mapnik/src/libxml2_loader.cpp

/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2007 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
 *
 *****************************************************************************/

#include <mapnik/libxml2_loader.hpp>

#include <mapnik/config_error.hpp>

#include <boost/utility.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/filesystem/operations.hpp>

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

#include <iostream>

using boost::property_tree::ptree;
using namespace std;

//#define DEFAULT_OPTIONS (XML_PARSE_NOENT | XML_PARSE_NOBLANKS | XML_PARSE_DTDLOAD | XML_PARSE_NOCDATA)
#define DEFAULT_OPTIONS (XML_PARSE_NOERROR | XML_PARSE_NOENT | XML_PARSE_NOBLANKS | XML_PARSE_DTDLOAD | XML_PARSE_NOCDATA)

namespace mapnik 
{
class libxml2_loader : boost::noncopyable
{
public:
    libxml2_loader(const char *encoding = NULL, int options = DEFAULT_OPTIONS, const char *url = NULL) :
        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( const std::string & filename, ptree & pt )
    {
        boost::filesystem::path path(filename);
        if ( !boost::filesystem::exists( path ) ) {
            throw config_error(string("Could not load map file '") +
                               filename + "': File does not exist");
        }

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

        if ( !doc )
        {
            xmlError * error = xmlCtxtGetLastError( ctx_ );
            std::ostringstream os;
            os << "XML document not well formed";
            if (error)
            {
                os << ": " << std::endl << error->message;
                // remove CR 
                std::string msg = os.str().substr(0, os.str().size() - 1);
                config_error ex( msg );

                os.str("");
                os << "(encountered in file '" << error->file << "' at line "
                   << error->line << ")";

                ex.append_context( os.str() );

                throw ex;
            }
        }

        /*
          if ( ! ctx->valid ) 
          {
          std::clog << "### ERROR: Failed to validate DTD."
          << std::endl;
          }
        */
        load(doc, pt);
    }

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

    void load_string( const std::string & buffer, ptree & pt, std::string const & base_url )
    {
        if (!base_url.empty())
        {
            boost::filesystem::path path(base_url);
            if ( ! boost::filesystem::exists( path ) ) {
                throw config_error(string("Could not locate base_url '") +
                                   base_url + "': file or directory does not exist");
            }                    
        }

        xmlDocPtr doc = xmlCtxtReadMemory(ctx_, buffer.data(), buffer.length(), base_url.c_str(), encoding_, options_);

        load(doc, pt);
    }

    void load( const xmlDocPtr doc, ptree & pt )
    {
        if ( !doc )
        {
            xmlError * error = xmlCtxtGetLastError( ctx_ );
            std::ostringstream os;
            os << "XML document not well formed";
            if (error)
            {
                os << ": " << std::endl << error->message;
            }
            throw config_error(os.str());
        }

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

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

private:
    void append_attributes( xmlAttr * attributes, ptree & pt)
    {
        if (attributes)
        {
            ptree::iterator it = pt.push_back( ptree::value_type( "<xmlattr>", ptree() ));
            ptree & attr_list = it->second;
            xmlAttr * cur_attr = attributes;
            for (; cur_attr; cur_attr = cur_attr->next )
            {
                ptree::iterator it = attr_list.push_back(
                    ptree::value_type( (char*)cur_attr->name, ptree() ));
                it->second.put_value( (char*) cur_attr->children->content );
            }
        }
    }

    void populate_tree( xmlNode * node, ptree & pt )
    {
        xmlNode * cur_node = node;

        for (; cur_node; cur_node = cur_node->next )
        {
            switch (cur_node->type) 
            {
            case XML_ELEMENT_NODE:
            {
                ptree::iterator it = pt.push_back( ptree::value_type(
                                                       (char*)cur_node->name, ptree() ));
                append_attributes( cur_node->properties, it->second);
                populate_tree( cur_node->children, it->second );
            }
            break;
            case XML_TEXT_NODE:
                pt.put_value( (char*) cur_node->content );
                break;
            case XML_COMMENT_NODE:
            {
                ptree::iterator it = pt.push_back(
                    ptree::value_type( "<xmlcomment>", ptree() ));
                it->second.put_value( (char*) cur_node->content );
            }
            break;
            default:
                break;

            }
        }
    }

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

void read_xml2( std::string const & filename, boost::property_tree::ptree & pt)
{
    libxml2_loader loader;
    loader.load( filename, pt );
}
void read_xml2_string( std::string const & str, boost::property_tree::ptree & pt, std::string const & base_url)
{
    libxml2_loader loader;
    loader.load_string( str, pt, base_url );
}

} // end of namespace mapnik