkAndInvalidate()
+{
+    ::BaseLib::checkAndInvalidate(_ctree);
+}
+
+ConfigTreeTopLevel
+makeConfigTree(const std::string& filepath, const bool be_ruthless,
+               const std::string& toplevel_tag)
+{
+    ConfigTreeNew::PTree ptree;
+
+    // note: Trimming whitespace and ignoring comments is crucial in order
+    //       for our configuration tree implementation to work!
+    try {
+        read_xml(filepath, ptree,
+                 boost::property_tree::xml_parser::no_comments |
+                 boost::property_tree::xml_parser::trim_whitespace);
+    } catch (boost::property_tree::xml_parser_error e) {
+        ERR("Error while parsing XML file `%s' at line %lu: %s.",
+            e.filename().c_str(), e.line(), e.message().c_str());
+        std::abort();
+    }
+
+    DBUG("Project configuration from file \'%s\' read.", filepath.c_str());
+
+    if (auto child = std::move(ptree.get_child_optional(toplevel_tag))) {
+        return ConfigTreeTopLevel(filepath, be_ruthless, std::move(*child));
+    } else {
+        ERR("Tag <%s> has not been found in file `%s'.",
+            toplevel_tag.c_str(), filepath.c_str());
+        std::abort();
+    }
+}
+
+}

BaseLib/ConfigTreeUtil.h

+/**
+ * \copyright
+ * Copyright (c) 2012-2016, OpenGeoSys Community (http://www.opengeosys.org)
+ *            Distributed under a Modified BSD License.
+ *              See accompanying file LICENSE.txt or
+ *              http://www.opengeosys.org/project/license
+ *
+ */
+
+#ifndef BASELIB_CONFIGTREEUTIL
+#define BASELIB_CONFIGTREEUTIL
+
+#include "ConfigTreeNew.h"
+
+namespace BaseLib
+{
+
+/*! Manages a ConfigTree and the <tt>boost::property_tree</tt> it depends on.
+ *
+ * The whole purpose of this class is making the management of said dependency easy.
+ */
+class ConfigTreeTopLevel final
+{
+public:
+    /*! Construct a new instance from the given data.
+     *
+     * \param filepath stored for use in error/warning messages
+     * \param be_ruthless if true, then warnings will raise errors, .i.e. lead to program abortion,
+     *                    else warnings will only warn
+     * \param ptree the underlying ptree of the created ConfigTree
+     */
+    explicit ConfigTreeTopLevel(std::string const& filepath,
+                                bool const be_ruthless,
+                                ConfigTreeNew::PTree&& ptree);
+
+    /*! Access the contained ConfigTree.
+     *
+     * The non-const version of this method has not been implemented in order to prevent invalidating
+     * the \c _ctree when it is passed around. In order to check and invalidate \c _ctree use the provided
+     * member function.
+     */
+    ConfigTreeNew const& operator*() const;
+
+    /*! Access the contained ConfigTree.
+     *
+     * The non-const version of this method has not been implemented in order to prevent invalidating
+     * the \c _ctree when it is passed around. In order to check and invalidate \c _ctree use the provided
+     * member function.
+     */
+    ConfigTreeNew const* operator->() const;
+
+    /*! Check if the contained ConfigTree has been processed entirely.
+     *
+     * This only checks the top level, as usual with ConfigTree instances.
+     *
+     * \post Afterwards the contained ConfigTree instance must not be used anymore!
+     */
+    void checkAndInvalidate();
+
+private:
+    ConfigTreeNew::PTree const _ptree; //!< <tt>boost::property_tree</tt> that underlies \c _ctree
+    ConfigTreeNew              _ctree; //!< ConfigTree depending on \c _ptree
+};
+
+/*! Create a ConfigTree from an XML file.
+ *
+ * \param filepath     see ConfigTreeTopLevel::ConfigTreeTopLevel()
+ * \param be_ruthless  see ConfigTreeTopLevel::ConfigTreeTopLevel()
+ * \param toplevel_tag name of the outermost tag in the XML file. The returned ConfigTree is rooted
+ *                     one level below that tag.
+ *
+ * The parameter \c toplevel_tag is provided for compatibility with our existing configuration
+ * files whose toplevel tags are written in camel case, which conflicts with the naming rules of
+ * ConfigTree. Via that parameter the naming rules do not apply to the toplevel tag.
+ *
+ * Unfortunately the XML parser shipped with <tt>boost::property_tree</tt> does not fully support
+ * the XML standard. Additionally there might be encoding issues. From their docs:
+ *
+ * > Please note that RapidXML does not understand the encoding specification. If you pass it a
+ * > character buffer, it assumes the data is already correctly encoded; if you pass it a filename,
+ * > it will read the file using the character conversion of the locale you give it (or the global
+ * > locale if you give it none). This means that, in order to parse a UTF-8-encoded XML file into
+ * > a wptree, you have to supply an alternate locale, either directly or by replacing the global one.
+ *
+ * \see http://www.boost.org/doc/libs/1_60_0/doc/html/property_tree/parsers.html
+ */
+ConfigTreeTopLevel
+makeConfigTree(std::string const& filepath, bool const be_ruthless,
+               std::string const& toplevel_tag);
+
+}
+
+#endif