mapnik/src/libxml2_loader.cpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2021 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifdef HAVE_LIBXML2

// mapnik
#include <mapnik/xml_loader.hpp>
#include <mapnik/xml_node.hpp>
#include <mapnik/config_error.hpp>
#include <mapnik/util/trim.hpp>
#include <mapnik/util/noncopyable.hpp>
#include <mapnik/util/fs.hpp>

// libxml
#include <libxml/parser.h>
#include <libxml/tree.h>
#include <libxml/parserInternals.h>
#include <libxml/xinclude.h>

// stl
#include <stdexcept>

#if LIBXML_VERSION >= 20900
#define DEFAULT_OPTIONS                                                                                                \
    (XML_PARSE_NOERROR | XML_PARSE_NOENT | XML_PARSE_NOBLANKS | XML_PARSE_DTDLOAD | XML_PARSE_NOCDATA |                \
     XML_PARSE_HUGE | XML_PARSE_BIG_LINES)
#elif LIBXML_VERSION >= 20703
#define DEFAULT_OPTIONS                                                                                                \
    (XML_PARSE_NOERROR | XML_PARSE_NOENT | XML_PARSE_NOBLANKS | XML_PARSE_DTDLOAD | XML_PARSE_NOCDATA | XML_PARSE_HUGE)
#else
#define DEFAULT_OPTIONS                                                                                                \
    (XML_PARSE_NOERROR | XML_PARSE_NOENT | XML_PARSE_NOBLANKS | XML_PARSE_DTDLOAD | XML_PARSE_NOCDATA)
#endif

namespace mapnik {
class libxml2_loader : util::noncopyable
{
  public:
    libxml2_loader(const char* encoding = nullptr, int options = DEFAULT_OPTIONS, const char* url = nullptr)
        : ctx_(0)
        , encoding_(encoding)
        , options_(options)
        , url_(url)
    {
        LIBXML_TEST_VERSION;
        ctx_ = xmlNewParserCtxt();
        if (!ctx_)
        {
            throw std::runtime_error("Failed to create parser context.");
        }
    }

    ~libxml2_loader()
    {
        if (ctx_)
        {
            xmlFreeParserCtxt(ctx_);
        }
    }

    void load(std::string const& filename, xml_node& node)
    {
        if (!mapnik::util::exists(filename))
        {
            throw config_error(std::string("Could not load map file: File does not exist"), 0, filename);
        }

        xmlDocPtr doc = xmlCtxtReadFile(ctx_, filename.c_str(), encoding_, options_);

        if (!doc)
        {
            xmlError* error = xmlCtxtGetLastError(ctx_);
            if (error)
            {
                std::string msg("XML document not well formed:\n");
                msg += error->message;
                // remove CR
                msg = msg.substr(0, msg.size() - 1);
                throw config_error(msg, error->line, error->file);
            }
        }
        load(doc, node);
    }

    void load(const int fd, xml_node& node)
    {
        xmlDocPtr doc = xmlCtxtReadFd(ctx_, fd, url_, encoding_, options_);
        load(doc, node);
    }

    void load_string(std::string const& buffer, xml_node& node, std::string const& base_path)
    {
        if (!base_path.empty())
        {
            if (!mapnik::util::exists(base_path))
            {
                throw config_error(std::string("Could not locate base_path '") + base_path +
                                   "': file or directory does not exist");
            }
        }
        // NOTE: base_path here helps libxml2 resolve entities correctly: https://github.com/mapnik/mapnik/issues/440
        xmlDocPtr doc = xmlCtxtReadMemory(ctx_, buffer.data(), buffer.length(), base_path.c_str(), encoding_, options_);

        load(doc, node);
    }

    void load(const xmlDocPtr doc, xml_node& node)
    {
        if (!doc)
        {
            std::string msg("XML document not well formed");
            xmlError* error = xmlCtxtGetLastError(ctx_);
            if (error)
            {
                msg += ":\n";
                msg += error->message;
                throw config_error(msg, error->line, error->file);
            }
            else
            {
                throw config_error(msg);
            }
        }

        int iXIncludeReturn = xmlXIncludeProcessFlags(doc, options_);

        if (iXIncludeReturn < 0)
        {
            xmlFreeDoc(doc);
            throw config_error("XML XInclude error.  One or more files failed to load.");
        }

        xmlNode* root = xmlDocGetRootElement(doc);
        if (!root)
        {
            xmlFreeDoc(doc);
            throw config_error("XML document is empty.");
        }

        populate_tree(root, node);
        xmlFreeDoc(doc);
    }

  private:
    void inline append_attributes(xmlAttr* attributes, xml_node& node)
    {
        for (; attributes; attributes = attributes->next)
        {
            node.add_attribute(reinterpret_cast<const char*>(attributes->name),
                               reinterpret_cast<const char*>(attributes->children->content));
        }
    }

    void inline populate_tree(xmlNode* cur_node, xml_node& node)
    {
        for (; cur_node; cur_node = cur_node->next)
        {
            switch (cur_node->type)
            {
                case XML_ELEMENT_NODE: {
                    xml_node& new_node =
                      node.add_child(reinterpret_cast<const char*>(cur_node->name), cur_node->line, false);
                    append_attributes(cur_node->properties, new_node);
                    populate_tree(cur_node->children, new_node);
                }
                break;
                case XML_TEXT_NODE: {
                    std::string trimmed(reinterpret_cast<const char*>(cur_node->content));
                    mapnik::util::trim(trimmed);
                    if (trimmed.empty())
                        break; // Don't add empty text nodes
                    node.add_child(trimmed.c_str(), cur_node->line, true);
                }
                break;
                case XML_COMMENT_NODE:
                    break;
                default:
                    break;
            }
        }
    }

    xmlParserCtxtPtr ctx_;
    const char* encoding_;
    int options_;
    const char* url_;
};

void read_xml(std::string const& filename, xml_node& node)
{
    libxml2_loader loader;
    loader.load(filename, node);
}
void read_xml_string(std::string const& str, xml_node& node, std::string const& base_path)
{
    libxml2_loader loader;
    loader.load_string(str, node, base_path);
}

} // end of namespace mapnik

#endif